WO1995025437A1 - Process for producing brightly-coloured vegetable protein hydrolysates - Google Patents

Abstract

Vegetable protein hydrolysates with improved colour quality are obtained by a) extracting protein-containing vegetable flours at a pH beyond the isoelectrical range of the protein, possibly in the presence of adsorbents and b) hydrolysing the protein hydrolysate thus obtained in the presence of adsorbents with alkalis, acids and/or enzymatically in the manner known per se. The substances are suitable as components of surface-active agents and in the production of derivatives, e.g. possibly cationically modified condensation products with fatty acids.

Description

 Process for the preparation of light colored vegetable protein hydrolyzates

Field of the Invention

The invention relates to a process for the production of vegetable protein hydrolyzates of improved color quality, in which protein-containing vegetable meal is extracted under defined conditions and the resulting protein isolates are then hydrolyzed in a manner known per se in the presence of suitable adsorbents.

State of the art

Degradation products of polypeptides, so-called protein hydrolysates, have been known for a long time. Although they have no detergent properties because of the lack of a lipophilic group, they are used in a large number of surface-active agents because of their dispersing properties and their ability to favorably influence the dermatological compatibility of anionic surfactants by interaction with the protein molecules of the skin used. Review articles on this can be found, for example, by A. Domsch et al. in doctor Cosmetol. 13, 524 (1983), G. Schuster et al. in Cosme .Toil., 99, 12 (1984) and H. Lindner in Perfume.Cosmet. , .66., 85 (1985).

Protein hydrolyzates based on animal collagen are usually obtained. In recent years, however, there has been a trend towards vegetable products, for example based on soybeans.

From the French published patent application FR 2542013 (ABC), for example, the hydrolysis of plant proteins by means of special lactic acid bacteria in the presence of hydrocarbons is known. US Pat. No. 4,757,007 (Nisshin) describes the partial hydrolysis of soy proteins with proteases in fractions of different solubility in trichloroacetic acid, separation of the fractions at a pH of 7, removal of non-hydrolyzed fractions and purification of the products by ultrafiltration. The subject of European patent application EP-A 0187048 (Novo) is the enzymatic degradation of soy proteins by treatment with special proteases. EP-A 0298419 (Katayama) discloses the production of protein hydrolyzates with an average molecular weight of 500 to 90,000 by stepwise alkaline, acidic and / or enzymatic degradation of wheat or soy proteins. Finally, EP-A 0363771 (Nestle) reports on a process for the production of protein hydrolyzates, in which vegetable proteins are hydrolyzed with hydrochloric acid, non-hydrolyzed constituents are separated off, made alkaline to destroy undesired chlorinated compounds and the resulting products are then acidified. What is common to the prior art methods, however, is that the resulting protein hydrolyzates do not meet the requirements of the market for very little colored products with regard to their color quality. The object of the invention was therefore to provide such light-colored protein hydrolysates on a plant basis.

Description of the invention

The invention relates to a method for producing light-colored vegetable protein hydrolyzates, in which

a) protein-containing vegetable meal extracted at a pH outside the isoelectric range of the protein, if appropriate in the presence of adsorbents, and b) the protein extract obtained in the presence of adsorbents is hydrolyzed in an alkaline, acidic and / or enzymatic manner known per se.

Surprisingly, it was found that color-causing constituents contained in protein-containing vegetable flours, in particular phenols, aromatic hydroxycarboxylic acids and phythic acid, by extraction of the protein outside the isoelectric range with bases or preferably acids, optionally in the presence of adsorbents at 30 to Allow 80 and preferably 40 to 50 ° C to separate. Traces of color still present can finally be removed if the subsequent hydrolysis of the protein isolates is carried out in the presence of, for example, activated carbon. Vegetable flour

With regard to the feasibility of the method according to the invention, it is not tied to the nature of the plant flour used. In practice, however, the choice of input materials will primarily depend on availability and protein content. Typical examples are therefore almond flour, cereal flour, in particular wheat flour, potato flour and preferably soy flour, and mixtures thereof. Typically, the commercially available flours mentioned have a protein content of approximately 40 to 50% by weight.

Extraction process

The method according to the invention includes the knowledge that vegetable proteins have a minimum solubility in the vicinity of their isoelectric point or area. Accordingly, the extraction of the protein from the protein-containing vegetable meal can be carried out at a pH either below or above the isoelectric range of the protein. In practice, for example, an alkaline extraction at pH values in the range from 8 to 14 and preferably 8.5 to 10 comes into consideration. With regard to the color quality of the resulting hydrolysates, however, acid extraction at pH values in the range from 1 to 3 and preferably 2 to 2.5 has proven to be particularly advantageous.

In order to carry out the extraction, the vegetable flour is first optionally in a sufficient amount of water dispersed with heating and then adjusted to the desired pH with an acid or base, preferably hydrochloric acid, citric acid or sodium hydroxide solution. The protein goes into solution, while carbohydrates, fats and, above all, the undesired potential color carriers remain in the insoluble residue, which can be separated from the valuable filtrate, for example, by filter suction, filter presses or separators.

In a preferred embodiment, the extraction is carried out several times, i.e. the protein is precipitated from the filtrate obtained in the first extraction, washed, redispersed in water, redissolved with acid or base and the residue is separated off again. This process can in principle be repeated in any number, but in practice it has been shown that more than three runs do not lead to any measurable color improvement in the end products. To increase the yield, the remaining insoluble residues can be extracted again, if necessary after combining.

A further advantageous embodiment of the method according to the invention consists in a change in pH during the extraction. This means that the extraction is carried out in two stages, ie first in the alkaline range and then in the acidic environment or vice versa. If desired, the protein hydrolyzates can be further purified by ultrafiltration and / or diafiltration before the hydrolysis; such a step can also follow the hydrolysis. The solids content of the aqueous solutions obtainable after extraction is determined by the amount of water required for the dispersion and is generally 5 to 40, preferably 10 to 20,% by weight. Based on the solid, the proportion of plant proteins is above 80, preferably 90 to 98% by weight.

Adsorbents

To remove residual traces of undesirable color sources, it has proven to be advantageous to use the protein isolates pre-cleaned by extraction together with suitable adsorbents in the hydrolysis. In a special embodiment of the invention, the adsorbents can also be added at the extraction stage. Examples of suitable adsorbents are silica gels, aluminum oxides and preferably activated carbons, which can be used in amounts of 0.1 to 15, preferably 1 to 5% by weight, based on the nitrogen content of the protein isolates.

Hvdrolvseverfahren

The hydrolysis of the protein iso-prepurified by extraction can be carried out in a manner known per se in an alkaline, acidic and / or enzymatic way, the latter being preferred. For this purpose, an alkaline aqueous suspension of the protein isolate is usually mixed with suitable enzymes, for example proteases, and the adsorbent and over degraded for a period of 1 to 24 hours at the optimum temperature of the enzymes used, for example at 50 to 70 ° C. If the digestion is carried out in the presence of calcium oxide or hydroxide as the base, calcium peptides are formed which have to be filtered off from the residue. If the alkali peptides are desired, it is advisable to treat the calcium peptides with soda or potash solution and then to separate off the sparingly soluble calcium carbonate. It is also possible to precipitate the calcium in the form of calcium sulfate or calcium oxalate. The sparingly soluble salts are preferably separated off in the presence of filter aids by means of suction filters or filter presses. Aqueous protein hydrolyzate solutions are obtained which, if necessary, can be concentrated, for example using downdraft evaporators. The hydrolysates obtainable by the process according to the invention have an average molecular weight in the range from 100 to 30,000, preferably 100 to 10,000 and in particular 2000 to 5000 and a solids content of about 5 to 50% by weight.

Industrial applicability

The vegetable protein hydrolyzates obtainable by the process according to the invention are distinguished by a particularly advantageous color quality.

Another object of the invention relates to their use as ingredients of surface-active agents, for example as soil dispersants in liquid detergents or components which improve skin tolerance in cosmetic products.

Finally, the invention relates to their use for the production of light-colored vegetable secondary products such as, for example, N-acylated, N-alkylated, esterified and N-acylated or N-alkylated and also esterified protein hydrolyzates.

The following examples are intended to explain the subject matter of the invention in more detail without restricting it.

Examples

I. Preparation of the protein isolates

Example 1;

400 kg of soy flour (protein content: approx. 48% by weight) were placed in a 10-m ^ stirred tank and suspended in 4000 l of water. By adding conc. Hydrochloric acid was the pH of the

Solution lowered to 2.5, whereby the protein went into solution. The aqueous solution was then separated off from the residue.

Example 2;

The aqueous protein solution from Example 1 was adjusted to a pH of 4.5 by adding sodium hydroxide solution and the soy protein was precipitated. The backlog was

«See, redispersed in water and dissolved by adding hydrochloric acid (pH = 2.5).

Example 3;

Analogously to Example 1, 400 kg of almond flour (protein content approx. 42% by weight) were suspended in 4000 l of water, adjusted to a pH of 2 using hydrochloric acid and then separated using a separator. Example 4 t

Analogously to Example 1, 400 kg of wheat protein (protein content approx. 40% by weight) and 20 kg of activated carbon were suspended in 4000 l of water, adjusted to a pH of 2 using hydrochloric acid, stirred at 40 ° C. for 0.5 h and separated by a separator.

Example 5;

Analogously to Example 1, 400 kg of potato protein (protein content approx. 45% by weight) were suspended in 4000 l of water, adjusted to a pH of 2 using hydrochloric acid and then filtered.

Example 6;

Analogously to Example 1, 400 kg of soybean meal with the addition of 20 kg of activated carbon were suspended in 4000 l of water, adjusted to a pH of 9 with sodium hydroxide solution and stirred at 45 ° C. for 1 hour, the soy protein dissolving. The aqueous solution was then separated off from the residue using a separator. The residue was extracted again and the combined extracts processed together. Example 7t

The aqueous protein solution from Example 6 was adjusted to a pH of 4.5 by adding hydrochloric acid and the soy protein was precipitated. The residue was washed several times, redispersed in water and dissolved again by adding sodium hydroxide solution (pH 10).

II. Preparation of the protein hydrolyzates

9000 l of water were placed in a 15-r_3 stirred tank and 3 kg of sodium sulfite and 30 kg of activated carbon were added at 55 to 60 ° C. Then 1000 kg of soy isolate (according to Examples 1 to 8) were added and the mixture was stirred to form a 10% by weight suspension. The pH of the reaction mixture was then adjusted to 9.5 by adding calcium oxide and 5 kg of alkalase were added. The enzymatic degradation was carried out at 60 ° C. over a period of 2 h.

After completion of the enzymatic hydrolysis step, the pH of the mixture was adjusted to 4.2 by adding hydrochloric acid. The reaction mixture was then heated to 80 ° C., a further 10 kg of activated carbon and 120 kg of filter aid (Perlite ( ^R) P50) were added and the mixture was stirred for 30 minutes.

The reaction product was then filtered through a filter press and the filtrate was adjusted to a pH of 11.5 with calcium oxide. After a residence time of 30 min at 90 ° C., the solution was filtered, sodium carbonate solution was added and the calcium salts which had precipitated were again separated off using a filter press. The filtrate was concentrated in a downflow evaporator to a content of 41% Brix and finally filtered blank after a storage period of 3 days.

The Lovibond color numbers of the protein hydrolyzates were determined in a 1 cm cuvette in accordance with DIN ISO 4630 after the hydrolyzate had been stored at 40 ° C. for 4 weeks. The color numbers of hydrolysates, which are based on the iso- latex according to Examples 1 to 7, but without the use of active carbon in the extraction and / or hydrolysis. The results are summarized in Table 1:

Table 1:

Eg isolate according to extraction and color number

Example hydrolysis process Lovibond

Red Yellow

9 1 with activated carbon 3.0 14.6

10 2 with activated carbon 1.9 7.1

11 3 with activated carbon 2.0 8.7

12 4 with activated carbon 2.0 12.9

13 5 with activated carbon 3.3 14.5

14 6 with activated carbon 2.9 13.0

14 7 with activated carbon 2.0 7.9

VI 1 without activated carbon 3.7 18.2

V2 2 without activated carbon 2.1 10.8

V3 3 without activated carbon 2.4 12.8

V4 4 without activated carbon 2.8 25.4

V5 5 without activated carbon 6.5 32.0

V6 6 without activated carbon 3.1 16.0

V7 7 without activated carbon 3.6 18.9

Claims

claims 1. Process for the preparation of light-colored vegetable protein hydrolyzates, in which a) protein-containing vegetable meal at a pH outside the isoelectric range of the protein, optionally in the presence of adsorbents, and b) the protein extract obtained in the presence of adsorbents in a manner known per se, alkaline, acidic and / or enzymatic hydrolyzed. 2. The method according to claim 1, characterized in that one uses soy flour, almond flour, corn flour and / or potato flour. 3. Process according to claims 1 and 2, characterized gekenn¬ characterized in that the extraction is carried out at a pH below the isoelectric range of the protein. 4. The method according to claims 1 and 2, characterized gekenn¬ characterized in that one carries out the extraction at a pH above the isoelectric range of the protein protein. 5. The method according to claims 1 to 4, characterized gekenn¬ characterized in that the extraction is carried out several times. 6. The method according to claims 1 to 5, characterized gekenn¬ characterized in that the extraction in two stages, i.e. first in the alkaline range and then in the acid medium or vice versa. 7. The method according to claims 1 to 6, characterized gekenn¬ characterized in that activated carbon is used as the adsorbent in amounts of 0.1 to 15 wt .-% - based on the nitrogen content of the protein isolate. 8. Use of the light-colored vegetable protein hydrolysates by the process according to claims 1 to 7 as ingredients for surface-active agents. 9. Use of the light-colored vegetable protein hydrolysates by the process according to claims 1 to 7 for the production of light-colored vegetable N-acylated, N-alkylated, esterified and N-acylated or N-alkylated and also esterified protein hydrolysates.