Heat-coagulated gel strength adjuster for egg white protein

Abstract

[Problem] The purpose of the present invention is to provide a technology that enables control for increasing or decreasing the heat coagulation gel strength of egg white protein, and that has little effect on taste. [Solution] This heat coagulation gel strength regulating agent for egg white protein contains a protein deamidase and can control the increase or decrease of the heat coagulation gel strength of egg white protein.

Description

[Technical Field]

[0001] The present invention relates to an agent for adjusting the strength of a heat-coagulated gel of egg white protein. [Background technology]

[0002] Egg white proteins have the property of forming a gel network upon thermal coagulation, and this property is an important factor in determining the texture characteristics of foods cooked with egg white.

[0003] In addition to utilizing the inherent coagulation properties of eggs during cooking, techniques have been reported for improving the quality of the resulting cooked food. For example, Patent Document 1 shows that the texture of the resulting processed egg food can be densified by adding transglutaminase to egg-based raw materials and then cooking and heating them. Furthermore, Patent Document 2 shows that immersing processed egg foods such as boiled eggs in a solution containing transglutaminase can impart firmness and elasticity compared to products not treated with transglutaminase.

[0004] Furthermore, research into the coagulation properties of eggs has also reported that the addition of salt increases jelly strength, while the addition of sugar decreases it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-250651 [Patent Document 2] Japanese Patent Application Publication No. 2017-175976 [Non-patent literature]

[0006] [Non-Patent Document 1] Cooking Science Vol.15 No.2(1982)p.114-118 Summary of the Invention [Problem to be solved by the invention]

[0007] Because the thermal coagulation properties of egg white protein are utilized in a wide range of cooked foods, it is believed that the versatility of egg white protein could be further expanded if it were possible to control the increase / decrease (increase or decrease) of its thermally coagulated gel strength by a means that does not significantly affect the taste. However, in the methods using transglutaminase as in Patent Documents 1 and 2, only the effect based on the enzyme property of catalyzing the cross-linking reaction of proteins, i.e., the effect of increasing the thermally coagulated gel strength of egg white protein, can be expected, and in the method using seasonings such as salt or sugar as in Non-Patent Document 1, the range of application to cooked foods is limited due to the significant effect on the taste.

[0008] Therefore, an object of the present invention is to provide a technology that can control the increase / decrease (increase or decrease) of the heat-coagulated gel strength of egg white protein while minimizing the effect on taste. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors unexpectedly discovered that protein deamidase (protein glutaminase) can both increase and decrease the heat-coagulated gel strength of egg white protein, depending on the amount added. The present invention was completed based on this finding and through further research. Specifically, the present invention provides the following aspects.

[0010] Item 1. A heat-coagulated gel strength adjuster for egg white protein, containing protein deamidase. Item 2. The heat-coagulated gel strength adjuster according to Item 1, which is used in the production of a food product containing a heat-coagulated gel of egg white protein. Item 3. The heat-coagulated gel strength adjuster according to Item 1 or 2, wherein the amount of protein deamidase used per 1 g of egg white protein is 0.1 to 19 U, and the agent is used to increase the heat-coagulated gel strength of egg white protein. Item 4. The thermally coagulated gel strength adjuster according to Item 1 or 2, wherein the amount of protein deamidase used per 1 g of egg white protein is 20 U or more and the agent is used to reduce the thermally coagulated gel strength of egg white protein. Item 5. A method for adjusting the strength of a heat-coagulated gel of an egg white protein, comprising: step 1 treating an egg white protein with a protein deamidase; and step 2 heat-coagulating the treated egg white protein. Item 6. A method for producing a gelling material, comprising the step of treating a material containing egg white protein with an agent for adjusting the heat-coagulated gel strength of egg white protein, which agent contains protein deamidase, to obtain a gelling material with an adjusted heat-coagulated gel strength. Item 7. A method for producing a food product, comprising the step of heating and solidifying the gelling material obtained by the production method according to Item 6. Item 8. A method for producing a food product, comprising the steps of preparing a mixture of the gelling material obtained by the production method according to Item 6 with other food materials, and heating the mixture at a temperature at which the gelling material solidifies. [Effects of the Invention]

[0011] According to the present invention, a technology is provided that makes it possible to control the increase / decrease (increase or decrease) of the heat-coagulated gel strength of egg white protein, with little effect on taste. [Brief explanation of the drawings]

[0012] [Figure 1] This shows the results of adjusting the heat-coagulated gel strength by PG treatment for 5 w / v% dilution of egg white albumin. [Figure 2] This shows the results of adjusting the heat-coagulated gel strength by PG treatment for 10 w / v% diluted egg albumin. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1. Heat-coagulated gel strength adjuster for egg white protein The agent for adjusting the strength of a heat-coagulated gel of egg white protein of the present invention is characterized by containing protein deamidase.

[0014] 1-1.Active ingredients Protein deamidase is included as an active ingredient in the agent for adjusting the thermally coagulated gel strength of egg white protein of the present invention. The protein deamidase is not particularly limited in type or origin, as long as it is an enzyme that degrades amide group-containing side chains of proteins without cleaving peptide bonds or cross-linking proteins. Examples of protein deamidase include protein deamidase derived from the genera Chryseobacterium, Flavobacterium, Empedobacter, Sphingobacterium, Aureobacterium, or Myroides, as disclosed in JP2000-50887A, JP2001-218590A, and WO2006 / 075772A1, and commercially available protein glutaminases derived from the genus Chryseobacterium. These protein deamidating enzymes may be used singly or in combination of two or more.

[0015] Among these protein deamidating enzymes, from the viewpoint of further enhancing the effect of adjusting the heat-coagulated gel strength of egg white protein, protein deamidating enzymes derived from the genus Chryseobacterium are preferred, protein glutaminases derived from the genus Chryseobacterium are more preferred, and protein glutaminase derived from the species Chryseobacterium proteolyticum is even more preferred.

[0016] Protein deamidase can be prepared from a culture medium of a microorganism from which the above-mentioned protein deamidase is derived. Specific preparation methods include methods of recovering protein deamidase from the culture medium or cells of the above-mentioned microorganism. For example, when a protein deamidase-secreting microorganism is used, the cells can be recovered from the culture medium in advance by filtration, centrifugation, or the like, as necessary, and the enzyme can then be separated and / or purified. When a protein deamidase-nonsecreting microorganism is used, the cells can be recovered from the culture medium in advance by pressure treatment, ultrasonic treatment, or the like, as necessary, and the enzyme can then be separated and / or purified. The enzyme can be separated and / or purified by any known protein separation and / or purification method, without any particular limitation, and examples of the method include centrifugation, UF concentration, salting out, and various chromatography methods using ion exchange resins, etc. The separated and / or purified enzyme can be powdered by a drying method such as freeze-drying, vacuum drying, or spray drying. Furthermore, the enzyme can also be powdered by the drying method using an appropriate excipient and / or drying aid. Alternatively, the isolated and / or purified enzyme can be liquefied by adding an appropriate additive and sterilizing by filtration.

[0017] Commercially available protein deamidating enzymes can also be used, and a preferred example of a commercially available protein glutaminase is "Amano" 500 manufactured by Amano Enzyme Inc.

[0018] The content of protein deamidase in the agent for adjusting the strength of a heat-coagulated egg white protein gel of the present invention is not particularly limited, and examples thereof include 0.1 to 10,000 U / g, preferably 1 to 8,000 U / g, 10 to 6,000 U / g, 50 to 4,000 U / g, 100 to 2,000 U / g, 150 to 1,000 U / g, 200 to 800 U / g, more preferably 300 to 700 U / g, even more preferably 400 to 600 U / g, and even more preferably 450 to 550 U / g.

[0019] Regarding the activity of protein deamidase, one unit (1 U) is defined as the amount of enzyme that metabolizes 1 μmol of ammonia per minute using benzyloxycarbonyl-L-glutaminylglycine (Z-Gln-Gly) as a substrate.

[0020] 1-2.Other ingredients The agent for adjusting the strength of a heat-coagulated egg white protein gel of the present invention may contain other components in addition to the protein deamidase, to the extent that the effects of the present invention are not affected. Examples of other components include enzymes other than the above-mentioned specific protein glutaminase, additives, etc.

[0021] Examples of other enzymes include amylases (α-amylase, β-amylase, glucoamylase), glucosidases (α-glucosidase, β-glucosidase), galactosidases (α-galactosidase, β-galactosidase), proteases (acid proteases, neutral proteases, alkaline proteases), peptidases (leucine peptidases, aminopeptidases), lipases, esterases, cellulases, phosphatases (acid phosphatases, alkaline phosphatases), nucleases, deaminases, oxidases, dehydrogenases, glutaminase, pectinases, catalases, dextranases, transglutaminase, pullulanases, etc. These other enzymes may be contained singly or in combination.

[0022] Examples of additives include excipients, buffers, suspending agents, stabilizers, preservatives, antiseptics, and physiological saline. Examples of excipients include starch, dextrin, maltose, trehalose, lactose, D-glucose, sorbitol, D-mannitol, sucrose, and glycerol. Examples of buffers include phosphates, citrates, and acetates. Examples of stabilizers include propylene glycol and ascorbic acid. Examples of preservatives include phenol, benzalkonium chloride, benzyl alcohol, chlorobutanol, and methylparaben. Examples of preservatives include ethanol, benzalkonium chloride, parahydroxybenzoic acid, and chlorobutanol. These additives may be contained alone or in combination.

[0023] 1-3. Formulation The form of the agent for adjusting the strength of a thermally coagulated egg white protein gel of the present invention is not particularly limited, and examples thereof include liquid and solid forms (powder, granules, etc.) Preparation into these forms may be carried out by a generally known method.

[0024] 1-4.Applications The agent for adjusting the heat-coagulated gel strength of an egg white protein of the present invention is used for the purpose of increasing or decreasing the gel strength of a gel produced by thermal coagulation of an egg white protein. Specifically, the agent for adjusting the heat-coagulated gel strength of an egg white protein of the present invention can be used as an agent that provides the protein deamidase that treats the egg white protein in a method for adjusting the heat-coagulated gel strength of an egg white protein, which method includes step 1 of treating the egg white protein with a protein deamidase and step 2 of thermally coagulating the treated egg white protein.

[0025] The egg white protein is not particularly limited as long as it is an egg white protein from an avian egg, but is preferably an egg white protein from an avian egg for eating, more preferably an egg white protein from a chicken egg. Furthermore, the egg white protein is not particularly limited as long as it is a protein that constitutes egg white, and examples thereof include ovalbumin, ovotransferrin, ovomucoid, ovomucin, etc., and these egg white proteins may be used alone or in combination. Among these egg white proteins, at least ovalbumin is preferably included, from the viewpoint of further enhancing the effect of adjusting the heat-coagulated gel strength of the egg white protein.

[0026] The specific form of the egg white protein in step 1 is not particularly limited as long as it contains egg white protein that has not been heat-coagulated, and examples include purified egg white protein, raw egg white, dried egg white, raw whole egg, dried whole egg, and mixtures of these with other components (e.g., other food ingredients, etc.).

[0027] The dilution rate of the egg white protein in step 1 is not particularly limited, but may be, for example, 0.1 to 30 w / v%, preferably 0.3 to 25 w / v%, more preferably 0.6 to 20 w / v%, even more preferably 1 to 15 w / v%, and even more preferably 3 to 12 w / v%.

[0028] The gel strength regulator of egg white protein heat-coagulated gel of the present invention can be controlled to increase or decrease the gel strength of the gel formed by thermal coagulation of egg white protein by adjusting the amount of protein deamidase used relative to the amount of egg white protein in step 1. For example, when the gel strength of the gel formed by thermal coagulation of egg white protein is to be increased, the amount of protein deamidase used relative to the amount of egg white protein can be made smaller, whereas when the gel strength of the gel formed by thermal coagulation of egg white protein is to be decreased, the amount of protein deamidase used relative to the amount of egg white protein can be made larger.

[0029] More specifically, when the gel strength of a gel formed by thermal coagulation of egg white protein is to be increased, the amount of protein deamidase to be used per 1 g of egg white protein is, for example, 0.1 to 19 U, preferably 0.25 to 15 U, 0.5 to 11 U, 0.75 to 7.5 U, 1 to 4 U, more preferably 1.5 to 3.5 U, even more preferably 2 to 3 U, and even more preferably 2.2 to 2.8 U.

[0030] Furthermore, when reducing the gel strength of the gel formed by thermal coagulation of egg white protein, the amount of protein deamidase used per 1 g of egg white protein can be increased, and examples of the amount used include 5 U or more, 10 U or more, preferably 15 U or more, 20 U or more, more preferably 25 U or more, even more preferably 50 U or more, still more preferably 100 U or more, and still more preferably 200 U or more. In this case, the upper limit of the amount of protein deamidase used per 1 g of egg white protein is not particularly limited, and examples include 500 U or less, 400 U or less, 300 U or less, and 260 U or less.

[0031] The temperature for the protein deamidating treatment in step 1 is not particularly limited as long as it is lower than the thermal coagulation temperature of egg white protein, and can be appropriately determined by a person skilled in the art based on the optimal temperature of protein deamidating enzyme, etc., but is preferably 35 to 65°C, 35 to 60°C, or 35 to 59°C, more preferably 36 to 55°C, even more preferably 37 to 55°C, even more preferably 38 to 50°C, and even more preferably 39 to 45°C.

[0032] The treatment time with protein deamidating enzyme in step 1 is not particularly limited and may be appropriately determined depending on the preparation scale of the composition, etc., and may be, for example, 0.5 hours or more, preferably 1 hour or more, more preferably 1.5 hours or more, and even more preferably 2 hours or more, 8 hours or more, 12 hours or more, or 20 hours or more. The upper limit of the above-mentioned time range is not particularly limited, and may be, for example, 30 hours or less, 24 hours or less, 12 hours or less, 8 hours or less, 6 hours or less, or 4 hours or less.

[0033] The treatment temperature in step 2 is not particularly limited as long as it is a temperature at which the egg white protein can be thermally coagulated, and may be determined appropriately depending on the type of egg white protein to be treated, and examples include 60°C or higher, preferably 65°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, and even more preferably 78°C or higher. The upper limit of the treatment temperature range is not particularly limited as long as a thermally coagulated gel of egg white protein is obtained, and can be determined appropriately by those skilled in the art depending on the form of the egg white protein. For example, when the agent for modulating the strength of a thermally coagulated egg white protein gel of the present invention is used in the production of the foods described below, treatment can be carried out at a heating temperature normally used for cooking such foods.

[0034] As described above, the agent for adjusting the strength of a heat-coagulated gel of an egg white protein of the present invention can increase or decrease the strength of the heat-coagulated gel of an egg white protein, thereby further diversifying the texture characteristics of foods cooked with egg white protein. Thus, the agent for adjusting the strength of a heat-coagulated gel of an egg white protein of the present invention can be preferably used in the production of foods containing a heat-coagulated gel of an egg white protein.

[0035] Foods containing a thermally coagulated gel of egg white protein are not particularly limited as long as they are foods obtained by cooking with egg white, but from the viewpoint of further enhancing the effect of adjusting the strength of the thermally coagulated gel of egg white protein, non-emulsified foods are preferred. Further specific foods include cooked egg foods (e.g., boiled eggs, soft-boiled eggs, poached eggs, scrambled eggs, thick omelets, rolled omelets, egg fillings for Tianjin rice bowls, egg yolks, quiches, omelets, thin omelets (omelette sheets, shredded omelets), chawanmushi, egg tofu, etc.), and foods using egg white as a binder (fish paste foods such as kamaboko, chikuwa, hanpen, datemaki, and fish sausage; processed meats such as hamburger steaks, meatballs, patties, meatloaf, and minced meat cutlets; and foods in which these are replaced with plant-based artificial meat, etc.).

[0036] In the methods for producing these foods, the above-mentioned step 1 can be carried out at any stage of the normal cooking steps carried out to cook the foods, at which time the egg white protein has not yet been thermally coagulated, and then a normal cooking step (a step corresponding to the above-mentioned step 2) for thermally coagulating the egg white protein can be carried out.

[0037] 2. Method for adjusting the strength of heat-coagulated gel of egg white protein As described above, protein deamidase, which is the active ingredient of the agent for adjusting the heat-coagulated gel strength of egg white protein of the present invention, can adjust the heat-coagulated gel strength of egg white protein by increasing or decreasing it. Thus, the present invention also provides a method for adjusting the heat-coagulated gel strength of egg white protein, which includes step 1 of treating an egg white protein with protein deamidase and step 2 of heat-coagulating the treated protein.

[0038] In the method for adjusting the strength of a heat-coagulated egg white protein gel of the present invention, the types and amounts of components used, the conditions for each step, and the like are as shown in the section "1. Agent for adjusting the strength of a heat-coagulated egg white protein gel."

[0039] 3. Manufacturing method of gelling material As described above, protein deamidase can adjust the gel strength of the gel produced by thermal coagulation of egg white protein by increasing or decreasing it, and egg white protein treated with protein deamidase can be used as a gelling material with an adjusted thermally coagulated gel strength.

[0040] Therefore, the present invention also provides a method for producing a gelling material, which includes a step of treating a material containing egg white protein with an agent for adjusting the heat-coagulated gel strength of egg white protein, which agent contains protein deamidase, to obtain a gelling material with an adjusted heat-coagulated gel strength.

[0041] The agent for adjusting the strength of a heat-coagulated gel of an egg white protein, which contains protein deamidase, is as described above in the section "1. Agent for adjusting the strength of a heat-coagulated gel of an egg white protein."

[0042] Specifically, examples of materials containing egg white protein in the method for producing a gelling material of the present invention include purified egg white protein, raw egg white, dried egg white, raw whole egg, and dried whole egg.

[0043] Furthermore, the amount of protein deamidating enzyme used, the treatment temperature, the treatment time, and the like when treating a material containing egg white protein are as described in the explanation of step 1 in "1-4. Use" of "1. Agent for adjusting strength of thermally coagulated gel of egg white protein."

[0044] The form of the gelling material with an adjusted thermally coagulated gel strength obtained by the method for producing a gelling material of the present invention is not particularly limited, as long as the egg white protein is not thermally coagulated. For example, the form of the gelling material with an adjusted thermally coagulated gel strength may be liquid or solid (frozen, freeze-dried, spray-dried, etc.).

[0045] 4. Food manufacturing methods The gelling material having an adjusted thermally coagulated gel strength can be used to produce a variety of foods. Therefore, the present invention also provides a method for producing foods using the gelling material having an adjusted thermally coagulated gel strength.

[0046] An example of the method for producing the food product of the present invention includes a step of heat-coagulating the gelling material having the above-mentioned adjusted thermally coagulated gel strength.

[0047] In the above example of the food production method, the heat coagulation temperature is not particularly limited as long as it is a temperature at which the egg white protein can be thermally coagulated, and may be determined appropriately depending on the type of egg white protein used as a raw material for the gelling material, and examples include 60° C. or higher, preferably 65° C. or higher, more preferably 70° C. or higher, even more preferably 75° C. or higher, and even more preferably 78° C. or higher. There are no particular limitations on the upper limit of the treatment temperature range, but this can be determined appropriately by those skilled in the art depending on the form of the food to be produced.

[0048] Foods obtainable by one example of the above-mentioned food manufacturing method include cooked egg foods, and more specifically, include boiled eggs, soft-boiled eggs, poached eggs, scrambled eggs, thick omelets, rolled omelets, egg ingredients for Tianjin rice bowls, egg scrambled eggs, tamagoyaki (egg-covered eggs), quiche, omelets, thin omelets (omelet rice sheets, shredded omelets), chawanmushi (savory egg custard), egg tofu, etc.

[0049] Another example of the method for producing a food product of the present invention includes the steps of preparing a mixture of the gelling material having the above-mentioned adjusted thermal coagulation gel strength with other food materials, and heating the mixture at a temperature at which the gelling material coagulates by heating.

[0050] Other food ingredients and heating conditions to be used in the above-mentioned other examples of food production methods can be appropriately determined by those skilled in the art depending on the form of the food to be produced, as long as the temperature is such that egg white protein can be thermally coagulated.

[0051] Other examples of foods obtainable by the above-mentioned food manufacturing methods include foods that use egg white as a binder, and more specifically, fish paste foods such as kamaboko, chikuwa, hanpen, datemaki, and fish sausage; processed meats such as hamburger steaks, meatballs, patties, meatloaf, and minced meat cutlets; and foods in which these are replaced with plant-based artificial meat. [Example]

[0052] The present invention will be specifically described below with reference to examples, but the present invention should not be construed as being limited to the following examples.

[0053] Enzymes used As the protein deamidase, PG-500 (Protein-glutaminase "Amano" 500; protein glutaminase derived from Chryseobacterium proteolyticum; hereinafter also referred to as "PG") was used.

[0054] The protein deamidase activity was measured by the following method. To 1 mL of 0.2 M phosphate buffer (pH 6.5) containing 30 mM Z-Gln-Gly, 0.1 mL of the sample solution containing protein deamidase was added, and the mixture was left at 37°C for 10 minutes. After that, 1 mL of 0.4 M TCA solution was added to stop the reaction. As a blank, 1 mL of 0.4 M TCA solution was added to 1 mL of 0.2 M phosphate buffer (pH 6.5) containing 30 mM Z-Gln-Gly, and 0.1 mL of the sample solution containing protein deamidase was further added, and the mixture was left at 37°C for 10 minutes.

[0055] The amount of ammonia generated in the reaction solution was measured using an Ammonia Test Wako (Fujifilm Wako Pure Chemical Industries, Ltd.) 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 an ammonia standard solution (ammonium chloride).

[0056] The activity of protein deamidase was calculated using the following formula, where 1 unit (1U) is the amount of enzyme required to produce 1 μmol of ammonia per minute. In the formula, the volume of the reaction solution is 2.1, the volume of the enzyme solution is 0.1, Df is the dilution factor of the enzyme solution, and 17.03 is the molecular weight of ammonia.

[0057]

number

[0058] Test Example 1 0.5 g of ovalbumin (Fujifilm Wako Pure Chemical Corporation) was weighed into a 50 mL tube, and 10 mL of 50 mM phosphate buffer (pH 7.0) was added (ovalbumin dilution rate: 5 w / v%). PG was added at 2.5 U, 25 U, or 250 U per 1 g of ovalbumin substrate, and the mixture was allowed to react at 40°C for 2 or 24 hours. The entire reaction mixture was transferred to a Petri dish and heated at 80°C for 1 hour to allow thermal coagulation. The gel strength of the heat-coagulated ovalbumin gel was measured using a rheometer (Sun Scientific Co., Ltd.). The obtained heat-coagulated gel strength was converted into a relative amount (%), with the gel strength of the heat-coagulated ovalbumin gel obtained in the same manner except without the addition of PG being taken as 100%. The results are shown in Figure 1.

[0059] As shown in Figure 1, when 2.5 U of PG was added to 1 g of egg white albumin, the gel strength of the heat-coagulated gel increased. On the other hand, when 25 U or 250 U of PG was added to 1 g of egg white albumin, the gel strength of the heat-coagulated gel decreased.

[0060] Test Example 2 In a 50 mL tube, 1.0 g of ovalbumin was weighed and 10 mL of 50 mM phosphate buffer (pH 7.0) was added to give an ovalbumin dilution rate of 10 w / v% and a PG treatment time of 24 hours, and the relative gel strength (%) of the heat-coagulated ovalbumin gel was obtained in the same manner as in Test Example 1. The results are shown in Figure 2.

[0061] As shown in Figure 2, when 2.5 U of PG was added to 1 g of egg white albumin, the gel strength of the heat-coagulated gel increased. On the other hand, when 25 U or 250 U of PG was added to 1 g of egg white albumin, the gel strength of the heat-coagulated gel decreased.

Claims

1. 1. A heat-coagulated gel strength adjuster for egg white protein, comprising protein deamidase, The amount of the protein deamidase used is when the heat-coagulated gel strength adjuster is used to increase the heat-coagulated gel strength of the egg white protein, the amount of the protein deamidase used per 1 g of the egg white protein is 1 to 7.5 U; when the heat-coagulated gel strength adjuster is used to reduce the heat-coagulated gel strength of the egg white protein, the amount of the protein deamidase used per 1 g of the egg white protein is 200 to 500 U; A heat-coagulated gel strength adjuster that is used by adjusting the strength so that the gel is solidified.

2. The heat-coagulated gel strength adjuster according to claim 1 , which is used in the production of a food product containing a heat-coagulated gel of egg white protein.

3. A method for adjusting the strength of a thermally coagulated gel of an egg white protein, comprising: step 1 treating an egg white protein with a protein deamidase; and step 2 thermally coagulating the treated egg white protein, In the step 1, the amount of the protein deamidase used is When the strength of the heat-coagulated gel is to be increased, the amount of the protein deamidase used per 1 g of the egg white protein is 1 to 7.5 U; In the case of reducing the strength of the heat-coagulated gel, the amount of the protein deamidase used per 1 g of the egg white protein is 200 to 500 U; A method for adjusting the strength of a thermally solidified gel.

4. The method includes a step of treating a material containing egg white protein with an agent for adjusting thermal coagulation gel strength of egg white protein, which agent contains protein deamidase, to obtain a gelling material having an adjusted thermal coagulation gel strength, The amount of the thermally coagulated gel strength adjuster used is In order to obtain a gelling material adjusted to enhance the heat-coagulated gel strength, the amount of the protein deamidating enzyme used per 1 g of the egg white protein is 1 to 7.5 U, In order to obtain a gelling material adjusted to reduce the thermally coagulated gel strength, the amount of the protein deamidating enzyme used per 1 g of the egg white protein is 200 to 500 U, The method for producing a gelling material is adjusted so that the gelling material is:

5. A method for producing a food product, comprising a step of heating and solidifying the gelling material obtained by the method according to claim 4.

6. 5. A method for producing a food product, comprising the steps of: preparing a mixture of the gelling material obtained by the method of claim 4 with other food materials; and heating the mixture at a temperature at which the gelling material solidifies.

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