CA2128240C

CA2128240C - Method of preparing a dietary low cholesterol whole egg or egg yolk product, and the further processing of the product to give foods

Info

Publication number: CA2128240C
Application number: CA002128240A
Authority: CA
Inventors: Martin Jackeschky
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-01-24
Filing date: 1992-01-24
Publication date: 2003-09-16
Anticipated expiration: 2012-01-24
Also published as: JPH07503840A; AU1168492A; ES2096069T3; GR3022177T3; AU671796B2; EP0621754B1; EP0621754A1; JP3024798B2; CA2128240A1; WO1993014649A1; ATE143770T1

Abstract

A method for preparing a dietetic, cholesterol-reduced whole egg or egg yolk product is characterized by dehydrating the whole egg or the yolk and then by mixing it with a low-cholesterol extractant based on liquid food oils, the extractant being allowed to act, and this reactant then being removed from the egg substance during a de-oiling stage.

Description

212240;
A METHOD OF PREPARING A DIETARY, CHOLESTEROL-REDUCED
WHOLE EGG OR EGG YOLK PRODUCT, AND ITS PROCESSING INTO FOODSTUFFS
The invention relates to a method for preparing a dietetic, cholesterol-reduced, whole egg or egg yolk product, and also to the products themselves and their use as initial materials for making foodstuffs. Moreover the invention relates to an egg extract resulting as a byproduct from performing the method and its use as a foodstuff additive.
The terms above of whole egg or egg yolk relate primarily to chicken eggs. Aside from nutritionally physiologically valuable components such as proteins, for instance vitellin, phosphorus lipids (lecithins), chicken eggs also contain medically undesirable materials such as cholesterol.
Cholesterol is present in the fat fraction of the egg yolk and, together with the equally undesirable saturated fatty acids, amounts to about 20 % of the valuable weight of the yolk.
As regards using eggs in dietetic foodstuffs, it is espe-cially desirable to reduce the cholesterol proportion in the yolk.
It is known in this respect to remove the fat fraction of the egg yolk by total extraction with a solvent such as hexane. While this procedure allows removing the cholesterol, on the other hand the medically desirable lecithins are also extracted, at least in part. Moreover it is impossible to entirely remove the extractant, for instance hexane, from the egg yolk without thereby harming the product.
Another way to remove cholesterol from the egg yolk is by means of high-pressure extraction using super-critical fluids such as C02. High-pressure extraction allows selectively REPLACEMENT SHEET
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removing cholesterol together with other fats contained in the egg yolk without thereby reducing the lecithin content.
However this procedure incurs the drawback that essentially the cholesterol shall be absorbed by the fluid flow as the last substance of the egg yolk fat fraction and consequently long treatment times are required. As a result, partial denaturing of the egg yolk proteins may easily take place at the temperatures and pressures of high-pressure extraction.
Another way to remove cholesterol from yolk is by adding cyclodextrin to the liquid yolk. Cyclodextrin selectively encloses cholesterol. Following a given time of application, the cyclodextrin together with the enclosed matter can be removed from the yolk. But on economic grounds this procedure is not yet widely marketed.
Accordingly it is the object of the present invention to create a medically acceptable method for the preparation of cholesterol-reduced, full egg or egg yolk products.
Another object of the invention is to make available especially appropriate cholesterol-reduced, full egg or egg yolk products.
Essentially the method of the invention consists in dehydrating the initial material in the form of full eggs or egg yolks and thereupon treating this substance with an extractant based on a low-cholesterol, liquid food oil. The principle of the method is that the mixture being created from the fat fraction of the egg yolk and the added liquid food oil acquires a substantially uniform concentration of all fat components. In other words, the cholesterol from the egg yolk fat fraction uniformly disperses in the low-cholesterol extractant. After the extractant has been removed, a substantial part of the egg yolk cholesterol can therefore be eliminated in a single extraction step.
If as proposed the extraction procedure is repeated several times, then the cholesterol proportion in the egg yolk is easily lowered by at least 95~.

Depending on what the fat content of the final product shall be, the last de-oiling stage can be implemented in the manner defined in claim 3 whereby the extractant is removed only in part.
Various food oils are conceivable as extractants.
Illustratively, if a product is desired of which the egg-yolk composition corresponds substantially to that of the natural egg yolk, but lacking cholesterol, then claim 4 defines using low-cholesterol egg oil. Such egg oil may be prepared for instance by first extracting yolk with an arbitrary food oil and then removing cholesterol from the extract. Contrary to the conditions within the yolk, cholesterol is easily removed in a conventional manner from a fatty liquid. The de-cholesterinized extract of the first treatment stage can be used again as an extractant and becomes enriched in egg oil. When such treatment is repeated several times, an extractant increasingly enriched in yolk fats will be obtafined which essentially evinces the composition of egg oil without cholesterol. If egg oil so enriched is used as the extractant, a cholesterol-free egg product is obtained which in other respects corresponds to the natural egg composition. However such a procedure is comparatively costly.
As a rule therefore an extractant namely a conventional vegetal food oil will be used. All vegetal food oils are appropriate, for instance wheat germ oil, sunflower oil, soybean oil, palm oil or thistle oil. These oils may be used individually or in mixtures. Besides their economy, such extractants offer the further advantage of removing or lowering also the undesired animal saturated fatty acids besides the cholesterol and that where called for enrichment with unsaturated, vegetal fatty acids and oil-soluble vitamins will be possible.

The de-oiling stage, namely the removal of excess extractants by known current procedures, is advantageously carried out for instance by decanting, separation, filtration, and especially by centrifuging.
Advantageously and before being treated with the extractant, the full egg or the yolk will be spray-dried and formed by instantization to sizes of 150 to 300u. When spray-dried, the water is withdrawn in especially gentle manner from the initial material full egg or the yolk, and the powder granulated by instantization furthermore is de-oiled especially easily and uniformly.
Nevertheless the extract cannot be fully removed from the treated egg material by the above described de-oiling procedure. In almost all cases however the main interest will be to make a product free of cholesterol; the complete removal of any fat is not mandatory. On the contrary, it may be advantageous that the cholesterol-free product in addition contain for instance high-grade fatty acids from vegetal oils.
Nonetheless it may be necessary -- for instance regarding the nutrition of athletes -- to make available a full egg or yolk product entirely free of fat. In such a case the invention provides that the practically cholesterol-free egg substance obtained following the last de-oiling stage be additionally extracted with supercritical fluids. Appropriately, the egg substance so prepared shall be formed into a grain size of 0.5 to 2 mm prior to fluid extraction. The fluid flows especially easily through such a granulated egg substance. However the described high-pressure extraction makes sense only when the extractants are vegetal food oils and where multiple extraction is carried out.
In contrast to animal fats, vegetal fats disperse relatively easily in the fluid flow and can be extracted within short treating intervals. The initially described S
drawbacks when treating natural egg yolk with supercritical fluids do not arise in such a procedure; therefore a fully fat-free product is prepared in gentle manner. In this respect it was furthermore found advantageous if, from 0.1 to 20 of an electrolyte, for instance cooking salt and/or sodium citrate are added to the initial material prior to spray drying. The presence of such salts in the egg substance additionally protects against any protein denaturing.
In an alternative to the just above described fluid extraction or as a preliminary stage thereto, at least during the last de-oiling stage, that is the removal of the excess extractant, an inert gas possibly at excess pressure be forced through the egg substance in order to remove in this manner any oil not firmly absorbed, as a rule the complete method of the invention advantageously being carried out in an inert gas atmosphere.
As already mentioned initially, the medically undesired substances, in particular cholesterol, are contained almost exclusively in the yolk. The pure chicken egg white substantially consists of a mixture of albumin and globulin and as such is dietetically unobjectionable. Accordingly most cases will not require using the whole egg for the method of the invention; instead it will be enough to solely treat the yolk. Treating only the yolk offers the advantage that controlled extraction is then possible. Moreover the quantities to be processed are then less. Therefore it may be assumed as a rule that egg yolk will be processed in the method of the invention.
In cases where egg yolk is the initial material while a substantially whole egg composition is desired as the dietetic end product one can rnix the treated mass of yolk with spray-dried protein in such an amount as corresponds to the natural whole egg composition.

Furthermore the invention concerns a dietetic egg yolk or a whole egg product which can be prepared by extraction using vegetal food oils. As a rule the cholesterol-lowering products still contain some extractant; in other words the initial fat fraction contained in the yolk was replaced in part or in whole by vegetal food oil. Such products therefore are not only low in cholesterol, but also they are enriched with essential vegetal fatty acids, whereby they are especially valuable dietetically.
The egg products of the invention can be prepared by extraction using arbitrary vegetal food oils. Accordingly an arbitrary number of different products based on the different food oils also are conceivable. Preferably however the product shall contain "red palm oil" at least admixed to another vegetal food oil. "Red palm oil" is an excellent anti-oxidant and assures long storage life of the egg products of the invention, i.e., that they shall not rancidify prematurely.
Another advantageous egg product essentially contains the same fat proportion as an untreated whole egg or yolk, except that the fat fraction of the egg product consists of vegetal food oil. Illustratively such a product may be used and processed exactly like yolk in the quantities specified in recipes.
The egg products prepared by the method of the invention are directly applicable to the preparation of dietetic foodstuffs. They contain no substances which must be listed under law. The extraction or preparation of the products are implemented solely with unobjectionable foodstuffs. Therefore the invention also concerns the use of the egg products prepared by the method of the invention when making dietetic foodstuffs.
The extractant removed from the egg substance during de-oiling accumulates as a byproduct in the course of the method of the invention. Depending on the implementation of said method, the natural yolk fats and any other oil-soluble substances in this extractant will be enriched to much different degrees. It was found in the first place that this egg extract is an excellent emulsifier. Furthermore the S cholesterol enriched in the extract can be easily removed, for instance by means of. an enclosure compound (adductive crystallization). Accordingly the egg extract may be used as a natural colorant (yolk color) or as a flavoring agent (aroma) in foodstuffs, without entailing a declaration of additive.
The invention is elucidated below by means of several Examples and a Figure.

1,000 g of spray-dried normal egg yolk powder are suspended in 1.5 liter of 40°C soybean oil and following a rest of about 10 min for the extractant to act are de-oiled in a screen centrifuge (centrifuge coefficient 1,300) and are after-treated four times each time with 0.5 liter soybean oil at 40°C. Then the egg substance was centrifuged dry for about 10 min. The yield was 1,085 g. The residual cholesterol proportion was 239 mg/100 g of powdered egg.

Processing takes place as in Example 1. However the drying procedure was modified in such manner that the spray-dried yolk powder grains evinced higher porosity. The mean grain size was 225u. In this Example the yield was 1,040 g and the residual cholesterol was 223 mg/100 g of powdered egg.

Processing is carried out in the manner of Example 1;
the powdered egg serving as the initial material was spray-dried in the manner of Example 2. In deviation from the procedure of Example 1 however, both the centrifuge space and the pre-introduction vessel were filled with an inert gas (in this instance COZ) and kept at slight excess pressure. The inert gas was made to circulate between the centrifuge and the pre-introduction vessel.
The yield was 976 g and the residual cholesterol was 200 mg/100 g of powdered egg.

Processing was carried out as in Example 3. However a mixture of 0.250 liter soybean oil and 0.250 liter "red palm oil" was used for the fourth de-oiling. On account of its natural composition, "red palm oil" is a highly effective antioxidant. The extraordinarily high content of provitamin A
(carotene) and the very high content of provitamin E
(tocopherol) provide long-term protection and prevent premature rancidity of the egg product treated with palm oil.
The yield was 977 g with a residual cholesterol of 200 mg/100 g of powdered egg.
Analysis of the powdered egg obtained in the manner of Example 4 shows the following composition in comparison with the untreated powdered egg.
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212~2~0 COMPONENT UNITS sAMPLE 4 Initial material MEAN VALUES
water g 3.0 3.4 protein g 34.8 31.7 fats g 56.0 59.3 carbohydrates g 2.5 2.1 minerals g 3.7 3.5 vitamin A mg 20.5 1.79 vitamin E mg 215.0 5.60 palmitic acid C16:0 g 13.10 12.80 stearic acid C18:0 g 2.10 4.30 palmitoleic acid C16:1 g 0.24 4.10 oleic acid C18:1 g 16.96 26.40 linoleic acid C18:2 g vitamin F 21.41 10.80 linolenic acid C18:3 9 vitamin E 2.85 1.65 arachidonic acid C2o:0 g 0.10 0.30 g 0.01 0.10 fatty acid C22:0 g 0.01 0.10 fatty acid C22:6 lecithin (egg) mg 12,40 0 12,500 cholesterol mg 200 3,015 sitosterol mg 138 0 stigmasterol mg 52 0 campesterol mg 48 0 The above Table shows the ade available by possibilities m the invention when usi ng different oils (in this case vegetal soybean oil and palm oi l) in the extraction:

1. lowering the cholesterol more than 90 %, content by 2. practically unchanged lecithin, content in egg 3. increasing the provitamin content ten-fold, A

4. increasing the provitamin content forty-fold, E

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5. increasing the provitamin F content about 100 %.
EXAMPLE 5.
The processing is that of Example 3. However the after-treatment each time with 0.5 liter soybean oil took place not 5 four times, but eight times. The residual cholesterol in the powder egg now was only 51 mg/100 g of powdered egg, the total sterol content being 210 mg/100 g of powdered egg. This is a cholesterol rinsing rate of about 98 %.
Regarding the Examples discussed above, it may be concluded 10 that the oil content of powdered yolk can be substantially lowered using an efficient centrifuge or by extended after-centrifuging, the residual cholesterol content then being reduced again. A similar effect is achieved by passing the inert rinsing gas of Example 3 in pressurized manner through the egg substance.

In order to test the quality, powdered egg prepared in the manner of Example 4 was admixed in lieu of fresh yolk into 80 %
mayonnaise, 50 % salad mayonnaise, 25 % salad dressing and into egg-butter cream.
Standard recipes were used, each time exchanging 15 g of fresh yolk specified in the recipe with 7.65 g of the powdered yolk prepared in the manner of the invention and dissolved in 7.65 g water. In each case the quantity of yolk of the mayonnaise/dressings was 7.5 % of the oil content relative to fresh yolk. Fresh yolk is converted into spray-dried powdered yolk in the following manner:
WEIGHT OF AN AVERAGE EGG = 50 g egg shell 6 g proportion of yolk 15 g / spray-dried 7.65 g egg white proportion 29 g / spray-dried 3.77 g SUM 5o g 11.42 g Independent testers evaluated the products made from stan-REPLACEMENT SHEET
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~12~~~0 dard recipes using low-cholesterol powdered egg yolk. All products were rated "good" for appearance (same optical image), consistency (creaminess and feel to palate) and taste. No after-taste or other significant difference with products from fresh yolks was found.

Furthermore, according to the naturally found proportions, 7.65 g of the powdered yolk prepared in the manner of Example 4 were mixed with 3.77 g of spray-dried protein powder and thereby 11.42 g of a product evincing the composition of whole-egg powder were obtained. Batches of 11.42 g of this product when dissolved in 32.58 ml water were easily processed in lieu of eggs in various recipes.
To demonstrate for instance the comparable quality of whole egg products so prepared, the following dishes were prepared as if in a kitchen and then tested:
a) scrambled egg with bacon b) noodles c) omelets/pancakes d) mixed cake with sand tart e) doughnuts.
First a ready-mix was prepared for the products c), d) and e) corresponding to US industrial recipes; (a "ready-mix" is a pre-mixture containing all components such as eggs, spices etc and requiring only being stirred with water and milk prior to preparation). Again when testing the appearance and the taste, no perturbing difference over normal egg made comparison products was found.
The Examples 8, 9 and 10 below concern treating natural egg yolk and egg yolk processed in the manner of the invention with supercritical fluids. All three tests were carried out under the same, following conditions:
1) The yolk used as the initial material was dried to 2 %
residual moisture using pre-dried inert gas at 50°C, REPLACEMENT SHEET
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212$20 2) The extraction vessel (diameter = 11.5 cm) was filled with 1,000 g of egg product without raising the pressure, 3) extraction was carried out with pure COZ
at 40°C, a pressure of 5,000 psi and a flow of 33 g COZ/h per gram of yolk.

Normal, commercial powdered egg yolk was dried as stated above to a residual 2 % moisture and was loosely filled into the extraction vessel. Extraction was carried out as in point 3) for 4.5 h. When opening the apparatus, it was found the gas had formed channels and hence that extraction had taken place irregularly in the extraction cake. The loss in weight of the powdered egg was 35 %, the residual cholesterol content of the extracted yolk was 1.34 %.

Powdered egg yolk was washed with soybean oil in the manner of Example 3 and then was granulated in a fluidized-bed granulator to a grain size of 1 - 2 mm and dried to a residual moisture of 2 %. The dried yolk so prepared was filled into the extraction vessel and then was extracted under the conditions listed in the above point 3) for 3.5 h. The weight loss of the yolk granulate was 37 %, the residual cholesterol content of the extracted yolk was 0.069 % for a total sterol content of 0.11 %.
EXAMPLE 10:
Processing was carried out essentially as in Example 9 except that 1.5 % of a mixture of cooking salt and calcium citrate was added to the yolk powder prior to spray-drying.
Extraction lasted about 3 h. The weight loss of the yolk granulate was 43 % for an oil yield of 41.1 %, the cholesterol content being 0.031 % and the sterol content was 0.07 %.
The course of extraction in Examples 8, 9 and 10 is shown in REPLACEMENT SHEET
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the attached graph.
By using powdered eggs with lowered oil contents (see note in Example 5), it is possible to improve the economy of C02 extraction which -- as shown by the attached graph -- is poorest in Example 8 and best in Example l0.
In a further analysis, the egg granulate prepared in Exam-ples 9 and 10 evinced a practical absence of fat. Both granulates were creamy-white, lacked odor and evinced a slight yolk taste. Furthermore they were well soluble, and the lecithin content converted into fresh yolk practically was the same as the content of untreated yolk. Accordingly the granulates of Examples 9 and 10 are well suited for recovery diets rich in protein and lecithin.
The last Example 11 concerns the vegetal oil used as extrac-tant in the methods of Examples 1 through 4. This vegetal oil following extraction was collected separately and then treated as follows:
The extraction oil separated from the powdered yolk and the extraction oil obtained from the first after-rinse were com-biped. Analysis showed the following composition:
Total sterol content: 1,442 %
of which cholesterol 0.945 %
stigmasterol 0.065 campesterin 0.178 sitosterin 0.254 and lecithin 0.0099 The combined extraction oils were stored at 20°C for 3 days and on further days at 10 to 12°C.
During this time waxy components settled at the bottom. The clear supernatant substance was decanted, the murky bottom substance was centrifuged at 10°C or forced out by a filter press.
The cholesterol was recovered from the clear oil by known procedures such as enclosure compounds and by extraction.
Following this treatment the clear oil could be used in many REPLACEMENT SHEET
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applications, for instance as emulsifier, flavoring agent (aroma) or yolk colorant.
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Claims

1. A method for the preparation of a dietetic, cholesterol-reduced whole egg or egg yolk product, wherein cholesterol and lipids are removed from the yolk, said method comprising the steps of:
(a) dehydrating the whole egg or yolk substance by spray drying;
(b) forming a grain size of about 150µ to about 300µ;
(c) suspending the spray dried egg substance in a liquid food oil or a mixture of liquid food oils while maintaining the grain size;
(d) dispersing the cholesterol and lipid fraction from the spray dried egg substance in the liquid food oil while maintaining the grain size; and (e) removing the cholesterol and lipid fraction enhanced liquid food oil.

2. The method of claim 1 wherein the grain size is formed by spray drying.

3. The method of claim 1 wherein the grain size is formed by agglomeration.

4. The method of claim 1 wherein the suspending, dispersing and removing steps are repeated at least one more time.

5. The method of claim 4 wherein the suspending, dispersing and removing steps are repeated at least one more time and in the last removing step, only a portion of the cholesterol and lipid fraction enhance liquid food oil is removed.

6. The method of claim 1 wherein the liquid food oil is selected from the group consisting of a cholesterol-reduced egg oil, a mixture of liquid food oils containing a cholesterol-reduced egg oil, a vegetal oil, a mixture of vegetal oils, and mixtures thereof.

7. The method of claim 1 wherein the liquid food oil is removed by centrifuging, decanting, separation, or filter pressing.

8. The method of claim 4 further comprising the step of extracting the egg substance with supercritical fluids after removing the cholesterol and lipid fraction enhanced liquid food oil.

9. The method of claim 4 wherein the egg substance is agglomerated to form a grain size of about 0.5 mm to about 2 mm; and further comprising the step of extracting the agglomerated egg substance with a supercritical fluid after removing the cholesterol and lipid fraction enhanced liquid food oil.

10. The method of claim 8 further comprising the step of adding about 0.1 to 2% of an electrolyte to the whole egg or yolk prior to dehydrating the whole egg or yolk.

11. The method of claim 9 further comprising the step of adding about 0.1 to 2% of an electrolyte to the whole egg or yolk prior to dehydrating the whole egg or yolk.

12. The method of claim 8 further comprising passing an inert gas through the egg substance during the extracting step.

13. The method of claim 9 further comprising passing an inert gas through the egg substance during the extracting step.

14. The method of claim 4 wherein the suspending, dispersing and removing steps are repeated at least one more time and in the last removing step an inert gas is passed through the egg substance.