A method for reducing the precipitation of white spots during the production of yeast extract

Abstract

The application discloses a method for reducing white point precipitation in a yeast extract production process, which comprises the following steps: mixing edible yeast with water, heating, adjusting the pH value of the system, adding protease, and incubating for enzyme hydrolysis until the degree of hydrolysis reaches more than 20%, then heating to inactivate the enzyme, collecting the supernatant to obtain a yeast hydrolysate; adding propyl mercaptan with a solid content of 0.2% to 0.5% of the mass of the yeast hydrolysate, and heating for 12 to 16 hours to obtain a yeast reaction solution. The method uses propyl mercaptan, which not only affects the taste and smell of food, but also participates in Maillard reaction and mercaptan-sulfinylation reaction, thereby changing the appearance quality, flavor and stability of food. In the yeast extract processing process, the external addition of propyl mercaptan and the reaction with the yeast hydrolysate solve the problem of "white point" of the yeast extract in the concentration stage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of yeast extract preparation, and particularly relates to a method for reducing the precipitation of white spots in the production process of yeast extract. BACKGROUND

[0002] Edible yeast has a protein content of more than 45% (calculated on a dry basis) and is rich in various flavor precursor substances, and is an excellent raw material for producing high-quality food ingredients and flavoring bases. Yeast extract is a natural food ingredient obtained through a series of processes under the action of enzymes in edible yeast or additional food processing enzymes. Yeast extract is often applied to various processed foods due to its good flavor and taste, as well as its rich content of amino acids, vitamins, minerals and polypeptides and other nutrients, and has a broad market prospect.

[0003] The market competitiveness of yeast extract is closely related to its flavor quality, and more and more producers optimize the flavor quality of yeast extract by increasing the degree of hydrolysis of yeast extract. The production process of yeast extract usually includes autolysis and enzymolysis, enzyme inactivation, separation, concentration, sterilization or spray drying, etc. Optimizing the early autolysis and enzymolysis process to improve the degree of hydrolysis of yeast extract is a simple and efficient method.

[0004] However, during the production of yeast extract, white precipitates, commonly known as "white spots", often appear during the concentration stage, which causes many problems in the sale and application of yeast extract: (1) affecting the appearance quality of yeast extract products, which easily causes users to doubt the quality, thereby limiting its sale and use; (2) affecting the purity of yeast extract, reducing the stability of the product, and thus affecting the shelf life and storage safety; (3) increasing the processing procedures for removing "white spots" in yeast extract, thereby increasing the complexity and cost of production. Therefore, reducing or eliminating the formation of "white spots" in the production process of yeast extract is a technical problem that needs to be solved in the yeast extract industry.

[0005] It is found in the research and actual production of yeast extract that the appearance of "white spots" in the concentration process of yeast extract is closely related to the high degree of hydrolysis of yeast extract. In the industrial preparation of yeast extract, enterprises often increase the content of flavor peptides and free amino acids in the product by increasing the degree of enzymatic hydrolysis of yeast extract to obtain yeast extract with better flavor quality, but this also increases the probability of "white spots" in the concentration process of the enzymatic product.

[0006] Studies have shown that the aggregation and precipitation of free tyrosine is the direct cause of the "white spot" of yeast extract. Because the solubility of tyrosine in water is very low, the content of free tyrosine is relatively low during the enzymatic hydrolysis stage due to the high water content and temperature in the system, and precipitation generally does not occur. However, when the yeast enzymatic hydrolysate is concentrated, the water content in the enzymatic hydrolysate becomes lower and lower, and the concentration of free tyrosine in the system becomes higher and higher. When the concentration of free tyrosine in the enzymatic hydrolysate is higher than the solubility content, precipitation occurs, and "white spots" appear in the system.

[0007] In research and actual industrial production, it is found that when the degree of hydrolysis of yeast enzymatic hydrolysate exceeds 20%, aggregation and precipitation easily occur during the concentration stage, thereby producing "white spots". In order to solve the problem of the large amount of free tyrosine precipitating to form "white spots" during the production of yeast extract, researchers have tried various methods, including filtration, repeated centrifugal separation, addition of active agents, and optimization of production equipment. However, the above methods will increase the production cost to varying degrees, and the effect is unstable, the application cost is high, and even the flavor quality of the yeast extract product will be affected. Therefore, it is particularly important to choose a preparation process that reduces the precipitation of "white spots" without affecting the degree of hydrolysis and flavor quality of the yeast extract product, thereby improving the market competitiveness and cost performance of the product. SUMMARY

[0008] The purpose of the present application is to provide a method for reducing the precipitation of "white spots" during the production of yeast extract. This process solves the problem of insoluble "white spots" caused by the precipitation of hydrophobic compounds such as tyrosine during the production of yeast extract without affecting the flavor of yeast extract, maximally eliminates the hidden danger of "white spots", and improves the quality of yeast extract.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] A method for reducing the precipitation of "white spots" during the production of yeast extract, comprising the following steps:

[0011] (1) Mix edible yeast with a certain amount of water, heat to 50-60℃, adjust the pH value of the system, add protease, and hydrolyze until the degree of hydrolysis reaches more than 20%, then heat to kill the enzyme, then centrifugal separation, collect the supernatant to obtain yeast enzymatic hydrolysate;

[0012] (2) Adjust the pH value of the yeast enzymatic hydrolysate to 5.5-6.5, add propyl mercaptan at a concentration of 0.2%-0.5% of the solid content of the yeast enzymatic hydrolysate, stir uniformly, then heat to 40-55℃, and react for 12-16h to obtain yeast reaction liquid.

[0013] The yeast in step (1) is fresh yeast milk, active dry yeast, or inactivated dry yeast powder.

[0014] The amount of water added in step (1) is preferably such that the solid content is 10-18%.

[0015] In step (1), the pH is adjusted using a 0.3-0.6 mol / L NaOH solution and a 0.3-0.6 mol / L HCl solution to the optimum pH for the protease participating in the reaction.

[0016] The protease in step (1) is one or more of acid protease, neutral protease, alkaline protease, trypsin, papain, bromelain, flavourzyme or ficin.

[0017] Preferably, the protease consists of bromelain and flavourzyme, or consists of alkaline protease and flavourzyme, or consists of trypsin and flavourzyme.

[0018] The total amount of protease added in step (1) is not more than 1% of the dry matter mass of the yeast raw material.

[0019] The enzyme inactivation in step (1) is at 90-95°C for 15-30 min.

[0020] The centrifugation in step (1) can use a tubular centrifuge or a disc centrifuge, and the centrifugation parameters can be adjusted according to the centrifugation effect of the centrifuge, with the centrifugation of the supernatant in a laboratory centrifuge at 4000 x g for 10 min having no obvious visible precipitate as the criterion.

[0021] In step (2), the pH is adjusted using a 0.3-0.6 mol / L NaOH solution and a 0.3-0.6 mol / L HCl solution.

[0022] The uniform stirring in step (2) is carried out at not higher than 30°C.

[0023] After the yeast reaction solution is concentrated (preferably to a solid content of 50-70%) in step (2), sterilization treatment is carried out to obtain a paste-like yeast extract.

[0024] After the yeast reaction solution is concentrated (preferably to a solid content of 30-45%) in step (2), sterilization and spray drying are carried out to obtain a powder-like yeast extract.

[0025] The concentration is carried out at 50-55°C and -0.09 mPa to -0.095 mPa under reduced pressure.

[0026] The sterilization is preferably carried out at 90-95°C for 30 min.

[0027] The spray drying inlet temperature is 185-190 DEG C, and the outlet temperature is 80-85 DEG C.

[0028] The present application has the following advantages and effects relative to the prior art:

[0029] (1) The method of the present application utilizes propyl mercaptan, which not only affects the taste and odor of food, but also participates in Maillard reaction and mercaptan-sulfinylation reaction, thereby changing the appearance quality, flavor and stability of food. In the process of yeast extract processing, the reaction of externally added propyl mercaptan with yeast enzymatic hydrolysate solves the problem of "white spots" in the concentration stage of yeast extract.

[0030] (2) The method of the present application solves the problem of "white spots" in the concentration stage of yeast extract by combining mild heat reaction with the conventional preparation process of yeast extract. The present application does not need to increase additional production equipment, has low production cost, no pollution, simple operation, strong implementability and easy popularization.

[0031] (3) The present application not only solves the problem of white spot precipitation, but also has a positive effect on the taste and odor of yeast extract product, thereby comprehensively improving the flavor quality of yeast extract, meeting the high quality requirements of the market for products, and improving the overall economic benefit of yeast extract. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The precipitation rate of the yeast extract. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below in combination with examples and drawings, but the embodiments of the present application are not limited thereto.

[0034] The experimental methods of the test indexes involved in the embodiments of the present application are as follows:

[0035] (1) "White spot" collection method: white spots will precipitate during the concentration of yeast enzymatic hydrolysate. The "white spots" insoluble substances are obtained by repeatedly washing with ultrapure water and separating the precipitate by multiple high-speed centrifugation (8000xg, 20min).

[0036] (2) Determination method of degree of hydrolysis: the degree of hydrolysis DH (Degree of hydrolysis) of protein represents the degree or percentage of peptide bond cleavage in the hydrolysis process of protein. The present application adopts online determination, refers to the pH-stat method, and calculates the degree of hydrolysis by adding the amount of base or acid used to maintain the system based on the release or absorption of protons in the protein hydrolysis process. The calculation formula is as follows:

[0037] DH = h ÷ h tot × 100% = B x N b÷ (a x M p x h tot ) x 100%

[0038] In the formula, B is the volume of lye, N b is the concentration of lye, a is the dissociation degree of amino group, M p is the total content of protein in the substrate g, h tot is the total number of peptide bonds in the protein in the substrate mmol / g, and h is the number of peptide bonds cleaved.

[0039] (3) The determination method of the precipitation rate: in the production process of yeast extract, the precipitate is the insoluble "white point" produced after the yeast proteolysis liquid is concentrated and collected after centrifugal separation. The precipitation rate quantifies the proportion of the precipitate produced in the concentration process in the total mass of the yeast proteolysis liquid. The calculation formula is as follows:

[0040] Precipitation rate = white point mass ÷ yeast proteolysis liquid mass x 100%

[0041] (4) The determination method of amino acids: the content and proportion of each free amino acid in the sample are determined by using L8900 automatic amino acid analyzer, and the pretreatment is in accordance with GB5009.124-2016 and GB / T30897-2020.

[0042] Example 1

[0043] A method for reducing the precipitation of white points in the production process of yeast extract, comprising the following steps:

[0044] (1) 650 g of fresh yeast milk (moisture content is about 84.0%) is mixed with 43 g of water, and the initial pH of the system is adjusted to 7.5 by using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution at 55°C, then 0.4 g of bromelain (Guangxi Nanning Zhengdong Food Co., Ltd., enzyme activity is 500,000 U / g) and 0.3 g of flavor protease Flavourzyme500MG (Novozymes) are added, and hydrolysis is carried out at constant temperature for 22 h, then the temperature is raised to 95°C for 15 min for enzyme inactivation, then the material is cooled to 70°C, and the supernatant is collected by using a tubular centrifuge, and 82.1 g of yeast proteolysis liquid A is obtained;

[0045] (2) The pH of the yeast proteolysis liquid A is adjusted to 5.5 by using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, 0.25 g of propyl mercaptan is added, and stirring is carried out uniformly at room temperature (about 25°C), and the yeast reaction liquid A is obtained after reaction at 45°C for 12 h;

[0046] (3) The yeast reaction solution A was concentrated to a solid content of 50% at 50°C, -0.090 mPa, and then the sample was placed at 95°C for 30 min for sterilization treatment to obtain a paste-like yeast extract product A.

[0047] The results of the degree of hydrolysis and appearance of the yeast extract product A are shown in Table 1.

[0048] The results of the free amino acid content and proportion of the yeast extract product A are shown in Table 2.

[0049] The results of the precipitation rate of the yeast extract product A are shown in the following table Figure 1 .

[0050] Example 2

[0051] A method for reducing the precipitation of white spots in the production process of yeast extract, comprising the following steps:

[0052] (1) 100 g of active dry yeast powder (moisture content about 6.8%) was mixed with 521.4 g of water, then heated to 55°C, and then the initial pH of the system was adjusted to 8.5 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, then 0.5 g of alkaline protease (Novozymes, enzyme activity 80-100 million U / g) and 0.2 g of flavor protease Flavourzyme 500MG (Novozymes) were added, and after hydrolysis at 70°C for 22 h, the enzyme was inactivated by heating to 95°C for 15 min, then the material was cooled to 70°C, and the supernatant was collected by tube centrifuge to obtain a yeast hydrolysate B with a solid content of 76.7 g;

[0053] (2) The pH of the yeast hydrolysate B was adjusted to 6.0 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, 0.3 g of propyl mercaptan was added, and the mixture was stirred uniformly at room temperature (about 25°C), and then reacted at 40°C for 14 h to obtain a yeast reaction solution B;

[0054] (3) The yeast hydrolysate B was concentrated to a solid content of 55% at 50°C, -0.095 mPa, and then the sample was placed at 95°C for 30 min for sterilization treatment to obtain a paste-like yeast extract product B.

[0055] The results of the degree of hydrolysis and appearance of the yeast extract product B are shown in Table 1.

[0056] The results of the free amino acid content and proportion of the yeast extract product B are shown in Table 2.

[0057] The results of the precipitation rate of the yeast extract product B are shown in the following table Figure 1 .

[0058] Example 3

[0059] A method for reducing the precipitation of white spots in the production process of yeast extract, comprising the following steps:

[0060] (1) 100 g of inactivated dry yeast powder (moisture content of about 5.3%) was mixed with 531.3 g of water, then heated to 55°C, and then the initial pH of the system was adjusted to 8.0 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, then 0.6 g of trypsin (Guangxi Nanning Pangbo Biological Engineering Co., Ltd., enzyme activity of 3000-4000 U / g) and 0.2 g of Flavourzyme 500MG (Novozymes) were added, and the hydrolysis was carried out at 25°C for 25 h, then the temperature was raised to 95°C for 15 min to inactivate the enzyme, then the material was cooled to 70°C, and a tubular centrifuge was used to separate and collect the supernatant, obtaining 72.8 g of yeast enzyme hydrolysate C with a solid content of 60%;

[0061] (2) The pH of the yeast enzyme hydrolysate C was adjusted to 6.5 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, 0.35 g of propyl mercaptan was added, and the mixture was stirred uniformly at room temperature (about 25°C), then the temperature was raised to 50°C and the reaction was carried out for 16 h to obtain yeast reaction liquid C;

[0062] (3) The yeast reaction liquid C was concentrated to a solid content of 60% at 55°C and -0.095 mPa, then the sample was placed at 95°C for 30 min for sterilization treatment to obtain a paste-like yeast extract product C.

[0063] The results of the degree of hydrolysis and the appearance of the yeast extract product C are shown in Table 1.

[0064] The results of the free amino acid content and the proportion of the yeast extract product C are shown in Table 2.

[0065] The results of the precipitation rate of the yeast extract product C are shown in the following table Figure 1 .

[0066] Comparative Example 1

[0067] A method for reducing the precipitation of white spots in the production process of yeast extract (compared with the embodiment, without adding propyl mercaptan and without subsequent heat reaction), comprising the following steps:

[0068] (1) Take 100 g of inactivated dry yeast powder (moisture content 5.3%) and mix it evenly with 531.3 g of water, then heat it to 55°C, adjust the initial pH of the system to 8.0, then add 0.6 g of pancreatin (Guangxi Nanning Pangbo Biological Engineering Co., Ltd., enzyme activity 3000-4000 U / g) and 0.2 g of flavor protease Flavourzyme 500MG (Novozymes), hydrolyze for 25 h, then heat to 95°C for 15 min to inactivate the enzyme, then cool the material to 70°C, separate and collect the supernatant using a tubular centrifuge, and obtain 72.8 g of yeast enzyme hydrolysate 1;

[0069] (2) Concentrate the yeast enzyme hydrolysate 1 to a solid content of 60% at 55°C and -0.095 mPa, then place the sample at 95°C for 30 min for sterilization treatment to obtain a paste-like yeast extract product 1.

[0070] The degree of hydrolysis and appearance of the yeast extract product 1 are shown in Table 1.

[0071] The free amino acid content and proportion of the yeast extract product 1 are shown in Table 2.

[0072] The precipitation rate of the yeast extract product 1 is shown in the following table Figure 1 .

[0073] Comparative Example 2

[0074] A method for reducing the precipitation of white spots in the production of yeast extract (without adding propyl mercaptan compared to the example), comprising the following steps:

[0075] (1) Take 100 g of inactivated dry yeast powder (moisture content 5.3%) and mix it evenly with 531.3 g of water, then heat it to 55°C, adjust the initial pH of the system to 8.0 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, then add 0.6 g of pancreatin (Guangxi Nanning Pangbo Biological Engineering Co., Ltd., enzyme activity 3000-4000 U / g) and 0.2 g of flavor protease Flavourzyme 500MG (Novozymes), hydrolyze for 25 h, then heat to 95°C for 15 min to inactivate the enzyme, then cool the material to 70°C, separate and collect the supernatant using a tubular centrifuge, and obtain 72.8 g of yeast enzyme hydrolysate 2;

[0076] (2) Adjust the pH of the yeast enzyme hydrolysate 2 to 6.5 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, and incubate at 50°C for 16 h, then cool to room temperature to obtain yeast reaction liquid 2;

[0077] (3) The yeast reaction solution 2 was concentrated to a solid content of 60% at 55°C and -0.095 mPa, and then the sample was placed at 95°C for 30 min for sterilization treatment to obtain a paste-like yeast extract product 2.

[0078] The degree of hydrolysis and appearance of the yeast extract product 2 are shown in Table 1.

[0079] The free amino acid content and proportion of the yeast extract product 2 are shown in Table 2.

[0080] The precipitation rate of the yeast extract product 2 is shown in the following table Figure 1 .

[0081] Comparative Example 3

[0082] A method for reducing the precipitation of white spots in the production of yeast extract (compared with the examples, excessive addition of propyl mercaptan), comprising the following steps:

[0083] (1) 100 g of inactivated dry yeast powder (moisture content 5.3%) was mixed with 531.3 g of water, then heated to 55°C, and then the initial pH of the system was adjusted to 8.0 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, then 0.6 g of pancreatin (Guangxi Nanning Pangbo Biological Engineering Co., Ltd., enzyme activity 3000-4000 U / g) and 0.2 g of Flavourzyme 500MG (Novozymes) were added, and hydrolysis was carried out at 70°C for 25 h, then the temperature was raised to 95°C for 15 min to inactivate the enzyme, then the material was cooled to 70°C, and a tubular centrifuge was used to separate and collect the supernatant, obtaining a yeast hydrolysate 3 with a solid content of 72.8 g;

[0084] (2) The pH of the yeast hydrolysate 3 was adjusted to 6.5 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, 1.0 g of propyl mercaptan was added, and the mixture was stirred uniformly at room temperature (about 25°C), and then the reaction was carried out at 50°C for 16 h to obtain a yeast reaction solution 3.

[0085] (3) The yeast reaction solution 3 was concentrated to a solid content of 60% at 55°C and -0.095 mPa, and then the sample was placed at 95°C for 30 min for sterilization treatment to obtain a paste-like yeast extract product 3.

[0086] The degree of hydrolysis and appearance of the yeast extract product 3 are shown in Table 1.

[0087] The free amino acid content and proportion of the yeast extract product 3 are shown in Table 2.

[0088] The precipitation rate of the yeast extract product 3 is shown in the following table Figure 1 .

[0089] Comparative Example 4

[0090] A method for reducing the precipitation of white spots in the production of yeast extract (compared with the example, insufficient amount of propyl mercaptan is added), comprising the following steps:

[0091] (1) 100 g of inactivated dry yeast powder (moisture content 5.3%) was mixed with 531.3 g of water, then heated to 55°C, and then the initial pH of the system was adjusted to 8.0 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, then 0.6 g of pancreatin (Guangxi Nanning Pangbo Biological Engineering Co., Ltd., enzyme activity 3000-4000 U / g) and 0.2 g of Flavourzyme 500MG (Novozymes) were added, and the hydrolysis was carried out at 25°C for 25 h, then the temperature was raised to 95°C for 15 min to inactivate the enzyme, then the material was cooled to 70°C, and the supernatant was collected by using a tubular centrifuge, and 72.8 g of yeast hydrolysate 4 was obtained;

[0092] (2) The pH of the yeast hydrolysate 4 was adjusted to 6.5 using 0.5 mol / L NaOH solution and 0.5 mol / L HCl solution, 0.05 g of propyl mercaptan was added, and the mixture was stirred uniformly at room temperature (about 25°C), and then the reaction was carried out at 50°C for 16 h to obtain yeast reaction liquid 4.

[0093] (3) The yeast reaction liquid 4 was concentrated to a solid content of 60% at 55°C and -0.095 mPa, and then the sample was sterilized at 95°C for 30 min to obtain a paste-like yeast extract product 4.

[0094] The degree of hydrolysis and appearance of the yeast extract product 4 are shown in Table 1.

[0095] The free amino acid content and proportion of the yeast extract product 4 are shown in Table 2.

[0096] The precipitation rate of the yeast extract product 4 is shown in the following table Figure 1 .

[0097] Table 1 Degree of hydrolysis and sensory properties of yeast extract

[0098]

[0099] Table 1 is a summary table of the degree of hydrolysis and sensory properties of the yeast extract obtained in the examples and comparative examples, and Table 2 is the free amino acid composition of the yeast extract, Figure 1 the precipitation rate of the yeast extract obtained in the examples and comparative examples.

[0100] According to the results in Table 1, the degree of hydrolysis of the yeast extract prepared in the examples and comparative examples all reached more than 20%, and the yeast extract products A-C prepared by the method of the present application (Examples 1-3) all did not appear "white point" precipitation; while the yeast extract products of other comparative examples all appeared visible "white point" precipitation, except that the yeast extract 3 of Comparative Example 3 did not appear "white point" precipitation, indicating that the method of the present application can better improve the problem of "white point" precipitation of high degree of hydrolysis yeast extract in the production process.

[0101] The difference between Comparative Example 2 and the method of the present application is that propyl mercaptan is not added to the yeast enzymatic hydrolysate, and Comparative Example 1 not only does not add propyl mercaptan but also does not carry out subsequent reaction (16h at 50℃), both of which appear obvious "white point" precipitation, which is because propyl mercaptan is added to the yeast enzymatic hydrolysate and reacts. As a kind of sulfur-containing compound with strong reducing property, appropriate amount of propyl mercaptan can not only directly improve the flavor quality of the yeast extract, but also inhibit the generation of "white point" in the production process of the yeast extract when it reacts with the yeast extract. The difference between Comparative Examples 3 and 4 and the method of the present application is that the amount of propyl mercaptan added exceeds the range specified in the present application. Although excessive addition of propyl mercaptan can solve the problem of "white point" precipitation, it also causes incomplete reaction of propyl mercaptan, resulting in prominent sulfur odor of the yeast extract product 3, which seriously affects its flavor quality; while too little amount of propyl mercaptan added, it also cannot effectively react with the "white point" composition, resulting in the appearance of "white point" precipitation in the yeast extract 4.

[0102] Table 2 is the free amino acid composition of the yeast extract prepared in the comparative examples and examples, from which it can be seen that the content of free tyrosine in the yeast extract products prepared by the method of the present application (Examples 1-3) is low (1.07-1.35mg / mL), accounting for only 1.33%-1.58%. Among them, the content of tyrosine in the product yeast extract A obtained in Example 1 is 1.07mg / mL, which is generally difficult to form "white point" precipitation at this concentration, because propyl mercaptan has reacted with free tyrosine in the yeast extract, reducing the content of free tyrosine in the yeast extract, thereby effectively inhibiting the formation of "white point" in the concentration process of the yeast extract.

[0103] However, the content of free tyrosine in the yeast extract of Comparative Example 1 is as high as 5.14mg / mL, accounting for 5.70%, which makes the yeast extract 1 present obvious "white point", which is mainly because propyl mercaptan is not added in Comparative Example 1 to react with the yeast extract, and the content of free tyrosine in the yeast extract product 1 is 4.07mg / mL higher than that of the yeast extract product A in the example, resulting in the appearance of "white point".

[0104] Comparative Example 2 did not add propyl mercaptan, and although a certain thermal reaction was carried out in the subsequent stage, the free tyrosine content of the obtained yeast extract was still high (5.13 mg / mL), and "white spots" appeared, indicating that without the addition of propyl mercaptan, the thermal reaction of the yeast extract alone was not effective in inhibiting the generation of "white spots".

[0105] The tyrosine content of the yeast extract prepared in Comparative Example 3 was 1.05 mg / mL, so that the yeast extract did not appear "white spots" during the entire production process, but due to incomplete reaction of propyl mercaptan, the sulfur odor of propyl mercaptan itself adversely affected the flavor quality of the yeast extract 3 (showing a distinct sulfur odor); for Comparative Example 4, the content of propyl mercaptan added was much lower than in the examples, and as a result, the tyrosine content of the yeast extract in Comparative Example 4 was as high as 4.88 mg / mL, which was 3.81 mg / mL higher than the yeast extract A prepared by the method of the present application, and the "white spots" were not effectively resolved, indicating that the addition of an appropriate amount of propyl mercaptan to the yeast enzymatic hydrolysate for thermal reaction could positively affect the overall quality of the final yeast extract.

[0106] Figure 1 The higher the precipitation rate of the yeast extract prepared in the examples and comparative examples, the more precipitates, and the greater the possibility of "white spots" appearing, so reducing the precipitation rate is also an effective indication of the inhibition of "white spots" precipitation. As can be seen from the figure, the precipitation rates of the products prepared according to the method of the present application (yeast extract products A-C) are all less than 0.2%, which is much lower than the precipitation rates of the yeast extracts in the comparative examples. The yeast extract products prepared in Comparative Examples 1, 2, and 4 have high precipitation rates, indicating that only mild thermal reaction or the addition of less than the specified amount of propyl mercaptan in the present application has little effect on inhibiting the precipitation of "white spots" in the yeast extract. Only by adding an appropriate amount of propyl mercaptan to react with the hydrophobic substances in the yeast extract can the content of the hydrophobic substances be reduced to make them exist stably in the solution, thereby achieving the effect of reducing the precipitation of "white spots" during the production process.

[0107] The yeast extract prepared by the method of the present application not only has excellent flavor, but also avoids the generation of "white spots" during the concentration process, which significantly improves the stability and appearance quality of the yeast extract product, and has good application prospects.

[0108] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included within the scope of protection of the present application.

[0109]

Claims

1. A method for reducing white spot precipitation during yeast extract production, characterized in that... Includes the following steps: (1) Mix edible yeast with water, heat to 50-60℃, adjust the pH of the system, add protease, keep warm and hydrolyze until the degree of hydrolysis reaches more than 20%, heat to inactivate the enzyme, then centrifuge and collect the supernatant to obtain yeast hydrolysate. (2) Adjust the pH of the yeast hydrolysate to 5.5-6.5, add 0.2%-0.5% of the solids in the yeast hydrolysate, stir evenly, then heat to 40℃-55℃ and keep warm for 12-16 hours to obtain the yeast reaction solution. The protease described in step (1) is composed of bromelain and flavor protease, or alkaline protease and flavor protease, or pancreatic enzyme and flavor protease. In step (1), the total amount of protease added shall not exceed 1% of the dry matter mass of the yeast raw material.

2. The method according to claim 1, characterized in that: The yeast mentioned in step (1) is fresh yeast milk, active dry yeast, or inactivated dry yeast powder.

3. The method according to claim 1, characterized in that: The mixing process described in step (2) is carried out at a temperature not exceeding 30°C.

4. The method according to claim 1, characterized in that: The yeast reaction solution described in step (2) is concentrated and then sterilized to obtain a paste-like yeast extract.

5. The method according to claim 4, characterized in that: The concentration mentioned refers to concentrating the product to a solids content of 50-70%.

6. The method according to claim 1, characterized in that: After the yeast reaction solution described in step (2) is concentrated, it is sterilized and spray-dried to obtain powdered yeast extract.

7. The method according to claim 6, characterized in that: The concentration mentioned refers to concentrating the product to a solids content of 30-45%.

8. The method according to any one of claims 4 to 7, characterized in that: The concentration is carried out under reduced pressure at 50–55°C and -0.09 mPa to -0.095 mPa.

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