IMPROVING TEXTURE OF PROTEIN

Abstract

The present invention addresses the problem of providing a method for improving a texture of a protein. By allowing a protein deamidase to act on a substrate protein, a feeling of the protein on a tongue can be smoothened, and the texture thereof can be improved.

Claims

1. A method for improving a texture of a protein, the method comprising allowing a protein deamidase to act on the protein.

2. The method for improving a texture of a protein according to claim 1, wherein the protein deamidase is an enzyme that deamidates an amide group of a glutamine residue in the protein.

3. The method for improving a texture of a protein according to claim 2, wherein the protein deamidase is a protein glutaminase.

4. The method for improving a texture of a protein according to claim 1, wherein the protein is a vegetable protein.

5. The method for improving a texture according to claim 4, wherein the vegetable protein is a vegetable protein in a vegetable protein solution.

6. The method for improving a texture of a protein according to claim 4, wherein the vegetable protein is a soybean protein or an oat protein.

7. The method for improving a texture of a protein according to claim 1, wherein the method smoothens a feeling of the protein on a tongue.

8. An agent for improving a texture of a protein comprising a protein deamidase in a protein.

9. A protein comprising a smooth feeling on a tongue due to an action of a protein deamidase on the protein.

10. A food or beverage or a pharmaceutical product comprising the protein according to claim 9.

Description

EXAMPLES

[0039] Hereinafter, the present invention will be further described with reference to Examples.

[0040] In the following Examples, activity of a protein glutaminase was measured by the method described below using Z-Gln-Gly-OH (N-benzyloxycarbonyl-L-glutaminyl-glycine) as a substrate unless otherwise specified.

[0041] <Method for Measuring Activity of Protein Glutaminase>

[0042] To 100 μl of a 176 mmol/l phosphate buffer solution (pH 6.5) containing 10 mmol/l Z-Gln-Gly-OH, 10 μl of an enzyme solution is added, and the mixture is incubated at 37° C. for 60 minutes. Then, 100 μl of a 12% trichloroacetic acid solution is added to stop the reaction. After centrifugation (15,000 rpm, 4° C., 5 minutes), the supernatant is measured using F-kit ammonia (manufactured by Boehringer Mannheim GmbH) as follows (A1). Separately, measurement is performed in the same manner using water instead of the enzyme solution (A2). To 100 μl of F-kit ammonia reagent 2, 10 μl of the supernatant and 190 μl of water are added, the mixture is allowed to stand at room temperature for 5 minutes, and then absorbance (E1) at 340 nm is measured using 100 μl of the mixture. After 1.0 μl of reagent 3 (glutamate dehydrogenase) is added to the remaining 200 μl, the mixture is further allowed to stand at room temperature for 20 minutes, and then absorbance (E2) at 340 nm of the remaining 200 μl is measured. An amount of an enzyme liberating 1 μmol of ammonia per minute under the above conditions is defined as 1 unit, and the activity is determined according to the following formula.

U/ml=1.76×[A1(E1−E2)−A2(E1−E2)]

Example 1

[0043] An effect of a protein glutaminase (PG) on improving a texture of a protein was examined using an oat beverage (raw materials, water, oat, chicory root fibre, sunflower oil, calcium, sea salt, gellan gum, vitamins, protein content 0.2 g/100 mL, Alpro). To the oat beverage, a protein glutaminase (product name: protein glutaminase “Amano” 500, manufactured by Amano Enzyme Inc.) was added in an amount of 5 U per g of a substrate protein, and after mixing, a reaction was caused at 50° C. for 30 minutes. The reaction was terminated by treatment at 95° C. for 10 minutes. The enzyme-treated (PG-treated) oat beverage was subjected to sensory evaluation and measurement of a coefficient of friction. The coefficient of friction was measured by tribology measurement in which a sample was placed on an artificial tongue and slid at a specific speed. Specifically, with 200 μL of the enzyme-treated oat beverage to which artificial saliva (solution at pH 6.7 containing 50 U/ml α-amylase, 25.7 mM NaCl, 8.6 mM K.sub.2HPO.sub.4, 4.7 mM Na.sub.2CO.sub.3, and 2% (w/w) mucin; manufactured by Sigma-Aldrich Co. LLC) was added so as to have a concentration of 15% (v/v) interposed between an artificial tongue (made of silicone resin) and an artificial palate (made of polydimethylsiloxane), the artificial tongue was slid on the artificial palate at a load of 0.5 N to measure the coefficient of friction on the artificial tongue. An oat beverage not subjected to enzyme treatment (PG treatment) was also measured in the same manner. A ratio (%) of the coefficient of friction of the sample with PG treatment to the coefficient of friction (COF) of the sample without PG treatment was calculated for each slide speed, and an effect of PG treatment was evaluated.

[0044] The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Coefficient of friction (COF) Ratio Slide speed Without With (to without PG (mm/s) PG treatment PG treatment treatment) 7 0.40 0.37 92% 18 0.39 0.32 84% 35 0.36 0.30 83% 53 0.33 0.29 86% 70 0.31 0.28 91%

[0045] As shown in Table 1, it was found that by treating the oat beverage with the protein glutaminase, the coefficient of friction with the artificial tongue in the presence of the artificial saliva was significantly reduced. Also in the sensory evaluation, it was confirmed that a feeling on the tongue became smooth when treated with protein glutaminase.

Example 2

[0046] Evaluation was performed in the same manner as in Example 1, except that the protein raw material used was changed to soy milk (raw materials, water, hulled soya beans protein content 3.0 g/100 mL, Alpro).

[0047] The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Coefficient of friction (COF) Ratio Slide speed Without With (to without PG (mm/s) PG treatment PG treatment treatment) 7 0.49 0.43 87% 18 0.46 0.39 84% 35 0.42 0.34 81% 53 0.39 0.31 79% 70 0.36 0.28 76%

[0048] As shown in Table 2, it was found that by treating the soy milk with the protein glutaminase, the coefficient of friction with the artificial tongue in the presence of the artificial saliva was significantly reduced. Also in the sensory evaluation, it was confirmed that a feeling on the tongue became smooth when treated with protein glutaminase.

INDUSTRIAL APPLICABILITY

[0049] According to the method for improving a texture of the present invention, a coefficient of friction in the mouth is reduced, and a protein having a smooth feeling on the tongue can be obtained. The protein obtained by the present invention is used, for example, in the field of food processing such as dairy substitutes (cheeses substitutes, fermented milk substitutes) using vegetable materials or vegetable milk. Furthermore, as a novel protein-derived material, the protein can also be used as a material for medical supplies and supplements.

[0050] The present invention is not limited to the description of the embodiments of the invention and Examples above. Various modifications that can be easily conceived by those skilled in the art without departing from the scope of the claims are also included in the present invention. The entire contents of the articles, published patent publications, patent publications, and the like specified in this specification are incorporated herein by reference.