GB2087897A - Process for producing a soy- bean extract, and extract obtained thereby - Google Patents

Abstract

A process for preparing a water- soluble, soybean extract having a high proteinic value, comprising heating defatted soybean flour to remove moisture, solvent residues and to effect a partial sterilization, whereafter the material is subjected to aqueous phase extraction at boiling point and the boiled mixture is filtered so as to discard a solid cake (essentially cellulose), the filtrate is boiled and filtered again to discard a second insoluble fraction, the second filtrate being the liquid which contains the proteinic fraction of soybean as its nearly exclusive component, whereupon the liquor is evaporated to dryness and the expected soybean extract is ground, stored and packaged. The extract has a pleasant smell and taste, is fairly water-soluble and its proteinic contents is mainly in the form of amino-acids, thus readily assimilable.

Description

SPECIFICATION Process for producing a soybean extract, and extract obtained thereby It is a fact that it would be extremely advantageous to be able to replace foods based on animal proteins, which might be held responsible for a number of serious alterations in the metabolism, by a correct nourishment based on vegetable proteins: in this connection, the following literature sources can be indicated: Noseda, Fragiacomo, Bosia, Ramelli, Sirtori, Behandlung der Hyperilipidamie Typ II Soja Bohnen.. Schweizerische Medizinische Wochenschrift 47, 109, (1979); Sirtori, C. R.

Agradi, E., Conti, F. Mantero, O. Gatti,E.: Soybean-Protein Diet in the Treatment of Type II Hyperlipoproteinaemia, The Lancet, 5, 275-278 (1977); International Conference on Atherosclerosis, Milan, November 1977, Fondazione Lorenzini; Liebermeister H., Toluipur H., Senkung des Cholesterinspiegels durch Zusatz von Pektinen und Sojaprotein zur Reduktionsdiät, Deutsche Medizinische Wochenschrift, 10, 333 (1980).

Soybean is known long since as a source of vegetable proteins, since its seeds shows an average composition in which the protein contents is about 40%.

However, it has not been possible, up to now, to prepare any products which consisted exclusively of the proteinic fraction of soybeans and having acceptable organoleptic properties: in this connection, it is known that European and American peoples tend to reject in food the additions of soybean proteins as they are available today, for example in the form of flours or seeds of said Leguminosa plant, just because they are held unpalatable.

It would be desirable, in this respect, to have soybean proteins in the form of a concentrated product of pleasing taste and easy to administer, for example in a highly watersoluble form, thus ready for instant use.

Another problem connected with the use of the soybean proteins such as available today from the prior art has an outstanding importance as it has been ascertained that the capability of the human system to assimilate the raw soybean proteins is low: this is essentially due to the fact that the proteinic molecules of soybean are complex and would require, for a correct assimilation, to previously be split into simpler molecules, or, more particularly, into the fundamental aminoacids which compose them.

An object of the present invention is thus to provide a soybean extract, under an easily administerable form and having a satisfactory palatability, water-soluble both in the cold and the hot characterized by a high contents of proteins in the form of individual aminoacids, among which the essential and the non-essential aminoacids, and devoid of any substance foreign to the natural components of soybean.

In order that such an object may be achieved, this invention suggests a process for the preparation of a soybean extract having the properties enumerated above, characterized in that defatted soybean flour is subjected to the following steps: a) dry heat treatment, upon addition of distilled water in an amount of from 3% to 5%; b) extraction in aqueous phase at the boiling point temperature; c) filtration, upon cooling, of the aqueous mixture as obtained in said stage b), with consequential separation of a filtrate and a solid phase; d) boiling the filtrate as obtained at stage c) with attendant formation of a soluble fraction which contains the useful components of soybean and an insoluble fraction; e) filtration of the mixture as obtained in said stage d) in order to separate as a filtrate said soluble fraction from said insoluble fraction; and f) evaporation and drying of the filtrate coming from said stage e) to give said soybean extract.

The extract thus obtained is finally subjected to grinding, and then to storage or packaging.

It is appropriate to state, at the outset, that the starting soybean, which can be obtained, already in the state of a flour from oil-mills or Husbandry Associations, or which can be obtained prior to carrying out the grinding of the soybeans, must be defatted: this is mainly due to the fact that, as is known, the lipid fraction of soybean is mainly composed of glycerides, the esterifying fatty acids of which are partially unsaturated or unsaturated to a high degree, such as oleic, linoleic and linolenic acid, liable to originate phenomena of rancidity which would render the palatability of the extract at least questionable.

The working conditions provided by the process of this invention will now be described in greater detail hereinafter.

The treatment according to the stage a) is preferably carried out at a temperature above 100"C, preferably between 11 5'C and 120"C until a constant weight is obtained for the flour being treated, in a dryer, the operation being effected either statically or in motion. It is preferred that such a treatment is forerun by a laboratory test, working on a small amount of flour, 1 5 to 20 gram-samples being sufficient, in order to be able to preset the time required by the treatment.

When working under static conditions, Pyrex-glass or steel trays are brought in a thermostat to constant weight, whereafter the soybean flour is added and weighed both prior to the treatment and during progress thereof until a constant weight is read. A technical scale is used. The dry-heat treatment requires a period of time not shorter than 6 hours approximately.

As a result of this treatment, the flour takes a brown hue, a pleasant smell and is ready for the subsequent treatments.

On an industrial scale, the stage a) can well be carried out in motion (rotary kilns) by forwarding soybean directly from the storage bins to the kiln, by a screw convey or under these conditions, the duration of the treatment is shortened, especially if the rotary kiln is equipped with an exhausting system.

Soybean, after having undergone the dryheat treatment, is fed to an autoclave for carrying out the stage b). This stage b) is carried out by bringing to a continuous boil, under atmospherical pressures, or in a pressurized autoclave, the soybean flour in distilled water. The conveyance of the flour exiting the stage a) can take place by gravity, by arranging the autoclave opening just beneath the discharge end of the kiln, or by means of conveyor chains. The autoclave is fitted with a stirrer, either central or laterally mounted, a central stirrer with a gland being preferred, an inspection glass, a sheathed thermometer, a bottom sink, a heating jacket oprated with steam or by shielded resistors.

It is preferred to feed water first and then soybean, with stirring. The mixture is brought to a boil for a net time not shorter than 6 hours. The extraction and hydrolysis operation is denounced, after about 2 hours as from starting the heating, by an impressing foam production: this can be monitored only by reducing heating. The autoclave is fitted with a reflux column.

As the stage b) is over, the soybean-water mixture is allowed to cool to room temperature and then subjected to the filtration provided by the stage c): this is intended for separating, as the liquid fraction, a liquid phase which contains the useful components to be subsequently processed, and a solid fraction which is a filter cake.

It is advisable not to discontinue the stirring of the mixture after boiling, or during cooling, to prevent jamming the discharge gate of the autoclave. Cooling can be effected in the autoclave itself by having cool water flowing through the jacket, if heating had been made by steam. If, conversely, heating has been made with an oil bath, it is more advisable to dump the oil into an open vat, still with stirring: the vat must have a discharge port.

As the mass has attained the environmental temperature, it is dumped into a centrifugation apparatus. Filtration is preferably carried out with a very-fine-mesh cloth and proceeds rather slow, so that centrifugation has proven to be the most suitable among the known filtering systems. It is necessary that a cake is obtained, which is a well dried solid residue in order to prevent the loss of active principles, and it is suggested that the filter cake is washed until the mother liquors do not react any more with an aqueous-alcholic solution of ninhydrin. It is appropriate that the centrifuging apparatus is positioned immediately beneath the discharge port of the autoclave or the cooling vat. The cake is prevailingly cellulose. The filtrate is a cloudy liquor, strongly coloured, having a pleasant smell.Its composition is rather complex: in addition to containing the proteins and the aminoacids, it contains a number of mineral substances coming from soybean (magnesium, calcium, manganese, iron and others), carbohydrates, prevailingly split (sucrose, raffinose, pentosans and others). lecithin and decomposition products of lecithin, cephalin and finally inositol hexaphosphates. Should this liquor be evaporated to dryness under atmospherical pressure or in a vacuo, a solid would be obtained which is highly hygroscopic, nearly insoluble in hot water and having both an unpleasant smell and taste.

It is thus imperative to insolubilize all the components foreign to proteins and aminoacids in order to remove them from the filtrate in question.

Just to this end, the stage d) of the process is performed and it can be carried out either under atmospherical pressure or in a vacuo.

The separation of the proteins and the aminoacids is obtained by boiling the filtrate coming from the centrifuge. The liquid extract must be boiled in an autoclave equipped with a central (or a lateral) stirrer, an inspection glass, a sheathed thermometer, a heating jacket, a bottom discharge port and a vacuum fitting.

As can be seen in the laboratory by operating with a sample of extract having a volume from 100 mls to 200 mis, the liquid, when boiled, becomes definitely hazy and a bulky precipitate is formed, which is composed of inorganic and organic phosphates, inositol hexaphosphates, a few globulins and, lastly, small amounts of fatty acids and fats. Thus, the liquor must be boiled until, taking a sample cooling and filtering, the filtrate does not become cloudy any more on further boiling.

It is not quite easy to forecast how such time this stage will require, but, as an average, a boiling time of about 3 hours should suffice.

Inasmuch as the subsequent stage of the process is the filtration of the entire extract, if heating has been carried out with steam, the operation can be extended to such an extent as to obtain a not too thick liquor in order that filtration may be more convenient.

Stage d) is characterized by a considerable foam build-up and this can be controlled by monitoring the heating temperature. Thereafter, the stage e) of the process is started, that is, the separation of the soluble extract from the insolubles. The liquid to be filtered in this stage has a volume which is nearly one third of the starting liquor volume. The filtration of this mass is a very cumbersome operation.

The centrifugal apparatuses fitted with filtering cloths have proven inadequate. Also the filtration by suction (filter papers, filtering diaphragms, filtering cartridges) may lead to an unsatisfactory results. On the contrary, the use of hydro-extractors (whizzers) has proven an advantage since these machines permit to separate the particles in suspension. In any case, the filtrate must be clear and should not become hazy on further heating. The insoluble residue which is left in the autoclave as well as in the centrifuge can easily be removed by washing it with an aqueous acidic solution of a mineral or an organic acid. Now, the stage f) of the process can be proceeded with, that is, the evaporation and drying of the liquid filtrate.The evaporation of the filtrate, preliminary to drying, can be carried out both on revolving rollers, and in usual static dryers with a slight air stream, and, also, in stirred autoclaves, both under normal pressure and in a vacuo. Irrespective of the adopted run, special care should be given to the selection of the material for carrying out the drying stage: the most suitable material has proven to be Moplen (Trade Mark by Montedison, a polypropylene resin). Moplen (Trade Mark) trays filled to about one half of their volume with the liquor to be evaporated and placed in a drying chest heated to a temperature not higher than 1 00'C, permit a quick drying when operating both under atmospherical pressure and in a vacuo.From among all the methods which have been tested, the latter procedure seems the aptest because it enables the trays, which contain the useful product in the form of a demoisturized block, to the grinding station. It suffices, now, to remove the solid from the trays by means of Moplen (Trade Mark) paddles to carry out the grinding of the so dried solids. The product can be powdered easily and the operation does not present any special difficulties. Care must be taken in cleaning the mill after grinding, in order not to jeopardize the subsequent frinding operations: it is imperative to wash with hot distilled water and to feed the washing liquids afterwards to the drying stage preliminary to grinding. The ground solids thus obtained can now be packaged. Packaging into individual dosage units or multiple dosage units must be carried out in a demoisturized atmosphere.

A summarized example of a practical embodiment of the process according to the invention is reported hereinafter, with particular emphasis to the substances being treated, the size of the apparatus used in the installation for carrying out the process and the times required to carry out the several stages.

EXAMPLE 1 20 g of defatted soybean flour to which 3% to 5% of distilled water has been added, coming from an oil mill, that is stripped of its liquid fraction which can be extracted under pressure or with solvents, are subjected to dry heat treatment for about 6 hours at 115"C-120"C in a dryer until the flour has a constant weight, that is, about 100 kg. The flour thus treated is subjected to the extraction stage with aqueous hydrolysis, to boiling for about 6i hours in an autoclave having a volume of about 1 500 litres, which has previously been charged with about 800 liters of distilled water. The selection of this volume is also justified by the fact that, during progress of extraction, an impressive foam build-up is experienced.The aqueous mixture thus obtained is subjected, upon cooling, to centrifugal filtration: this takes about 3 hours and the centrifuge can have such a size as to work in a single step or also in 2 or 3 sequential stages. Centrifugation produces a cake having a weight of from 50 kg to 85 kg (dry weight, as a function of the starting soybean material), and about 800 liters of filtrate. The cake is washed in the centrifuge and the washing waters are checked with an aqueous-alcoholic solution of ninhydrin. The filtrate is boiled in an autoclave for about 3 hours, to obtain a residual volume of about 250 liters. For this operation, the same autoclave as used in the previous aqueous extraction can be adopted.

Then upon appropriate cooling, the separation of the two phases, that is, the soluble and the insoluble, are proceeded with in a hydroextractor (whizzer), that which takes about 4 hours. The filtrate is subjected to evaporation and drying in Moplen (Trade Mark) trays in the interior of a dryer, under atmospherical pressure or in a vacuo, for a total time of 10 hours. The dried product is dumped into a mill and a quick grinding operation is effected, which is encouraged by the crumbliness of the product, whereafter the product is stored in evacuated chests or it is sent to packaging in a demoisturized atmosphere. The quantity of end product thus obtained may vary from 1 5 kg to 50 kg, consistently with the composition of the starting soybean material. The Maillard reaction has already taken place in the two initial stages.

In the process of the invention, the heat treatment of the defatted soybean flour in the stage a) has proven to be particularly critical, inasmuch as it has been ascertained that it conditions all of the subsequent stages. In this latter connection, it is observed that, if the defatted soybean material coming from the oil mills is to be stored for a long time, it is advisable to store it after having subjected it to such heat treatment.

The dry-heat treatment, according to the stage a), of the defatted soybean flour is directed to remove possible solvent residues and the moistures which are present therein and to forestall possible fermentation proc esses while concurrently effecting a preliminary and partial process of sterilization. As a matter of fact, is not unlikely to find an imposing bacterial contamination in the soybean flour coming from the mills or the Husbandry Associations.

Soybean flour which has not been subjected to such a preliminary heat treatment may undergo a considerable loss of its contents of aminoacids and extractable proteins, very presumably due to enzymic reactions.

Also the stage b) is outstandingly important to the ends of the invention, inasmuch as it permits to hydrolyze the soybean proteins by exploiting the action of the enzyme systems originally contained in the plant seeds, and also to extract from the starting material all the useful components which can be extracted. In addition, the aqueous extraction at the boiling point temperature involves also the destruction of the antienzymes, such as antitripsin, and of the growth-inhibiting factors.

The solid cake as obtained from filtration according to the stage c) of the process, as outlined above, is nearly entirely composed of cellulose. It may be used, upon drying and grinding, as a fodder additives or as a soybean bran, in tablets or otherwise, and is thus an appreciable by-product of the process.

Equally critical is the role played by the stage d) of separation of a useful soluble fraction, essentially consisting of proteins and aminoacids, from an insoluble fraction to be discarded. This residue is composed of phosphates and inositol hexaphosphates, both organic and inorganic.

In this stage, besides the protein hydrolysis, a number of hydrolysis reactions take place, which involve other components of the starting soybean, such as albumins, phosphorus compounds, lecithins, cephalins, carbohydrates and others. In this stage, all the components, the presence of which would have a detrimental bearing both on the organoleptic characteristics and on the solubility of the final extract, are removed by precipitation without using any reactants which could be a pollution source.

The soybean extract as obtained with the process of this invention is a coffee-coloured powder, definitely hydroscopic and fairly soluble (from 20% to 30% according to the temperature) in water, also cold. The pH of a 10% aqueous solution of the extract is about 4-4.2. At any rate, the pH of the extract in aqueous solution may vary according to the several types of starting soybean materials and thus to their different contents of aminoacids: these latter can be monoamino- or diamino monocarboxylic acids, or monoamino- or diamino bicarboxylic acids.

The composition of a sample of final extract according to the invention is reported by way of example hereunder.

Moisture at 105 'C 7.83% Proteins (Nx6.25) on the extract as such 41.43% Ash, on the extract as such 11.26% Carbohydrates, upon inversion on the extract as such 14.40% Composition, in terms of aminoacids, on the sample as such:: Aspartic acid 7.48% Threonine 1.40% Serine 1.66% Glutamic acid 10.59% Proline 1.78% Glycine 1.70% Alanine 1.34% Valine 1.07% Methionine 0.37% Isoleucine 1.11 % Leucine 1.62% Thyrosine 0.88% Phenyl-alanine 1.07% Lysine 4.26% Histidine 1.65% NH3 1.77% Arginine 4.22% Tryptophan 1.43% The composition reported above must be regarded as a mere example of the final extract according to the invention. It is apparent, in fact, that such a composition is a function of the composition of the starting soybean material, which can vary within certain limits according to the type of Leguminosa plant, the country of origin, the environmental conditions and other factors.

The soybean extract as obtained by the process of the invention thus shows that it has the properties sought for from the very start, that is, above all, it is a product having an extremely high contents of proteins and in which the proteins are present in the form of their fundamental components which can be most easily assimilated: it is devoid of those substances which are present in natural soybean seeds and which could be objectionable especially from the point of view of their organoleptic properties, and it is also devoid of any additive or any substance foreign to the natural soybean: finally, it is in the form of a ready for use product which can conveniently be administered since it is highly watersoluble. The organoleptic characteristics of the extract can be compared to those of common beverages, such as coffee.

A product having such properties has proven to be electively indicated, in general, for a correct proteinic nutrition in replacement for a diet rich with animal proteins and; more particularly, for treating clinical cases in which a hyperproteinic diet is required. It can be observed, in this connection, that 100 g of sirloin contain about 21 g of proteins, whereas the extract according to the invention has a proteinic contents of as much as 41% which, most advantageous is in the form already split into the essential aminoacids.

The administration of the soybean extract can be effected both by dissolving the extract as such in water, or concurrently with other foods.

In order that the advantages of the invention may be best appreciated, it is appropriate to reiterate that the European populations, along with a predominant portion of the North-American and South-American peoples have never given any great consideration to soybeans, as such or in its several conventional preparations, due to their organoleptic characteristics.

The addition of even slight amounts of soybean flour to the wheatmeal or maize meal for preparing bread and alimentary pastes have never been accepted hitherto. Not even the mock-beefsteaks made of mixtures of animal meats and soybean derivatives have ever found a favourable acceptance, in Italy or elsewhere.

The soybean proteins, the organoleptic characteristics of which are not such as to make them palatable, would be extremely useful, instead, in the hyperproteinic diets, to replace animal proteins wholly or partially.

The soybean proteins have a bearing on a particular metabolism type which involves, quite especially, the proteins and a few lipids, triglycerides and cholesterol. Soybean proteins would thus be extremely helpful for a correct diet in the treatment of metabolism troubles.

For such uses, soybean must be stripped both of its lipid fraction and its cellulose fraction.

These objectives are achieved, with advantage, by the soybean extract made according to the invention, as outlined above.

Finally, it is quite appropriate to recall that it would be quite a painstaking task to modify the organoleptic characteristics of soybean seeds as such.

Claims (9)

1. Process for the production of a watersoluble soybean extract having a high proteinic contents, characterized in that natural defatted soybean flour is subjected to the following stages: a) a dry-heat treatment, b) an aqueous-phase extraction at the boiling point temperature, c) a filtration of the aqueous mixture coming from the stage b), to separate a filtrate and a solid cake, d) a boil of the filtrate as obtained in the previous stage c), to produce a soluble fraction which contains the useful components of soybean, and an insoluble fraction, e) a filtration of the mixture as obtained in the previous stage d) to separate, as a filtrate, said soluble fraction from said insoluble fraction, f) an evaporation and a drying of the filtrate coming from the previous stage e), to produce the expected soybean extract.

2. Process according to Claim 1, characterized in that said stage a) is carried out in a dryer at a temperature above 100"C until obtaining a constant weight of the starting soybean material.

3. Process according to Claim 1, characterized in that said stage b) is carried out by charging an autoclave with distilled water, then with the soybean material and bringing said mixture to a boil.

4. Process according to Claim 1, characterized in that said stage c) is carried out by centrifuging the aqueous mixture upon an appropriate cooling step.

5. Process according to Claim 1, characterized in that said stage (e) is carried out by using a hydroextractor so as to make possible the removal of the particles of said insoluble fraction in suspension.

6. Process according to Claim 1, characterised in that the soybean extract coming from said stage f) is subjected to grinding prior to being stored or packaged.

7. Process for the production of soybean extract substantially as described herein.

8. Soybean extract obtained by a process according to any one of the preceding claims.

9. Any novel feature or combination of features described herein.