Method for producing milk protein solution

Abstract

Provided is a technique capable of suppressing an increase in viscosity of a milk protein solution under heating or under acidic conditions. Also provided is a technique capable of improving sandiness of a milk protein solution under heating or under acidic conditions (preferably a technique capable of suppressing an increase in viscosity of a milk protein solution and also capable of improving sandiness of a milk protein solution under heating or under acidic conditions).　Further provided is a method for producing a modified milk protein solution, the method including a step for adding a protease / peptidase having an LAP activity (enzyme 1) to a milk protein solution. Further provided is a method for suppressing an increase in viscosity of a milk protein solution, the method including a step for adding the enzyme 1 to a milk protein solution. Further provided is a method for improving sandiness of a milk protein solution, the method including a step for adding the enzyme 1 and phospholipase D (enzyme 2) to a milk protein solution. Further provided is an enzyme preparation which contains the enzyme 1 (or the enzymes 1 and 2).

Description

Method for producing milk protein solution

[0001] The present invention relates to a method for producing a modified milk protein solution; a method for inhibiting an increase in viscosity of a milk protein solution; a method for improving the roughness of a milk protein solution; and an enzyme preparation for modifying a milk protein solution.

[0002] With growing health consciousness, demand for protein-containing foods is increasing, and in particular, beverages that are easy to consume are popular with a wide range of consumers. Milk proteins are commonly used in beverages, but milk protein solutions have a problem in that their manufacturing suitability deteriorates due to increased viscosity when heated or under acidic conditions, making it difficult to further increase the protein content. Another problem is that milk proteins aggregate when heated or under acidic conditions. Aggregation deteriorates manufacturing suitability, making it difficult to further increase the protein content. Furthermore, aggregation causes a rough texture, resulting in a decrease in palatability. It is desirable to develop a technology that can suppress the increase in viscosity of milk protein solutions when heated or under acidic conditions. It is also desirable to develop a technology that can suppress the aggregation of milk proteins in milk protein solutions when heated or under acidic conditions (and thereby improve the roughness of milk protein solutions).

[0003] Patent Literature 1 discloses a method for producing a dairy product additive, comprising subjecting a mixture of (i) cream and (ii) a whey protein preparation to a homogenization process. Patent Literature 2 discloses a method for preparing a protein composition containing a protein hydrolysate, comprising: a) providing a raw material mixture containing at least one protein and milk lecithin; b) adding at least one phospholipase to convert the milk lecithin; and c) hydrolyzing the protein. However, it was not known that adding a specific enzyme of the present invention described below to a milk protein solution can suppress viscosity increase under heating or acidic conditions. It was also not known that adding a specific enzyme combination of the present invention described below to a milk protein solution can suppress aggregation of milk proteins in the milk protein solution under heating or acidic conditions (and thereby improve the roughness of the milk protein solution).

[0004] Special table 2004-505644 Publication Special table 2016-523095

[0005] An object of the present invention is to provide a technology that can suppress an increase in viscosity of a milk protein solution when heated or under acidic conditions. A further object of the present invention is to provide a technology that can suppress aggregation of milk proteins in a milk protein solution when heated or under acidic conditions (and thereby improve the roughness of the milk protein solution) (preferably a technology that can suppress an increase in viscosity of a milk protein solution when heated or under acidic conditions and improve the roughness).

[0006] The present inventors conducted extensive research to solve the above problems and found that adding a protease having leucine aminopeptidase (hereinafter sometimes referred to as "LAP" (leucyl aminopeptidase)) activity or a peptidase having LAP activity to a milk protein solution and causing an enzymatic reaction can produce a milk protein solution in which viscosity increase upon heating or under acidic conditions is suppressed. Furthermore, the present inventors found that adding phospholipase D to a protease having LAP activity or a peptidase having LAP activity and causing an enzymatic reaction can suppress viscosity increase of the milk protein solution upon heating or under acidic conditions, and can also produce a milk protein solution in which roughness due to aggregation of milk proteins upon heating or under acidic conditions is improved. Based on this finding, the present inventors conducted further research and completed the present invention.

[0007] That is, the present invention provides the following: [1] A method for producing a modified milk protein solution, comprising the step of adding a protease having LAP activity or a peptidase having LAP activity to a milk protein solution. [2] The production method according to [1] above, wherein the content of milk protein in the milk protein solution is 1% by weight or more. [3] The production method according to [1] or [2] above, which further comprises the step of adding phospholipase D to the milk protein solution. [4] A method for suppressing an increase in viscosity of a milk protein solution, which comprises the step of adding a protease having LAP activity or a peptidase having LAP activity to the milk protein solution. [5] The method for suppressing an increase in viscosity of the milk protein solution according to [4] above, wherein the content of milk protein in the milk protein solution is 1% by weight or more. [6] The method for suppressing an increase in viscosity of a milk protein solution at a pH of 3 to 5, according to [4] or [5] above. [7] A method for improving roughness of a milk protein solution, comprising the step of adding a protease having LAP activity or a peptidase having LAP activity, and phospholipase D to the milk protein solution. [8] The method for improving roughness according to [7] above, wherein the milk protein content in the milk protein solution is 1% by weight or more. [9] The method for improving roughness according to [7] or [8] above, which is a method for improving roughness of a milk protein solution having a pH of 3 to 5.

[10] An enzyme preparation for modifying a milk protein solution, comprising a protease having LAP activity or a peptidase having LAP activity.

[11] The enzyme preparation according to

[10] above, further comprising phospholipase D.

[0008] According to the present invention, it is possible to provide a method for producing a modified milk protein solution (particularly a milk protein solution in which an increase in viscosity is suppressed) by adding a protease having LAP activity or a peptidase having LAP activity to a milk protein solution and causing an enzymatic reaction; a method for suppressing an increase in viscosity of a milk protein solution; and an enzyme preparation for modifying a milk protein solution (particularly for suppressing an increase in viscosity of a milk protein solution). The modified milk protein solution obtained by the production method of the present invention, which uses a protease having LAP activity or a peptidase having LAP activity, has an inhibited increase in viscosity under low pH conditions, and is therefore advantageous in that it can be incorporated into acidic foods and beverages. Furthermore, the present invention can provide a method for producing a modified milk protein solution (particularly a milk protein solution in which viscosity increase is suppressed and roughness is improved) by adding a protease having LAP activity or a peptidase having LAP activity, and phospholipase D to a milk protein solution and causing an enzymatic reaction; a method for improving the roughness of a milk protein solution; and an enzyme preparation for modifying a milk protein solution (particularly for suppressing viscosity increase and improving roughness of a milk protein solution). The modified milk protein solution obtained by the production method of the present invention, which uses a protease having LAP activity or a peptidase having LAP activity, and phospholipase D, has a suppressed increase in viscosity and suppressed roughness under low pH conditions, and is therefore advantageous in that it can be incorporated into acidic foods and beverages.

[0009] FIG. 1 shows the viscosity measurement results in Test Example 1. FIG. 2 shows the viscosity measurement results in Test Example 2. FIG. 3 shows the viscosity measurement results in Test Example 5. FIG. 4 shows the viscosity measurement results in Test Example 6. FIG. 5 shows the viscosity measurement results in Test Example 9. FIG. 6 shows the viscosity measurement results in Test Example 10. FIG. 7 shows the viscosity measurement results in Test Example 11. FIG. 8 shows the viscosity measurement results in Test Example 12. FIG. 9 shows the viscosity measurement results in Test Example 13. FIG. 10 shows the viscosity measurement results in Test Example 14. FIG. 11 shows the viscosity measurement results in Test Example 15. FIG. 12 shows the viscosity measurement results in Test Example 16. FIG. 13 shows the viscosity measurement results in Test Example 17.

[0010] The present invention is described in detail below. The method for producing a modified milk protein solution of the present invention is characterized by comprising a step of adding a protease having LAP activity or a peptidase having LAP activity (sometimes referred to as "enzyme (1)" in this specification) to a milk protein solution, which is a raw material. In this specification, the "protease having LAP activity or the peptidase having LAP activity" (enzyme (1)) is sometimes abbreviated as "protease / peptidase having LAP activity."

[0011] In the production method of the present invention, the milk protein solution as a raw material (i.e., the target to which the enzyme (1) is added) may be any milk protein solution in which the milk protein is wholly or partially dissolved in an edible liquid such as water. In the present invention, the milk protein may be any protein derived from milk, such as milk, skim milk powder, whole milk powder, milk protein concentrate (MPC), whey protein (whey), whey protein isolate (WPI), whey protein concentrate (WPC), casein, and lactoferrin.

[0012] In the production method of the present invention, the content of milk protein in the raw material milk protein solution is, for example, 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, even more preferably 4% by weight or more, and even more preferably 5% by weight or more, relative to the total amount of the milk protein solution. In the production method of the present invention, the content of milk protein in the raw material milk protein solution is, for example, 25% by weight or less, preferably 20% by weight or less, more preferably 15% by weight or less, and even more preferably 10% by weight or less, relative to the total amount of the milk protein solution. In the production method of the present invention, the content of milk protein in the raw material milk protein solution is, for example, 1 to 25% by weight, preferably 2 to 25% by weight, more preferably 3 to 25% by weight, even more preferably 4 to 25% by weight, even more preferably 5 to 25% by weight, even more preferably 5 to 20% by weight, even more preferably 5 to 15% by weight, and even more preferably 5 to 10% by weight, relative to the total amount of the milk protein solution. According to the present invention, by adding the enzyme (1), an increase in the viscosity of the milk protein solution can be suppressed even when the milk protein solution contains a high concentration of milk protein.

[0013] In the production method of the present invention, it is preferable to further add phospholipase D (sometimes referred to as "enzyme (2)" in this specification). According to the present invention, by adding the above enzymes (1) and (2), not only can an increase in viscosity of the milk protein solution be suppressed, but also roughness due to aggregation of the milk protein in the milk protein solution can be improved, even when the milk protein solution contains a high concentration of milk protein. The above enzymes (1) and (2) are described below.

[0014] (1) Protease / Peptidase Having LAP Activity Proteases and peptidases having LAP activity are enzymes that act on the N-terminal amino acid of a peptide to liberate the amino acid.

[0015] As used herein, a "protease with LAP activity" refers to a protease that acts on the N-terminal amino acid of a protein or peptide to liberate the amino acid. As used herein, a "peptidase with LAP activity" refers to a peptidase that acts on the N-terminal amino acid of a protein or peptide to liberate the amino acid.

[0016] As used herein, the activity unit of a protease / peptidase having LAP activity is measured and defined as follows:

[0017] The enzyme is reacted with L-leucyl-p-nitroanilide hydrochloride as a substrate, and the resulting paranitroaniline (pNA) is quantified colorimetrically to determine leucine aminopeptidase activity. The method and definition for measuring the activity unit for Denatzyme LEP10P (Nagase & Co., Ltd.) and Sumitzyme FLAP-G (Shin-Nihon Chemical Industry Co., Ltd.) are shown below. The activity unit can also be measured in a similar manner for other proteases / peptidases having LAP activity (e.g., Sumitzyme LP50D (Shin-Nihon Chemical Industry Co., Ltd.) and Sumitzyme ACP-G (Shin-Nihon Chemical Industry Co., Ltd.)).

[0018] The activity unit of Denatzyme LEP10P (Nagase & Co., Ltd.) is measured and defined as follows: 0.1 mL of enzyme solution is mixed with 1.5 mL of substrate solution containing L-leucyl-p-nitroanilide hydrochloride, and the mixture is allowed to react at 37°C for 10 minutes. After the reaction is stopped, the absorbance at a wavelength of 405 nm is measured to determine the amount of paranitroaniline. The amount of enzyme that produces 1 μmol of paranitroaniline per minute using L-leucyl-p-nitroanilide hydrochloride as a substrate is defined as 1 U (unit).

[0019] The activity unit of Sumiteam FLAP-G (Shin Nippon Chemical Industry) is measured and defined as follows: 0.1 mL of enzyme solution is mixed with 4 mL of substrate solution containing L-leucyl-p-nitroanilide hydrochloride, and the mixture is allowed to react at 40°C for 5 minutes. After the reaction is stopped, the absorbance at a wavelength of 405 nm is measured to determine the amount of paranitroaniline. The amount of enzyme that produces 1 μmol of paranitroaniline per minute using L-leucyl-p-nitroanilide hydrochloride as a substrate is defined as 1 U (unit).

[0020] Commercially available "proteases / peptidases having LAP activity" can be used, and examples thereof include Sumiteam LP50D (Shin-Nihon Chemical Industry Co., Ltd.), Sumiteam ACP-G (Shin-Nihon Chemical Industry Co., Ltd.), Sumiteam FLAP-G (Shin-Nihon Chemical Industry Co., Ltd.), and Denatym LEP 10P (Nagase & Co., Ltd.). In the present invention, the "protease / peptidase having LAP activity" is particularly preferably a peptidase having both exo-type activity and LAP activity. Examples of peptidases having both exo-type activity and LAP activity include Sumiteam LP50D (Shin-Nihon Chemical Industry Co., Ltd.), Sumiteam ACP-G (Shin-Nihon Chemical Industry Co., Ltd.), Sumiteam FLAP-G (Shin-Nihon Chemical Industry Co., Ltd.), and Denatym LEP 10P (Nagase & Co., Ltd.).

[0021] In the present invention, the amount of "protease / peptidase having LAP activity" to be added is preferably 0.001 U or more, more preferably 0.01 U to 1000 U, and even more preferably 0.1 to 100 U in terms of enzyme activity per 1 g of protein.

[0022] The activity time (reaction time) of a "protease / peptidase having LAP activity" is not particularly limited as long as it is a time that allows the enzyme to act on the protein substrate, but examples include 0 minutes or more, 1 minute or more, 3 minutes or more, 5 minutes or more, 10 minutes or more, 20 minutes or more, and 30 minutes or more. Other examples include 168 hours or less, 148 hours or less, 72 hours or less, 48 ​​hours or less, 24 hours or less, 12 hours or less, 6 hours or less, 3 hours or less, 2 hours or less, and 1 hour or less. A practical activity time is preferably 0 to 148 hours, and more preferably 30 minutes to 148 hours. The activity temperature (reaction temperature) is also not particularly limited as long as it is within a range in which the enzyme maintains its activity, but a practical temperature of 0 to 60°C is preferred. The enzymatic reaction can be terminated, for example, by heating at 70 to 90°C for 5 to 10 minutes.

[0023] (2) Phospholipase D Phospholipase is an enzyme that has the activity of hydrolyzing phospholipids. In this specification, the activity unit of phospholipase D is measured and defined as follows: 0.1 mL of enzyme solution is mixed with 0.9 mL of substrate solution containing phosphatidylcholine, and the mixture is reacted at 37°C for 30 minutes. After the reaction is stopped, 50 μL of the reaction solution is added to 1 mL of color-developing solution containing choline oxidase, peroxidase, etc., and the mixture is reacted for 5 minutes. After the reaction is stopped, the amount of dye produced from choline is measured. The amount of enzyme that liberates 1 μmol of choline per minute at 37°C using phosphatidylcholine as a substrate is defined as 1 U (unit). Commercially available phospholipase D may be used, for example, Denatym PMD-P1 (Nagase & Co., Ltd.).

[0024] In the present invention, the amount of phospholipase D added is preferably 0.002 U or more, more preferably 0.02 to 5500 U, more preferably 0.2 to 550 U, even more preferably 4 to 550 U, and even more preferably 4 to 260 U in terms of enzyme activity per 1 g of protein.

[0025] The reaction time, reaction temperature, and method for terminating the enzyme reaction of phospholipase D are the same as those of the protease / peptidase having LAP activity described above.

[0026] In the production method of the present invention, the milk protein solution may contain additives commonly used in the food industry other than the above-mentioned components. Examples of additives include stabilizers (e.g., pectin and soybean polysaccharides). In the present invention, the use of phospholipases A1 and A2 is undesirable because they cause bitterness and acridness.

[0027] The modified milk protein solution of the present invention can be obtained by the production method of the present invention described above. "Modified" means that the properties of the milk protein solution, such as viscosity and roughness, under heating and / or acidic conditions have been changed by an enzymatic reaction. The production method of the present invention using a protease / peptidase with LAP activity can obtain a milk protein solution in which the increase in viscosity under heating and / or acidic conditions is suppressed. Furthermore, the production method of the present invention using a protease / peptidase with LAP activity and phospholipase D can obtain a milk protein solution in which the increase in viscosity under heating and / or acidic conditions is suppressed and the roughness under heating and / or acidic conditions is improved.

[0028] The improved milk protein solution of the present invention exhibits suppressed viscosity increase under low pH conditions. The improved milk protein solution of the present invention exhibits suppressed viscosity increase, for example, at pH 5.5 or below, or at pH 5 or below (preferably pH 4.9 or below, pH 4.8 or below, pH 4.7 or below, pH 4.6 or below, pH 4.5 or below, or pH 4.4 or below, more preferably pH 4.3 or below). The improved milk protein solution of the present invention exhibits suppressed viscosity increase, for example, in the range of pH 3 to 5.5 or pH 3 to 5 (preferably pH 3.5 to 4.9, pH 3.5 to 4.8, pH 3.5 to 4.7, or pH 3.5 to 4.6, more preferably pH 3.5 to 4.5, pH 3.5 to 4.4, or pH 3.5 to 4.3).

[0029] The viscosity of the modified milk protein solution of the present invention can be measured using a Brookfield type viscometer (e.g., DV1MLVTJ0, manufactured by Brookfield). The viscosity of the modified milk protein solution of the present invention, measured using a Brookfield type viscometer (DV1MLVTJ0, manufactured by Brookfield) at 8°C, 6 rpm, and 60 seconds later, is preferably 80% or less, more preferably 60% or less, when the viscosity of a milk protein solution produced under the same conditions except for not adding the enzyme is taken as 100% (see Test Examples 1, 2, 5, 6, and 9 to 13 described below).

[0030] The modified milk protein solution of the present invention can be safely ingested by humans and non-human animals (e.g., mammals and birds, such as livestock, poultry, and laboratory animals) either directly or by adding it to food (feed). The modified milk protein solution of the present invention can also be used as a raw material for food (feed) (e.g., dairy products such as yogurt and cheese). For example, yogurt can be produced by adding lactic acid bacteria to the modified milk protein solution of the present invention as a raw material and fermenting it.

[0031] In this specification, the term "food" is a concept that broadly encompasses anything that can be taken orally (excluding pharmaceuticals), and includes not only so-called "foods" but also beverages, health supplements, health functional foods (e.g., foods for specified health uses, foods with functional claims, foods with nutrient functions), supplements, etc.

[0032] The modified milk protein solution produced by the production method of the present invention using a protease / peptidase having LAP activity is advantageous in that, when incorporated into acidic foods and beverages, it shows a suppressed increase in viscosity compared to conventional milk protein solutions.The modified milk protein solution produced by the production method of the present invention using a protease / peptidase having LAP activity and phospholipase D is advantageous in that, when incorporated into acidic foods and beverages, it shows a suppressed increase in viscosity and suppressed roughness compared to conventional milk protein solutions.

[0033] The present invention also relates to a method for suppressing an increase in viscosity of a milk protein solution. The method for suppressing an increase in viscosity of a milk protein solution is characterized by comprising a step of adding a protease / peptidase having LAP activity (enzyme (1)) to a milk protein solution. The definition, examples, etc. of the milk protein solution to which the enzyme (1) is added, and the definition, examples, etc. of the enzyme (1) are the same as the definition, examples, etc. of the milk protein solution and the definition, examples, etc. of the enzyme (1) in the production method of the present invention described above. The method of the present invention suppresses an increase in viscosity of a milk protein solution under low pH conditions. The method of the present invention suppresses an increase in viscosity, for example, at pH 5.5 or below, or pH 5 or below (preferably pH 4.9 or below, pH 4.8 or below, pH 4.7 or below, pH 4.6 or below, pH 4.5 or below, or pH 4.4 or below, more preferably pH 4.3 or below). The method of the present invention suppresses viscosity increase, for example, in the range of pH 3 to 5.5 or pH 3 to 5 (preferably in the range of pH 3.5 to 4.6, more preferably in the range of pH 3.5 to 4.5, pH 3.5 to 4.4, or pH 3.5 to 4.3).

[0034] The present invention also relates to a method for improving the roughness of a milk protein solution. The method for suppressing an increase in viscosity of a milk protein solution is characterized by comprising the step of adding (1) a protease / peptidase having LAP activity and (2) phospholipase D to a milk protein solution. The definitions and examples of the milk protein solution to which the enzymes (1) and (2) are added, and the definitions and examples of the enzymes (1) and (2), are the same as those of the milk protein solution and the enzymes (1) and (2) in the production method of the present invention described above. The method of the present invention improves the roughness of a milk protein solution under low pH conditions. The method of the present invention improves the roughness of a milk protein solution, for example, at pH 5.5 or below, or pH 5 or below (preferably pH 4.9 or below, pH 4.8 or below, pH 4.7 or below, pH 4.6 or below, pH 4.5 or below, or pH 4.4 or below, more preferably pH 4.3 or below). The method of the present invention improves the roughness of a milk protein solution, for example, in the range of pH 3 to 5.5 or pH 3 to 5 (preferably in the range of pH 3.5 to 4.9, pH 3.5 to 4.8, pH 3.5 to 4.7, or pH 3.5 to 4.6, more preferably in the range of pH 3.5 to 4.5, pH 3.5 to 4.4, or pH 3.5 to 4.3).

[0035] The present invention also relates to an enzyme preparation containing a protease / peptidase having LAP activity (enzyme (1)). The enzyme preparation of the present invention can be used in the method of producing a modified milk protein solution of the present invention and the method of suppressing an increase in viscosity of a milk protein solution. It is preferable that the enzyme preparation of the present invention further contains phospholipase D (enzyme (2)). The enzyme preparation of the present invention containing enzymes (1) and (2) can be used in the method of improving the roughness of a milk protein solution of the present invention, in addition to the above-mentioned methods. The definitions and examples of the milk protein solution to which the enzymes (1) and (2) are added, and the definitions and examples of the enzymes (1) and (2) are the same as the definitions and examples of the milk protein solution and the definitions and examples of the enzymes (1) and (2) in the production method of the present invention described above.

[0036] The present invention will be described in more detail below based on examples and test examples, but the present invention is not limited to these.

[0037] In the following examples and comparative examples, the enzymes shown in Table 1 and the protein raw materials and stabilizers shown in Table 2 were used. In this specification, "% by weight" means w / w%.

[0038]

[0039]

[0040] Test Example 1: Investigation of the Effect of Improving the Physical Properties of Whey Protein (Amount of Peptidase with LAP Activity Added) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase with LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples 1-1 to 1-7 and Comparative Example 1-2) Protein raw materials and water were mixed in the amounts shown in Table 3-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 3-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples 1-1 to 1-7 and Comparative Example 1-2. (Production of Sample of Comparative Example 1-1 (Control)) Sample of Comparative Example 1-1 (Control) was produced using the same method as Example 1-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-2, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 1. The amount of enzyme (wt%) in each sample is also shown in Table 3-2.

[0041]

[0042]

[0043] The results in Figure 1 show that the samples (whey protein solutions) of Examples 1-1 to 1-7, which were produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase with LAP activity), had lower viscosities than the sample of Comparative Example 1-1, which was produced without using any enzymes, and the sample of Comparative Example 1-2, which was produced using Denatzym PMD-P1 but not Denatzym LEP10P.

[0044] Test Example 2: Investigation of the Effect of Improving the Physical Properties of Whey Protein (Amount of Peptidase with LAP Activity Added) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase with LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples 2-1 to 2-5 and Comparative Example 2-2) Protein raw materials and water were mixed in the amounts shown in Table 4-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 4-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, and an aqueous citric acid solution was added to adjust the pH to 3.8, followed by diluting to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples 2-1 to 2-5 and Comparative Example 2-2. (Production of Sample of Comparative Example 2-1 (Control)) Sample of Comparative Example 2-1 (Control) was produced using the same method as Example 2-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each of the samples of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 2. The amount of enzyme (wt%) in each sample is also shown in Table 4-2.

[0045]

[0046]

[0047] The results in Figure 2 show that the samples (whey protein solutions) of Examples 2-1 to 2-5, which were produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase with LAP activity), had lower viscosities than the sample of Comparative Example 2-1, which was produced without using any enzymes, and the sample of Comparative Example 2-2, which was produced using Denatzym PMD-P1 but not Denatzym LEP10P.

[0048] Test Example 3: Investigation of the Effect of Improving the Physical Properties of Whey Protein (Amount of Phospholipase D Added) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase having LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples 3-1 to 3-7) Protein raw materials and water were mixed in the amounts shown in Table 5-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 5-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize, and then cooled to below 10°C with cold water to produce samples of Examples 3-1 to 3-7. (Production of Sample of Comparative Example 3-1 (Control)) Sample of Comparative Example 3-1 (control) was produced using the same method as Example 3-1, etc., except that no enzyme was added. (Sensory Evaluation of Each Sample) Each sample of Examples 3-1 to 3-7 and Comparative Example 3-1 was subjected to a sensory evaluation of roughness, bitterness, and astringency according to the following evaluation method. The results (average scores from five panelists) are shown in Table 5-3. The amount of enzyme blended (wt%) in each sample is also shown in Table 5-2.

[0049] [Method of evaluating roughness] Five panelists evaluate the results based on the following criteria, with the control being given a score of 1. A score of 3 or higher is considered effective. 1 point: Strongly rough 2 points: Rough 3 points: Very little roughness (a level where the difference from the control is clearly noticeable) 4 points: Almost no roughness 5 points: No roughness at all

[0050] [Method for evaluating bitterness and astringency] Five panelists evaluate the tastes based on the following criteria, with the control being given a score of 5. A score of 3 or less is considered a negative evaluation. 1 point: Strong bitterness and astringency 2 points: Bitterness and astringency are felt 3 points: Slight bitterness and astringency are felt (a level that may be bothersome for some people) 4 points: Almost no bitterness and astringency are felt 5 points: No bitterness and astringency are felt

[0051]

[0052]

[0053]

[0054] The results in Table 5-3 show that the samples (whey protein solutions) of Examples 3-2 to 3-7, which were produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (an exopeptidase with LAP activity), were good, with roughness scores of 3 or more, and that roughness was suppressed compared to the sample of Comparative Example 3-1 (control) produced without using an enzyme, and the sample of Example 3-1 produced using Denatzym LEP10P but not Denatzym PMD-P1. Furthermore, the samples (whey protein solutions) of Examples 3-1 to 3-7 were good, with bitterness / acidity scores exceeding 4 points.

[0055] Test Example 4: Investigation of the Effect of Improving the Physical Properties of Whey Protein (Comparison with Phospholipase A1 and A2) The following test was conducted to investigate the effect of enzymes (combinations of phospholipase D and peptidases with LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples 4-1 to 4-4) Protein raw materials and water were mixed in the amounts shown in Table 6-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 6-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize, and then cooled to below 10°C with cold water to produce samples of Examples 4-1 to 4-4. (Production of Sample of Comparative Example 4-1 (Control)) Sample of Comparative Example 4-1 (control) was produced using the same method as Example 4-1, etc., except that no enzyme was added. (Sensory Evaluation of Each Sample) Each sample of Examples 4-1 to 4-4 and Comparative Example 4-1 was subjected to a sensory evaluation of roughness, bitterness, and astringency using the same evaluation method as in Test Example 3. The results (average scores from five panelists) are shown in Table 6-3. The amount of enzyme (wt%) in each sample is also shown in Table 6-2.

[0056]

[0057]

[0058]

[0059] The results in Table 6-3 show that the sample (whey protein solution) of Example 4-2, which was produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (an exopeptidase with LAP activity), had a roughness rating of 3 or more, which was good, and that the roughness was suppressed compared to the sample of Comparative Example 4-1 (control) produced without using an enzyme, and the samples of Examples 4-1, 4-3, and 4-4 produced using Denatzym LEP10P but not Denatzym PMD-P1. Furthermore, the samples (whey protein solutions) of Examples 4-1 and 4-2 had bitterness / acidity ratings of over 4, which were good. On the other hand, the sample of Example 4-3 produced using a combination of phospholipase A1 and Denatzyme LEP10P (an exopeptidase with LAP activity), and the sample of Example 4-4 produced using a combination of phospholipase A2 and Denatzyme LEP10P (an exopeptidase with LAP activity) were rated as 3 points or less for bitterness / acidity.

[0060] Test Example 5: Investigation of the Effect of Improving the Physical Properties of Whey Protein (Comparison of Various Peptidases) The following test was conducted to investigate the effect of enzymes (combinations of peptidases having phospholipase D and LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples 5-1 to 5-3 and Comparative Example 5-2) Protein raw materials and water were mixed in the amounts shown in Table 7-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 7-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples 5-1 to 5-3 and Comparative Example 5-2. (Production of Sample of Comparative Example 5-1 (Control)) Sample of Comparative Example 5-1 (Control) was produced using the same method as Example 5-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples 5-1 to 5-3 and Comparative Examples 5-1 to 5-2, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 3. The amount of enzyme (wt%) in each sample is also shown in Table 7-2.

[0061]

[0062]

[0063] The results of Figure 3 show that the sample (whey protein solution) of Example 5-1 produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Sumityme ACP-G (endo- and exo-type peptidases having LAP activity), the sample (whey protein solution) of Example 5-2 produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Sumityme FLAP-G (exo-type peptidase having LAP activity), and the sample (whey protein solution) of Example 5-3 produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exo-type peptidase having LAP activity) had a lower viscosity than the sample of Comparative Example 5-1 produced without using enzymes. On the other hand, the sample of Comparative Example 5-2, which was produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Sumitzyme P (an endopeptidase without LAP activity), showed no decrease in viscosity compared to the sample of Comparative Example 5-1, which was produced without using any enzymes.

[0064] Test Example 6: Investigation of the Effect of Improving the Physical Properties of Milk Protein (Amount of Peptidase with LAP Activity Added) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase with LAP activity) on improving the physical properties of milk protein. (Production of Samples of Examples 6-1 to 6-6 and Comparative Example 6-2) Protein raw material, stabilizer, and water were mixed in the amounts shown in Table 8-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 8-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, and an aqueous citric acid solution was added to adjust the pH to 3.8, followed by diluting to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples 6-1 to 6-6 and Comparative Example 6-2. (Production of Sample of Comparative Example 6-1 (Control)) Sample of Comparative Example 6-1 (Control) was produced using the same method as Example 6-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples 6-1 to 6-6 and Comparative Examples 6-1 to 6-2, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 4. The amount of enzyme (wt%) in each sample is also shown in Table 8-2.

[0065]

[0066]

[0067] The results in Figure 4 show that the samples (milk protein solutions) of Examples 6-1 to 6-6, which were produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase with LAP activity), had lower viscosities than the sample of Comparative Example 6-1, which was produced without using any enzymes, and the sample of Comparative Example 6-2, which was produced using Denatzym PMD-P1 but not Denatzym LEP10P.

[0068] Test Example 7: Investigation of the Effect of Improving the Physical Properties of Milk Protein (Amount of Phospholipase D Added) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase with LAP activity) on improving the physical properties of milk protein. (Production of Samples of Examples 7-1 to 7-7) Protein raw material, stabilizer, and water were mixed in the amounts shown in Table 9-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 9-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, and an aqueous citric acid solution was added to adjust the pH to 3.8, followed by diluting to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize, and then cooled to below 10°C with cold water to produce samples of Examples 7-1 to 7-7. (Production of Sample of Comparative Example 7-1 (Control)) Sample of Comparative Example 7-1 (control) was produced using the same method as Example 7-1, etc., except that no enzyme was added. (Sensory Evaluation of Each Sample) Each sample of Examples 7-1 to 7-7 and Comparative Example 7-1 was subjected to a sensory evaluation of roughness, bitterness, and astringency using the same evaluation method as in Test Example 3. The results (average scores from five panelists) are shown in Table 9-3. The amount of enzyme (wt%) in each sample is also shown in Table 9-2.

[0069]

[0070]

[0071]

[0072] The results in Table 9-3 show that the samples (milk protein solutions) of Examples 7-2 to 7-7, which were produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (an exopeptidase with LAP activity), had reduced roughness compared to the sample of Comparative Example 7-1 (control) produced without using any enzymes, and the sample of Example 7-1 produced using Denatzyme LEP10P but not Denatzyme PMD-P1. Furthermore, the samples (milk protein solutions) of Examples 7-2 to 7-7, which were produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (an exopeptidase with LAP activity), were evaluated as good with a roughness score of 3 or higher. Furthermore, the samples (milk protein solutions) of Examples 7-1 to 7-7 were good, with bitterness and astringency ratings exceeding 4 points.

[0073] Test Example 8: Investigation of the Effect of Improving the Physical Properties of Milk Protein (Comparison with Phospholipase A1 and A2) The following test was conducted to investigate the effect of enzymes (combinations of phospholipase D and peptidases with LAP activity) on improving the physical properties of milk protein. (Production of Samples of Examples 8-1 to 8-4) Protein raw materials, stabilizers, and water were mixed in a blender (product name: Bamix, manufactured by ESGE) in the amounts shown in Table 10-1. Enzymes were added to the resulting mixture in the amounts shown in Table 10-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize, and then cooled to below 10°C with cold water to produce samples of Examples 8-1 to 8-4. (Production of Sample of Comparative Example 8-1 (Control)) Sample of Comparative Example 8-1 (control) was produced using the same method as Example 8-1, etc., except that no enzyme was added. (Sensory Evaluation of Each Sample) Each sample of Examples 8-1 to 8-4 and Comparative Example 8-1 was subjected to a sensory evaluation of roughness, bitterness, and astringency using the same evaluation method as in Test Example 3. The results (average scores from five panelists) are shown in Table 10-3. The amount of enzyme (wt%) in each sample is also shown in Table 10-2.

[0074]

[0075]

[0076]

[0077] The results in Table 10-3 show that the sample (milk protein solution) of Example 8-2, which was produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase with LAP activity), had a roughness rating of 3 or more, which was good, and that roughness was suppressed compared to the sample of Comparative Example 8-1 (control) produced without using enzymes, and the samples of Examples 8-1, 8-3, and 8-4 produced using Denatzym LEP10P but not Denatzym PMD-P1. Furthermore, the samples (milk protein solutions) of Examples 8-1 and 8-2 had bitterness / acidity ratings of over 4, which were good. On the other hand, the sample of Example 8-3 produced using a combination of phospholipase A1 and Denatzyme LEP10P (an exopeptidase with LAP activity), and the sample of Example 8-4 produced using a combination of phospholipase A2 and Denatzyme LEP10P (an exopeptidase with LAP activity) were rated as 3 points or less for bitterness and astringency.

[0078] Test Example 9: Investigation of the Effect of Improving the Physical Properties of Milk Protein (Comparison of Various Peptidases) The following test was conducted to investigate the effect of enzymes (combinations of phospholipase D and peptidases with LAP activity) on improving the physical properties of milk protein. (Production of Samples of Examples 9-1 to 9-3 and Comparative Example 9-2) Protein raw material, stabilizer, and water were mixed in a blender (product name: Bamix, manufactured by ESGE) in the amounts shown in Table 11-1. Enzymes were added to the resulting mixture in the amounts shown in Table 11-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples 9-1 to 9-3 and Comparative Example 9-2. (Production of Sample of Comparative Example 9-1 (Control)) Sample of Comparative Example 9-1 (Control) was produced using the same method as Example 9-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples 9-1 to 9-3 and Comparative Examples 9-1 to 9-2, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 5. The amount of enzyme (wt%) in each sample is also shown in Table 11-2.

[0079]

[0080]

[0081] The results of Figure 5 show that the sample (milk protein solution) of Example 9-1, which was produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Sumityme LP50D (endo- and exo-peptidases having LAP activity), the sample (milk protein solution) of Example 9-2, which was produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Sumityme FLAP-G (exo-peptidase having LAP activity), and the sample (milk protein solution) of Example 9-3, which was produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exo-peptidase having LAP activity), all had lower viscosities than the sample of Comparative Example 9-1, which was produced without using any enzymes. On the other hand, the sample of Comparative Example 9-2, which was produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Sumitzyme P (an endopeptidase without LAP activity), showed almost no decrease in viscosity compared to the sample of Comparative Example 9-1, which was produced without using any enzymes.

[0082] Test Example 10: Investigation of the Effect of Improving the Physical Properties of Whey Protein The following test was conducted to investigate the effect of an enzyme (peptidase with LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples 10-1 and 10-2) Protein raw materials and water were mixed in the amounts shown in Table 12-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 12-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples 10-1 and 10-2. (Production of Sample of Comparative Example 10-1 (Control)) Sample of Comparative Example 10-1 (Control) was produced in the same manner as Example 10-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples 10-1 to 10-2 and Comparative Example 10-1, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 6. The amount of enzyme (wt%) in each sample is also shown in Table 12-2.

[0083]

[0084]

[0085] The results in Figure 6 show that the sample (whey protein solution) of Example 10-1 produced using Denatzyme LEP10P (an exopeptidase having LAP activity) and the sample (whey protein solution) of Example 10-2 produced using Sumitzyme FLAP-G (an exopeptidase having LAP activity) had lower viscosities than the sample of Comparative Example 10-1 produced without using an enzyme.

[0086] Test Example 11: Investigation of the Effect of Improving the Physical Properties of Milk Protein The following test was conducted to investigate the effect of an enzyme (peptidase with LAP activity) on improving the physical properties of milk protein. (Production of Sample of Example 11-1) Protein raw material, stabilizer, and water were mixed in a blender (product name: Bamix, manufactured by ESGE) in the amounts shown in Table 13-1. The enzyme was added to the resulting mixture in the amount shown in Table 13-1, and the mixture was heated to 55°C for 30 minutes in a constant temperature water bath (product name: windowed constant temperature water bath, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added, the pH was adjusted to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a constant temperature water bath (product name: windowed constant temperature water bath, manufactured by Advantec) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce the sample of Example 11-1. (Production of Sample of Comparative Example 11-1 (Control)) A sample of Comparative Example 11-1 (control) was produced in the same manner as in Example 11-1, except that no enzyme was added. (Measurement of Viscosity of Each Sample) The viscosity of each sample of Example 11-1 and Comparative Example 11-1, which had been adjusted to an acidic pH (pH 3.8) as described above, was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield). The results are shown in Figure 7. The amount of enzyme (wt%) in each sample is also shown in Table 13-2.

[0087]

[0088]

[0089] The results in Figure 7 show that the sample (milk protein solution) of Example 11-1 produced using Denatzyme LEP10P (an exopeptidase having LAP activity) had a lower viscosity than the sample of Comparative Example 11-1 produced without using the enzyme.

[0090] Test Example 12: Investigation of the Effect of Improving the Physical Properties of Whey Protein (Amount of Peptidase with LAP Activity Added) The following test was conducted to investigate the effect of an enzyme (peptidase with LAP activity) on improving the physical properties of whey protein. (Production of Samples of Examples A-1 to A-10) Protein raw materials and water were mixed in the amounts shown in Table 14-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 14-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, an aqueous citric acid solution was added to adjust the pH to 3.8, and the mixture was diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples A-1 to A-10. (Production of Sample of Comparative Example A-1 (Control)) The sample of Comparative Example A-1 (control) was produced in the same manner as Example A-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each of the samples of Examples A-1 to A-10 and Comparative Example A-1, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 8. The amount of enzyme (wt%) in each sample is also shown in Table 14-2.

[0091]

[0092]

[0093] The results in FIG. 8 show that the samples (whey protein solutions) of Examples A-1 to A-10, which were produced using Denatzym LEP10P (an exopeptidase having LAP activity), had lower viscosities than the sample of Comparative Example A-1, which was produced without using an enzyme.

[0094] Test Example 13: Investigation of the Effect of Improving the Physical Properties of Milk Protein (Amount of Peptidase with LAP Activity Added) The following test was conducted to investigate the effect of an enzyme (peptidase with LAP activity) on improving the physical properties of milk protein. (Production of Samples of Examples B-1 to B-10) Protein raw material, stabilizer, and water were mixed in the amounts shown in Table 15-1 using a blender (product name: Bamix, manufactured by ESGE). The enzyme was added to the resulting mixture in the amount shown in Table 15-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to below 10°C with cold water, and an aqueous citric acid solution was added to adjust the pH to 3.8, followed by diluting to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to below 10°C with cold water to produce samples of Examples B-1 to B-10. (Production of Sample of Comparative Example B-1 (Control)) Sample of Comparative Example B-1 (control) was produced using the same method as Example B-1, etc., except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples B-1 to B-10 and Comparative Example B-1, which had been adjusted to an acidic pH (pH 3.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield Co., Ltd.). The results are shown in Figure 9. The amount of enzyme (wt%) in each sample is also shown in Table 15-2.

[0095]

[0096]

[0097] The results in FIG. 9 show that the samples (milk protein solutions) of Examples B-1 to B-10, which were produced using Denatzym LEP10P (an exopeptidase having LAP activity), had lower viscosities than the sample of Comparative Example B-1, which was produced without using an enzyme.

[0098] Test Example 14: Investigation of the effect of improving the physical properties of whey protein (confirmation of the effect of suppressing viscosity increase when the pH of a whey protein solution is changed) The following test was conducted to investigate the effect of an enzyme (peptidase with LAP activity) on improving the physical properties of whey protein (the effect when the pH of a whey protein solution is changed). (Production of Samples of Examples C-1 to C-7) Protein raw materials and water were mixed in the amounts shown in Table 16-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 16-1, and the mixture was heated at 55°C for 30 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. Thereafter, the mixture was cooled to 10°C or below with cold water, and an aqueous citric acid solution was added to adjust the pH to the pH shown in Table 16-1 (i.e., Example C-1 was adjusted to pH 3, Example C-2 to pH 3.5, Example C-3 to pH 4, Example C-4 to pH 4.5, Example C-5 to pH 4.8, Example C-6 to pH 5, and Example C-7 to pH 5.5), and then diluted to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to 10°C or below with cold water to produce samples of Examples C-1 to C-7. (Production of Samples of Comparative Examples C-1 to C-7 (Controls for Examples C-1 to C-7)) A sample of Comparative Example C-1 (a control for Example C-1) was produced in the same manner as Example C-1, except that the enzyme was not added. A sample of Comparative Example C-2 (control for Example C-2) was prepared in the same manner as Example C-2, except that no enzyme was added. A sample of Comparative Example C-3 (control for Example C-3) was prepared in the same manner as Example C-3, except that no enzyme was added. A sample of Comparative Example C-4 (control for Example C-4) was prepared in the same manner as Example C-4, except that no enzyme was added. A sample of Comparative Example C-5 (control for Example C-5) was prepared in the same manner as Example C-5, except that no enzyme was added. A sample of Comparative Example C-6 (control for Example C-6) was prepared in the same manner as Example C-6, except that no enzyme was added.A sample of Comparative Example C-7 (a control for Example C-7) was produced in the same manner as Example C-7, except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each of the samples of Examples C-1 to C-7 and Comparative Examples C-1 to C-7, which had been adjusted to an acidic pH (pH 3, pH 3.5, pH 4, pH 4.5, pH 4.8, pH 5, or pH 5.5) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield). The results are shown in Figure 10. The amount of enzyme (wt%) in each sample is also shown in Table 16-2.

[0099]

[0100]

[0101] The results in Figure 10 showed the following: The sample of Example C-1 (whey protein solution, pH 3) produced using Denatzym LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example C-1 (control) (whey protein solution, pH 3) produced without using an enzyme. The sample of Example C-2 (whey protein solution, pH 3.5) produced using Denatzym LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example C-2 (control) (whey protein solution, pH 3.5) produced without using an enzyme. The sample of Example C-3 (whey protein solution, pH 4) produced using Denatzym LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example C-3 (control) (whey protein solution, pH 4) produced without using an enzyme. The sample of Example C-4 (whey protein solution, pH 4.5) produced using Denatzym LEP10P (exopeptidase having LAP activity) showed a lower viscosity than the sample of Comparative Example C-4 (control) (whey protein solution, pH 4.5) produced without the enzyme. The sample of Example C-5 (whey protein solution, pH 4.8) produced using Denatzym LEP10P (exopeptidase having LAP activity) showed a lower viscosity than the sample of Comparative Example C-5 (control) (whey protein solution, pH 4.8) produced without the enzyme. The sample of Example C-6 (whey protein solution, pH 5) produced using Denatzym LEP10P (exopeptidase having LAP activity) showed a lower viscosity than the sample of Comparative Example C-6 (control) (whey protein solution, pH 5) produced without the enzyme.The sample of Example C-7 (whey protein solution, pH 5.5) produced using Denatzym LEP10P (an exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example C-7 (control) (whey protein solution, pH 5.5) produced without using an enzyme. The above results show that the samples of Examples C-1 to C-7 (whey protein solutions) produced using Denatzym LEP10P (an exopeptidase having LAP activity) had a lower viscosity in the sample pH range of 3 to 5.5 than the samples of Comparative Examples C-1 to C-7 (controls) produced without using an enzyme.

[0102] Test Example 15: Investigation of the effect of improving the physical properties of whey protein (confirmation of the effect of suppressing viscosity increase when the pH of a whey protein solution is changed) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase having LAP activity) on improving the physical properties of whey protein (the effect when the pH of a whey protein solution is changed). (Production of Samples of Examples D-1 to D-7) Protein raw materials and water were mixed in the amounts shown in Table 17-1 using a blender (product name: Bamix, manufactured by ESGE). Enzymes were added to the resulting mixture in the amounts shown in Table 17-1, and the mixture was heated at 55°C for 30 minutes in a constant temperature water bath (product name: constant temperature water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to 10°C or below with cold water, and an aqueous citric acid solution was added to adjust the pH to the pH shown in Table 17-1 (i.e., Example D-1 was adjusted to pH 3, Example D-2 to pH 3.5, Example D-3 to pH 3.8, Example D-4 to pH 4, Example D-5 to pH 4.5, Example D-6 to pH 5, and Example D-7 to pH 5.5), followed by dilution to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to 10°C or below with cold water to produce samples of Examples D-1 to D-7. (Production of Samples of Comparative Examples D-1 to D-7 (Controls for Examples D-1 to D-7)) A sample of Comparative Example D-1 (a control for Example D-1) was produced in the same manner as Example D-1, except that the enzyme was not added. A sample of Comparative Example D-2 (control for Example D-2) was produced in the same manner as Example D-2, except that no enzyme was added. A sample of Comparative Example D-3 (control for Example D-3) was produced in the same manner as Example D-3, except that no enzyme was added. A sample of Comparative Example D-4 (control for Example D-4) was produced in the same manner as Example D-4, except that no enzyme was added. A sample of Comparative Example D-5 (control for Example D-5) was produced in the same manner as Example D-5, except that no enzyme was added.A sample of Comparative Example D-6 (a control for Example D-6) was produced in the same manner as Example D-6, except that no enzyme was added. A sample of Comparative Example D-7 (a control for Example D-7) was produced in the same manner as Example D-7, except that no enzyme was added. (Measurement of Viscosity of Each Sample) For each sample of Examples D-1 to D-7 and Comparative Examples D-1 to D-7, which had been adjusted to an acidic pH (pH 3, pH 3.5, pH 3.8, pH 4, pH 4.5, pH 5, or pH 5.5) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield). The results are shown in Figure 11. The amount of enzyme (wt%) in each sample is also shown in Table 17-2.

[0103]

[0104]

[0105] The results in Figure 11 showed the following: The sample of Example D-1 (whey protein solution, pH 3), which was produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase having LAP activity), had a lower viscosity than the sample of Comparative Example D-1 (control) (whey protein solution, pH 3), which was produced without using the enzyme. The sample of Example D-2 (whey protein solution, pH 3.5), which was produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase having LAP activity), had a lower viscosity than the sample of Comparative Example D-2 (control) (whey protein solution, pH 3.5), which was produced without using the enzyme. The sample of Example D-3 (whey protein solution, pH 3.8) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity) showed a lower viscosity than the sample of Comparative Example D-3 (control) (whey protein solution, pH 3.8) produced without the enzyme. The sample of Example D-4 (whey protein solution, pH 4) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity) showed a lower viscosity than the sample of Comparative Example D-4 (control) (whey protein solution, pH 4) produced without the enzyme. The sample of Example D-5 (whey protein solution, pH 4.5) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity) showed a lower viscosity than the sample of Comparative Example D-5 (control) (whey protein solution, pH 4.5) produced without using any enzymes.The sample of Example D-6 (whey protein solution, pH 5) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity) showed a lower viscosity than the sample of Comparative Example D-6 (control) (whey protein solution, pH 5) produced without the enzyme. The sample of Example D-7 (whey protein solution, pH 5.5) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity) showed a lower viscosity than the sample of Comparative Example D-7 (control) (whey protein solution, pH 5.5) produced without the enzyme. The above results show that the samples (whey protein solutions) of Examples D-1 to D-7, which were produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity), had lower viscosities in the pH range of 3 to 5.5 compared to the samples of Comparative Examples D-1 to D-7, which were produced without using any enzymes.

[0106] Test Example 16: Investigation of the effect of improving the physical properties of milk protein (confirmation of the effect of suppressing viscosity increase when the pH of a milk protein solution is changed) The following test was conducted to investigate the effect of an enzyme (peptidase with LAP activity) on improving the physical properties of milk protein (the effect when the pH of a milk protein solution is changed). (Production of samples of Examples E-1 to E-6) Protein raw material, stabilizer, and water were mixed in a blender (trade name: Bamix, manufactured by ESGE) in the amounts shown in Table 18-1. Enzymes were added to the resulting mixture in the amounts shown in Table 18-1, and the mixture was heated to 55°C for 30 minutes in a thermostatic water bath (trade name: thermostatic water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to 10°C or below with cold water, and an aqueous citric acid solution was added to adjust the pH to the pH shown in Table 18-1 (i.e., Example E-1 was adjusted to pH 3, Example E-2 to pH 3.5, Example E-3 to pH 3.8, Example E-4 to pH 4, Example E-5 to pH 4.5, and Example E-6 to pH 4.8), followed by diluting to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to 10°C or below with cold water to produce samples of Examples E-1 to E-6. (Production of Samples of Comparative Examples E-1 to E-6 (Controls for Examples E-1 to E-6)) A sample of Comparative Example E-1 (a control for Example E-1) was produced in the same manner as Example E-1, except that the enzyme was not added. A sample of Comparative Example E-2 (control for Example E-2) was prepared in the same manner as Example E-2, except that no enzyme was added. A sample of Comparative Example E-3 (control for Example E-3) was prepared in the same manner as Example E-3, except that no enzyme was added. A sample of Comparative Example E-4 (control for Example E-4) was prepared in the same manner as Example E-4, except that no enzyme was added. A sample of Comparative Example E-5 (control for Example E-5) was prepared in the same manner as Example E-5, except that no enzyme was added. A sample of Comparative Example E-6 (control for Example E-6) was prepared in the same manner as Example E-6, except that no enzyme was added.(Viscosity Measurement of Each Sample) The viscosity of each of the samples of Examples E-1 to E-6 and Comparative Examples E-1 to E-6, which had been adjusted to an acidic pH (pH 3, pH 3.5, pH 3.8, pH 4, pH 4.5, or pH 4.8) as described above, was measured using a Brookfield type viscometer (DV1MLVTJ0, manufactured by Brookfield) at 8°C and 6 rpm for 60 seconds. The results are shown in Figure 12. The amount of enzyme (wt%) in each sample is also shown in Table 18-2.

[0107]

[0108]

[0109] The results in Figure 12 showed the following: The sample of Example E-1 (milk protein solution, pH 3) produced using Denatzym LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example E-1 (control) (milk protein solution, pH 3) produced without using an enzyme. The sample of Example E-2 (milk protein solution, pH 3.5) produced using Denatzym LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example E-2 (control) (milk protein solution, pH 3.5) produced without using an enzyme. The sample of Example E-3 (milk protein solution, pH 3.8) produced using Denatzym LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example E-3 (control) (milk protein solution, pH 3.8) produced without using an enzyme. The sample of Example E-4 (milk protein solution, pH 4) produced using Denatzyme LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example E-4 (control) (milk protein solution, pH 4) produced without the enzyme. The sample of Example E-5 (milk protein solution, pH 4.5) produced using Denatzyme LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example E-5 (control) (milk protein solution, pH 4.5) produced without the enzyme. The sample of Example E-6 (milk protein solution, pH 4.8) produced using Denatzyme LEP10P (exopeptidase having LAP activity) was shown to have a lower viscosity than the sample of Comparative Example E-6 (control) (milk protein solution, pH 4.8) produced without the enzyme. The above results show that the samples (milk protein solutions) of Examples E-1 to E-6, which were produced using Denatzyme LEP10P (an exopeptidase with LAP activity), had lower viscosities in the pH range of 3 to 4.8 compared to the samples of Comparative Examples E-1 to E-6, which were produced without using an enzyme.

[0110] Test Example 17: Investigation of the effect of improving the physical properties of milk protein (confirmation of the effect of suppressing viscosity increase when the pH of a milk protein solution is changed) The following test was conducted to investigate the effect of an enzyme (a combination of phospholipase D and a peptidase having LAP activity) on improving the physical properties of milk protein (the effect when the pH of a milk protein solution is changed). (Production of samples of Examples F-1 to F-5) Protein raw material, stabilizer, and water were mixed in a blender (trade name: Bamix, manufactured by ESGE) in the amounts shown in Table 19-1. Enzymes were added to the resulting mixture in the amounts shown in Table 19-1, and the mixture was heated at 55°C for 30 minutes in a constant temperature water bath (trade name: constant temperature water bath with window, manufactured by Advantec) to carry out an enzymatic reaction. The mixture was then cooled to 10°C or below with cold water, and an aqueous citric acid solution was added to adjust the pH to the pH shown in Table 19-1 (i.e., Example F-1 was adjusted to pH 3.5, Example F-2 to pH 3.8, Example F-3 to pH 4, Example F-4 to pH 4.5, and Example F-5 to pH 4.8), followed by diluting to 100% with water. The resulting solution was heated to 90°C for 10 minutes in a thermostatic water bath (product name: thermostatic water bath with window, manufactured by Advantec Co., Ltd.) to inactivate the enzyme and sterilize it, and then cooled to 10°C or below with cold water to produce samples of Examples F-1 to F-5. (Production of Samples of Comparative Examples F-1 to F-5 (Controls for Examples F-1 to F-5)) A sample of Comparative Example F-1 (a control for Example F-1) was produced in the same manner as Example F-1, except that the enzyme was not added. A sample of Comparative Example F-2 (a control for Example F-2) was produced in the same manner as Example F-2, except that no enzyme was added. A sample of Comparative Example F-3 (a control for Example F-3) was produced in the same manner as Example F-3, except that no enzyme was added. A sample of Comparative Example F-4 (a control for Example F-4) was produced in the same manner as Example F-4, except that no enzyme was added. A sample of Comparative Example F-5 (a control for Example F-5) was produced in the same manner as Example F-5, except that no enzyme was added.(Measurement of viscosity of each sample) For each of the samples of Examples F-1 to F-5 and Comparative Examples F-1 to F-5, which were adjusted to an acidic pH (pH 3.5, pH 3.8, pH 4, pH 4.5, or pH 4.8) as described above, the viscosity was measured at 8°C, 6 rpm, and 60 seconds using a Brookfield viscometer (DV1MLVTJ0, manufactured by Brookfield). The results are shown in Figure 13. The amount of enzyme (wt%) in each sample is also shown in Table 19-2.

[0111]

[0112]

[0113] The results in Figure 13 showed the following: The sample of Example F-1 (milk protein solution, pH 3.5), which was produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase having LAP activity), was shown to have a lower viscosity than the sample of Comparative Example F-1 (control) (milk protein solution, pH 3.5), which was produced without using the enzyme. The sample of Example F-2 (milk protein solution, pH 3.8), which was produced using a combination of Denatzym PMD-P1 (phospholipase D) and Denatzym LEP10P (exopeptidase having LAP activity), was shown to have a lower viscosity than the sample of Comparative Example F-2 (control) (milk protein solution, pH 3.8), which was produced without using the enzyme. The sample of Example F-3 (milk protein solution, pH 4) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase having LAP activity) showed a lower viscosity than the sample of Comparative Example F-3 (control) produced without using the enzyme (milk protein solution, pH 4). The sample of Example F-4 (milk protein solution, pH 4.5) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase having LAP activity) showed a lower viscosity than the sample of Comparative Example F-4 (control) produced without using the enzyme (milk protein solution, pH 4.5). The sample of Example F-5 (milk protein solution, pH 4.8) produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity) showed a lower viscosity than the sample of Comparative Example F-5 (control) (milk protein solution, pH 4.8) produced without using any enzymes.The above results show that the samples (milk protein solutions) of Examples F-1 to F-5, which were produced using a combination of Denatzyme PMD-P1 (phospholipase D) and Denatzyme LEP10P (exopeptidase with LAP activity), had lower viscosities in the pH range of 3.5 to 4.8 compared to the samples of Comparative Examples F-1 to F-5, which were produced without using any enzymes.

[0114] The modified milk protein solution obtained by the production method of the present invention has an advantage in that it can be incorporated into acidic foods and beverages because the increase in viscosity and roughness are suppressed under low pH conditions.

[0115] This application is based on patent application No. 2024-086682 filed in Japan, the contents of which are incorporated in their entirety herein.

Claims

1. A method for producing a modified milk protein solution, which comprises the step of adding a protease having LAP activity or a peptidase having LAP activity to a milk protein solution.

2. The method according to claim 1, wherein the milk protein content in the milk protein solution is 1% by weight or more.

3. The production method according to claim 1 or 2, further comprising the step of adding phospholipase D to the milk protein solution.

4. A method for inhibiting an increase in viscosity of a milk protein solution, comprising the step of adding a protease having LAP activity or a peptidase having LAP activity to the milk protein solution.

5. A method for inhibiting viscosity increase according to claim 4, wherein the milk protein content in the milk protein solution is 1% by weight or more.

6. The method for inhibiting viscosity increase according to claim 4 or 5, which is a method for inhibiting viscosity increase of a milk protein solution having a pH of 3 to 5.

7. A method for improving the roughness of a milk protein solution, comprising the step of adding a protease having LAP activity or a peptidase having LAP activity, and phospholipase D to the milk protein solution.

8. A method for improving roughness according to claim 7, wherein the milk protein content in the milk protein solution is 1% by weight or more.

9. The method for reducing roughness according to claim 7 or 8, which is a method for reducing roughness in a milk protein solution having a pH of 3 to 5.

10. An enzyme preparation for modifying a milk protein solution, containing a protease having LAP activity or a peptidase having LAP activity.

11. The enzyme preparation according to claim 10, further comprising phospholipase D.

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