Method for producing a liquid composition containing rice protein

Abstract

The purpose of the present invention is to provide a technique for producing a rice protein-containing liquid composition having improved smoothness. The rice protein-containing liquid composition, obtained by a method which is for producing a rice protein-containing liquid composition and comprises a step for treating a rice protein- containing liquid material with a protein deamidase, has improved smoothness.

Description

Technical Field

[0001] The present invention relates to a method for producing a rice protein-containing liquid composition.

Background Art

[0002] Against various backgrounds such as the recent health boom, responses to allergy issues, religious reasons, and the increase in opportunities to refrain from going out accompanying the spread of infectious diseases, nutrient-rich plant protein beverages with long shelf lives are gaining popularity as alternatives to animal milk.

[0003] Rice milk is attracting attention as the third type of milk following cow's milk and soy milk. Rice milk is a milk-form beverage obtained by saccharifying rice with enzymes, malted rice or the like, and further adding vegetable oil, salt and the like to adjust texture and / or taste. As technologies relating to methods for producing rice milk, Patent Document 1 describes a beverage composition made from brown rice obtained by adding protease, cellulase, pectinase and amylase to brown rice for decomposition treatment, and Patent Document 2 describes a rice saccharified liquid characterized by having an amino acid concentration of 0.12 to 0.45 mass%.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0005] Rice milk is commercially available, but it lacks smoothness and could be improved. This can be confirmed by the gritty texture felt on the tongue when it is put in the mouth, and more specifically by the high coefficient of friction measured using a device that simulates the inside of the mouth with an artificial tongue and artificial saliva. Therefore, the present invention aims to provide a technology for producing a liquid composition containing rice protein with improved smoothness. [Means for solving the problem]

[0006] The inventors have discovered that the smoothness of a resulting rice protein-containing liquid composition can be improved by treating a liquid material containing rice protein with a protein deamidation enzyme. This invention was completed by further investigation based on these findings.

[0007] In other words, the present invention provides inventions in the following embodiments. Item 1. A method for producing a rice protein-containing liquid composition, comprising the step of treating a liquid material containing rice protein with a protein deamidation enzyme. Item 2. The manufacturing method according to Item 1, wherein the liquid material containing rice protein is an aqueous dispersion of crushed rice. Item 3. A manufacturing method according to item 1 or 2, which does not include a step of treatment with a saccharifying enzyme. Item 4. A manufacturing method described in any of Items 1 to 3, which does not include a fermentation step. Item 5. A smoothing agent for liquid compositions containing rice protein, comprising a protein deamidase. Item 6. A viscosity enhancer for liquid compositions containing rice protein, comprising a protein deamidase. Item 7. A liquid composition containing rice protein and a protein deamidase, which is a rice odor reducing agent. [Effects of the Invention]

[0008] The present invention provides a technique for producing a liquid composition containing rice protein with improved smoothness. [Brief explanation of the drawing]

[0009] [Figure 1] The results of friction coefficient measurement for the rice protein-containing liquid composition prepared in Test Example 1 are shown. [Figure 2] This is a photograph of the appearance of the rice protein-containing liquid composition prepared in Test Example 3. [Modes for carrying out the invention]

[0010] 1. Method for producing a liquid composition containing rice protein The present invention relates to a method for producing a liquid composition containing rice protein, characterized by comprising the step of treating a liquid material containing rice protein with a protein deamidation enzyme. The method for producing the liquid composition containing rice protein of the present invention will be described in detail below.

[0011] 1-1. Liquid material containing rice protein The liquid material containing rice protein used in the present invention may be any liquid composition obtained from rice as a raw material. Examples of rice include brown rice, partially milled rice, germinated brown rice, germinated rice, and white rice.

[0012] A specific example of a liquid material containing rice protein is a liquid in which crushed rice is dispersed in water (hereinafter also referred to as "aqueous dispersion of crushed rice"). Crushing of rice can be carried out by any method, such as grinding and compression crushing. The aqueous dispersion of crushed rice can be prepared by crushing rice in water or by dispersing crushed rice in water.

[0013] Another specific example of a liquid material containing rice protein is a saccharifying enzyme-treated or fermented product of an aqueous dispersion of crushed rice. Examples of saccharifying enzymes used in the preparation of the saccharifying enzyme-treated product include α-amylase and glucoamylase. Examples of microorganisms used in the preparation of the fermented product include filamentous fungi such as Aspergillus oryzae, yeast, and lactic acid bacteria.

[0014] As still another specific example of the liquid material containing rice protein, there may be mentioned those obtained by adding oils and fats, seasonings, and / or other additives to the aqueous dispersion of the crushed rice product, or the above-mentioned saccharifying enzyme-treated product or fermented product. Examples of oils and fats include vegetable oils such as rice oil and sunflower oil. Examples of seasonings include salt. Examples of additives include emulsifiers, thickeners, minerals, and the like.

[0015] Among the above liquid materials containing rice protein, from the viewpoint of enhancing the viscosity of the resulting rice protein-containing liquid composition, an aqueous dispersion of a crushed rice product that has not undergone saccharification treatment and fermentation treatment is preferably mentioned. In addition, since the production method of the present invention can enhance the viscosity of the resulting rice protein-containing liquid composition, the liquid material containing rice protein does not need to contain oils, fats and thickeners. Furthermore, since the production method of the present invention can improve the smoothness of the resulting rice protein-containing liquid composition, the liquid material containing rice protein does not need to contain an emulsifier.

[0016] 1-2. Protein deamidation enzymes The protein deamidase can act on the liquid material containing rice protein to improve the smoothness of the resulting liquid composition containing rice protein. Further, in one embodiment of the present invention, the protein deamidase can act on the liquid material containing rice protein to enhance the viscosity of the resulting liquid composition containing rice protein and / or reduce the rice odor.

[0017] The protein deamidase used in the present invention is an enzyme that exhibits an action of decomposing the amide group-containing side chain of a protein without accompanying cleavage of peptide bonds and crosslinking of the protein, and its type, origin and the like are not particularly limited. In addition, as long as the above action is the main activity, it may further have an action of decomposing the amide group-containing side chain of the protein accompanied by cleavage of peptide bonds and crosslinking of the protein.

[0018] Examples of protein deamidase include enzymes that deamidate glutamine residues in proteins to convert them into glutamic acid (e.g., protein glutaminase), and enzymes that deamidate asparagine residues in proteins to convert them into aspartic acid (e.g., protein asparaginase).

[0019] More specific examples of protein deamidase include protein deamidases derived from the genus Chryseobacterium, genus Flavobacterium, genus Empedobacter, genus Sphingobacterium, genus Aureobacterium, genus Myroides, genus Luteimicrobium, genus Agromyces, genus Microbacterium, or genus Leifsonia. These protein deamidases are known, and reference can be made to, for example, JP2000-50887A, JP2001-218590A, WO2006 / 075772A1, WO2015 / 133590, etc. One of these protein deamidases may be used alone, or a plurality of types may be used in combination.

[0020] Among these protein deamidases, from the viewpoint of further improving the smoothness of the resulting rice protein-containing liquid composition, or in addition, from the viewpoint of enhancing viscosity and / or reducing rice odor, a protein deamidase derived from the genus Chryseobacterium is preferred, a protein glutaminase derived from the genus Chryseobacterium is more preferred, a protein glutaminase derived from the species Chryseobacterium proteolyticum is even more preferred, and a protein glutaminase derived from the Chryseobacterium proteolyticum strain 9670 is still more preferred.

[0021] Protein deamide enzymes can be prepared from the culture medium of the microorganism from which the above-mentioned protein deamide enzymes originate. Specific preparation methods include recovering the protein deamide enzyme from the culture medium or cells of the above-mentioned microorganisms. For example, when using a protein deamide enzyme-secreting microorganism, the cells can be recovered from the culture medium by filtration, centrifugation, etc., as needed, and then the enzyme can be separated and / or purified. When using a protein deamide enzyme-non-secreting microorganism, the cells can be recovered from the culture medium by filtration, centrifugation, enzyme lysis, etc., as needed, and then the cells can be disrupted to expose the enzyme before separating and / or purifying it. The enzyme separation and / or purification method can be any known protein separation and / or purification method without particular limitation, such as centrifugation, UF concentration, salting-out, and various chromatography methods using ion exchange resins. The separated and / or purified enzyme can be powdered by drying methods such as freeze-drying or vacuum drying, and can also be powdered using appropriate excipients and / or drying aids in the drying method. Furthermore, the separated and / or purified enzymes can be liquefied by adding appropriate additives and sterilizing by filtration.

[0022] Commercially available products can also be used as protein deamide enzymes. A preferred example of a commercially available product is "Amano" 500 protein glutaminase (derived from Chryseobacterium proteoricum) manufactured by Amano Enzyme Co., Ltd.

[0023] The amount of protein deamidase used is not particularly limited, but examples of amounts used per gram of rice protein include 0.1U or more, 0.5U or more, and 1U or more. From the viewpoint of further improving the smoothness of the resulting rice protein-containing liquid composition, or in addition to increasing viscosity and / or reducing rice odor, the amount of protein deamidase used per gram of rice protein is preferably 2U or more, 4U or more, 5U or more, more preferably 7U or more, 8U or more, 10U or more, and even more preferably 14U or more. The upper limit of the range of amounts of protein deamidase used per gram of rice protein is not particularly limited, but examples of amounts include 200U or less, 150U or less, 100U or less, 75U or less, 50U or less, 30U or less, and 20U or less.

[0024] Regarding the activity of protein deamidase enzymes, one unit (1U) is defined as the amount of enzyme that releases 1 μmol of ammonia per minute using benzyloxycarbonyl-L-glutaminylglycine (Z-Gln-Gly) as a substrate.

[0025] 1-3. Reaction conditions, etc. The temperature at which a liquid material containing rice protein is treated with a protein deamidation enzyme is not particularly limited and can be appropriately determined by those skilled in the art depending on the optimal temperature of the enzyme used, for example, 40 to 98°C is used.

[0026] Furthermore, in the manufacturing method of the present invention, the step of treating the liquid material containing rice protein with a protein deamidase may be carried out at a substantially single temperature within the above temperature range (within ±4°C of the set temperature, preferably within ±2°C, and even more preferably within ±1°C), or the set temperature may be gradually increased within the above temperature range.

[0027] Specifically, when processing at essentially a single temperature, the set temperature can be, for example, 40 to 98°C, preferably 43 to 75°C, more preferably 46 to 60°C, and even more preferably 48 to 55°C.

[0028] Furthermore, when processing by sequentially increasing the temperature, possible ways of setting the temperature include (i-1) setting the temperature in two stages, in which case preferably setting the difference between the first stage temperature and the second stage temperature to be, for example, 30 to 50°C, preferably 35 to 49°C, more preferably 40 to 48°C, and even more preferably 43 to 47°C; and (i-2) setting the temperature in three stages, in which case preferably setting the difference between the first stage temperature and the second stage temperature to be, for example, 20 to 30°C, preferably 23 to 27°C, and setting the difference between the second and third stage temperatures to be, for example, 5 to 15°C, preferably 8 to 12°C. More specifically, (ii-1) an embodiment in which the temperature is set in two stages, in which case the first stage set temperature is, for example, 40 to 75°C, preferably 44 to 60°C, more preferably 48 to 55°C, and the second stage set temperature is, for example, greater than 80°C and 98°C, preferably 83 to 98°C; (ii-2) an embodiment in which the temperature is set in three stages, in which case the first stage set temperature is, for example, 40 to 60°C, preferably 44 to 58°C, more preferably 48 to 55°C, the second stage set temperature is, for example, 60 to 77°C, preferably 70 to 77°C, more preferably 73 to 77°C, and the third stage set temperature is, for example, 83 to 98°C.

[0029] The enzyme treatment reaction time for the liquid material containing rice protein is not particularly limited and can be appropriately determined according to the preparation scale of the liquid material, the set temperature, the temperature setting method, etc., but for example, it can be 30 minutes or more, preferably 40 minutes or more, and the upper limit can be, for example, 20 hours or less or 17 hours or less.

[0030] 1-4. Other processes The manufacturing method of the present invention may include any additional steps besides the step of treating with the protein deamidation enzyme described above.

[0031] Other processes include, for example, a process of treating with a saccharifying enzyme, a fermentation process, and a cooling process and a process of adding additives, which are performed after the above-mentioned process of treating with a protein deamidation enzyme, which may be carried out at any stage.

[0032] Among the other steps described above, from the viewpoint of increasing the viscosity of the resulting rice protein-containing liquid composition, the steps of treatment with saccharifying enzymes and fermentation are preferably omitted. Examples of saccharifying enzymes used in the step of treatment with saccharifying enzymes include α-amylase and glucoamylase, and examples of microorganisms used in the fermentation step include filamentous fungi such as Aspergillus oryzae, yeast, and lactic acid bacteria.

[0033] 2. Smoothness enhancer for liquid compositions containing rice protein As described above, protein deamidase can improve the smoothness of liquid compositions containing rice protein. Therefore, the present invention also provides a smoothness enhancer for liquid compositions containing rice protein, which includes protein deamidase.

[0034] Furthermore, the improvement in smoothness can be confirmed by measuring the coefficient of friction of the liquid composition containing rice protein using a device that simulates the oral cavity with an artificial tongue and artificial saliva, and observing a decrease in the coefficient of friction obtained. Sensory evaluation can be confirmed by feeling a smoother sensation on the tongue when the liquid composition containing rice protein is held in the mouth.

[0035] The types of ingredients used and the amounts used in the above-mentioned smoothing agent are as shown in section 1, "Method for Producing a Rice Protein-Containing Liquid Composition."

[0036] 3. Viscosity enhancer and rice odor reducer for liquid compositions containing rice protein. As described above, in one embodiment of the present invention, the protein deamidase can enhance the viscosity of a liquid composition containing rice protein and / or reduce the rice odor. Accordingly, the present invention also provides a viscosity enhancer for a liquid composition containing rice protein, comprising a protein deamidase, and a rice odor reducer for a liquid composition containing rice protein, comprising a protein deamidase.

[0037] The types of components used and the amounts used in the viscosity enhancer and rice odor reducer described above are as shown in section 1, "Method for Producing a Rice Protein-Containing Liquid Composition." [Examples]

[0038] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0039] [Enzymes used] • PG (Protein-glutaminase "Amano" 500): Protein glutaminase derived from Chryseobacterium proteolyticum • E5NC (Cleistase E5NC): α-amylase derived from Bacillus amyloliquefaciens

[0040] [Method for measuring enzyme activity] (1) Method for measuring protein deamidation enzyme activity To 1 mL of 0.2 M phosphate buffer (pH 6.5) containing 30 mM Z-Gln-Gly, 0.1 mL of sample solution containing protein deamidase was added and left to stand at 37°C for 10 minutes. Then, 1 mL of 0.4 M TCA solution was added to stop the reaction. As a blank, 1 mL of 0.2 M phosphate buffer (pH 6.5) containing 30 mM Z-Gln-Gly was added to 1 mL of 0.4 M TCA reagent, and then 0.1 mL of sample solution containing protein deamidase was added and left to stand at 37°C for 10 minutes.

[0041] The amount of ammonia produced in the reaction solution was measured using the Ammonia Test Wako (Fujifilm Wako Pure Chemical Industries) for the solution obtained as described above. The ammonia concentration in the reaction solution was determined from a calibration curve showing the relationship between ammonia concentration and absorbance (630 nm) prepared using ammonia standard solution (ammonium chloride).

[0042] The activity of the protein deamide enzyme was calculated using the following formula, where 1 unit (1U) is defined as the amount of enzyme that produces 1 μmol of ammonia per minute. In the formula, the reaction volume is 2.1, the enzyme solution volume is 0.1, and Df is the dilution ratio of the enzyme solution. Also, 17.03 is the molecular weight of ammonia.

[0043]

number

[0044] (2) Method for measuring α-amylase activity 10 mL of 1% potato starch substrate solution (0.1 mol / L acetic acid (pH 5.0)) was heated at 37°C for 10 minutes, then 1 mL of sample solution containing α-amylase was added and immediately mixed. After letting this solution stand at 37°C for 10 minutes, 1 mL of this solution was added to 10 mL of 0.1 mol / L hydrochloric acid solution and immediately mixed. Next, 0.5 mL of this solution was measured, 10 mL of 0.0002 mol / L iodine solution (Japanese Pharmacopoeia) was added and mixed, and the absorbance (AT) at a wavelength of 660 nm was measured using water as a control. Separately, the same procedure was performed by adding 1 mL of water instead of the sample solution, and the absorbance (AB) was measured. One unit (1 U) of enzyme was defined as the amount that reduces the iodine-induced coloration of potato starch by 10% in 1 minute.

[0045]

number

[0046] [Test Example 1] Rice milk (Rice drink (Alnatura)) with the composition shown in Table 1 was used as a liquid material containing rice protein.

[0047] [Table 1]

[0048] Rice milk was treated with protein glutaminase (PG) at an amount of 5U per gram of rice protein, followed by treatment at 50°C for 30 minutes, and then at 95°C for 10 minutes to obtain a rice protein-containing liquid composition (Rice treated: Example 1). For comparison, the same procedure was performed except that PG was not used to obtain a rice protein-containing liquid composition (Rice control: Comparative Example 1).

[0049] The coefficient of friction of the two obtained rice protein-containing liquid compositions was measured using an artificial tongue and artificial saliva (a pH 6.7 solution containing 50 U / ml α-amylase, 25.7 mM NaCl, 8.6 mM K2HPO4, 4.7 mM Na2CO3, and 2% (w / w) mucin; manufactured by Sigma-Aldrich). Specifically, a mixture of 200 μL of the rice protein-containing liquid composition and artificial saliva was interposed between an artificial tongue (made of silicone resin) and an artificial palate (made of polydimethylsiloxane). The artificial tongue was then slid on the artificial palate with a load of 0.5 N, and the coefficient of friction on the artificial tongue was measured (with saliva). The results are shown in Figure 1(A). Figure 1(B) shows the results measured in the same manner except that artificial saliva was not used (no saliva). In these figures, the vertical axis represents the coefficient of friction, and the horizontal axis represents the speed at which the artificial tongue was slid.

[0050] As shown in Figure 1, the rice protein-containing liquid composition of Example 1 (Rice treated) was found to have a reduced coefficient of friction in an environment simulating the oral cavity where saliva is present, compared to the rice protein-containing liquid composition of Comparative Example 1 (Rice control).

[0051] Furthermore, the two obtained rice protein-containing liquid compositions were tasted and their texture was evaluated. As a result, it was confirmed that the rice protein-containing liquid composition obtained using PG in Example 1 (Rice treated) was significantly smoother than the rice protein-containing liquid composition in Comparative Example 1 (Rice control).

[0052] [Test Example 2] Rice milk with the composition shown in Table 2 (4 Care Balance Rice drink (4 Care Co.)) was used as the liquid material containing rice protein. In Table 2, jasmine brown rice refers to brown rice. This liquid material was not subjected to either saccharifying enzyme treatment or fermentation treatment.

[0053] [Table 2]

[0054] Rice milk was treated with PG at an amount of 9U per gram of rice protein, and then at 50°C for 4 hours to obtain a rice protein-containing liquid composition (Example 2). For comparison, the same procedure was performed except that PG was not used to obtain a rice protein-containing liquid composition (Comparative Example 2).

[0055] The two resulting liquid rice protein compositions were tasted and sensory evaluated for smoothness, viscosity, and the rice odor of the raw materials. As a result, compared to the liquid rice protein composition of Comparative Example 2, the liquid rice protein composition of Example 2 showed significantly improved smoothness, increased viscosity and richer flavor, and reduced rice odor.

[0056] [Test Example 3] 200g of rice was soaked in 400mL of water for 2 hours, and then the water was drained. 50g of the soaked rice (white rice) was then mixed with 200mL of water and homogenized at 16400rpm for 2 minutes to obtain an aqueous dispersion of crushed rice (a liquid material containing rice protein). This liquid material was not subjected to either saccharifying enzyme treatment or fermentation treatment.

[0057] Aqueous dispersions of crushed rice were treated with (or without) the enzymes shown in Table 3. Specifically, for Comparative Example 3, the aqueous dispersion of crushed rice was heated at 50°C for 1 hour, then at 75°C for 1 hour, and then at 85°C for 15 hours to obtain a liquid composition containing rice protein. For Comparative Example 4, after heating at 50°C for 1 hour, α-amylase was added and the mixture was treated at 75°C for 1 hour, and then heated at 85°C for 15 hours to obtain a liquid composition containing rice protein. For Example 3, PG was added and the mixture was treated at 50°C for 1 hour, then at 75°C for 1 hour, and then heated at 85°C for 15 hours to obtain a liquid composition containing rice protein. For Example 4, α-amylase was added and the mixture was treated at 75°C for 1 hour, then PG was added and the mixture was treated at 50°C for 1 hour, and then heated at 85°C for 15 hours to obtain a liquid composition containing rice protein.

[0058] For the four obtained rice protein-containing liquid compositions, the soluble protein concentration was measured using the BCA method, and sensory evaluation was performed on their ability to improve smoothness, increase viscosity, and suppress rice odor based on the following criteria. The results are shown in Table 3. In addition, approximately 15 ml of each of the four obtained rice protein-containing liquid compositions was placed in a transparent cup with a base diameter of 4 cm, and photographs of the appearance of the rice protein-containing liquid composition taken from the opening of the cup are shown in Figure 2.

[0059] <Improved smoothness> ××: Feels very rough. ×: It has a rough texture. △: Slightly rough texture can be felt. ○: Feels smooth

[0060] <Viscosity-enhancing properties> ××: The viscosity is too low, resulting in a bland texture. ×: Low viscosity △: Slightly low viscosity ○: The viscosity has increased, resulting in a richer flavor. ◎: It has a high viscosity, almost to the point of becoming gel-like, and has a strong, rich flavor.

[0061] <Rice odor suppression> ××: A strong rice smell can be detected. ×: A rice-like smell can be detected. △: A slight rice-like smell can be detected. ○: The rice smell is very faint.

[0062] [Table 3]

[0063] As shown in Examples 3 and 4 of Table 3, treating the aqueous dispersion of crushed rice with PG significantly improved smoothness compared to the case without enzyme treatment (Comparative Example 3) and the case with treatment with the saccharifying enzyme α-amylase (Comparative Example 4). Furthermore, as shown in Table 3, among Examples 3 and 4, Example 3, which was not treated with α-amylase, also showed a significant increase in viscosity and a strong richness. In other words, Example 3 was a rice milk that achieved a creamy texture due to its significantly improved smoothness and strong richness. As shown in Figure 2, Examples 3 and 4 were semi-transparent, Comparative Example 3 was opaque, and Example 3 was gelled and also highly opaque in appearance, reflecting its viscosity characteristics visually. In addition, as shown in Examples 3 and 4, treating the aqueous dispersion of crushed rice with PG significantly reduced the rice odor of the raw material.

Claims

1. A method for producing a liquid composition containing rice protein, comprising the step of treating a liquid material containing rice protein with a protein deamidase of 1 U or more per gram of rice protein.

2. The manufacturing method according to claim 1, wherein the liquid material containing rice protein is an aqueous dispersion of crushed rice.

3. The manufacturing method according to claim 1 or 2, which does not include a step of treatment with a saccharifying enzyme.

4. A manufacturing method according to any one of claims 1 to 3, which does not include a fermentation step.

5. A viscosity enhancer for a liquid composition containing rice protein, comprising a protein deamidase, The liquid composition containing the rice protein is an aqueous dispersion of crushed rice, and A viscosity enhancer that is not used in combination with saccharifying enzymes.

6. A liquid composition containing rice protein and a protein deamidase is used as a rice odor reducer, A rice odor reducing agent for which the protein deamidase is used at a rate of 1 U or more per gram of rice protein in the liquid composition.

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