Ice recrystallization inhibitor, method for producing frozen or freeze-dried food, and fermented soybean product or extract thereof

Abstract

To provide an ice recrystallization retardant capable of favorably maintaining a quality of a frozen food or a freeze-dried food, a method of producing the frozen food or the freeze-dried food, and a soybean fermented product or an extract thereof to be used for producing the frozen food or the freeze-dried food.SOLUTION: An ice recrystallization retardant includes a soybean fermented product or an extract thereof.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ice recrystallization inhibitor, a method for producing a frozen food or a freeze-dried food, and a fermented soybean product or an extract thereof. [Background technology]

[0002] Food freezing is a widely used preservation technique that can maintain the quality of food for a long period of time. However, as ice crystals grow during the freezing process, it can cause problems such as deterioration of texture due to the destruction of cellular tissue, dripping after thawing or reconstitution, discoloration, and starch retrogradation. As a method for solving this problem, it has been proposed to add a substance that suppresses ice recrystallization to food. For example, Patent Documents 1 and 2 describe that when food is frozen in a state in which a plant-derived protein is added, ice recrystallization is suppressed and the quality is well maintained. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-69603 A [Patent Document 2] Special Publication No. 2012-121172 Summary of the Invention [Problem to be solved by the invention]

[0004] Finding new substances that can inhibit ice recrystallization will broaden the range of options for food freezing preservation techniques and contribute to the development of the food industry.

[0005] In view of the above circumstances, an objective of the present disclosure is to provide an ice recrystallization inhibitor that can maintain the quality of frozen foods or freeze-dried foods well, a method for producing frozen foods or freeze-dried foods, and a soybean fermentation product or an extract thereof for use in producing frozen foods or freeze-dried foods. [Means for solving the problem]

[0006] The means for solving the above problems are as follows. <1> An ice recrystallization inhibitor comprising a fermented soybean product or an extract thereof. <2> The fermented soybean product includes miso. <1> The ice recrystallization inhibitor according to claim 1. <3> The soybean fermentation product or extract thereof contains a component having a molecular weight of 140,000 to 160,000. <1> or <2> The ice recrystallization inhibitor according to claim 1. <4> Further comprising collagen peptides, <1> ~ <3> The ice recrystallization inhibitor according to any one of claims 1 to 7. <5> The mass ratio of the fermented soybean product or extract thereof to the collagen peptide (fermented soybean product or extract thereof:collagen peptide) is 1:1 to 1:100. <5> The ice recrystallization inhibitor according to claim 1. <6> For use in producing frozen or freeze-dried foods, <1> ~ <5> The ice recrystallization inhibitor according to any one of claims 1 to 7. <7> A method for producing a frozen food or freeze-dried food, comprising the steps of adding a fermented soybean product or an extract thereof to a food, and freezing the food. <8> A fermented soybean product or an extract thereof for use in the manufacture of frozen or freeze-dried foods. Effect of the Invention

[0007] According to the present disclosure, there are provided an ice recrystallization inhibitor that can maintain the quality of frozen foods or freeze-dried foods well, a method for producing frozen foods or freeze-dried foods, and a soybean fermentation product or an extract thereof for use in producing frozen foods or freeze-dried foods. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional photograph of frozen and dried tofu in an embodiment. [Diagram 2] 1 is a cross-sectional photograph of frozen and dried tofu in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described in detail. However, the scope of the present invention is not limited to the following description. In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively.

[0010] <Ice recrystallization inhibitor> The ice recrystallization inhibitor of the present disclosure includes a soybean fermentation product or an extract thereof. The present inventors have found through their investigations that a fermented soybean product or an extract thereof has the effect of inhibiting ice recrystallization, a finding that has not been reported before.

[0011] In the present disclosure, the term "ice recrystallization inhibitor" refers to a substance or composition that has the effect of inhibiting the growth of ice crystals. The above-mentioned action of the ice recrystallization inhibitor is considered to occur by the ice recrystallization inhibitor binding to the crystal surface of the ice crystal and inhibiting further binding of free water to the ice crystal. More specifically, when the ice recrystallization inhibitory activity (RI) measured by the method described in the examples below is less than 1, it can be judged that the inhibitor has an action of inhibiting the growth of ice crystals.

[0012] Since the ice recrystallization inhibitor of the present disclosure contains a fermented soybean product or an extract thereof, it is highly safe with no risk of causing side effects to the living body or the environment. Furthermore, since the raw materials are processed products rather than fresh produce, it is easy to increase production and has excellent productivity.

[0013] In the present disclosure, the type of soybean fermented product is not particularly limited, and may be selected from fermented foods that use soybeans as a raw material, such as miso, soy sauce, natto, etc. Alternatively, it may be a product obtained by fermenting soybeans for non-edible purposes. From the viewpoint of effective utilization of food waste, the fermented soybean product may be residues, by-products, unnecessary inventory, etc. generated during the production of fermented foods. In one embodiment, the fermented soybean product may be miso. Examples of miso include rice miso (miso produced using rice koji), barley miso (miso produced using barley koji), and soybean miso (miso produced using soybean koji), and can be used without any particular limitation. The fermented soybean products may be used alone or in combination of two or more kinds.

[0014] The concentration of the fermented soybean product or an extract thereof contained in the ice recrystallization inhibitor is not particularly limited, and can be adjusted depending on the method and purpose of use. The ice recrystallization inhibitor may be in the form of a dry powder or a concentrated liquid, which is diluted with water or the like when used.

[0015] In the present disclosure, the fermented soybean product may be used as the ice recrystallization inhibitor as it is, or an extract of the fermented soybean product may be used as the ice recrystallization inhibitor. The method for obtaining an extract of the fermented soybean product is not particularly limited. For example, the fermented soybean product may be mixed with a solvent to dissolve it, and the residue may be separated by centrifugation, filtration, or the like to obtain the extract as a solution (extract liquid). The type of solvent is not particularly limited, and may be a water-soluble solvent such as water or alcohol, and is preferably water. When the fermented soybean product contains salt, a treatment for removing the salt (desalting) may be carried out as necessary.

[0016] From the viewpoint of obtaining a sufficient ice recrystallization suppressing effect, the RI of the ice recrystallization inhibitor is preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less.

[0017] From the viewpoint of obtaining a sufficient ice recrystallization inhibitory effect, the soybean fermentation product or extract thereof contained in the ice recrystallization inhibitor preferably contains a component having a molecular weight of 140,000 to 160,000, and more preferably contains a component having a molecular weight of 158,000.

[0018] Whether or not a fermented soybean product or an extract thereof contains a component having a molecular weight within the above range can be confirmed by a known method such as gel filtration chromatography.

[0019] The ice recrystallization inhibitor may further contain components other than the fermented soybean product or an extract thereof, and the solvent. For example, substances having an ice recrystallization inhibitory effect other than the fermented soybean product, storage stabilizers, thickeners, seasonings, etc. may be mentioned.

[0020] Substances other than fermented soybeans that have an ice recrystallization inhibitory effect can be used without particular limitation.Specific examples include proteins and polysaccharides derived from animals, plants, insects, fungi, microorganisms, etc.

[0021] The ice recrystallization inhibitor may contain a fermented soybean product or an extract thereof, and a collagen peptide. Collagen peptide is known to have an ice recrystallization inhibitory effect. As a result of the inventors' investigation, it was found that the combined use of collagen peptide and fermented soybean product or an extract thereof synergistically increases the ice recrystallization inhibitory effect compared to the use of collagen peptide alone, or fermented soybean product or an extract thereof alone.

[0022] From the viewpoint of effectively obtaining the above synergistic effect, the mass ratio of the fermented soybean product or extract thereof to the collagen peptide (fermented soybean product or extract thereof:collagen peptide) is preferably 1:1 to 1:100, more preferably 1:2 to 1:50, and even more preferably 1:5 to 1:20. The above mass ratios are values ​​calculated as solid contents.

[0023] Examples of collagen peptides include collagen peptides derived from cows, pigs, fish, etc., and these can be used without any particular restrictions.

[0024] The use of the ice recrystallization inhibitor is not particularly limited as long as it utilizes the ice recrystallization inhibitory effect. For example, it may be used in the production of frozen foods or freeze-dried foods, medicines, cosmetics, etc. Among them, it is preferably used in the production of frozen foods or freeze-dried foods.

[0025] <Method of manufacturing frozen or freeze-dried foods> The frozen or freeze-dried food of the present disclosure includes the steps of adding a fermented soybean product or an extract thereof to a food product and freezing the food product. The frozen food or freeze-dried food produced by the above method is less susceptible to deterioration in texture, dripping after thawing or reconstitution with water, discoloration, starch aging, etc., and maintains good quality.

[0026] In this disclosure, "food" includes anything intended for consumption or drinking by humans or animals and may be solid or liquid. The type of frozen food or freeze-dried food is not particularly limited and may be either fresh food or processed food. In addition, the frozen food or freeze-dried food may be a plant food such as vegetables or grains, or an animal food such as meat, fish, or dairy products.

[0027] The method for adding the fermented soybean product or an extract thereof to a food product is not particularly limited, and examples thereof include a method of immersing a food product in a solution containing the fermented soybean product or an extract thereof, and a method of mixing the fermented soybean product or an extract thereof with the raw materials of the food product. The amount of the fermented soybean product or its extract added to food is not particularly limited. For example, it may be added in the range of 0.0001 g to 1 g (in terms of solid content) per 100 g of food.

[0028] The method for freezing the food to which the fermented soybean product or its extract has been added is not particularly limited. For example, the food may be frozen in a temperature environment of -50°C to -18°C.

[0029] <Soybean fermentation product or its extract> The fermented soybean product or extract thereof of the present disclosure is for use in the production of frozen or freeze-dried foods. The details and preferred embodiments of the fermented soybean product or extract thereof according to the present disclosure are the same as the details and preferred embodiments of the fermented soybean product or extract thereof contained in the ice recrystallization inhibitor described above. EXAMPLES

[0030] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these.

[0031] (1) Preparation of miso extract 10 g of miso (rice miso) and 30 mL of distilled water were added to a 50 mL conical tube and stirred to obtain an aqueous solution of miso. Next, in order to remove salt from the aqueous solution, centrifugation was performed at 12,000 rpm for 15 minutes, and the supernatant was removed. 30 mL of distilled water was added to the precipitate, and centrifugation was performed twice in the same manner as above. The supernatant was then removed from the precipitate, and the precipitate was transferred to a 300 mL Erlenmeyer flask. 40 mL of distilled water was added to one tube's worth of precipitate, and the mixture was heated at 100°C for 30 minutes. The heated solution was centrifuged at 12,000 rpm for 15 minutes and filtered (using No. 5 filter paper) to prepare a miso extract with a final solid concentration of 1 mg / mL.

[0032] (2) Measurement of ice recrystallization inhibition activity (RI) Samples 1 to 5 were prepared by adding sucrose to the miso extracts obtained by varying the amount of distilled water so that the concentrations (mg / mL) were as shown in Table 1, and the RI of each sample was measured by the method described below.

[0033] (RI measurement method) A solution of an ice crystal growth inhibitor containing 30 w / v% sucrose is cooled to -40°C, then the temperature is raised to -6°C, and the average area A of the ice crystals observed after 30 minutes is measured. Separately, a 30 w / v% aqueous solution of sucrose is treated in the same way as a control, and the average area B of the ice crystals is measured. The value (A / B) obtained by dividing the measured average area A of the ice crystals of the ice crystal growth inhibitor by the average area B of the ice crystals of the control is the RI.

[0034] The average ice crystal area was calculated by dividing the total area of ​​ice crystals in an image of the frozen sample surface analyzed using an electron microscope and image analysis software (Scion Image) by the number of ice crystals. The average and standard deviation (n=5) of the RI measured for each sample are shown in Table 1.

[0035] [Table 1]

[0036] As shown in Table 1, there was a tendency for the RI value to decrease as the concentration of the miso extract increased.

[0037] (3) Gel Filtration Chromatography Hydrochloric acid was added to the miso extract (1 mg / mL) obtained in (1) above to adjust the pH to 3.0. Then, a double amount of ethyl acetate was added to fractionate into an ethyl acetate phase and an aqueous phase. The aqueous phase was concentrated to obtain a sample (1 mL) with a concentration of 20 mg / mL. Gel filtration chromatography was performed using Sepacryl S-200, and a peak was confirmed at a position corresponding to a molecular weight of 158,000.

[0038] About 10 samples were collected before and after the peak, and after concentrating them, the RI of the miso extract (0.1 mg / mL) was measured and found to be 0.53. These results suggest that a component with a molecular weight of about 158,000 contained in the miso extract is involved in the ice crystallization inhibition effect.

[0039] (4) RI measurement of collagen peptides Distilled water was added to bovine collagen peptide, a substance having an antifreeze effect, to prepare samples 11 to 16 with the solid content concentrations shown in Table 2. The average value and standard deviation (n=5) of the RI measured for each sample are shown in Table 2.

[0040] [Table 2]

[0041] As shown in Table 1, there was a tendency for the RI value to decrease as the concentration of bovine collagen peptide in the sample increased.

[0042] (5) RI measurement of miso extract + collagen peptide Samples 21 to 26 were prepared by mixing miso extract (0.1 mg / mL) with bovine collagen peptide having a solid content concentration shown in Table 3 in a volume ratio of 1:1. The average value and standard deviation (n=5) of the RI measured for each sample are shown in Table 2. Additionally, the difference in RI (ΔRI) between the samples containing the same amount of bovine collagen peptide was calculated for each of the samples 11 to 16 shown in Table 2. A positive ΔRI value means that the addition of miso extract to the sample containing bovine collagen peptide increased the antifreeze effect.

[0043] [Table 3]

[0044] As shown in Table 3, the RI of "Sample 23" containing miso extract (0.1 mg / mL) and bovine collagen peptide (1.0 mg / mL) in a 1:1 mixture ratio was 0.43, which was significantly lower than the RI (0.63) of "Sample 13" containing only bovine collagen peptide (1.0 mg / mL). Furthermore, it was significantly lower than the RI (0.56) of "Sample 1" containing only the same amount of miso extract (0.1 mg / mL). This suggests that the combined use of miso extract and bovine collagen peptide synergistically increases the ice crystallization inhibition effect compared to the use of only miso extract or only bovine collagen peptide.

[0045] Furthermore, unlike the concentration-dependent tendency seen in samples 1 to 5 containing only miso extract and samples 11 to 16 containing only bovine collagen peptide, the ΔRI of "sample 23" was the largest among samples 21 to 26 containing miso extract and bovine collagen peptide. This shows that when miso extract and bovine collagen peptide are used together, there is a suitable blend ratio for the expression of the ice crystallization inhibitory effect.

[0046] (6) Tofu frozen storage test 1 Silken tofu was cut into 1 cm cubes, lightly wiped dry with paper, and weighed. Ten pieces of cut tofu were then placed in a plastic bag, and soaked in 400 mL of distilled water containing 0.1% (v / v) or 10% (v / v) PM extract for 30 minutes. The "PM extract" used was a mixture of miso extract (0.1 mg / mL) and bovine collagen peptide (1.0 mg / mL) in a volume ratio of 1:1, and so on. After soaking, the tofu was taken out, lightly wiped dry, and stored in a freezer (-20°C) for one week. It was then left to thaw naturally at room temperature for three hours. As a control, the same treatment was carried out using distilled water (400 mL) that did not contain PM extract. The drip rate (mass%) of the thawed tofu was calculated using the following formula. Drip ratio = {(mass after thawing - mass before freezing) / mass before freezing} x 100

[0047] The drip rate was 35.2 mass% when immersed in distilled water containing 0.1% (v / v) PM extract, and 37.6 mass% when immersed in distilled water containing 10% (v / v) PM extract. This indicated that dripping was suppressed compared to 44.1 mass% when immersed in distilled water without PM extract.

[0048] (7) Tofu frozen storage test 2 A block of silken tofu was cut in half, drained on a mesh for 1 minute, and the mass was measured. Each piece of cut tofu was then placed in a plastic bag and soaked in distilled water (40 mL) containing 0.1% (v / v) or 10% (v / v) miso extract (1 mg / mL) for 30 minutes. After soaking, the tofu was taken out, wiped dry, and stored in a freezer (-20℃) for one week. It was then left to thaw naturally at room temperature for three hours, drained on a mesh for five minutes, and its mass was measured. As a control, the same treatment was carried out using distilled water (40 mL) that did not contain miso extract. The change in mass (g) of the tofu after thawing was calculated using the following formula. Mass change = (mass after thawing - mass before freezing)

[0049] The mass change when immersed in distilled water containing 0.1% (v / v) miso extract was 57.15 g, and the mass change when immersed in distilled water containing 10% (v / v) miso extract was 56.57 g. These mass changes were smaller than the 59.65 g observed when immersed in distilled water without miso extract.

[0050] (8) Tofu frozen storage test 3 Tofu (silk) was cut into 1 cm cubes and placed in a colander for 1 minute to drain the water. Distilled water (120 mL) containing 0.01% (v / v) miso extract (1 mg / mL) was added to 200 g of this tofu and soaked overnight in a refrigerator at -4°C. The water was then drained, and the cubes were placed in a freeze-dryer at -50°C and frozen overnight. They were then dried overnight. As a control, the same treatment was performed on tofu that had not been soaked in distilled water containing miso extract.

[0051] After soaking the tofu in hot water for one minute, six subjects tasted the tofu and rated its "smoothness" as an index of texture on a seven-point scale from -3 to +3. The higher the score, the smoother the tofu. The average evaluation score of the tofu that was frozen and dried after soaking in distilled water containing miso extract was 0.8, which was higher than the -0.5 of the tofu that was frozen and dried without soaking in distilled water containing miso extract, and the smoothness was evaluated as good. In addition, the P value of the two-sample t-test was 0.042, indicating a significant difference.

[0052] Next, the cross-section of the dried tofu was observed with a tabletop microscope (Hitachi High-Technologies Corporation, Miniscope TM4000plus MD). Figure 1 shows the cross-section of tofu that was frozen and dried after soaking in distilled water containing miso extract (magnification: 100x), and Figure 2 shows the cross-section of tofu that was frozen and dried without soaking in distilled water containing miso extract (magnification: 100x). As can be seen from a comparison of Figures 1 and 2, the tofu that was frozen and dried after soaking in distilled water containing miso extract has a finer mesh structure. This is thought to be because the growth of ice crystals during freezing was more suppressed. As a result, it is thought that the deterioration of the texture was more suppressed.

[0053] (9) Frozen storage test of chicken breast Chicken breast meat cut into approximately 50 g pieces was immersed in saline (2 mass%) containing 0.1% (v / v) miso extract (1 mg / mL) and stored in a refrigerator for 18.5 hours. After storage, the water was drained, the mass (before freezing) of each slice was measured, and 10 slices were placed in a plastic bag and stored in a freezer (-20°C) for one week. After that, the slices were naturally thawed at room temperature for 6 hours, and the mass (after freezing) was measured. As a control, the same treatment was performed using saline (2% (v / v)). The drip rate after thawing was calculated in the same manner as in (6). When the product was immersed in the salt solution containing the miso extract, the drip rate was 7.0±1.2% by mass, which was less than the 10.3±2.1% by mass when the product was immersed in the salt solution without the miso extract.

[0054] (10) Pork loin frozen storage test Pork loin cut into approximately 50 g pieces was immersed in a saline solution (2% by mass) containing 0.1% (v / v) miso extract (1 mg / mL) and stored in a refrigerator for 18.5 hours, and then immersed in a saline solution (2% (v / v)) containing 0.1% (v / v)% PM extract and stored in a refrigerator for 18.5 hours. After storage, the water was drained, the mass (before freezing) of each slice was measured, and 10 slices were placed in a plastic bag and stored in a freezer (-20°C) for one week. After that, the slices were naturally thawed at room temperature for 6 hours, and the mass (after freezing) was measured. As a control, the same treatment was performed using saline (2% (v / v)). The drip rate after thawing was calculated in the same manner as in (6). When soaked in the salt solution containing the miso extract, it was 4.8±1.4% by mass, and when soaked in the salt solution containing the PM extract, it was 4.6±1.1% by mass. This was less than the 7.5±2.4% by mass when soaked in the salt solution without the miso extract or bovine collagen peptide.

[0055] (11) Frozen storage test of edamame Edamame (with stems) were soaked in distilled water containing 0.1% (v / v) PM extract and stored in a refrigerator for 16 hours. After soaking, the pods were removed from the branches, placed in plastic bags, and stored in a freezer (-20°C) for 15 days, then thawed at room temperature. As controls, the same treatment was carried out using distilled water and distilled water containing 0.1% (v / v) bovine collagen peptide (1 mg / mL). The color of the pods before and after freezing was measured using a colorimeter (CM-5, Konica Minolta, Inc.). Specifically, the color difference (ΔE * ab), lightness (L value) and chroma (C value) were measured and their average values ​​were calculated. ΔE * It can be determined that the smaller the ab value, the more preferable it is, and the larger the L value and C value, the more preferable it is.

[0056] (L value) The average L value before freezing of edamame soaked in distilled water containing PM extract was 47.0, and there was no significant difference between the L value of edamame soaked in distilled water (46.0) and the L value of edamame soaked in distilled water containing only bovine collagen peptides (46.1). In contrast, the average L value after thawing of edamame soaked in distilled water containing PM extract was 38.5, which was higher than the L value of edamame soaked in distilled water (36.5) and the L value of edamame soaked in distilled water containing only bovine collagen peptide (35.8), indicating that darkening was more suppressed.

[0057] (C value) The average C value before freezing of edamame soaked in distilled water containing PM extract was 29.5, and there was no significant difference between the C value of edamame soaked in distilled water (29.6) and the C value of edamame soaked in distilled water containing only bovine collagen peptides (29.0). In contrast, the average C value after thawing of edamame soaked in distilled water containing PM extract was 23.4, which was higher than the C value of edamame soaked in distilled water (22.8) and the C value of edamame soaked in distilled water containing only bovine collagen peptide (21.9), and the vividness of the color was better maintained.

[0058] (ΔE * ab) The edamame soaked in distilled water containing PM extract showed a ΔE * The average ab value was 10.6, which was smaller than 11.7 for the soybeans soaked in distilled water and 12.6 for the soybeans soaked in distilled water containing only bovine collagen peptide.

[0059] From the above results, it was found that discoloration of edamame soaked in distilled water containing miso extract and bovine collagen peptide was suppressed compared to soaking in distilled water not containing these substances. Furthermore, it was found that edamame soaked in distilled water containing miso extract and bovine collagen peptide showed less discoloration than edamame soaked in distilled water containing only bovine collagen peptide.

[0060] (12) Cooked rice test (Preparation of cooked rice) Water (180 mL) and PM extract (20 mL) were added to rice (150 g), soaked for 1 hour, and then cooked. The cooked rice was cooled, wrapped in plastic wrap, and stored in a freezer (-20°C) for 2 weeks. As a control, the same treatment was carried out using 200 mL of water instead of PM extract.

[0061] (Making vinegared rice) Water (180 mL) and PM extract (20 mL) were added to rice (150 g), soaked for 1 hour, and then cooked. The resulting cooked rice was mixed with commercially available sushi vinegar (30 mL), cooled, wrapped in plastic wrap, and frozen for 2 weeks in a freezer (-20°C). As a control, the same process was carried out, except that the amount of water was changed to 200 mL instead of adding PM extract.

[0062] (Texture evaluation) After being frozen for two weeks, the cooked rice or vinegared rice was thawed naturally, and 18 subjects tasted it and rated the "chewy texture" as an index of texture using a score of 1 or 2. Specifically, the cooked rice or vinegared rice with PM extract added and the cooked rice or vinegared rice without PM extract added were scored as 1 if they felt it had a chewier texture, and 2 if they did not. From the test table, if the total score is 23 points or less, it can be judged that the chewy texture is significant, and if it is 31 points or more, it can be judged that the chewy texture is not significant. The total scores of the 18 panelists are shown in Table 4.

[0063] [Table 4]

[0064] As shown in Table 4, the total evaluation scores for both cooked rice and vinegared rice to which PM extract had been added were 23 points or less, and the rice was evaluated as having a significantly chewy texture.

[0065] (moisture content) The moisture content (mass%) of cooked rice or vinegared rice before freezing and that of cooked rice or vinegared rice after freezing and natural thawing were measured using a heat-dry moisture meter. The results are shown in Table 5.

[0066] [Table 5]

[0067] As shown in Table 5, no significant difference was observed in the change in moisture content before and after freezing for either cooked rice or vinegared rice to which PM extract was added, compared to cooked rice or vinegared rice to which PM extract was not added.

[0068] (whiteness) The WB value, which is an index of the whiteness of cooked rice or vinegared rice after natural thawing, was measured using a colorimeter. The results are shown in Table 6.

[0069] [Table 6]

[0070] As shown in Table 6, there was no significant difference in the WB value between cooked rice with and without PM extract, but the WB value of vinegared rice with PM extract added was lower than the WB value of vinegared rice without PM extract added. It is believed that the higher the WB value (whiter the rice), the more the starch has deteriorated and turned white. Therefore, it is believed that vinegared rice to which PM extract has been added has suppressed starch deterioration.

Claims

1. An ice recrystallization inhibitor comprising a fermented soybean product or an extract thereof and a collagen peptide, wherein the mass ratio of the fermented soybean product or an extract thereof to the collagen peptide (fermented soybean product or an extract thereof:collagen peptide) is 1:1 to 1:

100.

2. The ice recrystallization inhibitor of claim 1 , wherein the fermented soybean product comprises miso.

3. The ice recrystallization inhibitor according to claim 1 or 2, wherein the soybean fermentation product or extract thereof contains a component having a molecular weight of 140,000 to 160,000.

4. The ice recrystallization inhibitor according to any one of claims 1 to 3, for use in producing frozen foods or freeze-dried foods.

5. A method for producing a frozen food or a freeze-dried food, comprising the steps of adding an ice recrystallization inhibitor described in any one of claims 1 to 4 to a food, and freezing the food.

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