CA1247929A

CA1247929A - Soybean products

Info

Publication number: CA1247929A
Application number: CA000433360A
Authority: CA
Inventors: David A. Lewis; Victor M. Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-08-05
Filing date: 1983-07-27
Publication date: 1989-01-03
Also published as: JPH043939B2; FR2531319B1; GB8408341D0; WO1984000476A1; SG75587G; GB2135566B; JPS59501494A; FR2531319A1; ZA835518B; GB2135566A

Abstract

ABSTRACT
The invention relates to a method of producing a bland tasting full fat soy flour meal or grits (PSM) wherein the soybeans either whole or split are treated with live steam or water under atmospheric pressure at temperatures ranging between 85 to 100°C for 2 1/2 to 20 minutes or for an equal or shorter period under steam pressure in excess of atmospheric pressure, the combination of time and temperature under steam pressure in excess of atmospheric pressure being such that the degree of blandness in the resultant PSM is about equivalent to the blandness which results in the stated treatment under atmospheric pressure.
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Description

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Thls invention relates to soybean products for human consumption.
The need to utilise vegetable protein directly for human food is widely acknowledged and it is also qenerally known that soybeans contain a high proportion of protein and a valuable oil content.
Soybean crops are grown in very large tonnages in many regions of the world. However, the major proportion of the world soybean crop is used for the extraction of oil with the consequent production of huge tonnages of defatted soy meal or cake. Most of this meal or cake is used as stockfood.
Defatted soy meal, while high in protein, has an unacceptable flavour for use in human food, having a strong beany or bitter flavour and only as the result of expensive and capital-intensive further processing can this meal be converted into forms which are more acceptable to human taste. Even so~ a residual beany flavour usually persists which substantially reduces its consumer acceptance.
In some cases where the meal is intended for human consumption special steps are taken in the oil extraction and associated steps to improve the flavour, however the resultant meal still suffers to some degree from the above mentioned disadvantages.
If whole soybeans are simply ground to a meal or flour, the flavour is objectionable being described as ,, .

7~:3~ 3 "green", "painty" and "raw" such 1avours being a consequence of the enzymatic activity in the full-fat soy flour so prepared. What is more, raw soybeans or flour prepared therefrom contain certain anti-nutritional factors which affect digestion and absorption of food. It has been proved that it is very important to reduce substantially such factors in such soybean products for human consumption.
Since the mentioned anti-nutritional factors are rendered inactive by heat, it has become common practice to subject soybeans to heating, for example, toasting, and a similar toasting process is used to improve the nutritional quality of defatted soy bean meal or flakes after extraction of soybean oilsO However we observed that all commercially available full fat soy flours or defatted soy flours which we have examined still have a noticeable "beany" or "bitter" flavour and therefore are generally unsuitable for human food unless used as a very low proportion ingredient in food and/or used in conjunction with flavouring substances which will hide the "objectionable" flavours.
Mustakas et~al (U.S. Patent 3,290,155) have described a process for producing a superior full-fat soy flour usin~
dehulled full-fat soy bean flakes or grits as a raw material in conjunction with a screw-type extruder in which the soy material is heated to 115-145~C under a dynamic pressure of 375-400 p.s.i. so as to expel from the soybean flakes as much soy bean oil as can be resorbed by the flakes on release from the pressure zone. Even with the use of such specialised equipment, we observe that the full-fat soy flour still has the mentioned beany flavour, which carries over into food products prepared therefrom Further methods are described in the prior art whereby use of elevated temperatures on pre-hydrated soyabeans results in slightly improved edible properties. (Tussaud in UX Patent 364,309 used the action of sulphur dioxide at a temperature of 110C-140C for 25-40 minutes on soybeans which had been soaked in about 2 1/2 times their weight of water resulting in a final moisture content of 4 1/2%). Other methods use live steam in contact with whole or dehulled and split soybeans for periods of time, such as 25-40 minutes at 100C or about 5-10 minutes at an elevated steam pressure and a temperature well in excess of 100C but typically 120C-130C. We have observed that the resultant products display a noticeably beany flavour whicb limits their use to very low percentages of use in a food product.
In the preparation of many foods it is desirable to add extra protein of high quality. Many of such foods contain fats or oils. Full fat soy flour normally contains about 40~ of protein and about 18-20~ soy bean oil. Soy bean oil is of hiqh quality and includes a high proportion of unsaturated fatty acids a characteristic which is considerecl pre:Eerable for health reasons over more saturated fats.
In consequence it would be highly desirable if soy flours could be added to foods in any desired proportion without encountering the problem of off-flavors referred to and without the necessity of adding supplementary flavoring substances for the purpose of masking objectional flavors.
The invention resides in a method of processing soybeans, which comprises the steps of:
(a) treating dehulled soybeans (1) with live steam or water under atmospheric pressure, the soybeans being held at temperatures from 85 to 100CC for

2 1~2 to 20 minutes; or (2) with live steam under pressure in excess of atmospheric pressure or hot water under steam pressure in excess of atmospheric pressure, for a time period sufficient to avoid green, painty or raw flavors developing in the soybean product on storage but short enough such that beany or bitter flavors do not develop in the product; and (b) compressing the beans as they exit from step (,a) to flatten them and form a p~urality of cracks or fissures throughout the beans while allowing the beans to cool.
The invention further resides in a method of processing soybeans, which comprises the steps of treating dehulled soybeans with live steam or hot

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water under atmospheric pressure, the soybeans being held at temperatures ranging from 85 -to 100C for 2 1~2 to 20 minutes; thereafter compressing the soybeans to flatten them and form a plurality of cracks or fissures throughout the soybeans while allowing the beans to cool; subjecting the flattened soybeans to extraction by water to remove a substantial proportion of oligosaccharides therefrom; and thereafter reducing the flattened soybeans to a flour, meal or grits.
The invention still further resides in a method of processing soybeans, which comprises treating dehulled soybeans with live steam under pressure in excess of atmospheric pressure or hot water under steam pressure in excess of atmospheric pressure, the -treatment being continued for such a time period as to avoid green, painty or raw flavors developing in the soybean product on storage, the treatment being short enough that beany or bitter flavors do not develop in the soybean product; thereafter compressing the soybeans to flatten them and form a plurality of cracks or fissures throughout the soybeans while allowing the beans to cool; subjecting flattened soybeans to extraction by water to remove a substantial proportion of oligosaccharides therefrom; and thereafter reducing the flattened soybeans to a flour, meal or grits.

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The invention also resides in PSM (processed soy material) produced in accordance with the men-tioned process.
The beans are reduced in size for example by rolling as they exit from the steam treatment. The reasons for this are that the cooling of the beans is facilitated and the beans are softer when they are steaming hot so that less energy is needed for size reduction. Additionally, it is more economical and quicker to carry out a subsequent drying step (where this is required) after the beans have been so reduced in size.
If the beans are dehydrated after steaming it may be necessary to further pulverise the material after dehydration depending on the physical form and the ultimate use of the material. This further pulverising operation is very simple to carry out and because the beans have already been partly pulverised immediately after steaming only low energy consumption is involved in further pulverising operations.
A further advantage is that less heat is generated during grinding because the beans have already been partly pulverised.
For certain applications or for certain market areas it may be desirable to remove a substantial proportion of the oligosaccharides from soy beans, especially stachyose and rafEinose. This operation ~... . .

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may be easily incorporated into the process after the compression step in which the beans are compressed by passing them between smooth rollers in a roller mill set at a gap of 0.6 - 1.0 mm. The beans will exit from the mill in a well flattened out but in otherwise intact form.
The flattened beans while still hot may be subjec-ted to the percolating and extracting action of water, preferably hot, either on a batch basis, or preferably in a continuous operation for example by counter current ex-traction. The use of a basket ~ centrifuge or a con-tinuous centrifuge is a convenient final step before drying. Because the beans have been reduced in thickness and have a sintered structure induced in them as a consequence of the hot rolling operation, the soluble oligosaccharides are readily eluted~ The flattened beans remain intact. The extracted soybeans may then be further pulverised and/or dehydrated as described, or may be used directly in the preparation of other food products.

When processin~ c~ PSM is carriecl out at 100C, a treatment time of 7-12 minutes is preferred for many applications. However, where considerable further heating may be involved in the manufacture of the ultimate food product in which PSM is a significant `~ - 8 -~ .

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component, a period of treatment at 100C in steam of 2 1/2 - 5 minutes is preferred. This is because there exists the po-tential for contained PSM to develop to a degree some beany or bitter flavors if the food product in which the PSM is a component is held at an elevated temperature for an excessive period of time.
With regard to use of steam under pressure, examples show that to achieve an equal degree of blandness in the PSM as is achieved at 2 1/2 -20 minutes at 100C, the period of treatment is considerably shortened. Thus, treatment of dehulled split soybeans for 2-2 1/2 minutes at 135C
(103 X 10 N/m tl5 psi) gauge) is about equivalent to 20 minutes at 100C.
If it is desired to use steam under pressure, it will be necessary to carry out test runs to determine the - 8a -124'7~2~

duration oE heat treatment in live steam under a particular pressure (i.e. at a particular temperature in excess of 100C) which will result in the desired bland tasting product. The treatment will need to be long enough to avoid green, painty or raw flavours de~eloping in the PSM
on storage, but short enough so that beany or bitter flavours do not develop in the PSM.
It will be apparent to persons skilled in the use of pressure steam treatments that a wide range of temperatures may be achieved according to the pressure of steam used.
person of reasonable skill will be able to establish by preliminary tests based on the experience recorded herein, a temperature (pressure)/time combination which is appropriate for the available processing facilities and which will produce a suitably bland-flavoured PSM.
When particulate split soybeans are treated a~
increasingly elevated temperatures, the temperature differential between the surface and the center of a bean becomes greater. This leads to an increasing degree of overheating of the surface by the time the center is processed adequately to avoid "green" or "painty"
flavours. Thus, use of temperatures for processing in excess of about 120C results in products which tend to be less bland, even though the duration of the heat treatment is reduced, because the surface of the beans has been processed to the "beany" or "bitter" stage.

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7~ 3 The PSM produced according to the invention generally has a protein content of about 40-42% and a fat content of about 20-21% when prepared from dehulled beans depending on the composition of the original soybeans. The PSM thus produced represents an important source of high quality fat, as well as protein. The low cost of processing soybeans into PSM coupled with its extreme blandness of flavor, makes it a very sui-table ingredient for use in many fat-containing foods in which other commercially available full fat soy flour or other types of soy flours are unsuitable because of the residual beany flavor of the latter.
In the preferred embodiments of the invention, soybeans are processed to produce full fat soy flour, meal or grits in such a way that the end product, hereafter referred to processed soy material (PSM) is free or substantially free of the mentioned "beany", "bitter", "painty", "raw" or "green" flavors, and of such bland character that it may be used as or in food products suitable for human consumption in substantial proportion so that significant improvement in protein content thereof i~ achieved.
With the preferred embodiments of the invention, the nutritional quality of the PSM is maximised for human food use so that there be no problems from residual anti-trypsin factors or other anti-nutritional factors.

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In accordance with the preferred embodiments o~
the invention, the process is economical to carry out and does not require the use of expensive or specialised equipment.
In the preferred embodiments of the invention, the process has a low energy requirement and is capable of being operated by persons of reasonable skill but not requiring persons having a high degree of technical training and specialised skills.
The preferred embodiments of the invention can provide PSM which when dried is stable under atmospheric conditions and is able to be stored for long periods of time in a dry state without significant deterioration.
The preferred embodiments of the invention can pro-videPSM which should be capable of being used in the manufacture or preparation of more-or-less conventional foods which have a ready acceptance in all or most parts of the world. This is an important consideration since it is often found very difficult or impossible to introduce foods of special nutritional quality to peoples in need of such nutrition unless the foods are similar to or identical with the styles of foods with which such peoples are familiar.
We have found that the development of "green", "raw" or "painty" flavors is caused by the action of the enzymes of soybeans on the oil in the soybeans when the natural integral structure of the soybean is r~ ~s .~

partially or wholly destroyed by mechanical processing.
Whereas prior art methods describe the use of heat, applied in a variety of ways, as a means of producing full fat soy flours, surprinsingly we have found it is the very use of heat as previously described which can be in fact responsible for the development of "beany" and "bitter" flavors.
Thus we have found that he development of "beany" and "bitter" flavors can be caused as a consequence of subjecting the soybean material to time/temperature conditions beyond certain limits.
Experiments have shown that development of these undesirable flavors is not an "all or nothing"
phenomenon but that there can be a progressively increasing objectionable flavor developed in the soybean material as the time/temperature exposure ncreases.
Furthermore, we have also found that the same holds true for products which include a substantial proportion of PSM. If the product is subject to excessive time/temperature exposure the undesirable beany flavor can be induced in the prepared product even though the PSM used as a major ingredient at the commencement of the manufacturing process was bland in flavor. We have discovered, that as long as these principles are understood, it is possible to produce a wide variety of highly acceptable high protein foods, consisting of or containing PSM all having excellent storage life.

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The following examples illustrate the invention.
Example 1 Soybeans used were of sound quality, well cleaned and free from extraneous weed seeds and other materials. In carrying out the dehulling operation, the following steps were followed:
A) the beans were ~irst heated in a stream of hot dry air at a temperature of 90C for 5-8 minutes, or until the hulls become a little loosened from the cotyledons. It is only necessary that the hulls have become loosened to the extent that the entire hull can be easily removed by rubbing in the palm of the hand.
B) the warm surface-dried beans are passed through a hulling machine in which the beans are abraided against - 12a -,~ -'7~
themselves and also against an abrasive element which is included in such machines. Xt has been found that an abrasive rice whitener is very suitable for this purpose.
Machines manufactured by Satake Engineering Co. Ltd. of Tokyo, Japan, in particular model HS-2B have been found suitable for the dehulling step. It is important that the hulls are separated with a minimum of mechanical damage being done to the cotyledons, such as scratching, cracking or breaking. Avoidance of mechanical damage is especially important if the hulled soybeans are to be stored from some period of time prior to further processing. The reason for this is that when the cells of the soybean cotyledons are physically damaged at this stage, the enzymes present begin to react with the contained soybean oil, resulting in development of off flavours, especially "painty" or "green"
flavours or aromas.
C) the dehulled soybeans are then separated from the hulls as completely as possible, using aspiration equipment. At the same time the dehulled soybeans may be cooled down, which is especially important if the dehulled material is to be stored for some period of time before further processing.
D~ the dehulled soybeans were then subjected to a controlled heat treatment. The degree of heating of the beans is determined to some extent by the use to which the ultimate PSM will be put. In the example being described ~L2~L7~2~3 the dehulled soybeans are placed in a well insulated batch-type steamer so arranged that the steamer is filled from the top, and emptied from the bottom at the end of the steaming period. Live steam is fed into the soybeans through a vertical perforated tube running almost the full vertical length of the steamer. A supply of dry potable steam at atmospheric pressure is passed through the soybeans until the beans reach a temperature of 100C, as indicated by a thermometer as well as by the observation that live steam is escaping from the top of the mass of beans. The steam flow is maintained so that the beans are held at 100C for ten minutes. Then the steam is turned off and the hot steaming beans are dropped from the steamer into an insulated container.

While still very hot the soybeans were passed between smooth rollers in a roller mill with the gap between rolls set at 0.4mm. The soybeans exit from the mill in a flaked condition, the flakes having a plurality of cracks and fissures throughoutO The soybeans cool down to some degree during rolling due to loss of steam from the beans, especially as th~y are flattened by the rolls.
The soybean flakes were further dried in a forced draft dehydrator using hot air at an inlet temperature of 90C. The temperature of the flakes is kept below 80C. Because the flakes are very thin, and have a fractured structure they dry very rapidly in the '7~3Z~

dehydrator. The soybeans are dehydrated to about 3-4%
moisture content and cooled to 30C or less: theY may then be pulverised in a grinder to a deqree of fineness suitable for ~urther use applications.
In an alternate method the dehulled and split soy beans are fed at a uniform rate through a trap into a continuous steamer. This consists of a well insulated horizontal trough in which is turning a helix and paddles, the speed of which can be varied b~ an appropriate speed controller. Potable steam is injected into the base of the trough through a plurality of orifices. Thus as the split soybeans enter the trough through the trap they are subjected to rapid heating by live steam and are simultaneously mixed by the paddles to ensure uniform heaing and are transported through the steam zone. The speed of rotation of the helix is adjusted so that the residence time of the dehulled and split soybeans at 100C is 10 minutes. The treated beans exist from this continuous steamer directly into the nip of the smooth rolls of a roller mill described above, then are ~urther processed by dryinq and pulverisinq as described.
The pulverised PSM produced from the flaked dried soybeans had almost no flavour, being quite bland. The minimal flavour which could be detected is a pleasant slightly sweetr bu~tery, egg-like flavour. The PSM was completely lacking in any beany or bitter flavour, and was also lacking in painty or green flavour.

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Dehulled soybeans were treated as in example l except that the final dehydration step was omitted. The cooled flaked soybeans were frozen and packaged for further use then used as required in the preparation of various food products, for example for inclusions in high protein bread doughs. Alternately, the cooled flaked soybeans were used directly as an ingredient in high protein biscuits (cookies) without having to be held frozen. In this case the flakes were used in the manufacture o~ biscuits on the day of their manufacture, or held overnight in a cool-room.
Example III
Dehulled soybeans were processed as in example I
except that the time of steaming at 100C was varied to cover a range of periods of time, as shown. In each case the dried soya flakes were reduced to a fine meal usinq a laboratory grinder. The resultant soy flours were compared for flavour and appearance.

Time of steaming Colour of Flavour/aroma - at 100Csoy flour of soy flour -2 l/2 minutes light straw colour bland 5 minuteslight straw colour bland 7 minuteslight straw colour bland 10 minuteslight straw colour bland 15 minuteslight straw colour bland 20 minutesstraw colour almost bland and accepta~le as a bland product - 30 minutes darker straw colour slightly beany 40 minutes dark straw colour beany c~

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It ls apparent from the above results that with increasing time of steaming at 100C for longer than a~out 20 minutes there is deterioration in flavour of and appearance of the soy ~lour when tasted in the powdered form.
EXAMPLE IV
Dehulled and split soy beans were prepared as in example I (A,B,C) and were then subjected to a controlled heat treatment in heated water instead of in live steam.

The dehulled soybeans were added to an excess of water held at the temperatures and for the times shown in the results hereunder. The times of exposure were measured from the -time at which the temperature of the water returned to the stated temperature after addition of the dry dehulled beans.

After completion of each nominated heat treatment, the beans were removed from the water, quickly drained and weighed, then, while still hot, rolled into flakes, dried and pulverised as described in example I. The following observations were made to compare the various treatments:

Temp. of Duration Colour of soy Flavour/aroma of treatment of flour soy flour in water treatment 95C 20 mins Liqht straw Bland 95C 15 mins Light straw Bland 95C 10 mins Light straw Very slightly raw flavour 90 C 20 mins Light straw Bland 90C 15 mins Light straw Very slightly raw 85C 20 mins Light straw Almost bland 80C 20 mins Light straw Raw, green and painty .. ~

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It is apparent from the above results that whereas it is possible to produce a bland tasting soy flour or meal by subjec.ing t,he soybeans to heating for up to 20 minutes in water at 85C, the flavour quality of the resultant product is unacceptable if the temperature in water is at 80C for 20 minutes.
In an alternate method, the dehulled and split soybeans were fed continuously and at a controlled rate, into a continuous rotary wa-ter blancher in which the water was maintained at 95C. The speed of rotation of the screw section of the water blancher was controlled so that the beans were at 95C for a ~otal of 15 minutes ~efore being lifted from the hot water by the emptYing device on the blancher. The beans so treated passed across a dewatering screen, then fed while still very hot to a roller mill and were further processed as in example I to produce a dried and pulverised meal. The resultant product had a light straw colour and a completely bland flavour and aroma.
Comparat~ve ~xample I
Dehulled soybeans were processed as in exa~ple 1 except that instead of being steamed at atmospheric pressure at 100C, the beans ~ere steamed under pressure at 120C Eor periods of 2 1/2, 5, lO and 20 minutes. The following observations were made:

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Time of Pressure Colour of ~oy Flavour/aroma Steaming at 120C Flour of soy flour 2 1/2 minutes straw colour slightly beany 5 minutes dark straw colour beany 10 minutes light brown more beany 20 minutes medium brown very beany It is apparent when soybeans are treated at a temperature of 120C, as compared to example 3 (100C) 2 1/2 minutes exposure at 120C is approximately equivalent to 20-30 minutes at 100C as far as development of the beany flavour is concerned. Along with increase in beany flavour, there is also a pronounced darkening of the soy flour.
Example v Dehulled split soybeans were steamed in batches as described in Example I, except that the beans were held at 100C for quite short periodsr ranging from 30 seconds to 2 1/2 minutes, with an unheated control treatment. The heat-treated beans were flaked, dried and further pulverised as described. The unheated control was simply puLverised in the raw state. There was a marked range of flavour characters in the treatments as follows:

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Heat treatment - number E'lavour of soy flour of minutes at 100C (tasted 30 days after (steam heated) processin~) .0 mins Very raw,green,painty flavour 0.5 mins Raw, green, painty flavour 1.0 mins Raw, green, painty flavour 1.5 mins Less raw,green,painty flavour 2.0 mins Slight "raw'l flavour 2.5 mins Bland flavour It is apparent from this test that, under the above conditions of steaming of dehulled split soybeans, 2-2 1/2 minutes at 100C is the threshold minimum range for preventing the development of green, painty or raw flavours in soy flour~
EXA~IPLE VI
Dehulled soybeans were processed as in example V

except that instead of being processed in steam under pressure in excess of atmospheric pressure at a temperature of 120C, the beans were processed at higher temperatures. To achieve this on a batch basis, it was ne~essary to use a small pressure vessel with a quick release lid.

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Temp. in Duration Colour of soy Flavour/aroma of steam of flour soy ~lour under treatment pressure .
130C 0.5 min. straw slightly raw flavour 1.0 min. straw bland 1.5 min. dark straw reasonably bland 2.0 min. dark straw slightly beany 2~5 min. fawn beany 135C 0.5 min. straw bland 1.0 min. straw bland 1.5 min. dark straw slightly beany 2.0 min. fawn beany 2.5 min. light brown beany It is apparent from these results that with treatment in steam at increasing temperatures, time required to eliminate the green, raw or painty flavour is reduced.
Likewise the time required to induce a beany flavour is reduced.
It will be realised that a degree of delay is involved in reducing the pressure after each steam treatment so the beans can be removed from the vessel, and a similar delay is involved in each treatment.
It was observed that the flavour quality o~ a soy flour produced in steam at 100C and described as bland is of superior flavour as compared to the bland treatments produced at higher temperatures. It is believed that this may be because the surface of an individual soybean reaches a higher temperature when treated at, say 130C before the centre of the bean reaches a temperature adequate to prevent development of a raw flavour in the centre tissue.
At that stage, the surface tissue may have then 79~

already developed a degree of beany flavour. The final flour may thus be a mixture of different flavour ~ualities to a greater extent than for treatments carried out at a lower temperature.
The foregoing examples are illustrative of the invention only and it will be appreciated that various times, temperatures and pressures may be selected within the ranges disclosed which will result in the production of a satisfactory productO
In order to evaluate the importance of the invention, the various samples of processed beans prepared as referred to herein were incorporated into a liquid formulation, in which form an~ flavour chanqes became ver~ perceptible to the palate. The liquid formulation used was in the nature of a milk-like beverage. The hulled soybeans variously treated and at ~% moisture content (103.g) were added to 1 litre of water to which had been added O.9g sodium bicarbonate. This was brought to the boil, then simmered 10 minutes. The weight of this was restored to the initial weight, then the mixture was ~lended in a liquidizer at full speed for l minute. To this was added 9g of bland vegetable oil, lg salt (NaCl) and 12.5g of sugar, and the mixture was blended for a further 1 minute at full speed.
The mixture was then homogenised in a laboratory homogeniser. The "milks" were chilled overnight, then tasted.

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Steaming treat- Flavour of Colour of Comments ment to which "milk" "milk"
hulled soybeans prepared had been exposed from product 2 1/2 mins Bland flavour Milky white Very 100C acceptable 5 mins Bland flavour Milky white Very 100C acceptable 10 mins Bland flavour Milky white Very 100C acceptable 20 mins Very slightly Slightly Reasonably 100C beany note darker acceptable 40 mins Slight beany Light brown Unacceptable 100C note colour 2.5 mins Very slight Light brown Reasonably 120C beany note colour acceptable 5 mins Slight beany Light brown Reasonably 120C note colour acceptable 10 mins Obvious beany Browner Ob~ectionable 120C flavour 20 mins Strong beany Quite browned Objectionable 120C flavour These results show that the flavour and colour differences between the various heat treatments follow through into a food product in which they are used.
Quite clearly, by use of other flavourants or seasonings it is possible to disguise a mild degree of beany flavour in a prepared food. However, the need to do this represents a serious limitation to the general utilisation of normal full fat soy flours.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of processing soybeans, which com-prises the steps of:
(a) treating dehulled soybeans (1) with live steam or water under atmospheric pressure, the soybeans being held at temperatures from 85° to 100°C for 2 1/2 to 20 minutes; or (2) with live steam under pressure in excess of atmospheric pressure or hot water under steam pressure in excess of atmospheric pressure, for a time period sufficient to avoid green, painty or raw flavours developing in the soybean product on storage but short enough such that beany or bitter flavors do not develop in said product;
(b) compressing the beans as they exit from step (a) to flatten them and form a plurality of cracks or fissures throughout the beans while allowing the beans to cool.

2. A method as claimed in claim 1, wherein the beans are subsequently reduced to a flour meal.

3. A method as claimed in claim 1, wherein in step (a) said beans are treated at temperatures ranging from 100° to 135°C for 30 seconds to 20 minutes.

4. A method as claimed in claim 1, wherein in step (a) said soybeans are treated with live steam or hot wa-ter under steam pressure of 103 x 103 N/m2 (15 psi) gauge for 2 1/2 minutes.

5. A method as claimed in claim 1, wherein in step (a) said beans are treated at temperatures ranging from 85 to 100°C for 2 1/2 to 15 minutes.

6. A method as claimed in claim 2, wherein the flattened soybeans resulting from compressing step (b) are dehydrated while keeping their temperature below 80°C prior to the step of reducing said flattened soy-beans to a flour, meal or grits.

7. A method of processing soybeans, which com-prises the steps of treating dehulled soybeans with live steam or hot water under atmospheric pressure, the soy-beans being held at temperatures ranging from 85° to 100°C for 2 1/2 to 20 minutes; thereafter compressing the soybeans to flatten them and form a plurality of cracks or fissures throughout the soybeans while allowing the beans to cool; subjecting the flattened soybeans to ex-traction by water to remove a substantial proportion of oligosaccharides therefrom; and thereafter reducing said flattened soybeans to a flour, meal or grits.

8. A method as claimed in claim 7, wherein said soybeans are held at temperatures ranging from 85° to 100°C for 2 1/2 to 15 minutes.

9. A method as claimed in claim 7, wherein the extracted soybeans are dehydrated while keeping their temperature below 80°C prior to reducing them to a flour, meal or grits.

10. A method of processing soybeans, which com-prises treating dehulled soybeans with live steam under pressure in excess of atmospheric pressure or hot water under steam pressure in excess of atmospheric pressure, said treatment being continued for such a time period as to avoid green, painty or raw flavors developing in the soybean product on storage, said treatment being short enough that beany or bitter flavors do not develop in said soybean product; thereafter compressing the soybeans to flatten them and form a plurality of cracks or fissures throughout said soybeans while allowing the beans to cool; subjecting flattened soybeans to extrac-tion by water to remove a substantial proportion of oli-gosaccharides therefrom; and thereafter reducing said flattened soybeans to a flour, meal or grits.

11. A method as claimed in claim 10, wherein the extracted soybeans are dehydrated while keeping their temperature below 80°C prior to reducing them to a flour, meal or grits.

12. A method as claimed in claim 10, wherein said soybeans are treated with live steam or hot water under steam pressure of 103 x 103 N/m2 (15 psi) gauge for 2 1/2 minutes.