SI9200283A - Process for enzymatic modification of gluten and hydrolysates thereof derived from wheat seed - Google Patents

Abstract

We propose a new procedure for enzyme modification wheat gluten, in which technical gluten suspend at a mixing intensity of 0.5 to 2 W / l either in acidic solution or alkaline solution, add proteolytic enzyme, then during gentle agitation let it hydrolyze, then cool the mixture to room temperature temperature, neutralize and decide the insoluble residue by centrifugation or filtration, the cake is washed evaporate with water and the whole solution to dryness with spray drying to isolate the powder product. Protein hydrolysates obtained by the above procedure, have improved functional properties, especially with respect to solubility, emulsifying and foaming properties.

Description

Technical field of the invention

The present invention relates to a novel process for the enzymatic modification of wheat 25 gluten and to the resulting protein hydrolysates with improved characteristics.

A technical problem

There was a need for a process by which protein 30 hydrolyzate could be produced from wheat-insoluble technical gluten (gluten flour), i.e. product with special functional properties, especially solubility, emulsifying and foaming properties.

The state of the art

Gluten is a complex blend of wheat protein. It has a unique place among plant proteins as an additive in the preparation of yeast dough products due to its ability to form a tough and elastic net that retains its shape even when baking the product. In its native state it has poor emulsifying abilities, which means that it cannot form stable emulsions, nor does it foam. It is practically insoluble in water in the neutral or alkaline pH range. Its use in dry or wet form is restricted to all those applications in industry where high water retention capacity, stable emulsion, stable foam formation and high solubility are required.

More than 100 years ago, researchers discovered that it is possible to obtain meat-flavored hydrolysates from protein or acid hydrolysis. They have found widespread use in the food industry either to improve the functional properties of a product or to increase its nutritional value. With the introduction of biotechnological processes into the food industry, enzymatic hydrolysis of plant proteins with various proteolytic enzymes has also emerged. The utility of enzymatic hydrolysis takes precedence over the conventional method because the hydrolysis process can be guided in the exact desired direction, easier to control and direct the course of hydrolysis, smaller substrate outputs are required, and the nutritional value of the product is provided. The hydrolysis parameters must be defined to prevent in particular the formation of bitter peptides and to ensure the continued quality of the product. (Jean Adler Nissen, Enyzmatic Hydrolysis of Proteins for Increased Solubility, J.Agric.Food Chem. 1976, Vol. 24, No.6.

Protein Quality and the Effects of Processing, Edited by R.Dixon Philli and John W.Finely, Marcel Dekker 1989).

Usually used as a raw material for the preparation of protein hydrolysates, commercially interesting plant proteins (soybean flour, wheat and corn gluten, technical casein). These materials are more difficult to handle than pure and well characterized proteins. Defined hydrolysis parameters must be provided to prevent the formation of undesirable taste and to ensure a consistent product quality. Various methods of modification of gluten proteins based on the principle of protein hydrolysis have been devised in order to improve the functional properties and preserve the nutritional value of the proteins as much as possible. Basic and acid hydrolysis under extreme conditions gives a well-soluble product, but the soapy taste of basic hydrolysis and the bitter taste of acid hydrolysis are problematic due to the excessive level of hydrolysis. Good results were obtained by mild acid hydrolysis, where altered functional properties were obtained without reducing the molar mass of the proteins.

(Y.Popineau, Biochemical and Functional Characterization of Gluten Proteins, Partially Deaminated by Mild Acid Treatment, Sciences des Aliments, 1989, Vol. 8, No. 4.)

Technical gluten is a water-insoluble complex protein fraction extracted from wheat flour after removal of all soluble substances. It is marketed as a light color, odorless and flavourless powder with high protein content (min.80%) and low fat content (max. 1.5%). It is a by-product of wheat starch production. Gluten insolubility in aqueous solutions is a major barrier to its widespread use in the food industry. The insolubility is due to the high concentration of non-polar amino acid residues such as proline, leucine and glutamine, and low concentration of ionizing chains such as lysine, arginine, glutamic and aspartic acid. In our Slovenian patent application no. No. 9200106, filed June 15, 1992, we have described a new process for the manufacture of water-soluble gluten in wheat, which otherwise produces quality hydrolysates.

However, care must be taken to produce bitter peptides during protein hydrolysis. Higher presence of hydrophobic amino acids implies a greater propensity to form bitter peptides. In the native state, amino acids are bound to the structure of the protein and thus inaccessible to taste receptors. Protein hydrolysis breaks down the structure of a protein molecule, cleaving peptides and amino acids that pass into solution and become accessible to taste receptors in the mouth. The formation of a bitter taste is inversely proportional to the solubility of the protein, therefore, the experimental data must be used to find the optimum level of hydrolysis according to the taste and solubility of the protein.

The resulting protein hydrolysates should be well soluble in water, light in color, odorless and tasteless. Water soluble protein hydrolysates are used in the food industry to increase the nutritional value of the finished product or to improve its functional properties. In the meat industry, they are used as a binder in the preparation of meat emulsions because they are practically odorless and tasteless. They are often used as protein stabilizers and emulsifiers of water-oil emulsions as a base for the preparation of mayonnaise and dressings of various flavors and consistencies. Addition of protein hydrolysates increases the intensity of the aroma and taste of the product.

4. Description of the solution to a technical problem with implementation examples

However, we have now found that we can solve all the above problems by enzymatic modification (hydrolysis) of proteins, where the solubility of proteins is increased and interactions between gliadin and gluteinins are decreased without reducing the nutritional value of the product.

The main advantage of the process is that enzymatic hydrolysis takes place in a biological system that, due to the precise specific action of the proteolytic enzyme, is more easily managed and more defined than in chemical hydrolysis. The resulting changes make it possible to improve the functional properties of proteins without impairing their nutritional value.

This also extends the usefulness of gluten to those areas of the industry where high water binding and retention capacity, stable emulsion, good foaming properties and solubility of the by-product are necessary.

The process of the invention is carried out by suspending the technical gluten at a stirring intensity of 0.5 to 2 W / 1 either in acidic solution with pH 2-6 or alkaline solution with pH 7-9 in a weight ratio of 0.5: 20 to 1: 20, a proteolytic enzyme is selected, e.g. of pepsin, papain, alkalase and neutrase, at a concentration of 0.1 - 3% per protein, and then, under gentle stirring, allowed to hydrolyze for 4 - 20 hours at a temperature of 20 ° to 60 ° C, then cool the mixture to room temperature, neutralize to pH 6 to 9 with 1 mol / l NaOH solution and decide the insoluble residue by centrifugation or filtration, wash the cake with water in an amount of one tenth of the filtrate volume and evaporate the whole solution to dryness by spray drying at 150 ° C inlet air to isolate the powder product .

The invention is explained by embodiments which are not intended to limit it.

EXAMPLE 1:

50 L of water was poured into a reactor with a strong stirrer and a heating-cooling element, and 100 ml of concentrated acetic acid solution was added to give a 0.1M solution. The pH is adjusted to 2 with concentrated hydrogen chloride solution. While stirring vigorously with a 10 cm diameter turbine mixer and 600 rpm, slowly add 2 kg of technical gluten until a smooth, lump-free liquid mass is obtained. Now the mixing intensity is reduced to 200 rpm of the agitator, the mixture is slowly warmed to 40 ° C, 0.5 g (1 mg / ml) of the enzyme (pepsin) is added and stirred for 6 - 10 hours to perform hydrolysis. The heating rate must be such that the foaming is controlled, otherwise the mixture may boil over. After completion of the hydrolysis, the mixture was cooled to room temperature and the action of the enzyme at pH 6.8 was deactivated by the addition of an IM sodium hydroxide solution. The insoluble residue is separated from the solution by centrifugation or filtration, the cake being washed with 5 l of water. The cloudy solution was evaporated to a dry, powdery product in a spray dryer at an inlet air temperature of 150 ° C.

The process is shown schematically in the block diagram of FIG.

EXAMPLE 2:

A variant of the procedure described in Example 1 is to mix water, a proteolytic enzyme and gluten in a specially prepared intensive mixer, then transfer to a reactor with a mild hydrolysis mixer and complete the hydrolysis according to the procedure described.

Product Features Moisture 8.8%

Protein 78.7%

Fat 1.9%

Ash 15.6%

Fiber 2.2%

N.S. I (Nitrogen solubility index): more than 88% at pH below 2, above 5

Amino acids Mol%

Asx 4.05

Thr 3.05

Ser 5.80

Glx 35.40

Dec 12.20

Gly 10.50

Ala 4.20

Val 4.60

Met 1.30

Ile 4.30

Leu 6.30

Tyr 1.50

Phe 4.50

His 2.50

Lys 1.07

Arg 2.00

EC (Emulsion Capacity): 1g of gluten hydrolyzate (in 1% aqueous solution) can emulsify 360 g of oil.

Hydrolysis rate: 15%.

Claims (2)

Patent claim A process for the enzymatic modification of wheat gluten, characterized in that the technical gluten is suspended at a mixing intensity of 0.5 to 2 W / 1 either in acidic solution with pH 2-6 or alkaline solution with pH 7-9, in a weight ratio of 0.5: 20 to 1: 20, the proteolytic enzyme selected e.g. of pepsin, papain, alkalase, and neutrase, at a concentration of 0.1 - 3% per protein, then, under gentle agitation, allowed to hydrolyze for 4 - 20 hours at a temperature of 20 ° to 60 ° C, then cool the mixture to room temperature, neutralize to pH 6 to 9 with 1 mol / l NaOH solution and decide the insoluble residue by centrifugation or filtration, wash the cake with water in an amount of one tenth of the volume of the filtrate, and evaporate the whole solution to dryness by spray drying, at an inlet air temperature of 150 ° C, to isolate the powder product. 2. Protein hydrolysates obtained by the method of claim 1. For the Boris Kidrič Institute of Chemistry, p.o .: 578-PIAGIep CHEMICAL INSTITUTE BORIS KIDRIC, p.o Our sign: 578-p / AG / ep