A method for preparing a nucleotide type yeast extract

Abstract

The present application relates to the technical field of nucleotide production, and particularly relates to a method for preparing nucleotide type yeast extract, in particular a method for preparing nucleotide type yeast extract by biological catalysis. The method comprises the following steps: (1) mixing yeast extract with RNA, adding a nuclease solution, performing first enzymolysis to obtain a first enzymolysis solution; (2) adding a deaminase to the first enzymolysis solution, performing second enzymolysis to obtain a second enzymolysis solution; (3) adjusting the pH of the second enzymolysis solution, and drying to obtain the nucleotide type yeast extract. The types, dosage, adding method, reaction temperature and pH of enzymolysis in the preparation process are optimized, the mass content of nucleotides in the prepared nucleotide type yeast extract reaches 40.8%, the mass content of amino acids reaches 16.1%, and the mass content of insoluble substances is only 1.1%, so the nucleotide type yeast extract has a good application prospect in the preparation of food flavoring agents.

Description

Technical Field

[0001] This invention relates to the field of nucleotide production technology, specifically to a method for preparing nucleotide-type yeast extracts, and more particularly to a biocatalytic method for preparing nucleotide-type yeast extracts. Background Technology

[0002] The taste of food is composed of its water-soluble substances, including nucleotides, amino acids, peptides, organic acids, organic bases, and inorganic ions. These substances undergo a series of complex and lengthy reactions within the body to produce sweet, bitter, or salty tastes. All the components mentioned above contain at least one of the five basic tastes: salty, sweet, sour, bitter, and umami. Flavor nucleotides are one such substance, and their types include, but are not limited to, inosinic acid, guanylic acid, cytidine acid, uridine acid, and xanthocyanidins. Flavor nucleotides have good flavor-enhancing properties in meat, fish, eggs, and dairy products, increasing their palatability. They can enhance sweetness, meatiness, and richness, while eliminating or inhibiting unpleasant flavors such as sourness, bitterness, fishiness, and burnt taste. To a certain extent, they can improve the palatability of seasonings. This effectively reduces the amount of additives used, lowers production costs, and makes food taste richer. Furthermore, flavor nucleotides can extend the shelf life of meat products during storage. Therefore, flavor nucleotides are frequently added to various seasonings, such as chicken bouillon, chicken powder, MSG, soy sauce, seasoning packets, soup bases, ketchup, and mayonnaise, to enhance their flavor and optimize their texture. They have broad application prospects in the food industry. Nucleotide-type yeast extract, also known as 5'-nucleotide-type yeast extract, contains disodium 5'-inosinate (IMP) and disodium 5'-guanylate (GMP). This is a new generation of nucleotide-based food flavor enhancers that can be directly added to food to enhance its flavor. Nucleotide-type yeast extraction is a novel compound microbial additive that can form various flavor compounds with different amino acids. It is one of the key flavor components in instant noodles, chicken bouillon, chicken powder, and flavor-enhancing soy sauces. Furthermore, nucleotide-type yeast extract is also an important raw material for the production of bioactive substances such as enzyme reaction inhibitors and enzyme inhibitors. Nucleotide-type yeast extract not only helps in anti-cancer treatment but also enhances the body's immune system and regulates nutrient metabolism, thus finding wide application in multiple industries, including food, medicine, and agriculture.

[0003] The preparation of nucleotide-type yeast extracts currently mainly employs several methods:

[0004] (1) Microbial fermentation method: By selecting specific production strains, biological fermentation is carried out to directly obtain the target product. This method produces fewer byproducts and has a lower cost, but it is limited by the characteristics of microorganisms.

[0005] (2) Chemical synthesis method: 5'-inosinate disodium (IMP) and 5'-guanylate disodium (GMP) are synthesized through a chemical reaction under the action of triethyl phosphate and phosphorus oxychloride. This method has high specificity and few by-products, but the chemical raw materials and organic solvents used are highly toxic, posing a significant hazard to operators and the environment. The process conditions are also harsh, and the subsequent extraction process is complex and costly.

[0006] (3) Biocatalytic method: Under the catalysis of phosphorylase, inosine or guanosine reacts with phosphate donors to produce disodium 5'-inosinate (IMP) and disodium 5'-guanylate (GMP). The advantages of this method include high specificity, diverse and low-cost sources of phosphate donors, simple and convenient extraction process, and minimal environmental impact. However, current biocatalytic methods face the problem of low conversion efficiency in the preparation of disodium 5'-inosinate (IMP) and disodium 5'-guanylate (GMP), and the extraction technology is also limited, resulting in low purity of the obtained nucleotide-type yeast extract, making it difficult to achieve both purity and yield. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a method for preparing nucleotide yeast extract that is efficient, high-yield, simple, has better flavor, and is safer, addressing the problems existing in the prior art.

[0008] To achieve the objectives of this invention, the following technical solution is adopted:

[0009] A method for preparing nucleotide-type yeast extract includes the following steps:

[0010] (1) Mix yeast extract with RNA, add nuclease solution, and perform first enzymatic hydrolysis to obtain first enzymatic hydrolysate; (2) Add deaminase to the first enzymatic hydrolysate to perform second enzymatic hydrolysis to obtain second enzymatic hydrolysate;

[0011] (3) Adjust the pH of the second enzymatic hydrolysate and dry it to obtain the final product.

[0012] In step (1), the yeast extract is mixed with RNA after enzymatic hydrolysis with a protease; the protease is any one or more combinations of papain, alkaline protease, or neutral protease; in the protease hydrolysis system, the concentration of the yeast extract is 80-100 g / L, and the concentration of the protease is 0.05-0.3 g / L; the enzymatic hydrolysis time is 0.5-4 h, and the hydrolysis temperature is 25-40℃. Preferably, the protease is any one or a combination of papain and alkaline protease; in the protease hydrolysis system, the concentration of the yeast extract is 100 g / L, and the concentration of the protease is 0.1-0.2 g / L; the enzymatic hydrolysis time is 4 h, and the hydrolysis temperature is 25℃. More preferably, the protease hydrolysis is carried out in an environment with a stirring speed of 120 rpm.

[0013] In step (1), the concentration of the yeast extract in the mixture is 80-100 g / L, and the mass ratio of RNA to the yeast extract is 1:1.5-2. Preferably, the mixture is a mixture of yeast extract and RNA in water. More preferably, the concentration of the yeast extract in the mixture is 100 g / L, and the mass ratio of RNA to the yeast extract is 1:2.

[0014] In step (1), the nuclease solution is an aqueous solution of ribonuclease with a concentration of 100-200 g / L; the initial flow rate of the feed is 1-2 mL / h, and the flow rate increases by 0.5-1 mL / h per hour. Preferably, the ribonuclease is nuclease P1, the nuclease solution has a concentration of 100 g / L, the initial flow rate is 1 mL / h, and the flow rate increases by 0.5 mL / h per hour.

[0015] In step (1), the first enzymatic hydrolysis has a pH of 5-7, a hydrolysis time of 3-10 hours, an initial hydrolysis temperature of 60-80°C, and employs a stepped cooling method, with the temperature decreasing by 3-8°C every half hour, resulting in a final temperature of 30-50°C. Preferably, the first enzymatic hydrolysis has a pH of 5±0.5, a hydrolysis time of 5 hours, an initial hydrolysis temperature of 70°C, and employs a stepped cooling method, with the temperature decreasing by 3°C every half hour, resulting in a final temperature of 40°C.

[0016] In step (2), the deaminase is added by feeding a deaminase solution at a concentration of 18-40 g / L. The initial flow rate is 1-2 mL / h, increasing by 0.5-1 mL / h per hour. The second enzymatic hydrolysis takes 3-10 hours, with an initial hydrolysis temperature of 30-50°C. A stepped cooling process is used, with the temperature decreasing by 2-3°C every half hour, until the temperature reaches 22-25°C, at which point a constant temperature reaction is performed. Preferably, the deaminase solution concentration is 18 g / L, the initial flow rate is 1 mL / h, increasing by 0.5 mL / h per hour, and the second enzymatic hydrolysis takes 8 hours, with an initial hydrolysis temperature of 40°C. A stepped cooling process is used, with the temperature decreasing by 2°C every half hour, until the temperature reaches 24°C, at which point a constant temperature reaction is performed.

[0017] In step (3), the pH is adjusted to 5-7; the drying is spray drying with an inlet air temperature of 150-200℃ and an outlet air temperature of 80-100℃. Preferably, centrifugation is performed before drying to remove insoluble matter. More preferably, the pH is adjusted to 6±0.5; the spray drying has an inlet air temperature of 150℃ and an outlet air temperature of 95℃.

[0018] Secondly, the present invention provides a nucleotide-type yeast extract prepared by the method described in the first aspect. The nucleotide content of the nucleotide-type yeast extract is greater than 35% w / w.

[0019] Thirdly, the present invention provides the application of the nucleotide-type yeast extract described in the second aspect in food flavoring agents.

[0020] The nucleotide-type yeast extract has a mass content of 0.01-0.3% in the food flavoring agent.

[0021] Beneficial effects:

[0022] This invention uses yeast extract and RNA as raw materials. Through a series of pH, temperature, and enzymatic hydrolysis adjustments, a solution rich in nucleotide-type yeast extract is prepared. This solution is then spray-dried to obtain a powder rich in nucleotide-type yeast extract. The preparation method designed in this invention is efficient and simple, requires no toxic reagents, has low restrictions on raw materials, is low-cost, and yields high output. The prepared nucleotide-type yeast extract has a nucleotide content of 40.8% (CMP content 7.18%, UMP content 10.44%, GMP content 12.25%, and IMP content 10.93%), an amino acid content of 16.1%, and an insoluble matter content of only 1.1%. Compared to raw yeast extract, the nucleotide content is increased by 2.8 times and the amino acid content by 4 times, showing promising application prospects in the preparation of food flavorings. Attached Figure Description

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0024] Figure 1 The process flow diagram for preparing the nucleotide-type yeast extract of the present invention.

[0025] Figure 2 This is a liquid chromatogram of five nucleotide standards. The peaks marked from left to right in the figure are 5'-cytidine disodium (CMP), 5'-uridine disodium (UMP), 5'-guanylate disodium (GMP), 5'-inosine disodium (IMP), and 5'-adenosine disodium (AMP).

[0026] Figure 3 This is a liquid chromatogram of four nucleotides in the nucleotide-type yeast extract prepared by the method described in Example 6. The peaks marked from left to right in the figure are CMP, UMP, GMP, and IMP. Detailed Implementation

[0027] This invention discloses a method for preparing nucleotide-type yeast extract. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and products of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0028] To further understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all reagents used in the embodiments of this invention are commercially available products and can be purchased through commercial channels. The yeast extract used as the raw material was purchased from Inner Mongolia Baihui Biotechnology Co., Ltd., and its nucleotide content was 10.8%, amino acid content was 3.25%, and insoluble matter content was 3.21%.

[0030] In the following examples, the papain activity was 200,000 U / g, the alkaline protease activity was 200,000 U / g, the neutral protease activity was 200,000 U / g, the nuclease P1 activity was 50,000 U / g, and the deaminase was adenylate deaminase with an activity of 500,000 U / g. The adenylate deaminase was purchased from Amano Enzyme Preparations (Jiangsu) Co., Ltd., Shanghai Branch.

[0031] The enzyme activity U of papain is defined as the amount of enzyme required to hydrolyze casein to produce 1 μg of tyrosine in 1 minute at 25°C and pH=7.

[0032] The enzyme activity U of alkaline protease is defined as the amount of enzyme required to hydrolyze casein to produce 1 μg of tyrosine in 1 minute at 40°C and pH=10.5.

[0033] The enzyme activity U of a neutral protease is defined as the amount of enzyme required to hydrolyze casein to produce 1 μg of tyrosine in 1 minute at 30°C and pH 7.5.

[0034] The enzyme activity U of nuclease P1 is defined as the amount of enzyme required to cause a change of 1.0 in the ΔA260 absorbance value within 30 minutes in a 2.625 mL reaction system at 37℃ and pH=8.

[0035] The enzyme activity U of adenosine deaminase is defined as the amount of enzyme required to convert AMP to 1 μg IMP in 1 min at 55°C and pH 5.6.

[0036] This invention uses liquid chromatography to detect the content of nucleotides. The specific method is as follows:

[0037] Mobile phase: Weigh 27.20 g of potassium dihydrogen phosphate into a beaker, add 2000 mL of ultrapure water, stir on a magnetic stirrer until the potassium dihydrogen phosphate is completely dissolved, and then adjust the pH to 5.6 with phosphoric acid.

[0038] Chromatographic column: C18-T reversed-phase column (250mm × 4.6mm, 5μm) or a column with equivalent performance. Flow rate: 1mL / min, wavelength: 254nm, column temperature: 25℃, injection volume: 10μL.

[0039] This invention uses an amino acid analyzer (ninhydrin post-column derivatization ion exchange chromatograph) to determine the amino acid content in materials. The specific method is as follows:

[0040] Mixed amino acid standard stock solution (1 μmol / mL): Accurately weigh each individual amino acid standard (accurate to 0.00001 g) into the same 50 mL beaker, dissolve in 8.3 mL of 6 mol / L hydrochloric acid solution, accurately transfer to a 250 mL volumetric flask, dilute to the mark with water, and mix well.

[0041] Mixed amino acid standard working solution (100 nmol / mL): Accurately pipette 1.0 mL of the mixed amino acid standard stock solution into a 10 mL volumetric flask, add pH 2.2 sodium citrate buffer solution to the mark, mix well, and this is the standard working solution.

[0042] Chromatographic column: sulfonic acid cation exchange resin. Detection wavelengths: 570 nm and 440 nm.

[0043] The process flow diagram for preparing the nucleotide-type yeast extract of this invention is as follows: Figure 1 As shown.

[0044] Example 1

[0045] (1) 50g of yeast extract and 25g of RNA were mixed in 500mL of water to form a solution. The pH was adjusted to 5±0.5 with 5mol / L sodium hydroxide and the solution temperature was adjusted to 70℃. 1g of nuclease P1 was added to carry out the first enzymatic hydrolysis reaction. The reaction was carried out for 5h to obtain the first enzymatic hydrolysate.

[0046] (2) Adjust the temperature of the first enzymatic hydrolysate to 40°C, add 0.18g of deaminase to carry out the second enzymatic hydrolysis reaction, and react for 8 hours to obtain the second enzymatic hydrolysate.

[0047] (3) Adjust the pH of the second enzymatic hydrolysis to 6±0.5, perform spray drying treatment, with an inlet air temperature of 150℃, an outlet air temperature of 95℃, and a peristaltic speed of 10rpm to obtain nucleotide-type yeast extract powder.

[0048] The tested sample contained 25% nucleotides, 2.19% amino acids, and 2.32% insoluble matter.

[0049] Example 2

[0050] (1) 50g of yeast extract and 25g of RNA were mixed in 500mL of water to form a solution. The pH was adjusted to 5±0.5 with 5mol / L sodium hydroxide and the solution temperature was adjusted to 70℃. 10mL of 100g / L nuclease P1 aqueous solution was added at an initial flow rate of 1mL / h and the flow rate was gradually increased by 0.5mL / h per hour to carry out the first enzymatic hydrolysis reaction. The reaction was carried out for 5h to obtain the first enzymatic hydrolysate.

[0051] (2) Adjust the temperature of the first enzymatic hydrolysate to 40°C, add 0.18g of deaminase, and carry out the second enzymatic hydrolysis reaction for 8 hours to obtain the second enzymatic hydrolysate.

[0052] (3) Adjust the pH of the second enzymatic hydrolysate to 6±0.5, spray dry, with an inlet air temperature of 150℃, an outlet air temperature of 95℃, and a peristaltic speed of 10rpm. Nucleotide-type yeast extract powder is obtained.

[0053] The test results showed that the nucleotide content was 36.4%, the amino acid content was 2.24%, and the insoluble matter content was 2.19%.

[0054] Example 3

[0055] (1) 50g of yeast extract and 25g of RNA were dissolved in 500mL of water to form a solution. The pH was adjusted to 5±0.5 with 5mol / L sodium hydroxide. The solution temperature was adjusted to 70℃. 10mL of 100g / L nuclease P1 aqueous solution was added at an initial flow rate of 1mL / h. The flow rate was gradually increased by 0.5mL / h per hour. At the same time, the temperature was decreased stepwise from 70℃ to 40℃, decreasing by 3℃ every half hour. The first enzymatic hydrolysis reaction was carried out for 5h to obtain the first enzymatic hydrolysate.

[0056] (2) 10 mL of a 18 g / L deaminase aqueous solution was added to the first enzymatic hydrolysate at an initial flow rate of 1 mL / h, gradually increasing the flow rate by 0.5 mL / h per hour. The temperature was gradually decreased from 40°C to 24°C in a stepwise manner, decreasing by 2°C every half hour, until a constant temperature reaction was carried out at 24°C. The total time for the second enzymatic hydrolysis reaction was 8 hours, yielding the second enzymatic hydrolysate.

[0057] (3) Adjust the pH of the second enzymatic hydrolysate to 6±0.5, spray dry, with an inlet air temperature of 150℃, an outlet air temperature of 95℃, and a peristaltic speed of 10rpm. Nucleotide-type yeast extract powder is obtained.

[0058] The tested samples showed that the nucleotide content was 40.3%, the amino acid content was 2.17%, and the insoluble matter content was 2.14%.

[0059] Example 4

[0060] (1) Mix 50g of yeast extract with 0.05g of papain in 500mL of water and perform proteolytic digestion at 25℃ for 4h to obtain proteolytic solution; add 25g of RNA to the proteolytic solution and stir at 25℃ and 120rpm for 4h. Then adjust the pH to 5±0.5 with 5mol / L sodium hydroxide, adjust the temperature to 70℃, add 1g of nuclease P1, and perform the first enzymatic digestion for 5h to obtain the first enzymatic digest.

[0061] (2) Adjust the temperature of the first enzymatic hydrolysate to 40°C, add 0.18g of deaminase, and carry out the second enzymatic hydrolysis reaction for 8 hours to obtain the second enzymatic hydrolysate.

[0062] (3) The pH of the second enzymatic hydrolysate was adjusted to 6±0.5 with 5mol / L sodium hydroxide, and then spray-dried at an inlet air temperature of 150℃, an outlet air temperature of 95℃, and a peristaltic speed of 10rpm. Nucleotide-type yeast extract powder was obtained.

[0063] Tests showed that the nucleotide content was 25.6% and the amino acid content was 13.4%, and sensory evaluation showed an enhanced umami flavor.

[0064] Example 5

[0065] (1) Mix 50g of yeast extract with 0.05g of alkaline protease and 0.05g of papain in 500mL of water and perform proteolytic reaction at 25℃ and 120rpm for 4h to obtain proteolytic hydrolysate; add 25g of RNA to the proteolytic hydrolysate and stir for 4h at 120rpm and 25℃, then adjust the pH to 5±0.5 with 5mol / L sodium hydroxide. Adjust the solution temperature to 70℃, add 10mL of 100g / L nuclease P1 aqueous solution at an initial flow rate of 1mL / h, gradually increase the flow rate by 0.5mL / h per hour, while the temperature is gradually decreased from 70℃ to 40℃ in steps, decreasing by 3℃ every half hour, and react for 5h to obtain the first enzymatic hydrolysate.

[0066] (2) 10 mL of a 18 g / L deaminase aqueous solution was added to the first enzymatic hydrolysate at an initial flow rate of 1 mL / h, gradually increasing the flow rate by 0.5 mL / h per hour. The temperature was gradually decreased from 40°C to 24°C in a stepwise manner, decreasing by 2°C every half hour, until a constant temperature reaction was carried out at 24°C. The total time for the second enzymatic hydrolysis reaction was 8 hours, yielding the second enzymatic hydrolysate.

[0067] (3) The pH of the second enzymatic hydrolysate was adjusted to 6±0.5 with 5mol / L sodium hydroxide, and then spray-dried at an inlet air temperature of 150℃, an outlet air temperature of 95℃, and a peristaltic speed of 10rpm. Nucleotide-type yeast extract powder was obtained.

[0068] The nucleotide content was found to be 40.5%, the amino acid content was 16.7%, and the insoluble matter content was reduced to 1.5%. Sensory evaluation showed an enhanced umami flavor profile.

[0069] Example 6

[0070] (1) Mix 50g of yeast extract with 0.05g of alkaline protease and 0.05g of papain in 500mL of water and perform a proteolytic reaction at 25℃ and 120rpm for 4h to obtain a proteolytic hydrolysate. Add 25g of RNA to the proteolytic hydrolysate and stir for 4h at 120rpm and 25℃. Then adjust the pH to 5±0.5 with 5mol / L sodium hydroxide and adjust the solution temperature to 70℃. Add 10mL of 100g / L nuclease P1 aqueous solution at an initial flow rate of 1mL / h, gradually increasing the flow rate by 0.5mL / h per hour, while simultaneously decreasing the temperature stepwise from 70℃ to 40℃, decreasing by 3℃ every half hour, for 5h. Obtain the first proteolytic hydrolysate.

[0071] (2) 10 mL of a 18 g / L deaminase aqueous solution was added to the first enzymatic hydrolysate at an initial flow rate of 1 mL / h, gradually increasing the flow rate by 0.5 mL / h per hour. The temperature was gradually decreased from 40°C to 24°C in a stepwise manner, decreasing by 2°C every half hour, until a constant temperature reaction was carried out at 24°C. The total time for the second enzymatic hydrolysis reaction was 8 hours, yielding the second enzymatic hydrolysate.

[0072] (3) Adjust the pH of the second enzymatic hydrolysate to 6±0.5 with 5mol / L sodium hydroxide. Centrifuge the resulting solution at 4000 rpm for 20 min. After centrifugation, take the supernatant and spray dry it at an inlet air temperature of 150℃, an outlet air temperature of 95℃, and a peristaltic speed of 10 rpm. Nucleotide-type yeast extract powder is obtained.

[0073] The nucleotide content was determined to be 40.8%, the amino acid content to be 16.1%, and the insoluble matter content to be reduced to 1.1%. The liquid chromatograms of the nucleotide standard and the nucleotide-type yeast extract prepared in this example are shown below. Figure 2 and Figure 3 As shown, the nucleotide yeast extract prepared by this invention contains 7.18% CMP, 10.44% UMP, 12.25% GMP, and 10.93% IMP.

[0074] This invention provides a method for preparing nucleotide-type yeast extracts. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing nucleotide-type yeast extract, characterized in that, Includes the following steps: (1) Mix the yeast extract with RNA, add nuclease solution, and perform the first enzymatic hydrolysis to obtain the first enzymatic hydrolysate; (2) Add deaminase to the first enzymatic hydrolysate and perform a second enzymatic hydrolysis to obtain a second enzymatic hydrolysate; (3) Adjust the pH of the second enzymatic hydrolysate, and dry it to obtain the final product; In step (1), the yeast extract is mixed with RNA after being hydrolyzed by a protease; the protease is any one or a combination of papain, alkaline protease, or neutral protease; in the protease hydrolysis system, the concentration of the yeast extract is 80-100 g / L, and the concentration of the protease is 0.05-0.3 g / L; the protease hydrolysis time is 0.5-4 h, and the hydrolysis temperature is 25-40 ℃; the nuclease solution is an aqueous ribonuclease solution with a concentration of 100-200 g / L; the initial flow rate of the fed-batch hydrolysis is 1-2 mL / h, and the flow rate increases by 0.5-1 mL / h per hour; the first hydrolysis is performed at a pH of 5-7, for a time of 3-10 h, with an initial hydrolysis temperature of 60-80 ℃, using a stepwise cooling method, decreasing the temperature by 3-8 ℃ every half hour, and the temperature at the end of the first hydrolysis reaction is 30-50 ℃. In step (2), the deaminase is added by feeding in the form of a deaminase solution with a concentration of 18-40 g / L; the initial flow rate of the feeding is 1-2 mL / h, increasing by 0.5-1 mL / h per hour; the second enzymatic hydrolysis takes 3-10 h, with an initial hydrolysis temperature of 30-50 ℃, using a step-down cooling method, decreasing by 2-3 ℃ every half hour, and isothermal reaction is carried out when the temperature drops to 22-25 ℃.

2. The method according to claim 1, characterized in that, In step (1), the concentration of the yeast extract in the mixed system is 80-100 g / L, and the mass ratio of the RNA to the yeast extract is 1:1.5-2.

3. The method according to claim 1, characterized in that, In step (3), the pH is adjusted to 5-7; the drying is spray drying, with an inlet air temperature of 150-200 ℃ and an outlet air temperature of 80-100 ℃.

4. The nucleotide yeast extract prepared by the method according to any one of claims 1-3.

5. The nucleotide-type yeast extract according to claim 4, characterized in that, Its nucleotide content is greater than 35% w / w.

6. The use of the nucleotide-type yeast extract according to claim 4 or claim 5 in food flavoring agents.

7. The application according to claim 6, characterized in that, The nucleotide-type yeast extract has a mass content of 0.01-0.3% in the food flavoring agent.

Images