OA11738A - Method of treating tobacco to reduce nitrosamine content, and products produced thereby. - Google Patents

Abstract

Methods of reducing the content of and preventing formation of carcinogenic nitrosamines in harvested leafy plants such as tobacco and marijuana are disclosed. The methods are directed to subjecting the plant to microwave and/or higher frequency radiation, at appropriate times in the cure cycle. With tobacco, products suitable for human consumption, such as cigarettes, cigars, etc., can be made in accordance with the present invention, having contents of tobacco-specific nitrosamines on a par with fresh-cut, green tocacco. In preferred embodiments, the resultant tobacco products are dried, golden-yellow leaves having almost negligible amounts of the known carcinogens NNN and NNK, in comparison to conventionally cured tobacco.

Description

I !

METHOD OF TREATING TOBACCO TO REDUCE NITROSAMINE CONTENT,

AND PRODUCTS PRODUCED THEREBY

Field Of The Invention

The présent invention relates to a method of treatingtobacco to reduce the content of, or prevent formation of,harmful nitrosamines which are normally found in tobacco. Theprésent invention also relates to tobacco products having low 9 nitrosamine content.

Cross-reference to Related Applications

This is application is a continuation-in-part of applicationSerial No. 08/879,905 filed June 20, 1997, which is a continuation-in-part of application Serial No. 08/757,104 filed 10 December 2, 199S, which is a continuation-in-part of application

Serial No. 08/739,942 filed October 30, 1996, now abandoned, which is a continuation-in-part of application Serial No.08/725,691, filed September 23, 1996, now abandoned, which is acontinuation-in-part of Application Serial No. 08/671,718, filedJune 28, 1996. The présent application and the applications recited above, with the exception of Application Serial No.08/671,718, filed June 28, 1996, claim priority to provisionalapplication Serial No. 60/023,205, filed August 5, 1996.

Backcyround Of The Invention 20 Others hâve described the use of microwave energy to dry agricultural products. Use of microwave energy to cure tobaccois disclosed in U.S. Patent No. 4,430,806 to Hopkins. In U.S. 1 117 3 8

Patent No. 4,898,189, Wochnowski teaches the use of microwavesto treat green tobacco in order to control moisture content inpréparation for storage or shipping. In U.S. Patent No.3,699,976, microwave energy is described to kill insectinfestation of tobacco. Moreover, techniques using imprégnationof tobacco with inert orgânic liquids (U.S. Patent No. 4,821,747)for the purposes of extracting expanded organic materials by asluicing means hâve been disclosed wherein the mixture wasexposed to microwave energy. In another embodiment, microwave q energy is disclosed as the drying mechanism of extruded tobacco- containing material (U.S. Patent No. 4,874,000). In U.S. PatentNo. 3,773,055, Stungis discloses the use of microwave to dry andexpand cigarettes made with wet tobacco.

Prior attempts to reduce tar and harmful carcinogenic 15 nitrosamines primarily hâve included the use of filters insmoking tobacco. In addition, attempts hâve been made to useadditives to block the effects of harmful carcinogens in tobacco.These efforts hâve failed to reduce the oncologie morbidityassociated with tobacco use. It is known that fresh-cut, green 20 tobacco has virtually no nitrosamine carcinogens. *See, e.g.,Wiernik et al, "Effect of Air-Curing on the Chemical Compositionof Tobacco," Recent Advances in Tobacco Science, Vol. 21, pp. 39et seq., Symposium Proceedings 49th Meeting Tobacco Chemists'Research Conférence, Sept. 24-27, 1995, Lexington, Kentucky 25 (hereinafter "Wiernik et al"). However, cured tobacco is known to contain a number of nitrosamines, including the harmful carcinogens N'-nitrosonornicotine (NNN) and 4-(N- nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK). It is widely 2 accepted that such nitrosamines are formed post-harvest, duringthe curing process, as described further herein. Unfortunately,fresh-cut green tobacco is unsuitable for smoking or otherconsumption. § In 1993 and 1994, Burton et al at the University of Kentucky carried out certain experiments regarding tobacco-specificnitrosamines (TSNA), as reported in the Abstract, "Réduction ofNitrite-Nitrogen and Tobacco N'-Spécifie Nitrosamines In Air-Cured Tobacco By Elevâting Drying Températures", Agronomy & ^0 Phytopathology Joint Meeting, CORESTA, Oxford 1995. Burton etal reported that drying harvested tobacco leaves for 24 hours at71°C, at various stages of air curing, including end of yellowing(EOY), EOY+3, EOY+5, etc. resulted in some réduction ofnitrosamine levels. Reference is also made to freeze drying andmicrowaving of certain samples, without detail or results.Applicant has confirmed that in the actual work underlying thisAbstract, carried out by Burton et al at the University ofKentucky, the microwave work was considered unsuccessful.Certain aspects of Burton et al's 1993-94 study are reported ingQ Wiernik et al, supra, at pages 54-57, under the heading "ModifiedAir-Curing". The Wiernik et al article postulâtes thatsubjecting tobacco leaf samples, taken at various stages of air-curing, to quick-drying at 70°C for 24 hours, would remove excesswater and reduce the growth of microorganisms; hence, nitrite andtobacco-specific nitrosamine (TSNA) accumulation would beavoided. In Table II at page 56, Wiernik et al includes some ofBurton et al ' s summary data on lamina and midrib nitrite and TSNAcontents in the KY160 and KY171 samples. Data from the freeze- 3 drying and the quick-drying tests are included, but there is nomention of the microwaved samples. The article contains thefollowing conclusion:

It can be concluded from this study that itk may be possible to reduce nitrite levels and accumulation of TSNA in lamina and midrib byapplying heat (70°C) to dark tobacco afterloss of cell integrity in the leaf. Dryingthe tobacco leaf quickly at this stage ofcuring reduces the microbial activity thata- occurs during slow curing at ambient température. It must be added, however,that such a treatment lowers the quality ofthe tobacco leaf.

Id. at page 56. The Weirnik et al article also discussestraditional curing of Skroniowski tobacco in Poland as an example 15 of a 2-step curing procedure. The article States that thetobacco is first air-cured and, when the lamina is yellow orbrownish, the tobacco is heated to 65°C for two days in order tocure the stem. An analysis of tobacco produced in this mannershowed that both the nitrite and the TSNA values were low, i.e., 2© less than 10 micrograms per gram and 0.6-2.1 micrograms pergrams, respectively. Weirnik et al theorized that these resultswere explainable due to the rapid heating whicn does not allowfurther bacterial growth. Weirnik et al also noted, however,that low nitrite and TSNA values, less than 15 micrograms per 2$ gram of nitrite and 0.2 microgram per gram of TSNA, were obtainedfor tobacco subjected to air-curing in Poland.

Summary of the Invention

One object of the présent invention is to substantiallyeliminate or reduce the content of nitrosamines in tobaccointended for smoking or consumption by other means. 4 4 / ** 3 8

Another object of the présent invention is to reduce the carcinogenic potential of tobacco products, including cigarettes, cigars, chewing tobacco, snuff and tobacco-containing gum and lozenges. 5 Still another object of the présent invention is to substantially eliminate or significantly reduce the amount oftobacco-specific nitrosamines, including N'-nitrosonornicotine(NNN), 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK),N' -nitrosoanatabine (NAT) and N'-nitrosoanabasine (NAB), in such 1© tobacco products.

Another object of the présent invention is to treat uncuredtobacco at an appropriate time post-harvest so as to arrest thecuring process without adversely affecting the tobacco'ssuitability for human consumption. 15 Another object of the présent invention is to reduce the content of tobacco-specific nitrosamines in fully cured tobacco.

Yet another object of the présent invention is to reduce thecontent of tobacco-specific nitrosamines, particularly NNN andNNK, and métabolites thereof in humans who smoke, consume or 20 otherwise ingest tobacco in sotne form, by providing a tobacco product suitable for human consumption which contains asubstantially reduced quantity of tobacco-specific nitrosamines,thereby lowering the carcinogenic potential of such product.Preferably, the tobacco product is a cigarette, cigar, chewing 25 tobacco or a tobacco-containing gum or lozenge.

The above and other objects and advantages in accordance with the présent invention can be obtained by a process for 5

* 4 ’ T R reducing the amount of or preventing formation of nitrosaminesin a harvested tobacco plant, comprising subjecting at least a portion of the plant to microwaveradiation, while said portion is uncured and in a State 5 susceptible to having the amount of nitrosamines reduced or formation of nitrosamines arrested, for a sufficient time toreduce the amount of or substantially prevent formation of atleast one nitrosamine.

It is preferred that in the process of the invention, the $0 step of subjecting to microwave radiation is carried out on a tobacco leaf or portion thereof after onset of yellowing in theleaf and prior to substantial accumulation of tobacco-specificnitrosamines in the leaf. It is also preferred that in theprocess of the invention, the step of subjecting to microwave 15 radiation is carried out prior to substantial loss of the leaf's cellular integrity.

In additional preferred embodiments of the process, thetobacco is flue tobacco and the step of subjecting to microwaveradiation is carried out within about 24 to about 72 hours post- 2© harvest, even more preferably within about 24 to about 36 hourspost-harvest.

In still other embodiments of the process, the harvestedtobacco is maintained under above-ambient température conditionsin a controlled environment prior to the step of subjecting to ^5 microwave radiation.

Preferred aspects of the process include a step, prior tosubjecting a tobacco leaf which preferably includes the stem tomicrowave radiation, of physically pressing the leaf to squeeze 6 1 4 1 8 excess moisture therefrom, to ensure more uniform drying by themicrowave unit. This step can be conveniently carried out bypassing the leaf through a pair of appropriately spaced rotatingcylindrical rollers prior to entering the microwave cavity. 5 In yet additional preferred embodiments of the invention, the microwave radiation has a frequency of about 900 to about2500 MHz, and is applied to the plant for a period of at leastabout 1 second, and preferably from about 10 seconds to about 5minutes at a predetermined power level. The power level usedgenerally détermines the length of time to which the tobacco issubjected to the microwave radiation, and can range from about600 to about 1000 watts when using conventional kitchen-typemicrowave ovens, up to several hundred or more kilowatts forcommercial, multimode applicators. Preferred power levels using 15 applicators designed to handle single leaves range from about 2to about 75 kilowatts, more preferably from about 5 to about 50kilowatts, which permit relatively rapid treatment to be carried out.

It is also preferred in accordance with the présent 2® invention that the microwave radiation is applied to the leaf orportion thereof for a time sufficient to effectively dry theleaf, without charring, so that it is suitable for humanconsumption.

The présent invention also seeks to subject tobacco leaves 25 to microwave radiation to prevent normal accumulation of at leastone tobacco-specific nitrosamine, such as N'-nitrosonornicotine,4- (N-nitrosomethylamino) -1- (3-pyridyl)-1-butanone, N' -nit.rosoanatabine and N'-nitrosoanabasine. 7 44 3 8

The présent invention in its broadest forms aiso encompassesa tobacco product comprising non-green tobacco suitable for humanconsumption and having a lower content of at least one tobacco-spécifie nitrosamine than conventionally cured tobacco. 5 In preferred embodiments, the non-green tobacco product has a TSNA (NNN, NNK, NAB and NAT) content of less than .2 μg/g, morepreferably less than about .15 gg/g, and even more preferablyless than about .1 Mg/g, an NNN content of less than about .15M9/9z more preferably less than about .10 ^g/g, and even morepreferably less than about .05 ^g/g, and an NNK content of lessthan about .002 Mg/g, more preferably less than about .001 ^g/g,and even more preferably less than about .0005 /zg/g.

The présent invention is also directed to a tobacco productcomprising dried yellow tobacco suitable for human consumption 15 and having a lower content of at least one tobacco-specificnitrosamine than conventionally cured tobacco. In preferredembodiments, the yellow tobacco product has a TSNA (NNN, NNK, NABand NAT) content, an NNN content, and an NNK content within theabove preferred ranges. 20 in other embodiments, the non-green or yellow tobacco product comprises non-green or yellow tobacco suitable for humanconsumption, and having a TSNA (NNN, NNK, NAB and NAT) contentwithin about 25% by weight of the content of such TSNA in thefreshly harvested green tobacco crop from which the product was 25 made. It is more preferred that the non-green or yellow tobaccoproduct hâve a TSNA content within about 10% by weight, morepreferably within about 5% by weight and most preferablyessentially approximating (e.g. within an amount up to several 8 14 7 7 8 percent by weight) the content of such TSNA in the freshlyharvested tobacco crop from which the product was made. It isalso preferred that the non-green or yellow tobacco productcomprises non-green or yellow tobacco suitable for humanconsumption, and having content of at least one TSNA selectedfrom NNN, NNK, NAB and NAT, which is within about 25% by weight,preferably within about 10% by weight, more preferably withinabout 5% by weight and most preferably essentially approximating(e.g. within an amount up to several percent by weight) of thej content of the corresponding TSNA or TSNAs in the freshly harvested green tobacco crop from which the product was made.

In yet additional embodiments of the invention, the non- green or yellow tobacco product comprises non-green or yellowtobacco suitable for human consumption, and having a TSNA (NNN, 15 NNK, NAB and NAT) content which is at least about 75% by weight,preferably at least about 90% by weight, more preferably at leastabout 95% by weight, and most preferably at least about 99% byweight lower than the content of such TSNA in a tobacco productof the same type made from the same tobacco crop as the product 20 of the invention, but which was cured in the absence of microwaveradiation or other techniques designed to reduce TSNA content.It is also preferred that the non-green or yellow tobacco productcomprises non-green or yellow tobacco suitable for humanconsumption, and having a content of at least one TSNA selected 25 from NNN, NNK, NAB and NAT which is at least about 75% by weight,preferably at least about 90% by weight, more preferably at leastabout 95% by weight, and most preferably at least about 99% byweight lower than the content of the corresponding TSNA or TSNAs 9 Λ 4 -7 3 8 in a tobacco product of the same type made from the sarae tobaccocrop as the product of the invention, but which was cured in theabsence of microwave radiation or other techniques designed toreduce TSNA content. 5 A preferred form of the présent invention relates to a tobacco product comprising tobacco having a reduced content ofat least one tobacco-specific nitrosamine, produced by a processcomprising subjecting the tobacco, while the tobacco is uncuredand susceptible to having formation of at least one tobacco- |© spécifie nitrosamine arrested, to microwave radiation.

In another embodiment, the présent invention is directed to a method for reducing the content of at least one tobacco-specif ic nitrosamine in cured brown tobacco, comprising rehydrating the cured brown tobacco, andÎ5 subjecting the rehydrated tobacco to microwave radiation at a predetermined energy level for a predetèrmined length of time.

Similarly, the présent invention includes within its scopea tobacco product comprising cured brown tobacco having a reducedcontent of at least one tobacco-specific nitrosamine, produced 2Θ by a process comprising rehydrating the cured brown tobacco, and subjecting the rehydrated tobacco to microwave radiation ata predetermined energy level for a predetermined length of time.

In yet another embodiment, the présent invention relates to 25 a method of manufacturing a tobacco product, comprising subjecting harvested tobacco leaves to microwave radiation, while said leaves are uncured and in a State susceptible tohaving the amount of tobacco-specific nitrosamines reduced or 10 formation of tobacco-specific nitrosamines arrested, for asufficient time to reduce the amount of or substantially preventformation of at least one tobacco-specific nitrosamine in theleaves, and 5 forming the tobacco product comprising the microwaved leaves, the tobacco product being selected from cigarettes,cigars, chewing tobacco, snuff and tobacco-containing gum andlozenges.

It has also been discovered that forms of electromagnetict© radiation having higher frequencies and shorter wavelengths thanthe microwave domain discussed above and in more detail below,can be used to achieve the basic objects of the présent invention- réduction or substantial élimination of TSNAs in tobaccoproducts, by treating the tobacco with such energy forms in the 19 same time frame post-harvest as discussed above with regard tothe microwave embodiment. Thus, the présent invention alsorelates to a method for reducing the amount of or preventingformation of nitrosamines in a harvested tobacco plant,comprising 20 subjecting at least a portion of the plant to radiationhaving a frequency higher than the microwave domain, while saidportion is uncured and in a State susceptible to having theamount of nitrosamines reduced or formation of nitrosamines arrested, for a sufficient time to reduce the amount of or2^ substantially prevent formation of at least one nitrosamine.

As with the microwave embodiments, it is preferred that inthe process of the invention, the step of subjecting to radiationhaving a frequency higher than the microwave domain is carried 11 117 3 8 out on a tobacco leaf or portion thereof after onset of yellowingin the leaf and prior to substantial accumulation of tobacco-specific nitrosamines in the leaf. It is also preferred that inthe process of the invention, the step of subjecting to such > radiation is carried out prior to substantial loss of the leaf'scellular integrity. Preferred energy sources capable ofproducing such radiation are described further below, and includefar-infrared and infrared radiation, UV (ultraviolet radiation),soft x-rays or lasers, accelerated particle beams such as 10 électron beams, x-rays and gamma radiation.

Brief Description of the Drawings FIG. 1 is a photograph illustrating "yellow" Virginia fluetobacco aged 24 to 72 hours post-harvest. FIG. 2 is a photograph illustrating low-ni tros amine microwaved "yellow" Virginia flue tobacco in accordance with the 15 présent invention.

Figure 3 is a partial, side-perspective illustration of amobile, commercial-scale microwave applicator which can beemployed to carry out the microwave treatment in accordance withthe présent invention. 2Θ

Detailed Description Of The Invention

It has been said that the practice of tobacco curing is moreof an art than a science, because curing conditions during anygiven cure must be adjusted to take into account such factors asvarietal différences, différences in leaves harvested from ®5 various stalk positions, différences among curing barns where 12 11 7 8 used, and environmental variations during a single season or overdifferent seasons, especially weather fluctuations when air-curing. For example, the practice of flue curing is empiricalto a certain degree, and is optimally carried out by individuals 5 who hâve accumulated expérience in this art over a significant period of time. See, e.g., Peele et al, "Chemical andBiochemical Changes During The Flue Curing Of Tobacco," RecentAdvances In Tobacco Science, Vol. 21, pp. 81 et seq., SymposiumProceedings 4 9th Meeting Chemists' Research Conférence, Septemberîô 24-27, 1995, Lexington, Kentucky (hereinafter "Peele et al").

Thus, one of ordinary skill in the art of tobacco curing wouldunderstand that the outer parameters of the présent invention,in its broadest forms, are variable to a certain extent dependingon the précisé confluence of the above factors for any given harvest.

In one preferred embodiment, the présent invention isfounded on the discovery that a window exists during the tobaccocuring cycle, in which the tobacco can be treated in a mannerthat will essentially prevent the formation of TSNA. Of course,the précisé window during which TSNA formation can be effectivelyeliminated or substantially reduced dépends on the type oftobacco, method of curing, and a number of other variables,including those mentioned above. In accordance with thispreferred embodiment of the présent invention, the windowcorresponds to the time frame post-harvest when the leaf isbeyond the fresh-cut or "green" stage, and prior to the time atwhich TSNAs and/or nitrites substantially accumulate in the leaf;this time frame typically corresponds to the period in which the 13 leaf is undergoing the yellowing process or is in the yellowphase, before the leaf begins to turn brown, and prior to thesubstantial loss of cellular integrity. Unless otherwise clearfrom the context, the terms "substantial" and "significant" as J used herein generally refer to prédominant or majority on arelative scale, give or take. During this time frame, the leavesare susceptible to having the formation of TSNAs substantiallyprevented, or the content of any already formed TSNAs reduced,by exposing the tobacco to microwave radiation at a predeterminedenergy level for a predetermined length of time, as discussedfurther below. This microwave treatment essentially arrests thenatural formation of TSNAs, and provides a dried, golden yellowleaf suitable for human consumption. If TSNAs hâve already begunto substantially accumulate, typically toward the end of theyellow phase, the application of microwave energy to the leaf inaccordance with the invention effectively arrests the naturalTSNA formation cycle, thus preventing any further substantialformation of TSNA. When yellow or yellowing tobacco is treated 80 in this fashion at the most optimal time in the curing cycle, theresulting tobacco product has TSNA levels essentiallyapproximating those of freshly harvested green tobacco, whilemaintaining its flavor and taste.

In another embodiment, the présent invention relates to 25 treatment of cured (brown) tobacco to effectively reduce the TSNAcontent of that cured tobacco, by rehydrating cured tobacco andsubjecting the rehydrated cured tobacco to microwave radiation,as described further below. 14 15

The présent invention is applicable to treatment of theharvested tobacco which is intended for human consumption. Muchresearch has been performed on tobacco, with particular referenceto tobacco-specific nitrosamines. Freshly harvested tobaccoleaves are called "green tobacco" and contain no knowncarcinogens, but green tobacco is not suitable for humanconsumption. The process of curing green tobacco dépends on thetype of tobacco harvested. For example, Virginia flue (bright)tobacco is typically flue-cured, whereas Burley and certain darkstrains are usually air-cured. The flue-curing of tobaccotypically takes place over a period of five to seven dayscompared to one to two+ months for air-curing. According toPeele et al, flue-curing has generally been divided into threestages: yellowing (35-40°C) for about 36-72 hours (althoughothers report that yellowing begins sooner than 36 hours, e.g.,at about 24 hours for certain Virginia flue strains), leaf drying(40-57°C) for 48 hours, and midrib (stem) drying (57-75°C) for48 hours. Many major Chemical and biochemical changes beginduring the yellowing stage and continue through the early phasesof leaf drying.

In a typical flue-curing process, the yellowing stage iscarried out in a barn. . During this phase the green leavesgradually lose color due to chlorophyll dégradation, with thecorresponding appearance of the yellow carotenoid pigments.According to the review by Peele et al, the yellowing stage offlue-curing tobacco is accomplished by closing external air ventsin the barn, and holding the température at approximately 35°-37°C. This process utilizes a controlled environment, maintains 15 117 3 8 the relative humidity in the barn at approximately 85%, limitsmoisture loss from the leaves, and allows the leaf to continuethe metabolic processes begun in the field. The operatorconstantly monitors the progress of the cure, primarily by 5 observing the loss of chlorophyll and green color from theleaves, and the development of the desired lemon to golden orangeleaf color.

With one particular variety of Virginia flue tobacco onwhich testing has been carried out as described herein, freshlyt© harvested green tobacco is placed in a barn for about 24-48 hours at about 100-110°F until the leaves turn more or less completelyyellow (see Figure 1) . The yellow tobacco has a reduced moisturecontent, i.e., from about 90 weight % when green, versus about70-40 weight % when yellow. At this stage, the yellow tobacco 13 contains essentially no known carcinogens, and the TSNA content is essentially the same as in the fresh-cut green tobacco. ThisVirginia flue tobacco typically remains in the yellow stage forabout 5-7 days, after which time the leaves turn from yellow tobrown. The brown Virginia flue tobacco typically has a moisture 2© content of about 11 to about 15 weight percent. The conversionof the tobacco from yellow to brown results in formation andsubstantial accumulation of nitrosamines, and an increasedmicrobial content. The exact mechanism by which tobacco-specificnitrosamines are formed is not clear, but is believed to be 25 enhanced by microbial activity, involving microbial nitratereductases in the génération of nitrite during the curing process. 16 „ 11738

Tobacco-specific nitrosamines are believed to be formed uponreaction of amines with nitrite-derived nitrosating species, suchas N02, N2O3 and N2O4 under acidic conditions. Weirnik et aldiscuss the postulated formation of TSNAs at pp. 43-45; a brief 5 synopsis is set forth below.

Tobacco leaves contain an abundance of amines in the formof amino acids, proteins, and alkaloids. The tertiary aminenicotine (referenced as (1) in the diagram below) is the majoralkaloid in tobacco, while other nicotine-type alkaloids are thel®'· secondary amines nornicotine (2), anatabine (3) and anabasine (4) . Tobacco also generally contains up to 5% of nitrate and traces of nitrite.

Nitrosation of nornicotine (2) , anatabine (3) , and anabasine(4) gives the corresponding nitrosamines: N' -nitrosonornicotine(NNN, 5), N'-nitrosoanatabine (NAT, 6), and N'-nitrosonabasine(NÂB, 7) . Nitrosation of nicotine (1) in aqueous solutionaffords a mixture of 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-z/ butanone (NNK, 8) (NNN, 5) and 4-(N-nitrosomethylamino)-4-(3- /‘- pyridyl)-1-butanal (NNA, 9). Less commonly encountered TSNAs, include NNAL (4-N-nitrosomethylamino)-1-(3-pyridyl)-1-butanol, 10) , iso-NNAL (4-N-nitrosomethylamino)-4- (3-pyridyl) - 1-butanol, 11) and iso-NNAC (4-(N-nitrosomethylamino)-4-(3-pyridyl)-butanoicacid, 12) . The formation of these TSNAs from the correspondingTobacco alkaloids is shown schematically below, using thedésignations 1-12 above (reproduced from Weirnik et al, supra,p. 44) : 17

t « Nicotine Déméthylation

2 s Nomlcotlne N -- 3 s Anatabîne 4 s Ànabxxine

NilroMtion—-——♦···

Réduction····—-— ϊ»>

U-üo-NNAL

It is now generally agreed that green, freshly harvestedtobacco contains virtually no nitrite or TSNA, and that thesecompounds are generated during curing and storage of tobacco.Studies hâve been made during the past decade to try to détermine $ the events related to the formation of TSNA during curing of tobacco, and several factors of importance hâve been identified.These include plant génotype, plant maturity at harvest, curingconditions and microbial activity.

Studies hâve shown that nitrite and TSNA accumulate on air- 10 curing at the time intervals starting after the end of yellowing and ending when the leaf turns completely brown, e.g., 2-3 weeksafter harvest for certain air-cured strains, and approximatelya week or so after harvest in flue-cured varieties. This is the 18

"'’S time during which loss of cellular integrity occurs, due tomoisture loss and leakage of the content of cells into theintercellular spaces. Therefore, there is a short window in timeduring air- curing when the cells hâve disintegrated, making the 5 nutrition available for microorganisms. Weirnik et al hâve suggested that nitrite may then substantially accumulate as aresuit of dissimilatory nitrate réduction, thus renderingformation of TSNA possible.

There are a few published reports on the effects of 10 microbial flora on the tobacco leaf during growth and curing andon cured tobacco, as cited in Weirnik et al. However, theinvolvement of microbial nitrite reductases in the génération ofnitrate during curing is presumed. When cell structure is brokendown after the yellow phase, and nutrients are made accessible 15 to invading microorganisms, these may produce nitrite underfavorable conditions, i.e., high humidity, optimal températureand anoxia. There is normally a rather short "window" in timewhen the water activity is still sufficiently high, and the cellstructure has disintegrated.

In accordance with the présent invention, the formation ofTSNAs in tobacco is substantially prevented or arrested bysubjecting the harvested leaves to microwave radiation under theconditions described herein. In one preferred embodiment, thetobacco leaves are exposed to the microwave energy at a time 25 between the onset of yellowing and the substantial loss ofcellular integrity. For optimal results, it is preferred to passthe harvested leaves through the microwave field as singleleaves, as opposed to stacks or piles of leaves. Treating the 19 14 "3 8 leaves in this manner has been determined to completely orsubstantially prevent the formation of tobacco-specificnitrosamines, including the known carcinogens NNN and NNK.

In accordance with preferred embodiments of the présent5 invention, non-green and/or yellow tobacco products can be obtained which are suitable for human consumption, and which hâvea lower content of at least one tobacco-specific nitrosamine thanconventionally cured tobacco. Green or fresh-cut tobacco isgenerally unsuitable for human consumption as noted above; "non-green" as used herein means means the tobacco has at least lostthe majority of chlorophyll, and includes without limitationpartially yellow leaves, full yellow leaves, and leaves whichhâve begun to turn brown in places. In preferred embodiments,the non-green tobacco product has a TSNA (NNN, NNK, NAB and NAT)content of less than .2 ^g/g, more preferably less than about .15/xg/g, and even more preferably less than about .1 ^g/g, an NNNcontent of less than about .15 gg/g, more preferably less thanabout .10 /xg/g, and even more preferably less than about .05/xg/g, and an NNK content of less than about .002 /xg/g, morepreferably less than about .001 μ%/<3, and even more preferablyless than about .0005 Mg/g. As noted above, given the number offactors which can influence TSNA formation in tobacco, one ofordinary skill in the art would understand that these numbers are not absolute, but rather preferred ranges.

The présent invention is also directed to a tobacco productcomprising dried yellow tobacco suitable for human consumptionand having a lower content of at least one tobacco-specificnitrosamine than conventionally cured tobacco. In preferred 20

embodiments, the yellow tobacco product has a TSNA (NNN, NNK, NABand NAT) content, an NNN content, and an NNK content within theabove preferred ranges.

In other embodiments, the non-green or yellow tobacco5 product comprises non-green or yellow tobacco suitable for humanconsumption, and having a TSNA (NNN, NNK, NAB and NAT) contentwithin about 25% by weight of the content of such TSNA in thefreshly harvested green tobacco crop from which the product wasmade. It is more preferred that the non-green or yellow tobacco 10 product hâve a TSNA content within about 10% by weight, morepreferably within about 5% by weight and most preferablyessentially approximating (e.g. within an amount up to severalpercent by weight) the content of such TSNA in the freshlyharvested tobacco crop from which the product was made. Forexample, the présent invention permits tobacco products to bemade which hâve a TSNA content within the above-described rangesas to amounts, whereas normally cured tobacco from the same cropwould typically generate many times the amount of TSNA in thefresh-cut tobacco. The présent invention can effectively lock 2© in the low amounts of nitrosamines found in fresh-cut greentobacco. It is also preferred that the non-green or yellowtobacco product comprises non-green or yellow tobacco suitablefor human consumption, and having content of at least one TSNAselected from NNN, NNK, NAB and NAT, which is within about 25% 25 by weight of, preferably within about 10% by weight of, morepreferably within about 5% by weight of, and most preferablyessentially approximating (e.g., within an amount up to severalpercent by weight) the content of the corresponding TSNA or TSNAs 21 1 4 “» T g in the freshly harvested green tobacco crop from which theproduct was made. In other words, the content of, e.g.( NNN inthe tobacco of the invention falls within the above ranges vis-a-vis the amount of NMN in the fresh-cut green tobacco, or the 5 amount of NNN + NNK in the tobacco of the invention falls withinthe above ranges vis-a-vis the amount of NNN + NNK in the fresh-cut green tobacco, etc. In making these comparisons, the fresh-cut green tobacco is preferably analyzed for TSNA content withinabout 24 hours after harvest. I© In yet additional embodiments of the invention, the non- green or yellow tobacco product comprises non-green or yellowtobacco suitable for human consumption, and having a TSNA (NNN,NNK, NAB and NAT) content which is at least about 75% by weight,preferably at least about 90% by weight, more preferably at least 15 about 95% by weight, and most preferably at least about 99% byweight lower than the content of such TSNA in a tobacco productof the same type made from the same tobacco crop as the productof the invention, but which was cured in the absence of microwaveradiation or other steps specifically designed to reduce the TSNAao content. It is also preferred that the non-green or yellowtobacco product comprises non-green or yellow tobacco suitablefor human consumption, and having a content of at least one TSNAselected from NNN, NNK, NAB and NAT which is at least about 75%by weight, preferably at least about 90% by weight, morepreferably at least about 95% by weight, and most preferably atleast about 99% by weight lower than the content of thecorresponding TSNA or TSNAs in a tobacco product of the same type(e.g., comparing a cigarette to another cigarette) made from the 22 1 4/7 7 8 same tobacco crop as the product of the invention, but which wascured in the absence of microwave radiation or other techniquesfor reducing TSNA content. In these embodiments, the TSNA weight % comparisons can be made by taking, for example, a cigarette 5 made using dried yellow tobacco in accordance with the présentinvention, and taking a cigarette made from tobacco from the samecrop as the dried yellow tobacco was made from, but curing it byconventional means without subjecting it to microwave radiation.

The yellow stage, in which the step of subjecting the 1® tobacco leaf to microwave radiation is preferably carried out,can be broadly defined in any one of the following ways: (a) by examining the color of the leaf, when the green color hassubstantially given way to a yellowish color; (b) by measuringthe percent of chlorophyll conversion to sugars; (c) by observing ^5 the onset of either nitrite formation or nitrosamine génération,which typically coïncide with the end of the yellow phase, or (d)by measuring the moisture content of the leaves, e.g., when theyhâve a moisture content from about 4 0 to about 70 percent byweight. If the microwave radiation is applied to green tobacco, 1® the arrestation or prévention of nitrosamine formation is notobserved. However, when microwave energy is applied after theonset of yellowing and prior to the loss of cellular integrityor substantial accumulation of TSNAs in the leaf, the observedréduction in the amount of, or prévention of formation ofnitrosamines is dramatic and unexpected, as shown by the datadiscussed below.

The optimal time for subjecting the harvested tobacco to themicrowave radiation during the yellow phase varies depending on 23 11738 a number of factors, including varietal différences,environmental variations, etc. Thus, within the time framebeginning with onset of yellowing (defined, e.g., by a loss ofthe majority of green color in the leaf) through the time at 5 which the leaf substantially loses cellular integrity (as itturns brown), one of ordinary skill in the art could déterminethe optimal time for carrying out the microwave treatment for anygiven variety of tobacco. For example, for a given génotype,sample leaves could be tested by the procedures described hereinto measure either nitrite or TSNA content, to identify therelative time in a given cure cycle at which significant TSNAaccumulation begins, or identify the transition phase in whichloss of cellular integrity occurs. While subjecting the leavesto the microwave radiation prior to significant TSNA accumulationfij is the most preferred form of the method of the présentinvention, the principles of the invention can also be appliedto tobacco leaves which are in the process of forming, and hâvealready accumulated significant amounts of TSNAs. When themicrowaving is carried out at this latter stage, further 2© formation of TSNAs can be effectively arrested. However, oncethe leaves are fully cured, TSNA levels hâve essentiallystabilized, and application of microwave radiation is ineffectiveto reduce the TSNA context, except under rehydration conditionsdescribed below. 25 Upon being subjected to microwave radiation in accordance with the présent invention, the tobacco leaf generally has areduced moisture content, i.e. less than about 10% by weight, andoften approximately 5%. If desired, the leaf can be rehydrated 24 ί 4 7 7% back to the typical moisture range for brown, cured tobacco(e.g., about 11-15% for Virginia flue) before manufacturing intotobacco products such as cigarettes.

The présent invention is applicable to ail strains of 5 tobacco, including flue or bright varieties, Burley varieties,dark varieties, oriental/Turkish varieties, etc. Within theguidelines set forth herein, one of ordinary skill in the artcould détermine the most efficient time in the cure cycle for I© carrying out the microwave step to achieve the objects andadvantages of the présent invention.

Preferred aspects of the process include a step, prior tosubjecting a tobacco leaf which preferably includes the stem tomicrowave radiation, of physically pressing the leaf to squeezeexcess moisture therefrom, to ensure more uniform drying by themicrowave unit. This step can be conveniently carried out bypassing the leaf through a pair of appropriately spaced rotatingcylindrical rollers prior to entering the microwave cavity. Sucha pressing step will aid in wringing moisture from the stem and, 2Θ to a lesser extent, the midrib and larger veins, and lead to abetter and more evenly dried product. The rollers can be madeof hard rubber, plastic or Steel and be of any desired length,and are preferably spaced about one-eighth to about one-quarterinch apart, but the distance is preferably selected so as to 25 accomodate the thickness of a single leaf, which can vary. Therollers can be belt or chain driven by an appropriately selectedmotor. Besides rotating rollers, other types of squeezing orpressing means could be used to accomplish the same resuit, if 25 ι i f U 8 desired, as would be apparent to one of ordinary skill in theart.

The above-described preferred embodiment of pressing theleaves permits more high-speed production to be carried out; 5 since the stems do not hâve to be eut out, and the microwave timecan be reduced. This embodiment is particularly advantageous fortobacco leaves destined to be used in cigarettes, which typicallycontain some tobacco stems as part of a blend. Alternatively,the pressing step can be omitted if desired, in applications to where the stem is trimmed from the leaves and discarded.

In another preferred embodiment, instead of pressing the leaves or cutting out the stems, the leaves can be subjected toa steam treatment prior to microwaving. As with the pressingstep, steaming the whole leaves, including the stems, has beento demonstrated to more evenly distribute the moisture in the stemsand larger veins, thus leading to more uniform drying of theentire leaves upon microwaving. As a resuit, the entire leavesincluding the stems can be used in tobacco products when thisparticular technique is employed. Although the details would be 2® apparent to one of ordinary skill in the art, successful resultshâve been obtained when the leaves hâve been placed in a suitablesteam vessel for a time sufficient to allow the leaves to becomesomewhat soft and pliable, generally from about 30 seconds up toabout five minutes. to The principles of the présent invention can also be applied to brown or already cured tobacco, which has been rehydrated.In such cases, while important and unexpected réductions in theamount of the TSNAs, particularly NNN .and NNK, are observed when 26 ί 4 *7 T η rehydrated brown tobacco is subjected to microwave radiation, theresults are not as dramatic as when the invention is applied touncured yellow tobacco, prior to the time when substantialquantities of TSNAs or nitrites hâve accumulated in the leaves: 5 Nonetheless, the addition of moisture to the cured leaves, such as by spraying with enough water to effectively soak the leaves,followed by microwaving the rehydrated leaves, reduces thecontent of TSNAs as demonstrated in the following Examples.

As noted above, when treating cured or brown tobacco, W microwaving alone has little effect on the nitrosamine content.

However, it has been determined that rehydration of the curedtobacco prior to subjecting it to microwave radiation facilitâtesthe action of the microwave energy in reducing nitrosamines. Inone preferred embodiment, the cured tobacco product is rehydrated 15 by adding an appropriate amount of water, generally at least about 10% by weight, up to the maximum absorption capacity,directly to the leaves. Exposure of the rehydrated leaves tomicrowave radiation, in the same manner as described herein withregard to the uncured tobacco, reduces the nitrosamine content,g© as shown below. The leaves can be wetted in any suitable fashion. If the cured tobacco is in a form other than leaves,such as reconstituted "sheet" tobacco, it can similarly berehydrated with, e.g., '10-70% by weight water,. and thenmicrowaved. Suitable microwave condition can be selectedgj depending on the degree to which the leaves are re-wetted, buttypically fall within the parameters discussed above for microwaving yellow tobacco. 27 117 7 8

In accordance with the présent invention, microwaving of therehydrated brown tobacco can preferably reduce the TSNA (NNN,NNK, NAB and NAT) content, measured individually or collectively,by at least about 25% by weight, more preferably by at leas't 5 about 35% by weight, and even more preferably by at least about50% by weight from the TSNA levels contained the cured browntobacco prior to rehydration.

The term "microwave radiation" as used herein refers toelectromagnetic energy in the form of microwaves having afrequency and wavelength typically characterized as fallingwithin the microwave domain. The term "microwave" generallyrefers to that portion of the electromagnetic specrrum which liesbetween the far-infrared région and the conventionalradiofrequency spectrum. The range of microwaves extends from 15 a wavelength of approximately 1 millimeter and frequency of about3 00,000 MHz to wavelength of 3 0 centimeters and frequency ofslightly less than about 1,000 MHz. The présent inventionpreferably utilizes high power applications of microwaves,typically at the lower end of this frequency range. Within this 2· preferred frequency range, there is a fundamental différencebetween a heating process by microwaves and by a classical way,such as by infrared (for example, in cooking): due to a greaterpénétration, microwaves generally heat quickly to a depth severalcentimeters while heating by infrared is much more superficial.In the United States, commercial microwave apparatuses, such askitchen microwave ovens, are available at standard frequenciesof approximately 915 MHz and 2450 MHz, respectively. Thesefrequencies are standard industrial bands. In Europe, microwave 28 10 15 30 frequencies of 2450 and 896 MHz are coramonly employed. Underproperly balanced conditions, however, microwaves of otherfrequencies and wavelengths would be useful to achieve theobjects and advantages of the présent invention.

Microwave energy can be generated at a variety of powerlevels, depending on the desired application. Microwaves aretypically produced by magnatrons, at power levels of 600-1000watts for conventional kitchen-level microwave apparatuses(commonly at about 800 watts), but commercial units are capableof generating power up to several hundred kilowatts, generallyby addition of modular sources of about 1 kilowatt. A magnatroncan generate either pulsed or continuous waves of suitably highfrequency.

The applicator (or oven) is a necessary link between themicrowave power generator and the material to be heated. Forpurposes of the présent invention, any desired applicator can beused, so long as it is adapted to permit the tobacco plant partsto be effectively subjected to the radiation. The applicatorshould be matched to the microwave generator to optimize powertransmission, and should avoid leakage of energy towards theoutside. Multimode cavities (microwave ovens), the dimensionsof which can be larger than several wavelengths if necessary forlarge samples, are useful. To ensure uniform heating in theleaves, the applicator can be equipped with a mode stirrer (ametallic moving device which modifies the field distributioncontinuously), and with a moving table surface, such as aconveyor belt. The best results are attained by single leaf 25 29 1© 2© thickness exposure to microwave radiation, as opposed to stacksor piles of leaves.

In preferred embodiments of the invention, the microwaveconditions comprise microwave frequencies of about 900 MHz toabout 2500 MHz, more preferably about 915 MHz and about 2450 MHz,power levels of from about 600 watts up to 300 kilowatts, morepreferably from about 600 to about 1000 watts for kitchen-typeapplicators and from about 2 to about 75 kilowatts, morepreferably from about 5 to about 50 kilowatts, for commercialmultimode applicators. The heating time generally ranges fromat least about 1 second, and more generally from about 10 secondsup to about 5 minutes. At power levels of about 800-1000 wattsthe heating time is preferably from about 1 minute to about 2½minutes when treating single leaves as opposed to piles orstacks. For commercial-scale applicators using higher powerlevels in the range of, e.g., 2-75 kilowatts, heating times wouldbe lower, ranging from about 5 seconds up to about 60 seconds,and generally in the 10-30 second range at, say, 50 kilowatts,again for single leaves as opposed to piles or stacks. Ofcourse, one of ordinary skill in the art would understand thatan optimal microwave field density could be determined for anygiven applicator based on the volume of the cavity, the powerlevel employed, and the amount of moisture in the leaves.Generally speaking, use of higher power levels will require lesstime during which the leaf is subjected to the microwaveradiation.

However, the above-described conditions are not absolute,and given the teachings of the présent invention, one of ordinary 23 30

skill in the art would be able to détermine appropriate microwaveparameters. The microwave radiation is preferably applied to theleaf or portion thereof for a time sufficient to effectively drythe leaf, without charring, so that it is suitable for human J consumption. It is also preferred to apply the microwaveradiation to the leaf or portion thereof for a time and at apower level sufficient to reduce the moisture content to belowabout 20 % by weight, more preferably about 10% by weight. 1© Ref erring now to Figure 3, an embodiment of a commercial scale microwave applicator is depicted in partial, perspectiveview. In particular, a Microdry 300 kw microwave tobacco dryingSystem 1 is shown, comprising a mobile truck frame 2 (front endat right side of drawing not shown), a conveyorized microwaveoven 3 which interiorly includes four modular oven cavities ofsingle wall construction (which can be suitably constructed from3003H14 aluminum) , each cavity measuring approximately 16' inlength x 84" in width x 48" in height. Each cavity is equippedwith four access doors located two per side. The doors are 2© double interlocked to prevent accidentai exposure to microwaveenergy.

In Figure 3, an automatic cutting mechanism 5 is shown,including multiple (e.g., twelve) rotating blades for removingthe stem from the leaves 4. The cutter can be a straight strip 2$ approximately 3.4" in width down the center of the leaves,manually fed. An appropriate guard can be provided, if desired,to prevent insertion of operators' hands. Although Figure 3depicts a stem cutting mechanism, as noted above the whole leavescan be used in accordance with other embodiments of the 31 Ή 7 7 8 invention. Thus, in place of the cutting mechanism, theapparatus could employ a steam vessel or a pair of rollers forpressing moisture frora the leaves.

Returning to Figure 3, after the stem cutting operation the5 eut tobacco leaves 6 are conveyed by a belt conveyor 7 to themain microwave oven 3 housing the four cavities. In oneembodiment, the System has an oven length of approximately 78feet. Leading into and within the oven, the conveyor system canalternatively comprise multiple, e.g., six, variable speed 1® polypropylene belts arranged in such a way so as to allow the eut stems to fall from between the pairs of belts and into a hopperlocated below the belts (not shown) . The belts will then carrythe eut tobacco leaves through one of two traps located one ateach of the cavities, designed to contain the microwave energy,and then into a selected cavity where each leaf is subjected tomicrowaving in accordance with the principles of the inventiondescribed above. After being microwaved, the conveyor carriesthe leaves through the cavity exit, through an oven dischargetrap and out of the oven where they are then conveyed into 860 appropriate vessels to be taken for further processing.

To remove the moisture laden air from the cavities and oven, an exhaust system including suitable blowers providingrecirculating air can be included in the system (see moistureexhaust vents, item 8 being one labeled as représentative, inFig· 3) . Also, if desired, the interior of the oven can betempérature controlled by appropriately spaced circulating airconvection heating sources so that the interior of the ovenoutside the microwave cavities is maintained at a preferred 32 ι ι / ο 6 constant température, e.g., 160-180° F, during conveyorized transport of the leaves.· In a mobile System such as depicted in

Figure ,3 for field usage; the electrical requirements can be supplied by a pair of conventional diesel-powered generators 9',5 10. Of course, the microwave drymg System can also be operatedin a fixed location, '= if desi'red, powered by conventionalelectrica,l sources.

Each of the four cavities within oven 3 in Fig. 3 receivesmicrowave ,energy from a corresponding Microdry Model IV-75microwave power source. The · microwave energy enters eachrespective cavity via a splitter through two ports located in thetop of each cavity. A mode stiirrer is located below the portsin each cavity to assist in the distribution Of the microwaveenergy. <Each microwave power unit is acompletely self-contained *5 cabinet that houses the required components to operate a 75 kWmagnetron. Controls for the microwave power are locatecf on thecabinet. The units are designed for unattended continupusoperation in an industrial environment. Each microwave powergenerator may be located at each cavity, or at a distance frbm 20 the cavity. However, at a distance of 50' , the transmission line-losses will be about 2%. Each power generator providèsadjustable microwave energy for industrial operation. The outputpower is adjustable from 0 to about 75 kW at the FCC assigneà frequency of 915 MHz, and is controlled by a solid State control 25 1 ** circuit manually adjusted by a control knob on the panel or by>remote control with a 4-20 milliamp control signal from a processcontroller. While the circuitry will control the power outputfrom zéro, the frequency spectrum becomes broad at levels below 33 14 3 8 about 5 kW. The. power generator for each cavity is basically adirect current power supply operating an industrial magnetronwhich is operated and profected by circuit functions designed forautomatic and manual operation. The electrical functions of the 5 generator are monitored by meters on the control panel, located on cabinet door. The metering includes anode current, anodevoltage, output power, filament current, electromagnet currentand reflected power. Operation of the electromechanical interlock functions are monitored by designated lamps located on 10 '' the control panel. Each miçrowave power generator cabinet hasfull width doors for maximum .accessibility to the components.A built-in electromagnetic interférence shielding enclosurehouses the magnetron and associated microwave compônents. A doorallows for installation of the magnetron and electromagnet. TheSystem includes a circulator and water load, mount’èd inside thecabinet, which functions as an isolator to protect the 'magnetronin the event of a high reflected power condition. The mi'crowavepower generator uses both forced air and water for cooling theheat producing components. The magnetron and electromagnet arewater cooled by a closed loop demineralized water System. Aseparate water source and a heat exchanger can be used to coolthe water in this loop. The separate water source also flowsthrough a water to air heat exchanger inside the cabinet to coolthe cabinet air. A high pressure centrifugal blower provides 25 cooling to the magnetron output window and the cathode structure.'

Water and cabinet températures are interlocked in the controlpower chain. Typical reference data for each microwave generatorin a System of this are as follows: 34 ή λ ~ι τ g

Power input 95 KVA, 440-480 VAC, 3 phase, 60 Hz

Power output 75 kW at 915 +/- 10 MHz

Magnetron tube CTL, CWM 75 I

Typical magnetron operation reference data are as follows: 5 AC filament voltage 11.4 V Filament current 85 A DC anode voltage 17 KV Anode current 5.0 A DC electromagnet current 4.3 A 1© Efficiency 80%

Further, a typical microwave generator can employ a carbon Steelenclosure and hâve an output connection (WR 975 waveguide) in thetop of the cabinet at an appropriate location.

In a throughput test, a microwave tobacco drying System15 generally designed as described above was effective to eliminateover 80% of the moisture content of the leaves. In particular,in one measured sample, 15 pounds of leaves with an assumedinitial water content of 85 wt% and solids content of 15 wt% wasconveyed through a microwave cavity in single leaf thickness at 8© a rate of about 180 lbs per hour. The leaves were weighed afterexiting the cavity. The ending weight was 4.6 lbs., or 31% ofthe initial weight. Thus, based on the initial assumed watercontent, therer remained 2.35 pounds of water in the leaves,corresponding to 18.5% of the initial water content.

As disclosed in FIG. 2, the microwave treatment of yellowtobacco in accordance with the présent invention preferablyresults in a dried, golden-colored tobacco product. The datapresented herein establish that such dried tobacco, in its 35 unsmoked form, has dramatically reduced carcinogenicnitrosamines, particularly NNN and NNK, as opposed to normallycured tobacco.

It has also been discovered that concentrated forms of5 electromagnetic radiation (i.e., concentrated as distinguished from general exposure to sunlight or electric light within thevisible spectrum) having higher frequencies and shorterwavelengths than the microwave domain discussed above, can beused to achieve the basic objects of the présent invention - 10 réduction or substantial élimination of TSNAs in tobacco

Products, by treating the tobacco with such energy forms inapproximately the same time frame post-harvest as discussed abovewith regard to the microwave embodiment. In other words, thesame general and preferred techniques and principles discussedabove regarding microwaving can be applied when such an alternatsenergy source is used; for example, the tobacco is treated withsuch radiation at approximately the same time f rames post-harvest, the leaves can be de-stemmed, pressed between rollersor steamëd prior to irradiation, etc.

However, while such alternate energy sources hâve beendetermined to significantly and desirably reduce or substantiallyeliminate or prevent formation of TSNAs, none of the otherembodiments tested to date hâve been as effective in drying the leaves as the microwave technique described in detail. Thus, 25 when using such an alternate energy source, it may be préférableto subject the irradiatëd tobacco. leaves to further processingto complété the curing cycle, such as combining the irradiationstep with a subséquent oven-drying or tumble-drying step. 36\ \ a \ ' 1 11 7 3 8

In particular, it is believed that any electromagneticradiation source, and accelerated particle beams such as électronbeams, having frequencies higher than the microwave domain withinthe conventional electromagnetic spectrum are operative to 5 significantly reduce, substantially eliminate and/or preventformation of TSNAs when tobacco is uncured and in a statesusceptible to having the amount of TSNAs reduced or formationthereof arrested. On a scale within the electromagnetic spectrumwhere microwaves are generally defined as inclusive of those W forms of electromagnetic radiation having a frequency of 1011 Hz and a wavelength of 3 x 10’3 meters, such energy sources include,without limitation, far-infrared and infrared radiation havingfrequencies of about 1012 to 1014 Hz and wavelengths of 3 x 10'4 to3 x 10‘6 meters, ultraviolet radiation having frequencies of ^5 about 1016 to 1018 Hz and wavelengths of 3 x 10"8 to 3 x 10‘10 meters, soft x-rays or lasers, cathode rays {a stream ofnegatively charged électrons issuing from the cathode of a vacuumtube perpendicular to the surface), x-rays and gamma radiationtypically characterized as having frequencies of 1021 Hz andhigher at corresponding wavelengths.

As would be apparent to one of ordinary skill in the art,the greater the dose of radiation delivered by the energy source,the less time the leaves need to be subjected thereto to achievethe desired results. Typically, radiation application times ofless than one minute, preferably less than 3 0 seconds and evenmore preferably less than about ten seconds are needed when usingsuch higher frequency radiation sources. Defined another way,radiation application times of at least about one second are 37 117 3 8 preferred. However, as shown in the Examples below, the exposurerate can be controlled to deliver the radiation dosage over time,if desired. For example, 1 megarad of radiation can be deliveredinstantaneously (as with the électron beam accelerator discussed $ below in Example 17) , or at a predetermined exposure rate (as exemplified by the closed chamber gamma irradiation testingdiscussed below in Example 19, wherein 1 megarad (10 kGrey) ofirradiation was delivered at an exposure rate of about .8 megaradper hour). When using high frequency radiation sources, it is 1© preferred to use an amount of radiation which achieves at least a 50% réduction in TSNAs, in comparison to untreated samples.While the particular radiation dosages and exposure rate willdépend on the particular equipment and type of radiation sourcebeing applied, as would be apparent to one of ordinary skill inthe art, it is generally preferred to subject the tobacco samplesto radiation of from about .1 to about 10 megarads, morepreferably from about .5 to about 5 megarads, and more preferablyfrom about .75 to about 1.5 megarads.

As illustrated in the following Examples, testing has been

20 carried out on various tobacco samples using an acceleratedélectron beam, a C02 laser and gamma radiation as exemplary ofthese additional radiation sources. In each instance, theuncured, irradiated tobacco samples were demonstrated to containsignificantly reduced and/or substantially eliminated TSNA contents. \

In yet another embodiment of the invention, treating thetobacco while in its susceptible State in a recirculating airconvection oven has also been demonstrated to reduce the TSNA 38 117 7 8 content, albeit with reduced leaf quality. Unlike a conventional baking oven which is not as effective in lowering TSNA content and also lowers the tobacco quality, heating in a recirculating air convection oven at températures of from about 100° to about 5 500° F, for periods ranging from one hour at the low end down to about 5 minutes at the high end of the température scale, canalso effectively reduce the content of or arrest formation ofTSNAs in tobacco while in its susceptible State as definedherein. Even more preferably, an oven combining recirculating 10 air convection heat and microwave radiation can shorten the heating time while providing improved quality to the leaves. Forexample, when a convection oven alone is used, the veins andstems are not completely dried at the time the lamina are dried,thus leading to overdried and crumbly lamina sections. Combiningthe microwave treatment with recirculating convection oven heatcan improve the leaf quality by giving a more uniformly driedproduct.

In another aspect, the présent invention relates to a methodfor reducing or substantially eliminating the content of tobacco- 20 spécifie nitrosamines in a human or animal subject who smokes, chews or otherwise ingests tobacco, by providing for consumptiona tobacco product having significantly reduced or substantiallyeliminated TSNAs.

Subjecting the uncured tobacco to microwave or other 25 radiation energy is demonstrated herein to be effective to provide tobacco hâve surprisingly low nitrosamine contents.

These techniques can be facilitated by peeling and disposing of the stem down one-third to one-half length of the tobacco leaf, 3 9 10 1? 20 i i t υ 8 especially in cases where the stem is to be discarded and themoisture-wringing or steaming steps described above are notemployed. Where the stem is removed in this manner, therésultant microwaved tobacco leaf does not require the use of -athrasher machine since the undesirable part of the stem isalready removed. As a resuit, the typical loss of tobaccoproduct associated with thrashing is eliminated, reducing tobaccowaste by approximately 10% to 30%.

The improved tobacco of the présent invention can besubstituted in whole or part for normally-cured tobacco in anytobacco product, including cigarettes, cigars, chewing tobacco,tobacco chewing gum, tobacco lozenges, tobacco pouches, snuff,or tobacco flavoring and food additives. For the purposes ofsmoking, the présent invention provides a less noxious odor whilemaintaining good smoking characteristics and providing fullflavor with normal nicotine content. For the purposes ofchewing, snuff, pouch and food additives, the tobacco of theprésent invention has a rich, pleasant flavor.

The présent invention is now illustrated by reference to thefollowing examples, which are not intended to limit the scope ofthe invention in any manner.

Example 1

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-ll0°F to begin the flue-curing process. Samples 1-3 were taken from the barn after the 25 leaves had turned yellow, about 24-36 hours post-harvest. Sample1 was a lamina sample, stripped of the midrib, and baked in a 40 convection air oven at about 400-500°C for about 1 hour, whichbrowned the lamina. Sample 2 was a yellow leaf, placed in aGoldstar Model MA-1572M microwave oven (2450 MHz), and heated onthe high power setting (1,000 watts) while rotating for about 2½minutes. Sample 3 was a yellow leaf, untreated, used as acontrol. Samples 4 and 5 remained in the curing barn underelevated température of about 180°F, Sample 4 being dried outsidethe racks and Sample 5 inside the racks. Sample 6 was a cured,brown leaf, having underwent the normal flue-cure process.

Analyses were performed on each sample to détermine NNN,NAT, NAB and NNK contents. In this and the following examples,"TSNA" represents the sum of these four tobacco-specificnitrosamines. Sample work-up and extraction followed a typicalprocedure for analysis of TSNAs (see, for example, Burton et al.,"Distribution of Tobacco Constituents in Tobacco Leaf Tissue.1. Tobacco-specific Nitrosamines, Nitrate, Nitrite andAlkaloids", J. Agric. Food Chem., Volume 40, No. 6, 1992), andindividual TSNAs were quantified on a Thermedics Inc. TEA Model543 thermal energy analyzer coupled to a Hewlett-Packard Model5890A gas chromatograph. The results are shown in Table 1 below.Ail data in each table below are presented in micrograms of thenitrosamine per gram of sample (i.e., parts per million or μg/g): 41 TABLE 1

Sample # NNN NAT + NAB NNK TSNA 1 - yellow baked lamina 0.0310 0.843 <0.0004 0.1157 2 - yellowmicrowaved <0.0004 <0.0006 <0.0005 <0.0014 3 - yellowcontrol 0.0451 0.1253 0.0356 0.2061 4 - rapiddryingoutsideracks 0.6241 1.4862 1.2248 3.3351 5 - rapiddryinginsideracks 0.7465 1.5993 1.3568 3.7044 6 - regularflue-cured 1.0263 1.7107 2.2534 4.9904

Example 2

Virginia flue tobacco was harvested. Sample 7 was a fresh-cut, green leaf used as a control, while Sample 8 was a fresh-cutgreen leaf which was subjected to microwave radiation in amultimode microwave applicator manufactured by MicroDry of 2 Louisville, Kentucky, operating at 2450 MHz at 2.5 kilowatts, forabout 2 0 seconds. Samples 9-12 were made from normally flue-cured brown tobacco. Sample 9 was tobacco from a formedcigarette; Sample 10 was loose, shredded tobacco for makingcigarettes; Samples 11 and 12 were the same as Samples 9 1© (cigarette) and 10 (loose) , respectively, except that each wassubjected to the same microwave conditions as Sample 8. TSNAcontents were analyzed in the same manner -as in Example 1. Theresults are shown in Table 2 below: 42 117 X θ

Table 2

Sample # NNN NAT + NAB NNK TSNA 7 - fresh leaf control <0.0104 0.126 0.0005 0.126 8 - freshleaf -microwaved 0.029 0.135 0.0004 0.164 9 - control cigarette 1.997 3.495 2.735 8.226 10 - control loose 2.067 3.742 2.982 8.791 11 ’ cigarette microwaved 2.056 3.499 2.804 8.359 12 - loosemicrowaved 2.139 3.612 2.957 . 8.707

Example 3

The following cigarette brands shown in Table 3 werepurchased at random at various retailers in Lexington, Kentucky,and analyzed for TSNA content using the procedure described inExample 1 :

Table 3

Sample # Code No. NNN NAT + NAB NNK TSNA 13- Marlboro -king-pc 288292 3.565 4.538 1.099 9.202 14- Marlboro -king-pc 288292 4.146 4.992 1.142 10.279 15- Marlboro -king-pc 288292 3.580 4.290 1.106 8.977 43 11 7 3 8

Sample # Code No. NNN NAT 4- NAB NNK TSNA 16- Marlboro. -king-pc 288292 3.849 4.748 1.130 9.728 17- Marlboro-lights-100's-bx 288192 4.604 5.662 1.223 11.489 18- Marlboro-lights-100's-pc 288182 3.471 3.859 1.211 8.541 19- Marlboro-lights-100's-pc 288182 3.488 4.136 1.074 8.698 20- Marlboro-lights-100's-pc 288182 3.566 4.240 1.164 8.970 21- Winston-100's-pc 123143 2.311 2.968 1.329 6.608 22- Winston- king 123103 2.241 2.850 1.256 6.348 23- Winston- king-bx 125123 2.162 2.831 1.326 6.319 24- Winston- king-bx 123123 2.577 3.130 1.207 6.914 25- Winston- king-pc 123103 1.988 2.563 1.234 5.786 26- Winston-lights-100' s-pc 123133 2.161 2.706 1.258 6.124 27- Winston-lights-100's-pc 123133 2.189 2.699 1.262 6.150 44 117 3 8

Sample # Code No. NNN NAT + NAB NNK TSNA 28- Winston-lights-100's-pc 123133 2.394 3.385 2.330 8.109

Example 4

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110°F to begin the flue-curing process. After the leaves turned yellow, about 24-36hours post-harvest, they were taken out of the barn and 5 microwaved in Goldstar Model MA-1572M microwave oven (2450 MHz) ,high power setting (1000 watts), for about 2½ minutes whilerotating. The leaves were effectively dried by this procedure,although they did not turn brown, but instead retained theirgolden-yellow color. The leaves were shredded and made intocigarettes. Samples 29-33 were taken from a batch labeled RedFull Flavor, while Samples 34-38 were taken from a batch labeledblue Light. Samples 39-42 were cigarettes purchased at a healthfood store, under the brand Natural American Spirit. Samples 29-42 were analyzed for TSNA content using the procedure described j in Example 1, and the results are shown in Table 4 below: 45 4 * “7 Ί θ

Table 4

Sample # NNN NAT + NAB NNK TSNÀ 29-RED FULL FLAVOR REP 1 0.138 0.393 <0.0005 0.532 30-RED FULL FLAVOR REP 2 0.192 0.231 <0.0005 0.423 31-RED FULL FLAVOR REP 3 0.129 0.220 <0.0007 0.349 32-RED FULL FLAVOR REP 4 0.145 0.260 <0.0007 0.406 33-RED FULL FLAVOR REP 5 0.140 0.293 <0.0006 0.434 AVG 0.149 0.279 <0.0006 0.429 STD 0.022 0.062 0.0001 0.059 34-BLUE LIGHT REP 1 0.173 0.162 <0.0005 0.335 35-BLUE LIGHT REP 2 0.046 0.229 <0.0005 0.275 36-BLUE LIGHT REP 3 0.096 0.188 <0.0005 0.285 37-BLUE LIGHT REP 4 0.067 0.215 <0.0005 0.282 38-BLUE LIGHT REP 5 0.122 0.218 <0.0005 0.341 AVG 0.101 0.202 <0.0005 0.304 STD 0.044 0.024 0.0000 0.028 39- NATURAL AMERICAN SPIRIT 0.747 1.815 1.455 4.017 46 1ΐ7χθ

Sample # NNN NAT + NAB NNK TSNA 40- NATURAL AMERICAN SPIRIT 0.762 1.805 1.458 4.025 41- NATURAL AMERICAN SPIRIT 0.749 1.826 1.464 4.039 42- NATURAL AMERICAN SPIRIT 0.749 1.760 1.462 3.971 AVG 0.752 1.802 1.460 4.013 STD 0.006 0.025 0.004 0.025 STD in the Tables herein is the standard déviation for the average of the samples shown.

Example 5

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110°F to begin the flue- £ curing process. Samples 43-44 were taken from the barn after theleaves had turned yellow, about 24-36 hours post-harvest, andsubjected to microwave radiation in the MicroDry multimodeapplicator described above for about 20 and 30 seconds,respectively, at a power level of about 6 kilowatts. Samples 43and 44 were dried, golden-yellow leaves after the microwaving.Samples 45-51 were made from brown, cured leaves having underwentthe normal flue-cure process. Sample 45 was a control; Samples46 and 47 were baked io a convection oven preheated to about 400-500 °F for about 1 and about 3 minutes, respectively; and Samples 15 48 and 49 were subjected to microwave radiation (915 MHz) in a

Waveguide applicator Model WR-975, a large multimode oven 47 manufacturée! by MicroDry (power settings from 0-75 KW) at 50kilowatts for about 10 and 40 seconds, respectively. Samples 50and 51 were eut (reconstituted sheet) tobacco made from the flue-cured leaves. Sample 50 was subjected to microwave radiation inthe Waveguide microwave oven at 50 kilowatts for about 1.5minutes, while Sample 51 was baked in a convection oven preheatedto about 400-500 °F for about 3 minutes. These samples wereanalyzed for TSNA content using the procedure described inExample 1, and the results are shown in Table 5 below:

Table 5

Sample # NNN NAT + NAB NNK TSNA 43-20 SECMICROWAVE <0.0106 <0.1068 <0.0007 <0.1181 44-30 SECMICROWAVE <0.0103 <0.1065 <0.0004 <0.1172 45-CONTROLNO MICRO 0.92 2.05 3.71 6.68 46-OVEN 1MIN 1.14 2.41 5.10 8.66 47-OVEN 3 MIN 0.89 2.06 2.68 5.64 48- WAVEGUIDE 10 SEC 50 KW 1.00 2.31 3.29 6.59 49- WAVEGUIDE 40 SEC 50 KW 0.62 1.55 1.69 3.86 50-CUT TOBACCO WAVEGUIDE 1.5 MIN 50 KW 4.22 4.91 0.99 10.12 51-CUT TOBACCO OVEN 3 MIN 4.76 5.60 1.08 11.44 48

Example 6

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing bar at about. 100-110°F to begin the flue-curing process. Samples 52-55 weire cigarettes made from yellowtobacco which had been pulled froijft,. the barn after about 24-36hours, and subjected to Microwave radiation in a Goldstarmicrowave oven, Model MA-1572M (2450 MHz), for about 2 minuteson the high power setting (1000 watts). Forcomparison, Samples i 61 and 62 were cigarettes made’ fromf leaves which had undergonethe normal flue-cure process,, withdïït tnicrq'wave treatment.Sample 56 was a cured leaf; Sample 57 was post-yellow, not fullycured; Sample 58 was a cured lamina, while Samp.les 59 and 60 werecured midribs. TSNA contents were measured as in Example 1, andthe results are set forth in Table 6 below: ' y,

A 49

Table 6

Sample # NNN NAT + NAB NNK TSNA 52- Goldsmoke cigarettes 0.12 0.23 0.03 0.38 53- Goldsmoke II, 85 mm 0.062 0.326 0.016 0.404 54- Goldsmoke 85 mm 0.128 0.348 0.029 0.504 55- Goldsmoke100' s Sample B 0.166 0.317 0.047 0.531 56-Sample M-M 3.269 4.751 0.833 8.853 57-Sample B-C 0.267 0.720 0.954 1.941 5 8 -LaminaM-C 0.933 1.456 1.968 \ \ \ 4.356 59-WM 0.996 1.028 0.408 2.432 60-SM 1.745 1.753 0.306 ’ ,3.804 61- Goldsmoke control 1.954 1.544 0.492 3.990 62- Goldsmoke control 1.952 1.889 0.424 4.2 65

Example 7 '( •i \

Virginia flue tobacco was harvested. Samples 63 and 66 wereuncured, fresh-cut green tobacco, although over a week lapsed.before TSNA measurements were taken, so some air-curing had takeriplace. The remaining leaves were placed in a curing barn ’atabout 100-110°F to begin the flue-curing process. Sample 68 wasa leaf taken from the barn after it had turned yellow, about 24-36 hours post-harvest, and was subjected to microwave radiation 50 § in the Waveguide multimode applicator described above, for about40 seconds at 25 kilowatts.

Samples 64/65 (leaves) and 67/70 (reconstituted sheettobacco, or "eut" tobacco) demonstrate the effects of the présent 5 invention when cured tobacco is rehydrated, then subjected to microwave radiation. Samples 64 and 65 were leaf samples havingundergone the normal flue-curing process; however, Sample 64 wasrehydrated by running under an open faucet for about 5-10seconds. The leaf absorbed significant moisture. Each of $0 Samples 64 and 65 was then microwaved in the Waveguide multimode applicator for about 40 seconds at 25 kilowatts. Samples 67 and70 were reconstituted sheet tobacco samples, made from curedleaves. Sample 67 was rehydrated by adding w^ter so that asignificant quantity was absorbed, then microwaved under theconditions described for Sample 64. Sample 70 was notmicrowaved. Samples 69, 71 and 72 are additional bured leaf samples, used as Controls. The TSNA contents were measured asin Example 1, and the results are shown in Table 7 belowt..

Table 7 \

Sample # NNN NAT + NAB NNK TSNA \ 63-CONTROL UNCURED 0.010 0.263 0.000 0.274 64-CURED 40 SEC(WET) 0.737 1.252 1.893 3.882 65-CURED 4 0 SEC 0.767 1.520 2.229 4.516 66-UNCURED 4 0 SEC 0.010 0.261 0.000 0.272 51 4-1-7

Sample # NNN NAT + NAB NNK TSNA . 67-CUT TOBACCO CURED 40 SEC (WET) 0.769 1.328 0.308 2.405 68-UNCURED 40 SEC 25 KW WAVEGUIDE 0.051 0.244 0.014 0.308 69-CUREDCONTROL 0.866 1.548 2.545 4.960 70-CONTROLCUT TOBACCO 1.872 2.536 0.789 5.197 71-CONTROL'AL' WHOLELEAF 0.230 0.606 0.746 1.582 72-SML WHOLE LEAF 0.413 0.884 1.514 2.810

Example 8

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110° F to begin the flue-curing process. Sample 73 was a leaf taken from the barn afterit turned yellow, about 24-36 hours post-harvest, and microwaved 5 in a Goldstar Model MA-1572M for about 2 minutes on the high setting. Samples 74-76 were flue-cured in the normal way.Sample 74 was a cured control. Samples 75 and 76 were rehydratedas in Example 7 (Sample 64) , then each sample was subjected tomicrowave radiation in the MicroDry applicator (2450 MHz) for 10 about 20 seconds (Sample 75) and about 40 seconds (Sample 76), respectively, at power levels of about 6 kilowatts. Samples 77-79 were reconstituted sheet tobacco, made from the flue-curedleaves. Sample 77 was a control, while Samples 78 and 79 wererehydrated as in Example 7 (Sample 67). Samples 78 and 79 were 52 microwaved in the MicroDry applicator for about 30 seconds each;Sample 78 rested on the oven bottom, while Sample 79 was raisedup several inches by resting the sheet sample on a styrofoam cup,which permitted more uniform heating. TSNA contents weremeasured as in Example 1, and the results are set forth in Table 8 below:

Table 8

Sample # NNN NAT + NAB NNK TSNA 73-yellow/microwaved 0.052 0.260 <0.0004 0.313 74-A-controlleaf,cured 1.168 1.904 1.662 4.734 75-B- 20SECONDS 0.791 1.705 1.115 3.611 76-C 40SECONDS 0.808 1.624 1.160 3.592 77- CONTROL- sheet 4.417 3.697 0.960 9.073 78-30 SECONDS 2.755 2.553 0.644 5.952 79-30 SECONDS ELEVATED 1.606 1.732 0.350 3.687 53

Example 9

Samples 80-81 were Redman chewing tobacco purchased âtretail. Sample 80 was a control, while Sample 81 was microwavedin a Goldstar Model MA-1572M for about 1-2 minutes on the highpower setting. Samples 82-83 were Skoal snuff purchased atretail. Sample 82 was a control, while Sample 83 was microwavedin the same manner as for Sample 81. TSNA contents weremeasured, and the results are shown in Table 9 below:

Table 9

Sample # NNN NAT + NAB NNK TSNA 80-CHEWING TOBACCO BEFORE 0.712 0.927 0.975 1.713 81-CHEWING TOBACCO AFTER 0.856 0.906 0.122 1.884 82-SNUFFBEFORE 4.896 10.545 1.973 17.414 83-SNUFFAFTER 6.860 14.610 1.901 23.370

Example 10

To test whether TSNAs accumulate over time even after yellowtobacco is microwaved in accordance with the présent invention,additional samples (designated -A) of the cigarettes teste'd inExample 4, Samples 29, 35 and 39 (control) were retested for TSNAcontent more than seven months after the TSNA contents were firstmeasured, as reported in Example 4. The results are shown below in Table 10 : 54

Table 10 117X8

Sample # NNN NAT NAB NNK TSNA 29A-RED FF REP#1 0.1109 0.1877 0.1078 0.0015 0.4079 35A-BLUE LIGHT REP #2 0.0508 0.1930 0.1075 0.0012 0.3525 3 9A-NATURALAMERICANSPIRIT REP #1 0.6151 1.2357 0.1072 0.9302 2.8882

Example 11

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110°F to begin the flue-curing process. After the leaves turned yellow, about 24-36hours post- harvest, they were taken from the barn and subjected J to microwave radiation in a Goldstar Model MA-1572M microwave oven for about 2 to 2½ minutes, on the high power setting. Eachof the leaves was a golden-yellow color, and effectively dried.Certain samples, designated by "ground", were later ground upinto a flour-like substance, which would be useful as, for 10 example, a gum, lozenge or food additive. After more than sixmonths from the time the leaves were microwaved, the TSNA contentof the following samples were measured using the proceduredescribed in Example 1. The results are shown in Table 11 below: 55

Table 11 ' 4 3 8

Sample # NNN NAT NAB NNK TSNA 84- ground 0.0013 0.0018 0.0018 0.0015 0.0064 85- ground 0.0469 0.0341 0.0011 0.0009 0.0831 86- ground 0.0009 0.0582 0.0013 0.0011 0.0615 87- ground 0.0113 0.1078 0.1078 0.0015 0.2284 88- ground 0.0569 0.1401 0.1071 0.0009 0.3051 89- ground 0.0109 0.1642 0.1073 0.0011 0.2835 90- ground 0.0008 0.0011 0.0011 0.0009 0.0038 91- ground 0.0009 0.0012 0.0012 0.0010 0.0044 92- ground 0.0012 0.1059 0.0017 0.0014 0.1101 93- ground 0.0013 0.0529 0.0019 0.0015 0.0576 94- ground 0.0012 0.0613 0.0017 0.0014 0.0657 95- ground 0.0506 0.0989 0.0013 0.0010 0.1518 96- ground 0.0017 0.0894 0.0024 0.0019 0.0954 97- ground 0.0012 0.0017 0.0017 0.0014 0.0061 98- ground 0.0016 0.0023 0.0023 0.0019 0.0082 99- ground 0.0342 0.0016 0.0016 0.0013 0.0386 100- ground 0.0014 0.0020 0.0020 0.0016 0.0070 101-leaf 0.0013 0.0539 <0.0019 <0.0016 0.0587 102-leaf 0.0009 0.0012 <0.0012 <0.0010 0.0043 56

Sample # NNN NAT NAB NNK TSNA 103- shredded leaves 0.0202 0.0327 <0.0007 <0.0006 0.0542

Example 12

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110°F to begin the flue-curing process. Samples 104 and 105 were leaf samples havingundergone the normal flue-curing process, without microwavetreatment. Sample 104 was a cured midrib, while Sample 105 wascured a lamina. Sample 106 was yellow tobacco, taken from thebarn after the leaves had turned yellow, about 24-36 hours postharvest. After being taken from the barn, the leaves weresubjected to microwave radiation in a Goldstar Model MA-1572M 1® microwave oven for about 2-2½ minutes, on the high power setting.

Each of the leaves was a golden-yellow color, and effectivelydried. Certain of the dried leaves were further processed in aconventional manner to form a ^tobacco extract, which wasdesignated Sample 107 for purposes of analysis. The TSNA 15 contents of Samples 104-107 were measured using the procedure described in Example 1. The results are shown in Table 12 below. 57

Table 12

Sample # NNN NAT &amp; NAB NNK TSNA 104 - control midrib 0.083 0.180 <0.003 0.266 105 - control lamina 0.928 1.367 2.613 4.908 106 - microwaved leaves <0.004 <0.006 <0.005 <0.015 107 - microwaved extract <0.004 <0.005 <0.004 <0.013

Bxample 13

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110°F to begin the flue-curing process. Samples 108 and 109 were leaf samples havingundergone the normal flue-curing process. Sample 108 was a cured 5 lamina, while sample 109 was a cured midrib. Samples 110 and 111 were yellow tobacco, taken from the barn after the leaves hadturned yellow, about 24-36 hours post-harvest. After being takenfrom the barn, Samples 110 and 111 were heated in a circulatingair convection oven, a Sharp Carousel Convection/Microwave Modelw No. R-9H84B. Sample 110 was rapidly heated at about 300°F forbetween 5-10 minutes. Sample 111 was more slowly heated at lowertempératures, starting at about 100°F and being stepped up toabout 150°F after more than 10 minutes, for a total heating timeof over 20 minutes. The TSNA contents of Samples 108-111 weremeasured using the procedure described in Example 1. The results are shown in Table 13 below. 58

Table 13 117 3 8

Sample # NNN NAT &amp; NAB NNK TSNA 108 - control lamina 1.267 2.509 1.377 5.153 109 - control midrib <0.004 0.464 <0.004 0.472 110 - convection- rapid <0.004 <0.005 <0.004 <0.013 111 - convection- slow <0.003 <0.004 <0.003 <0.010 .

Although the convection oven heating was shown to reduceTSNA levels, the quality of the tobacco was inferior to thatobtained upon microwaving in accordance with preferred examplesof the invention. Also, the heating time is necessarily longer 5 than when using the microwave radiation treatment or other forms of higher frequency radiation. In particular, the convectionheating was unable to lock the color in at the desired golden-yellow, and the lamina had a tendency to be over-dried andtherefore brittle, while the veins and midrib were not completely 10 dried. In contrast, in accordance with the most preferred embodiments of the invention, the microwaved leaves wereeffectively dried and retained a golden-yellow color after beingsubjected to treatment, while staying supple and pliable forfurther processing, especially as cigarettes. In convection-oven 0 produced samples, the lamina when dried has a tendency to crumble into a dust and small tobacco particles. 59

4 -7 Q

Example 14

Kentucky burley tobacco was harvested, and the leaves wereprocessed as follows after they began to turn yellow, about 24-48hours post-harvest. Samples 112-117 were leaf samples from thi-sbatch, further processed as follows. Sample 112 was microwaved § under approximately the same conditions as Sample 106 in Example 12. The leaves were a golden-yellow color and effectively dried.Samples 113, and 114 and 117 were heated in the same circulatingair convection oven as described in Example 13, Sample 113 beingheated under approximately the same conditions as Sample 110,t© Sample 114 being heated under approximately the same conditionsas Sample 111, and Sample 117 being heated at about 350°F forabout 20 minutes. The quality of Samples 113, 114 and 117 wasakin to that of Samples 110 and 111, as described in Example 13.Samples 115 and 116 were heated in the Sharp CarouselConvection/Microwave oven described in Example 13, using thecombined microwave (30%)/convection (300°C) feature until theleaves were effectively dried to golden-yellow color. The TSNAcontents of Samples 112-117 were measured using the proceduredescribed in Example 1. The results are shown in Table 14 below: 60 4 A -» «ττ q

» Q

Table 14

Sample # NNN NAT &amp; NAB NNK TSNA 112 - microwaved <0.007 <0.010 <0.008 <0.025 113 - convection <0.003 <0.004 <0.003 <0.010 114 - convection <0.012 <0.017 <0.014 <0.043 115 -microwave(30%)/convection <0.002 <0.003 <0.003 <0.008 116 -microwave(30%) /convection <0.002 <0.003 <0.002 <0.007 117 - convection 0.131 0.156 <0.003 0.290

Example 15

Virginia flue tobacco was harvested, and the leaves wereplaced in a curing barn at about 100-110°F to begin the flue-curing process. Samples 118-120 were leaf samples, taken fromthe barn after the onset of yellowing, and shortly thereafter 5 subjected to microwave radiation in a conventional kitchen-type microwave oven for about 2 to 2 1/2 minutes until the leaveswere effectively dried to a golden-yellow color, without burningor charring. Samples 121-123 were samples of Kentucky burleytobacco, harvested and processed after the onset of yellowing in 10 each instance as follows. Sample 121 was placed in a conventional steam tumble dryer typically used in the tobaccoindustry, at a température of about 200°F, until the leaves hadbrowned and dried somewhat. Sample 122 was microwaved in theabove-referenced Goldstar microwave on high for about 2 minutes, 61 11 7 3 8 the rehydrated with water and placed in the tumble dryer toimpart a slight browning to the leaves which is believed toenhance the flavor. Sample 123 was treated like Sample 122,except that it was microwaved for 1 minute and was not rehydrated 5 before being put in the tumble dryer. TSNA contents werelikewise measured as in Example 1, and the results are shown inTable 15 below:

Table 15

Sample # NNN NAT &amp; NAB NNK TSNA 118 <0.003 0.150 <0.003 0.156 119 <0.003 <0.004 <0.003 <0.010 120 <0.002 <0.003 <0.003 <0.008 121 0.486 1.059 <0.003 1.548 122 <0.004 <0.005 <0.004 <0.013 123 <0.003 <0.004 <0.004 <0.011

Example 16

North Carolina burley tobacco was harvested, and the leaveswere processed as follows after they began to turn yellow, about |0 2-3 days post-harvest. Sample 118 was a leaf sample which had been subjected to microwave radiation in the same type ofGoldstar microwave oven described above, on the high powersetting for about 2 minutes. After microwaving the leaves werea golden yellow color, and effectively dried. The TSNA content 62 117 38 was measured using the procedure described in Example 1. Theresults are shown in Table 16 below:

Table 16

Sample # NNN NAT &amp; NAB NNK TSNA 118 0.024 0.048 <0.001 0.073

Example 17

This example demonstrates the effectiveness of usingélectron beam radiation to reduce the content of, or 5 substantially prevent formation of TSNAs, in yellow tobaccosamples. North Carolina burley tobacco was harvested. Samples119-122 were leaf samples, air-cured by hanging outside in anormal manner, until the leaves were effectively dried and. brown.Sample 119 was untreated as a control. Samples 120 and 121 weresubjected to électron beam radiation on a conveyor belt using aDynamitron Electron Beam Accelerator, manufactured by RadiationDynamics, Inc. of Edgewood, N.Y., at an exposure rate of 1megerad. Sample 122 was subjected to microwave radiation in theGoldstar microwave oven for about 2 minutes on the high powersetting. Sample 123 was taken from the tip of a burley leafafter it had begun to turn yellow. Sample 124 was a leaf stemportion, taken from the same plant as Sample 123, and was stillsomewhat green-colored. Samples 125 and 126 were whole leafburley samples, at the yellow stage. Each of Samples 123-126 wassubjected to électron beam radiation using the above-describingDynamitron, in the same manner and under the same exposure rateas Samples 120 and 121, as described above. The above sampleswere tested to measure TSNA content according to the procedure 63 117 3 8 set forth in Example 1, and the results are shown in Table 17below:

Table 17

Sample # NNN NAT &amp; NAB NNK TSNA 119 -control,cured 3.6351 1.0847 0.0470 4.7668 120 - high power, cured 6.5718 3.7037 0.4368 10.7123 121 - low power, cured 4.4771 1.6112 0.7468 6.8369 122 - microwave,cured 4.8974 1.6393 1.1200 7.6567 123 - yellow tip 0.1812 0.3667 0.0013 0.5492 124 - green stem 0.1918 0.8310 0.0016 1.0243 125 - whole leaf 0.0014 0.1019 0.0016 0.1048 126 - whole leaf 0.0646 0.2465 0.0019 0.3130

Although the above data show that électron beam radiation is effective to prevent formation of substantial quantifies of5 tobacco-specific nitrosamines in the yellow leaf samples tested,the leaves were not dried as effectively as when leaves in asimilar State post-harvest were subjected to microwave radiation,as described in other examples of this application. Thus,commercial applications of the électron beam irradiation process 10 may require an additional drying step, such as conveying the irradiated leaves through a conventional drying oven, tofacilitate the curing process. 64 117 3 8

Example 18

This example demonstrates that high energy beams producedby lasers are also effective to achieve the low TSNA goals of theprésent invention. A C02 laser made by Luxar Corp., Model LX-20SP, was used to irradiate yellow Virginia flue tobacco leaves, 5 at about 2-3 days post-harvest. A NovaScan handpiece was used under the superpuise E program, wh^ch détermines the speed ofapplication in patterns per second. A setting of E10 was used,which delivers 10 patterns per second. Eight subsamples ofleaves, T-l to T-8, were irradiated according to the followingprotocol: ' E10 - 2 watts E10 - 4 watts T-l - 1 pass each side T-5 - 1 pass each side T-2 - 2 passes each side T-6 - 2 passes each side T-3 - 3 passes each side T-7 - 3 passes each side T-4 - 4 passes each side T-8 - 4 passes each side

At 2 watts, approximately 120 mJ of energy is delivered ineach scan or pass, while at 4 watts, approximately 240 mJ isdelivered in each such scan.

Subsamples T-l to T-4 were mixed and combined together toform leaf Sample 127, which was evaluated for TSNA content in thesame manner as described in Example 1. Subsamples T-5 to T-8were similarly mixed and combined together to form leaf Sample 65 11738 128, which was likewise evaluated for TSNA content. The results are shown in Table 18 below:

Table 18

Sample # NNN NAT &amp; NAB NNK TSNA 127 0.1031 0.2025 0.0006 0.3061 128 0.1019 0.1287 0.0010 0.2315

As with the samples described in Example 17, the C02 laserirradiated samples were not dried as effectively as the $ microwaved samples, although the TSNA contents were low, and therefore an additional drying step could be employed to speedthe curing process. Also, after.the C02 laser irradiation butprior to TSNA testing, six of the eight subsamples turnedsomewhat brown, with no apparent effect on TSNA content.

Example 19 10 This example demonstrates that gamma radiation is also effective in preventing formation of significant amounts of TSNAin yellow tobacco. Virginia flue tobacco was taken about 2-3days post harvest, just after the leaves had turned yellow. Eachof Samples 129-132 was taken from the lamina portion of the 15 yellow leaves, and subjected in an enclosed chamber to gammairradiation of 10 kGrey (1 megarad) at an exposure rate of 8kGrey (.8 megarad) per hour, for a total exposure time of about75 minutes. The irradiated samples were subsequently evaluatedas to TSNA content in the same fashion as described above, and 20 the results are shown below in Table 19: 66

Table 19

Sample # NNN NAT &amp; NAB NNK TSNA 129 0.098 0.225 0.057 0.380 130 <0.001 <0.001 <0.001 <0.003 131 <0.001 <0.001 <0.001 <0.003 132 0.033 0.079 <0.001 0.113

It will be apparent to those skilled in the art that variouschanges and modifications may be made in the preferredembodiments without departing from the spirit and scope of theclaimed invention. Therefore, the foregoing description is 5 intended to be illustrative only and should not be viewed in alimiting sense. 67

Claims (76)

11738 CLAIMS What is claimed is:

1. A process for reducing the amount of or preventing formation of nitrosaminesin harvested tobacco plant, comprising (i) a step of (a) removing stems from the tobacco leaves; (b) pressing the 5 tobacco leaves to remove excess moisture or (c) subjecting the tobacco leaves to a steam treatment, and (ii) a step of subjecting at least a portion of the plant to microwaveradiation, while said portion is uncured and in a State susceptible to having the amountof nitrosamines reduced or fomulation of nitrosamines arrested, for a sufïicient timeto reduce the amount of or substantially prevent formation of at least one nitrosamine,wherein said subjecting to microwave radiation is carried out on a tobacco leaf orportion thereof after onset of yellowing in the leaf and prior to substantialaccumulation of tobacco-specific nitrosamines in the leaf, and wherein said tobaccoleaf or portion thereof is arranged in single layer thickness without stacking or piling 15 of the leaves.

2. The process according to claim 1, wherein said step is (b) or (c) and thetobacco leaves contain stems.

3. A process of substantially preventing formation of nitrosamines in a harvestedtobacco plant, the process comprising 20 subjecting at least a portion of the plant to a concentrated form of radiation having a frequency higher than the microwave région of the electromagneticspectrum, while said portion is uncured, yellow, and in a State susceptible to havingthe formation of nitrosamines arrested, for a sufïicient time to substantially preventformation of at least one nitrosamine. 2j

4. The process according to claim 3, wherein said subjecting to radiation is carried out on a tobacco leaf or portion thereof prior to substantial accumulation oftobacco-specific nitrosamines in the leaf or portion thereof.

5. The process according to claim 3, wherein said subjecting to radiation iscarried out prior to substantial loss of the plant’s cellular integrity. 68

6. The process according to claim 3, wherein the tobacco is flue tobacco and saidsubjecting to radiation is carried out within about 24 to about 72 hours post-harvest.

7. The process according to claim 3, wherein said radiation is applied to the plantfor a period of at least about one second at a predetermined power level.

8. The process according to claim 3, wherein said subjecting to radiation prevents normal accumulation of at least one tobacco-specific nitrosamine in the leaf.

9. The process according to claim 8, wherein said at least one tobacco-specificnitrosamine is selected from the group consisting of N’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’-nitrosoanatabine and N’-nitrosoanabasine.

10. The process according to claim 4, wherein said subjecting to radiation iscarried out on tobacco leaves arranged in single layer thickness, without stacking orpiling of the leaves.

11. The process according to claim 10, fùrther comprising, prior to said subjecting15 to radiation, a step of (a) removing stems from the tobacco leaves, (b) pressing the tobacco leaves to remove excess moisture, or (c) subjecting the tobacco leaves to asteam treatment.

12. The process according to claim 3, further comprising drying the portion aftercarrying out the radiation step. 2Φ

13. The process according to claim 3, wherein said radiation is generated by alaser beam.

14. The process according to claim 3, wherein said radiation is an électron beamgenerated by an électron accelerator.

15. The process according to claim 3, wherein said radiation is gamma radiation. 25

16. A tobacco product comprising tobacco having a reduced content of at least one tobacco-specific nitrosamine, produced by a process comprising subjecting thetobacco, while the tobacco is uncured, yellow, and in a State susceptible to having theformation of said at least one tobacco-specific nitrosamine arrested, to a concentratedform of radiation having a frequency higher than the micro wave région of the jq electromagnetic spectrum.

17. The tobacco product according to claim 16, wherein said subjecting to 69 117 3 8 1© 15 2© 25 radiation is carried out prior to substantial accumulation of tobacco-specificnitrosamines in the leaf.

18. The tobacco product according to claim 16, wherein said subjecting to adiationis carried out prior to substantial loss of tobacco’s cellular integrity.

19. The tobacco product according to claim 17, wherein the tobacco is fluetobacco and said subjecting to radiation is carried out within about 24 to about 72hours post-harvest.

20. The tobacco product according to claim 16, wherein said microwave radiationis applied to the plant for a period of at least about one second at a predeterminedpower level.

21. The tobacco product according to claim 20, wherein said subjecting toradiation prevents normal accumulation of at least one tobacco-specific nitrosamine inthe leaf.

22. The tobacco product according to claim 21, wherein said at least one tobacco-specific nitrosamine is selected ffom the group consisting of N’-nitrosonomicotine,4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’-nitrosoanatabine and N’-nitrosoanabasine.

23. The tobacco product according to claim 17, wherein said subjecting toradiation is carried out on tobacco leaves arranged in single layer thickness, withoutstacking or piling of the leaves.

24. The tobacco product according to claim 23, further comprising, prior to saidsubjecting to radiation, a step of (a) removing stems from the tobacco leaves, (b)pressing the tobacco leaves to remove excess moisture, or (c) subjecting the tobaccoleaves to a steam treatment.

25. The tobacco product according to claim 16, further comprising drying theportion afiter carrying out the radiation step.

26. The tobacco product according to claim 16, wherein said radiation is generatedby a laser beam.

27. The tobacco product according to claim 16, wherein said radiation is anélectron beam generated by an électron accelerator.

28. The tobacco product according to claim 16, wherein said radiation is gammaradiation. 3© 70 117 3 8

29. A method for reducing the content of at least one tobacco-specifïc nitrosaminein cured brown tobacco, comprising rehydrating the cured tobacco, and subjecting the rehydrated tobacco to a concentrated form of radiation having a 5 frequency higher than the microwave région of the electromagnetic spectrum, at a predetermined energy level for a predetermined length of time.

30. The method according to claim 29, wherein said rehydrating step comprisesadding water to the cured tobacco so that the tobacco absorbs an amount of waterfrom about 10% by weight up to a maximum absorption capacity.

® 31. The method according to claim 29, wherein said at least one tobacco-specifïc nitrosamine is selected ffom the group consisting of N’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’-nitrosoanatabine and N’-nitrosoanabasine.

32. A method of manufacturing a tobacco product, comprising subjecting tobaccoleaves to a concentrated form of radiation having a frequency higher than themicrowave région of the electromagnetic spectrum, while said leaves are uncured andin a State susceptible to having the amount of tobacco-specifïc nitrosamines reducedor formation of tobacco-specifïc nitrosamines arrested, for a sufficient time to reducethe amount of or substantially prevent formation of at least one tobacco-specifïc guj nitrosamine in the leaves, and forming said tobacco product comprising the irradiatedleaves, the tobacco product being selected from the group consisting of cigarettes,cigars, chewing tobacco, snuff and tobacco-containing gum and lozenges.

33. The process according to claim 32, wherein the leaves are subjected to saidradiation after onset of yellowing in the leaves and prior to substantial accumulation 25 of tobacco-specifïc nitrosamines in the leaves.

34. A tobacco product comprising cured non-green or yellow Virginia fluetobacco suitable for human consumption, substantially free of organic liquids used toextract expanded organic materials and having a collective content of N’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’- 30 nitrosoanatabine and N’-nitrosoanabasine which is less than 0.2 pg/g.

35. A tobacco product comprising cured non-green or yellow tobacco suitable forhuman consumption, substantially free of organic liquids used to extract expanded 71 11738 organic materials and having a collective content of N’-nitrosonomicotine, 4-(N- nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’-nitrosoanatabine and N’- nitrosoanabasine which is 0.05 pg/g or less, wherein said cured non-green or yellow tobacco is selected from the group consisting of Virgina flue and Burley varieties.

$ 36. A tobacco product comprising cured non-green or yellow tobacco suitable for human consumption, in leaf form and having a collective content of N’-nitrosonomicotine, 4-(N-nitrosomethylamino)-1 -(3 -pyridyl)-1 -butanone, N’-nitrosoanatabine and N’-nitrosoanabasine which is 0.05 pg/g or less, wherein saidcured non-green or yellow tobacco is selected from the group consisting of Virginiaflue and Burley varieties.

37. A tobacco product comprising cured non-green or yellow Virgina flue tobaccosuitable for human consumption, in leaf form and having a collective content of N’-nitrosonomicotine, 4-(N-nitrosomethylamino)-1 -(3-pyridyl)-1 -butanone, N’-nitrosoanatabine and N’-nitrosoanabasine which is less than 0.2 pg/g. 15

38. A tobacco product comprising cured non-green or yellow tobacco suitable for human consumption, substantially free of organic liquide used to extract expandedorganic materials and having a collective content of N’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-1-butanone, N’-nitrosoanatabine and N’-nitrosoanabasine which is less than 0.2 pg/g, wherein said cured non-green or yellow 20 tobacco is selected from the group consisting of United States Virginia flue andUnited States Burley varieties.

39:\ A tobacco product comprising cured non-green or yellow tobacco suitable forhuman consumption, in leaf form and having a collective content of N’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’- 25 nitrosoanatabine and N’-nitrosoanabasine which is less than 0.2 pg/g, wherein saidcured non-green or yellow tobacco is selected from the group consisting of UnitedStates Virginia flue and United States Burley varieties.

40. A tobacco product comprising cured non-green or yellow tobacco suitable forhuman consumption, substantially free of organic liquids used to extract expanded jg organic materials and having a content of 4-(N-nitrosomethylamino)-l-(3-pyridyl)-1-butanone which is 0.002 pg/g or less.

41. A tobacco product comprising cured non-green or yellow tobacco suitable for 72 117 38 human consumption, in leaf form and having a content of 4-(N-nitrosomethylamino)- l-(3-pyrjdyl)-l-butanone which is 0.002 pg/g or less.

42. The tôbacco product of claim 40 or 41 wherein said content of 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone is 0.001 pg/g or less.

43. The tobacco product of any one of daims 35, 36, 38, 39, 4b, 41, and 42,wherein said cured non-green or yellow tobacco is a Virginia flue variety.

44. The tobacco product of any one of daims, 35, 36, 38, 39, 4j0, 41, and 42,wherein said cured non-green or yellow tobacco is a Burley variety.

45. The tobacco product of any one of claim 34, 37, 38, and 39, wherein said collective content is 0.15 pg/g or less. i '

46. The tobacco product of claim 45, wherein said collective contient is 0.1 pg/g orless.

47. The tobacco product of any one of daims 34-46, wherein said tobacco suitablefor human consumption is cured yellow tobacco.

48. The tobacco product of any one of daims 34-47, which is a product selectedfrom the group consisting of cigarettes, cigars, chewing tobacco, snuff, and tobacco-containing gum and lozenges.

49. Cured yellow tobacco suitable for human consumption and having a cofïtent ofN’-nitrosonornicotine which is less than about .15 pg/g.

50. Cured yellow tobacco according to claim 49, wherein said content is less thanabout .1 pg/g.

51. Cured yellow tobacco according to claim 50, wherein said content is less thanabout .05 pg/g.

52. Cured yellow tobacco suitable for human consumption and having a content of4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone which is less than about .002pg/g-

53. Cured yellow tobacco according to claim 52, wherein said content is less thanabout .001 pg/g.

54. Cured yellow tobacco according to claim 53, wherein said content is less thanabout .0005 pg/g.

55. A tobacco product comprising cured non-green or yellow tobacco suitable forhuman consumption and having a content of at least one tobacco-specific nitrosamine 50 73 11738 selected from the group consisting ofN’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’-nitrosoanatabine and N’-nitrosoanabasine which is within about 25% by weight of the content of said at leastone tobacco-specific nitrosamine in a freshly harvested green tobacco crop from J which the non-green or yellow tobacco was made.

56. The tobacco product according to claim 55, wherein said content is withinabout 10% by weight of the content of said at least one ,tobacco-specific nitrosaminein said green tobacco.

57. The tobacco product according to claim 56, wherein said content is within 10 about 5% by weight of the content of said at least one tobacco-specific nitrosamine insaid green tobacco. x

58. The tobacco product according to claim 55, which is a product selected from the group consisting of cigarettes, cigars, chewing tobacco, snuff and tobacco- .containing gum and lozenges. \

59. A tobacco product comprising cured non-green or yellow tobacco suitable forhuman consumption and having a content of at least one tobacco-specific nitrosamineselected from the group consisting of N’-nitrosonomicotine, 4-(N- nitrosomethylamino)-l-(3-pyridyl)-l-bütanone, N’-nitrosoanatabine andN’-nitrosoanabasine which is at least about 75% by weight lower than the content of said S® at least one tobacco-specific nitrosamine in cured brown tobacco made from the sametobacco crop from which the non-green or yellow tobacco was made, but which wascured in the absence of steps designed to reduce the content of said at least onetobacco-specific nitrosamine.

60. The tobacco product according to claim 59, wherein said content is at least 25 about 90% by weight lower than the content of said cured brown tobacco.

61. The tobacco product according to claim 60, wherein said content is at leastabout 95% by weight lower than the content of said cured brown tobacco.

62. The tobacco product according to claim 61, which is a product selected fromthe group consisting of cigarettes, cigars, chewing tobacco, snuff and tobacco-; 30 containing gum and lozenges. y J

63. A process of substantially preventing the formation of nitrosamines in a Jharvested tobacco plant, comprising: 74 117 3 8 drying at least a portion of the plant, while said portion is uncured, yellow, andin a State susceptible to having the formation of nitrosamines arrested, with circulatingair convection at a température of ffom about 100°F to about 500°F for a timesufficient to substantially prevent the formation of at least one nitrosamine.

64. The process of claim 63 wherein said drying with circulating air convection is carried out on a tobacco leaf or portion thereof prior to substantial accumulation ofnitrosamines in the leaf.

65. The process of claim 63 wherein said drying with circulating air convection iscarried out prior to substantial loss of the plant’s cellular integrity. I©

66. The process of claim 63 wherein said tobacco is Virginia flue tobacco and wherein said drying with circulating air convection is carried out within about 24 to72 hours post-harvest.

67. The process of claim 63 wherein said drying with circulating air convectionprevents normal accumulation of at least one tobacco-specific nitrosamine in the leaf. îÿ

68. The process of claim 67 wherein said at least one tobacco-specific nitrosamine is selected from the group consisting of N’-nitrosonornicotine, 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone, N’-nitrosoanatabine and N’-nitrosoanabasine.

69. The process of claim 68 wherein said portion of the tobacco plant, folio wing 20 said drying with circulating air convection, has a content of said at least one tobacco- specific nitrosamine which is at least 75% by weight lower than the content of said atleast one tobacco-specific nitrosamine in cured brown tobacco made ffom the sametobacco crop but which was cured in the absence of steps designed to reduce the 2^ content of said at least one tobacco-specific nitrosamine.

70. The process of claim 69 wherein said content is at least about 90% lower thanthe content in said cured brown tobacco.

71. The process of claim 70 wherein said content is at least about 95% lower thanthe content in said cured brown tobacco. 30

72. A process of substantially preventing the formation of 4-(N- nitrosomethylamino)-l-(3-pyridyl)-l-butanone in a harvested tobacco plant,comprising: drying at least a portion of the plant, while said portion is uncured, yellow, and 75 117 3 8 in a State susceptible to having the formation of 4-(N-nitrosomethylamino)-l-(3-pyridyl)-l-butanone arrested, with circulating air convection at a température of fromabout 100°F to about 500°F for a time sufficient to substantially prevent formation of4-(N-nitro somethylamino)-1 -(3 -pyridyl)-1 -butanone.

73. The process of claim 72 wherein said tobacco is Virginia flue tobacco and wherein said drying with circulating air convection is carried out within about 24 to72 hours post-harvest.

74. The process of claim 72 wherein said portion of the tobacco plant, followingsaid drying with circulating air convection, has a content of 4-(N- 1® nitrosomethylamino)-l-(3-pyridyl)-l-butanone which is at least 75% by weight lowerthan the content of 4-(N-nitrosomethylamino)-l-(3-pyridyl)-1-butanone in curedbrown tobacco made from the same tobacco crop but which was cured in the absenceof steps designed to reduce the content of said 4-(N-nitrosomethylamino)-l-(3-pyridyl)-1-butanone. |j

75. The process of claim 74 wherein said content is at least about 90% lower thanthe content in said cured brown tobacco.

76. The process of claim 75 wherein said content is at least about 95% lower thanthe content in said cured brown tobacco. 76