GB2151449A - Process for manufacturing peanut milk - Google Patents

Abstract

The process comprises partially roasting blanched partially defatted raw peanuts, grinding into a flour, forming a water flour suspension, extracting protein and homogenizing. In a preferred process, a lightly roasted (Gardner L Color 74) peanut flour is combined with water to form a slurry. The pH of the slurry is adjusted to between 7 and 8.6 and the slurry is then cooked at between 60 and 100 DEG C for between 5-90 minutes. The pH is then readjusted to approximately 7.0, and the slurry is then homogenized and centrifuged.

Description

SPECIFICATION Process for manufacturing peanut milk This invention relates to a process for preparing milk-like products from peanuts and more particularly to a method of manufacturing a peanut milk with excellent nutritional benefits and one containing the flavor of roasted peanuts without requiring the addition of flavor.

Generally, protein beverages formulated from plant sources are well known. Typically, they are based upon soybean flour which has been pre-treated to remove objectionable odors and "flavour notes." While removal of objectionable "flavor notes" would be a goal for most protein beverage processes employing plant sources, the manner in which removal is achieved would likely vary depending upon the particular plant source used. Each plant source type will have its own characteristic compliment of esters, aldehydes, amines and heterocycles, etc., which make up its "flavor notes." Moreover, removal of some but not all "notes" will depend upon the desired flavor of the end product. Consequently, the removal processes should be individually tailored to fit the characteristic complement and flavor desired.

A significant amount of work has been devoted to the identification of peanut flavor notes. In an article entitled "Peanut Quality: Its Relationship to Volatile Compounds-A Review" 1 70 ACS Symposium Series p. 147-161, Pattee, et al. (1981), the authors report various studies which identify volatile components in raw peanuts. The authors identified pentane, acetaldehyde, methanol, acetone, ethanol, and hexanal as major components of raw peanut flavor. Methyl formate, octane, 2-butanone, and pentanal were identified as minor components. The characteristic aroma and flavor of raw peanuts was suggested to arise from a physical interaction of the components listed above, with hexanal as the most significant contributor to this aroma.Other studies suggest that in addition to hexanal, octanal and possibly nonanal and 2-nonenal contribute to the "green or beany" flavor which is characteristic of raw peanuts.

In an article entitled ''Instrumental and Sensory Characteristics of Roasted Peanut Flavor Volatiles" ACS Symposium Series Vol. 170 p. 163, Buckholz, and Daun, (1981), the authors discussed the relative importance of various volatile compounds in the taste and aroma of roasted peanuts. The authors proposed that the most important constituents of peanuts responsible for the flavor formation during roasting are amino acids, sugars, proteins and lipids.

Generally, the roasting process (pyrolysis) requires that the peanut be subjected to internal temperatures between 130"C to 150"C, during which process, the typical roasted peanut flavor is produced. The roasting of the peanut promotes flavor changes that ultimately increase their palatability. The authors concluded that the aroma of fresh roasted peanuts is influenced by the roasting time and is a reflection of the changes in the ratios of carbonyl derivatives to pyrazine compounds. Good quality peanut flavor was related to a decrease in carbonyls and a subsequent increase in the pyrazines. Low molecular weight aldehydes were described as responsible for the harsh aroma associated with fresh roasted nuts.

Certain objectionable "flavor notes" of a typical peanut-derived beverage, be it made from raw peanuts or peanuts with a normal roast make the development of a peanut flavored beverage difficult. Removal of such objectionable odors would be advantageous but processing to remove some but not all peanut flavor components has proved to be a hard task. For example, U.S. patent 3,947,599 (Mitchell) removes essentially all peanut flavor from peanut meal by spraying a finely ground aqueous slurry of peanut meal onto a thin film evaporator and co-evaporating the volatile flavor components with a portion of the slurry water. U.S. patent 4,355,051 (Pominski) describes the removal of raw peanut taste by heating shelled, raw, unblanched (unskinned) peanuts to between 220"-250"C to reduce moisture and remove the odorous raw peanut volatiles.U.S. patent 3,800,056 (Mitchell) describes a process whereby raw, blanched, ground peanut meal is precooked with moist heat (live steam) to remove unpleasant peanut aroma.

The prior art teaches that the treatment of peanuts with hot water or steam volatilizes the components which would yield the raw peanut taste. Bitterness is avoided by not roasting the peanuts. The absence of a roasting step, however, typically produces a bland peanut milk having a slight raw peanut taste with its "green" notes rather than a pleasant recognizable peanut taste. U.S. patent 4,026,658 (Pominiski) discusses the preparation of a milk-like peanut drink utilizing peanut flour which is treated at a temperature and a moisture range sufficient to keep the peanuts in their raw state and not high enough to brown the peanuts.

According to the invention there is thus provided a process for making a peanut milk comprising the steps of: partially roasting blanched partially defatted raw peanuts to yield a roasted peanut; grinding said roasted peanuts into a flour, said flour having a colour indication between 50 and 74 in a Gardner L scale, said colour indication being related to the degree of roast of the roasted peanut; forming a flour and water suspension containing from 4.0 to 10.0% by weight of peanut flour; extracting protein from the flour in said flour and water suspension; and homogenizing said water flour suspension to form a homogenized peanut milk product.

The process according to the invention preferably includes the step of adding water to a lightly roasted, partially defatted peanut flour, having a Gardner L value of approximately between 60 and 74. The water flour suspension comprises preferably between 5.0 to 6.0% by weight peanut flour to yield a milk product having 2-3.5% protein. The extraction step preferably includes treating the water flour suspension with an alkaline substance to raise its pH to between 7.0 to 8.6. The suspension can then be heated to between 60"C-100"C for a predetermined penod ot time to simultaneously adjust the desired roasted flavor intensity and extract the protein from the flour.Heating at 80'C for 5-10 minutes yields a product having a slightly roasted peanut flavor without any "green" notes, The slurry is then homogenized after which its pH can be adjusted to between 6.5 and 7.5.

The objects and attendant advantages of the present invention will become more readily apparent by reference to the accompanying drawings, in which: Figure 1 is a schematic of a preferred process of the invention; and Figure 2 is a schematic of an alternate preferred process of the invention.

Figure 3 is a gas chromatogram of the methylene chloride extract of the raw peanut flour.

Figure 4 is a gas chromatogram of the methylene chloride extract of the lightly roasted peanut flour (Gardner L Color 74) used with the present invention.

Figure 5 is a gas chromatogram of the methylene chloride extract of the medium roasted oeanut flour (Gardner L Color 60) used with the present invention; and Figure 6 is a gas chromatogram of the methylene chloride extract of a dark roasted peanut flour (Gardner L Color 51).

In the preferred embodiment of the present invention a peanut milk is prepared using a lightly roasted, partially defatted peanut flour. The flour is commercially available from Seabrook Blanching Corp., P.O. Box 3049, Albany, Georgia under the Code No. 1 74. The partially defatted flour used in the preferred embodiment has a Gardner L value of between 60 to 74.

The Gardner color scale is a standard color scale and is described in the publication "Colorimetry," Nat. Bureau of Standards, Monograph 104, issued Jan. 1978, Library of Congress Catalog Card No. 67-62079. The Gardner L scale provides an indication of shades of light to dark. It has been found that flours having Gardner L values higher than 74 are insufficiently roasted and yield a peanut milk with a raw peanut flavor, while flours having Gardner L values below 60 are over-roasted and yield a bitter flavor to the milk, which is difficult to remove, and protein extraction yields are reduced.

The peanut milk of the present invention can be made by adding between about 5.5 to 6.0% by weight of partially defatted, lightly roasted peanut flour to between about 94 to 94.5% by weight of water. The amount of flour added to the suspension may vary depending upon the protein content desired in the end product. The protein content of the flour is in general between 20-40% by weight, and depends on the fat content of the flour. Generally it is desired to make an end product having a protein content close to cow's milk, i.e. 2-3.5% by weight.

The ingredients are mixed, and the pH of the slurry is then adjusted to a range of 7.0 to 8.6 to optimize protein yield. The slurry is then heated to between 60"-100"C. The time requirement of the heating (between 5 to 90 minutes) is dictated by the temperature and the amount of peanut flavor desired in the final milk. The time of heating is conveniently between 5 and 90 minutes and preferably between 5 and 60 minutes. To yield the peanut milk that has the pleasant slightly roasted peanut flavor of the preferred embodiment, heating at 80"C for 5-10 minutes is desirable. The pH of the peanut milk is then adjusted to a range of between 6.5. and 7.5 and the product is homogenized in a two step process.The first stage is performed between 65 and 95"C (150 to 200"F) and between 2 x 107 and 3.5 X 107 Nm-2 (3,000 and 5,000 psi), preferably at 80"C (176 F) and 2.4 X 107 Nm-2 (3,500 psi). In the second stage the homogenization pressure should be maintained between 1.7 X 106 and 5.2 X 106 Nm-2 (250 and 750 psi) with the preferred pressure being 3.4 X 106 Nm-2 (500 psi). It should be noted that although the adjustment of the pH to 7 is described before the homogenization step, it could well be accomplished after homogenization and the centrifugation step which is described below.

After homogenization, most of the insoluble and suspended (fibrous material) solids are separated by decanting, or centrifugation. Centrifugation should be at a sufficient angular velocity to separate the insoluble solids from the homogenized milk product but below the velocity where fat is separated from the homogenized milk product. It has been found that an upper limit of approximately 1 ,000 X g. is required, because at higher g's the fat contained in the milk product will tend to separate. Processing efficiency would suggest that the centrifuge should be run at the highest speed possible before separation of fat begins to occur. After the separation of the milk from the insoluble and suspended solids (fibrous material), the milk product can be flavored and modified by adding sugar, vitamins, a viscosity adjustment product, and salt.The product can then be pasteurized or sterilized by heating and packaged in commercially available packaging products such as aseptic packaging and the like.

The milk produced by the process can contain protein and fat at levels as high or higher than cows milk (3.5% protein/3.5% fat). Sugar and salt may be added to increase the palatability; as well as vitamins and minerals to deliver the degree of nutrition desired. Flavors such as chocolate, vanilla and strawberry, among others, can also be added.

In sensory evaluation data reported in the aforementioned Buckholz article, the darker and medium roast were consistently rated higher than the light roast. This is in contradistinction to the present invention in which the milk made from lightly roasted, partially defatted peanut flour is preferred rather than the milk made from the darker roasts. Accordingly, it has been discovered unexpectedly that a good tasting peanut milk should be made with a lightly roasted partially defatted peanut flour. The degree of roast is an important parameter in the making of a good tasting peanut milk. Milk made from raw peanuts has a "green or beany" flavor which is characteristic of components like hexanal, octanal and possibly nonanal and 2-nonenal.It has been found that peanut milk made with a medium to very dark roast flour, have characteristic bitter notes which cannot be removed during processing. The desirability of the invention is illustrated by the following examples.

In the peanut milk prepared in the following examples, partially defatted peanut flour prepared from high quality USDA grade of shelled raw peanuts that have been thoroughly cleaned, blanched and electronically sorted to remove any damaged or discolored nuts, was utilized. The nuts were hydraulically pressed without heat to remove 55% of the oil content by weight, and processed into flour of different roasts.

EXAMPLE 1 50 gms. of peanut flour having a Gardner L value of 74 was mixed with 950 gms. of water.

The pH was adjusted from 6.6 to 8.6 by adding a sufficient amount of a 50% NaOH solution.

The resulting mixture was then heated for 30 minutes at 95"C. Upon cooling, the cooked slurry was stored at 4"C overnight. Some sediment was seen in the bottom part of the container.

Analyses of the clarified milk showed it contained 3.7% of total solids and 2.0% protein representing 74% recovery of total solids and 100% extraction of protein. The peanut milk tasted smooth in texture and exhibited a light, pleasant roasted flavor.

EXAMPLE 2 (for purposes of comparison) 50 gms. of peanut flour having a Gardner L value of 74 was mixed with 950 gms. of water.

The pH was adjusted to 9.0 by adding 50% NaOH. The resulting mixture was then heated for 30 minutes at 95"C. Upon cooling the resulting milk was tasted, and was found to have an unpleasant alkaline taste. An attempt to lower the pH by addition of 6N HCI caused protein precipitation.

EXAMPLE 3 Three samples of toasted, partially defatted peanut flours ranging from (1) off-white, (2) very light brown, to (3) brown in color were compared for their extractibility. Thirty grams of flour and 270 grams of water were mixed in a blender for 30 seconds and filtered through six layers of cheesecloth. Analyses of the filtrates gave the following extraction data: TABLE I Sample % Total Solids (% Recovery) % Protein (% Recovery) 1 4.0 40 1.80 45.0 2 3.2 32 1.51 37.8 3 1.8 18 0.67 16.7 Thus, the greater the degree of roasting, the lower the resulting extraction of soluble solids and protein.

EXAMPLE 4 A large scale test run of peanut milk packaged in 250 ml Tetra Brik cartons was run. A batch of 450 litres (one hundred gallons) of peanut milk was made. A partially defatted, roasted peanut flour (Gardner L color 74) was used for making the peanut milk.

The protein beverages contain: 2% protein, 1.5% fat, 7% sugar, 0.1% salt and 25% U.S.

RDA of each of eleven vitamins (A, Bt, B2, B6, B12, C, D, E, folic acid, niacin and pantothenic acid) per 250 ml serving.

The processes for making the peanut milk comprised mixing the ingredients with a Tri-Clover blender, heating, homogenization (2 X 107 Nm-2, 3000 psig), UHT heating (135to, 276"F-6.7 seconds), cooling and aseptic packaging. The Cherry-Burrell UHT heating-homogenization system (NO BAC UNITHERM XIV, Ser. No. 442) and the Tetra Brik machine were used.

Upon mixing the ingredients, adjusting the pH as in Example 1 and heating for 30 minutes to 80"C (176 F), homogenization (2.4. X 107Nm-2, 3500 psig first stage, 3.4 x 106Nm-2, 500 psig second stage) and centrifugation (Westfalia Separator, Model MP 5004, Ser. No.

1639642, run at 6.5 speed setting) were carried out to increase soluble solid extraction and to remove the insoluble solids. The nutritional information and contents of the peanut milk product are shown in Tables Il-Ill below.

TABLE II NUTRITIONAL INFORMATION FOR PEANUT MILK Serving size: 250 ml Protein: 5 grams Carbohydrate: 20 grams Fat: 4 grams Calories: 136 PERCENT USRDA Protein: 8 Vitamin C: 25 Vitamin A: 25 Vitamin D: 25 Vitamin B1: 25 Vitamin E: 25 Vitamin B2: 25 Folic Acid: 25 Vitamin B6: 25 Niacin: 25 Vitamin B12: 25 Pantothenic Acid: 25 TABLE III PEANUT MILK FORMULA Ingredient e (wiz) Source Partially defatted, roasted 6.0 Jimbos Jumbos peanut flour Sugar, Granulated 7.0 Dixie Crystals Salt 0.1 Table salt Carrageenan 0.03 Viscarin 402 (FMC) Vitamin prefix 0.02 Bioblend (Henkel) Sodium ascorbate 0.0135 Pfizer Water 86.8365 Activated C-treated Total 100% EXAMPLE 5 The effect of flour concentration and extraction temperature on the final protein content of the product was determined using the following procedure.

Two, three kilograms samples of flour suspension in water containing respectively 5.5 and 6.0% flour (a lightly roasted, partially defatted peanut flour with Gardner L of 74-Seabrook Code No. 1 74 product) were adjusted to pH 7.2 and heated to temperatures ranging from 20'C to 95"C for thirty minutes. The heated slurries were then passed through a homogenizer (2.4 x 107Nm-2, 3000 psig first stage, 3.4 X 106Nm-2, 500 psig second stage), and centrifuged at 1000 X g for 10 minutes. The protein contents and the percentages of protein recovery are shown in Table IV.

TABLE IV % Flour Extraction Temperature t Protein % Protein Recovery 5.5 20'C 0.92 40.8 60-C 1.61 73.2 959C 1.97 89.5 6.0 60-C 1.63 67.9 80-C 1.99 82.9 Thus, increasing the extraction temperature resulted in an increased protein yield. It appeared that lower flour concentration favored somewhat higher extraction yield.

EXAMPLE 6 The effect of pH on protein extraction was determined by the following procedure.

An 8.4% flour in water slurry having a pH of 6.7 was adjusted to pH 7.1 with a sufficient volume of 50% NaOH. The flour used was as in Example 1.

Portions of the slurry before and after pH adjustment were centrifuged at 1000 x g for 10 minutes. The protein contents of the extracts were, in the order shown, 0.6 and 1.8% representing 19 and 41% protein recovery. Thus it was determined that processing at a higher pH yielded more efficient extraction.

EXAMPLE 7 Effect of mild alkaline and heat treatments.

Three thousand grams of a 8.4% flour in water slurry (pH = 6.7) was adjusted to pH 7.5 with a sufficient volume of 50% NaOH and heated to 60"C for 30 minutes with constant agitation.

The flour used was as in Example 1. A control slurry was prepared by agitating for one hour without pH adjustment and heating. The test and the control were separately passed through a homogenizer (2.4 x 107Nm-2, 3000 psig first stage, 3.4 X 1ONm-2, 500 psig second stage).

Two hundred grams of the homogenized slurry was then centrifuged at 1000 X g for 10 minutes. The yields of the supernatants and pellets are illustrated in Table V.

TABLE V Supernatant Pellet pH 6.7 170 grams (85%) 30 grams (15%) pH 7.5 . 172 grams (86z) 28 grams (14%) The total solids and the protein contents of the supernatants and the calculated recoveries from the original flour are shown in Table Vl.

TABLE VI pH 6.7 pH 7.5 % total solids 4.4 6.2 % total solids recovered 44.5 63.4 % protein 1.65 2.82 % protein recovered 41.7 72.1 EXAMPLE 8 The effect of homogenization conditions was determined as follows.

A 6% flour slurry (6500 grams) was adjusted to pH 8.0 with 2.4 grams of 50% NaOH. The flour used was as in Example 1. The slurry was heated to 96"C and maintained at that temperature for approximately 30 minutes. The total heating time was approximately 63 minutes. The cooked slurry was subdivided into three roughly equal portions. These portions were separately passed through a homogenizer at the following conditions: (1) 2.8 X 107Nm-2, 4000 psig total pressure (2.4 X 107Nm-2, 3500 psig first stage, 3.4 x 106Nm-2, 500 psig second stage) once, (2) 2.8 x 107Nm-2, 4000 psig total pressure twice through the same homogenizer (Gaulin Type LAB 100/100), and (3) 5.5 X 107Nm-2, 8000 psig total pressure once (Gaulin homogenizer Type 120 M38; 4.8 X 107Nm-2, 7000 psig first stage, 6.9 X 106Nm-2, 1000 psig second stage).The homogenized slurries were kept at 4"C overnight to settle the sediments. The pH, % total solids, and % protein of the supernatants are described in Table VII.

TABLE VII Treatments (1) (2) (3) - '7.2 7.2 7.1 % Total Solids 5.4 5.7 5.3 % Protein 2.50 2.49 2.43 EXAMPLE 9 50 gms of a peanut flour having a Gardner L value of 74 was mixed with 950 gms of water (5% flour slurry). The pH was adjusted from 6.6 to 8.6 by adding a sufficient amount of a 50% NaOH solution. The resulting mixture was heated to 80"C (175"F) and kept at this temperature for approximately 10 minutes. The pH of the cooked slurry was tested and readjusted to 7.0.

The slurry was then homogenized at 80"C (175"F) through two stages, 2.4 X 1 07Nm -2, 3,500 psi first stage, and 3.4 X 107Nm-2, 500 psi for the second stage. The homogenized product was then centrifuged at approximately 1,000 X g for 10 minutes. The supernatant was recovered as the peanut milk product. The resulting product was a pleasant tasting milk with a light peanut flour, EXAMPLE 10 Illustrated in Table VIII are the sensory evaluations of milk made in accordance with the method described in example 9 with flours having a different degree of roasts. Sample A was made with flour made with raw peanuts which are ground after pressing into a fine particular flour. The flour is 100% peanut, containing no additives.The degrees of roast of flours other than the raw flour is indicated by the Gardner L color scale. The Gardner L color is an indication of dark to light shades and is used in the trade to indicate the degree of roast. Gardner L color 74 is a light roast which yields a flour with a mild roasted peanut flavor. Gardner L color 60 is a medium roast with a more roasted flavor. Gardener L color 51 is a dark roast with a strong roasted peanut flavor, while Gardner L color 41 is a very dark roast with a very strong roasted peanut flavor.

Table VIII Sample GARDNER L Color Sensory Evaluation A greater than 80 (raw) Raw taste, green," beany notes, unpleasant B 74 Pleasant lightly roasted peanut taste C 60 Pleasant roasted peanut taste D 51 Strong roasted peanut taste, bitter notes E 41 Very strong burnt, bitter taste, unpleasant As shown in Table VIII, the peanut milk made with raw flour (sample A) had an unpleasant taste which was characterized as "green" or "beany". The milk made with flour having a Gardner L color 60 and 74 (samples B 8 C) had a pleasant light peanut taste with the Gardner L 74 being preferred. The darker roast flour, Gardner L color 51 and 41, (samples D 8 E) yielded a milk which has the characteristic dark roast flavor which gave the milk a biter note which was somewhat unpleasant.

EXAMPLE ii Illustrated in Figs. 3-6 are gas chromatograms of the methylene chloride extracts of the peanut flours used for making the peanut milks described in Example 1 0. The corresponding numerical data are set forth in Tables IX-XII.

Analytical Procedures Extraction of flavor components Raw and three toasted, partially defatted peanut flours were obtained from Flavor Nuts, Inc., Box 3409, Albany, Georgia 31706. One gram of each flour was extracted three times with 20 milliliters of methylene chloride (Burdick and Jackson glass distilled). The flavor extracts were combined and concentrated to 0.2 milliliter by blowing nitrogen gas. Four microliters of the flavor concentrate was applied to the gas chromotograph.

Gas Chromatographic Analysis A Hewlett Packard 5790A gas chromatograph was used with an IBM 9000 laboratory computer, which integrated, printed, and graphed the chromatographic peaks. A fused silica capillary column 60 meter in length was coated with J s W Scientific Carbowax 20M. The column flow rate was at 1 millimeter per minute. The flame ionization detector was operated at 250"C. The injector temperature was 200"C. The oven temperature was programmed from 60 to 120"C at 4"C per minute. The slope sensitivity, area reject, and attenuation were set at 1.0 microvolt per second, 0 and 10 X 4 respectively.

As shown in Figs. 3 through 6, a number of peaks were detected before the large solvent peak. Those peaks are highly volatile components, and solvent impurities.

Table IX (Figure 3 - Raw Peanut Flour Extract) (Sample A) Retention Time (min.) Area 2.777 6287 24.034 756 (peak c?) 42.116 1451 45.745 1638 49.505 1502 Table X (Fig. 4 - Lightly Roasted Peanut Flour Extract) Sample B Retention Time (min.) Area 3.918 742 9.931 1030 15.261 680 19.393 931 21.652 5778 (peak a) 22.741 31092 (peak b) 23.992 39804 (peak c) 28.377 2837 33.585 945 37.920 2445 (peak d) 42.056 4051 45.672 2508 49.418 3030 Table XI (Fig. 5 - Medium Roasted Peanut Flour Extract) Sample C Retention Time (min.) Area 2.752 2849 3.907 4978 5.487 2734 9.913 1332 11.914 4272 13.131 1484 14.083 909 15.361 969 19.388 3807 21.754 8908 (peak a) 22.793 27695 (peak b) 24.037 33241 (peak c) 25.688 898 29.154 1353 33.621 914 35.373 3236 37.956 14607 (peak d) 40.347 5753 42.1916 2965 49.688 3026 Table XII (Fig. 6 - Dark Roasted Peanut Flour Extract) Sample D Retention Time (min.) Area 21.703 1432 (peak a) 22.778 7781 (peak b) 24.028 11913 (peak c) 28.418 2288 33.623 1157 37.950 9530 (peak d) 40.309 852 42.090 2984 45.700 1953 49.442 2700 Peaks a, b, and c have been identified as isomers of 2, 4-Decadienal. Peak d is believed to be dihydrocoumarone (2, 3 dihydrobenzofuran).As shown in Fig. 3, the chromatogram of the new peanut flour extract does not show any significant peaks that are attributable to roasted peanut volatiles. The chromatogram of the lightly roasted flour extract shows a significant concentration of the isomers of 2, 4-decadienal and a relatively low concentration of dihydrocoumarone. It is apparent that as the degree of roast increases, the concentration of 2, 4 decadienal decreases and the concentration of dihydrocoumarone increases. It is believed that dihydrocoumarone may contribute to the unpleasant bitter notes of peanut milk made with dark roasted peanuts. Trans2, trans-4-decadienal was reported by Valradt, et al., Journal of Agriculture and Food Chemistry, 1971, 19, 972. as a compound present in the aroma of roasted peanuts. As shown in that article, a large number of compounds contribute to the taste and aroma of roasted peanuts.

Accordinoly. the concentrations of 2, 4-decadienal and dihydrocoumarone serve as good indicators of the desired degree of roast of the peanut flour to be used in making the peanut milk of the present invention. Low concentrations of 2, 4-decadienal indicate that the flour is insufficiently roasted to yield the milk of the preferred embodiment.

It is understood that the peanut milk made in accordance with this invention can be further modified by adding flavoring, vitamins, colorings and the like.

Claims (14)

1. A process for making a peanut milk comprising the steps of: partially roasting blanched partially defatted raw peanuts to yield a roasted peanut; grinding said roasted peanuts into a flour, said flour having a colour indication between 50 and 74 in a Gardner L scale, said colour indication being related to the degree of roast of the roasted peanut; forming a flour and water suspension containing from 4.0 to 10.0% by weight of peanut flour; extracting protein from the flour in said flour and water suspension; and homogenizing said water flour suspension to form a homogenized peanut milk product.

2. A process as claimed in claim 1 further comprising the step of: flashing off some of the undesired flavour volatiles present in the flour and water suspension.

3. A process as claimed in either preceding claim wherein said peanut flour has a colour indication between 60 and 74 in a Gardner L scale whereby a palatable peanut milk having a light peanut flavour is produced.

4. A process as claimed in any preceding claim wherein said flour water suspension contains between 5.0 and 6.0% by weight of peanut flour.

5. A process as claimed in any preceding claim wherein said extracting step comprises: adjusting the pH of the flour and water suspension to between 7.0 and 8.6.

6. A process as claimed in claim 5 wherein after the pH adjustment step the water and flour suspension is heated to a temperature of between 60"C and 100"C for a period of time sufficient to extract the desired amount of protein.

7. A process as claimed in claim 6 wherein said period of time is between approximately 5 and 90 minutes.

8. A process as claimed in claim 7 wherein said period of time is between approximately 5 and 60 minutes.

9. A process as claimed in any of claims 6 to 8 further comprising adding a sufficient amount of an acid to the water and flour suspension after the heating step to readjust the pH to between 6.5 and 7.5.

10. A process as claimed in any preceding claim further comprising adding a sufficient amount of an acid to the homogenized milk product to readjust the pH to between 6.5 and 7.5.

11. A process as claimed in any preceding claim further comprising separating large undissolved solids from said homogenized milk products..

1 2. A process as claimed in claim 11 wherein said separating step comprises: centrifuging said homogenized milk products at a sufficient angular velocity to separate the insoluble solids from the homogenized milk product but below the velocity where fat is separated from the homogenized milk product.

13. A process for making a peanut milk substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

14. A process for making a peanut milk substantially as herein described with reference to any of Examples 1 to 4 to 9.