Method for inducing aroma enhancement of egg yolk hydrolysate by utilizing Maillard reaction

Abstract

The invention discloses a method for inducing aroma enhancement of egg yolk hydrolysate by utilizing Maillard reaction, and belongs to the technical field of food processing. The method disclosed by the invention comprises the following steps: taking fresh egg yolk, homogenizing, adding water, adjusting the pH value to 7-8, respectively adding protease and cysteine endonuclease for reaction, and taking supernatant after the reaction, thereby obtaining the aroma-enhanced egg yolk protein hydrolysate. Then xylose is added, the initial pH is adjusted to 7.0-7.5, and homogenization treatment is performed; and carrying out spray drying on the homogenized system to obtain powder, placing the powder in a sealed container, and carrying out a dry heat reaction to obtain the aroma-enhanced egg yolk hydrolysate. The egg yolk hydrolysate is rich in characteristic volatile compounds such as furans, pyrazines, aldehydes and the like, presents rich toast bread fragrance, nut fragrance, soft meat fragrance and scorch fragrance, has excellent oxidation resistance, and improves flavor and optimizes taste experience through synergism of amino acid and nucleotide; the product is used as a natural flavor base material for food processing of seasonings, meat products, egg products and the like, the process is simple and controllable, and the method is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a method for enhancing the flavor of egg yolk hydrolysate using the Maillard reaction, belonging to the field of food processing technology. Background Technology

[0002] Egg yolk protein, a nutrient-rich natural protein resource, is abundant in various essential amino acids, phospholipids, and bioactive substances, and is widely used in food, health products, and feed additives. In food processing, the flavor characteristics of egg yolk protein directly determine the sensory quality and market competitiveness of the final product. How to improve the flavor of egg yolk protein through green and efficient technologies, reduce its potential fishy or off-flavors, and enhance its umami and characteristic aroma has become a research hotspot and technical challenge in the industry.

[0003] Currently, the Maillard reaction is one of the most widely used technologies in the food industry for enhancing the flavor of proteins. The combination of cysteine ​​and xylose, as a typical Maillard reaction precursor, can generate sulfur-containing volatile flavor compounds such as thiazoles and thiophenes through thermal reaction, significantly improving the flavor profile of protein products. Therefore, it is widely used in the flavor enhancement and modification of protein hydrolysates. Meanwhile, enzymatic hydrolysis technology, with its advantages of being mild, efficient, and environmentally friendly, has become a key means of pre-treating proteins and improving the efficiency of the Maillard reaction. By hydrolyzing egg yolk protein with proteases, large protein molecules can be degraded into smaller peptides and free amino acids, which not only improves the digestibility and absorption of proteins but also provides abundant reaction substrates for the Maillard reaction, further enhancing the flavor generation effect.

[0004] However, existing egg yolk protein flavoring technologies and related cysteine-xylose precursor application technologies still have many shortcomings, limiting their industrial application and product quality improvement: On the one hand, existing enzymatic hydrolysis processes mostly use single proteases or randomly combined complex proteases for hydrolysis, resulting in low efficiency of the subsequent xylose-cysteine ​​Maillard reaction, insufficient generation of flavor substances, and difficulty in achieving efficient and targeted enhancement of egg yolk protein flavor; on the other hand, some technologies, in order to compensate for insufficient flavor, adopt the method of directly adding exogenous cysteine ​​and xylose to the protein system as reaction precursors, which not only increases production costs, but also easily leads to uneven distribution of precursor substances, resulting in local over- or incomplete Maillard reaction, which in turn produces burnt bitterness and off-flavors, affecting the harmony and stability of product flavor. At the same time, the method of exogenous addition does not meet consumers' demand for products with "natural and clean labels," limiting the high-end application of products.

[0005] Furthermore, in existing compound enzymatic hydrolysis technologies, the amount of enzyme added is generally high, which not only increases production energy consumption and costs, but may also damage the functional properties of egg yolk protein due to excessive hydrolysis. At the same time, hydrophobic bitter peptides are easily generated in the enzymatic hydrolysis products, affecting the taste and flavor quality of the product. In addition, the mismatch between the enzymatic hydrolysis conditions and the subsequent Maillard reaction conditions will further reduce the flavor enhancement effect, resulting in problems such as a single flavor profile, insufficient aroma intensity, and poor quality stability, making it difficult to meet the modern food industry's pursuit of high quality, naturalness, and distinctive flavors.

[0006] To address the aforementioned technical challenges, the industry urgently needs to develop an egg yolk protein flavoring technology that can generate xylose-cysteine ​​Maillard reaction precursors in a targeted and efficient manner, while also considering cost control, product naturalness, and flavor stability. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for enhancing the flavor of egg yolk hydrolysates by inducing the Maillard reaction. This method effectively solves the technical problems of monotonous flavor in existing egg yolk protein hydrolysates, excessive browning due to the Maillard reaction, difficulty in flavor control, and the lack of utilization of the lipid synergistic flavor enhancement mechanism. It provides a simple, controllable, and industrially suitable process that achieves highly efficient flavor enhancement of egg yolk protein hydrolysates through an innovative design of "endogenously directed precursor generation + micro-enzymatic hydrolysis + synergistic thermal reaction," thereby improving product quality and market competitiveness and possessing significant industrial application value.

[0008] To achieve the above objectives, the following technical solution is provided: This invention provides a method for enhancing the flavor of egg yolk hydrolysate using the Maillard reaction, the method comprising the following steps: (1) Take fresh egg yolks, homogenize them, add water and adjust the pH to 7-8, add protease and cysteine ​​endopeptidase respectively to react, inactivate the enzymes after the reaction, centrifuge, take the supernatant, and obtain the flavor-enhanced egg yolk protein hydrolysate. (2) Add xylose to the flavored egg yolk protein hydrolysate obtained in step (1), then adjust the initial pH to 7.0~7.5 with citric acid solution, stir evenly and then homogenize using a high-pressure homogenizer; (3) The homogenized system in step (2) is prepared into powder by spray drying, placed in a sealed container, and subjected to dry heat reaction to obtain the flavored egg yolk hydrolysate.

[0009] In one embodiment, the ratio of water to fresh egg yolk in step (1) is 10~20:1, mL / g.

[0010] In one embodiment, the homogenization conditions in step (1) are 8000~12000 r / min and the time is 2~5 min.

[0011] In one embodiment, the pH in step (1) is 7.2 to 7.5.

[0012] In one embodiment, the protease in step (1) includes one or more combinations of papain, flavor protease, and serine endonuclease; preferably, it is a combination of papain and neutral protease.

[0013] In one embodiment, the amount of protease added in step (1) is 0.2~1.0g / 100g egg yolk, and the total enzyme activity is 1000-4000 U / g.

[0014] In one embodiment, the amount of papain added is 0.2~0.5g / 100g egg yolk; the amount of neutral protease added is 0.2~0.5g / 100g egg yolk.

[0015] In one embodiment, the amount of cysteine ​​endonuclease added in step (1) is 0.1~0.4g / 100g egg yolk.

[0016] In one embodiment, the reaction conditions in step (1) are 45~55°C, 2~5h, and pH 7.0-7.5.

[0017] In one embodiment, the enzyme inactivation conditions in step (1) are heating at 90-95°C for 10-15 min.

[0018] In one embodiment, the centrifugation conditions in step (1) are: 4000~6000 r / min, and the time is 10~20 min.

[0019] In one embodiment, the amount of xylose added in step (2) is 0.5%-3% of the mass of the hydrolysate of egg yolk protein.

[0020] In one embodiment, the conditions for the dry heat reaction in step (3) are: 80~100℃ and 2~4 days.

[0021] The present invention also provides a flavor-enhancing egg yolk protein hydrolysate obtained by the method described above.

[0022] In one embodiment, the flavor-enhancing egg yolk protein hydrolysate has a pH of 5.0-6.0, significantly improved surface hydrophobicity, is mainly composed of low molecular weight components with a molecular weight of less than 1000 Da, has a DPPH free radical scavenging rate of ≥60%, is rich in characteristic volatile compounds such as 2-pentylfuran, 2,5-dimethylpyrazine, and hexanal, and has GMP as the main taste-active nucleotide.

[0023] The present invention also provides an application of the above-described flavor-enhancing egg yolk protein hydrolysate in food processing.

[0024] In one embodiment, the application is as a natural flavor base used in the production of seasonings, meat products, egg products, and baked goods, with an addition amount of 0.5% to 3% of the mass of the food raw materials.

[0025] In one embodiment, the flavor-enhancing egg yolk protein hydrolysate is used to prepare a flavor-enhancing product with roasted and meaty aroma characteristics.

[0026] In one embodiment, the egg yolk protein hydrolysate is used to prepare a flavoring product with caramel and nutty aroma characteristics.

[0027] Beneficial effects: The method for enhancing the flavor of egg yolk hydrolysate by inducing the Maillard reaction in this invention has the following advantages compared with the prior art: (1) Existing technologies usually involve the exogenous addition of cysteine-xylose for the reaction. The core logic is "exogenous supplementation", that is, the direct addition of chemically synthesized or purified cysteine ​​and xylose to the protein system (un-hydrolyzed or simply hydrolyzed protein), and the generation of flavor by relying on the thermal reaction of exogenous precursor substances. However, the core logic of this invention is "endogenous directed generation". Through a precisely designed combination of micro-endonases and the enzymatic hydrolysis sequence, the egg yolk protein is degraded in a directed manner, and the cysteine ​​terminal peptide and free cysteine ​​are efficiently released from the egg yolk protein. Then, the Maillard reaction is carried out with the added xylose. There is no need to rely on the supplementation of exogenous cysteine, so as to achieve the endogenous synthesis and efficient utilization of flavor precursors. (2) Different sources of precursor substances: In the prior art, cysteine ​​is mainly added from external sources, and xylose is added from external sources. Neither of them depends on the enzymatic hydrolysis products of the protein itself. The cysteine ​​precursors (cysteine ​​terminal peptide and free cysteine) of the present invention are all derived from the directed enzymatic hydrolysis of egg yolk protein itself, and xylose is added from external sources in appropriate amounts. The precursor substances are natural and have better compatibility with the protein system. (3) Different enzymatic hydrolysis process design: If the existing technology uses enzymatic hydrolysis, it is mostly a simple hydrolysis of a single enzyme or a randomly combined enzyme, without a clear enzymatic hydrolysis sequence design, and no optimization for cysteine ​​release, resulting in a high amount of enzyme added; This invention uses one or more combinations of cysteine ​​endonuclease, papain, flavor protease, and serine endonuclease, and strictly controls the enzymatic hydrolysis sequence - cysteine ​​endonuclease is enzymatically hydrolyzed in the last step after the hydrolysis of other enzymes, while controlling the total amount of compound enzyme added to 0.2%-1% of the egg yolk raw material mass (trace addition), to achieve the targeted and efficient release of cysteine ​​precursor, taking into account both enzymatic hydrolysis efficiency and cost control; (3) Different synergies in the reaction system: In the prior art, the exogenously added cysteine ​​and xylose are easy to separate from the protein system, and the local concentration is easy to be too high or too low during the thermal reaction, resulting in uneven reaction; In this invention, the endogenously generated cysteine ​​precursor is evenly distributed in the egg yolk protein hydrolysate system, forming a stable reaction system with the added xylose, and the enzymatic hydrolysis conditions (pH 7.0-7.5, temperature 45-55℃) are synergistic with the initial pH (7.0-7.5) and thermal reaction conditions (80-100℃ constant temperature dry heat) of the subsequent Maillard reaction, further improving the reaction uniformity and flavor generation efficiency; In summary, this invention addresses the shortcomings of existing cysteine-xylose precursor addition technologies, including poor flavor stability, insufficient naturalness, high production costs, and low protein utilization. The advantages are: superior flavor quality and stability; enhanced naturalness, aligning better with industry trends; lower production costs and higher industrial feasibility; higher protein utilization and better retention of functional properties; and higher reaction efficiency and more abundant flavor compounds. Through an innovative design combining "endogenous targeted precursor generation + micro-enzymatic hydrolysis + synergistic thermal reaction," highly efficient flavor enhancement of egg yolk protein hydrolysates is achieved, improving product quality and market competitiveness, and demonstrating significant industrial application value. Attached Figure Description

[0028] Figure 1 The images show the results of electronic nose and electronic tongue tests performed on Example 1 and Comparative Examples 1-5. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0030] The testing method involved in this invention: 1. Determination of pH, browning intensity, and color difference pH measurements were performed directly using a calibrated pH meter. The sample was shaken and mixed thoroughly before measurement, and the measurement was conducted at room temperature. For browning intensity determination, 0.5 mL of sample was diluted 50 times, and its absorbance was read at 420 nm. Color difference measurements were performed as described in 4.2.5.

[0031] Egg yolk samples were taken, and a high-precision spectrophotometer was set to transmission mode. Measurements were performed using a 10 mm wide cuvette. Results are expressed as L... * (Brightness value), a * (Red / Green Value), b * (Yellow / Blue value) indicates.

[0032] 2. Molecular weight distribution Molecular weight distribution was determined by high-performance gel permeation chromatography (HPLC). A Waters 1525 HPLC system equipped with a 2487 UV detector and an Empower workstation was used. The mobile phase consisted of acetonitrile, water, and trifluoroacetic acid in a ratio of 45:55:0.1 (v / v / v) at a flow rate of 0.5 mL / min. Each sample was diluted to 10 mg / mL with the mobile phase and filtered through a 0.45 μm syringe filter before being injected into the chromatographic system. The column temperature was maintained at 30°C, and each sample was injected in a 10 µL volume for analysis. Molecular weight calibration curves were provided by Sigma-Aldrich, and the standards included cytochrome C (12384 Da), bovine insulin (5733 Da), bacitracin (1422 Da), glutathione (307 Da), and glycine (75 Da). Results were detected by setting the UV detector to 220 nm and analyzed using gel permeation chromatography software.

[0033] 3. DPPH free radical scavenging ability test The determination was performed according to GB / T 39100-2020, "Determination of Antioxidant Activity of Peptides: DPPH and ABTS Methods," with slight modifications. 2 mL of samples with concentrations of 0.4, 0.8, 12, 1.6, and 2.0 mg / mL were added to an equal volume of 0.1 mM DPPH solution and mixed. After reacting at room temperature in the dark for 30 min, the absorbance was measured at 517 nm. Anhydrous ethanol was used as a blank control. The calculation is shown in the formula: ×100 Note: In the formula, A1 is the absorbance of sample + DPPH, A2 is the absorbance of sample + anhydrous ethanol, and A3 is the absorbance of anhydrous ethanol + DPPH.

[0034] 4. Electronic tongue detection Weigh approximately 3.0 g of sample and add distilled water at a material-to-water ratio of 1:15 (w / v). Disperse the sample using a high-speed shear mixer at 10,000 r / min for 1 min. Then centrifuge at 5,000 r / min for 10 min to remove the precipitate. Collect the supernatant by vacuum filtration. Pour 35 mL of the filtrate into a sample cup for testing. The sampling time is 120 s, and each sample group is tested four times.

[0035] 5. Electronic nose detection Weigh approximately 2.0 g of sample into a headspace vial, tighten the cap, equilibrate at room temperature for 30 min, and then place it into the electronic nose autosampler. Injection conditions: incubation temperature 60℃, incubation time 10 min, incubation speed 500 r / min; injection volume 5 mL, injection temperature 250℃.

[0036] 6. Quantitative detection of volatile compounds Approximately 2.0 g of sample was weighed and placed into a headspace vial for SPME-GC-MS analysis. SPME conditions: extraction head aged at 250℃ for 5 min, incubation temperature 60℃, incubation time 10 min, incubation speed 500 r / min; extraction head inserted into the headspace vial for 10 min, followed by desorption at 250℃ for 5 min. GC conditions: DB-WAX capillary column (0.25 μm, 30 m × 250 μm); high-purity helium, flow rate 1 mL / min; injection port temperature 250℃, splitless injection, solvent delay 3 min. Temperature program: 40℃ held for 2 min, then increased to 180℃ at 5℃ / min, then increased to 250℃ at 10℃ / min, held for 3 min. MS conditions: electron ionization source 70 eV; ion source temperature 250℃; mass scan range m / z 30–500; full scan mode. Quantitative indicators such as the total number of volatile compounds and the total number of pyrazine compounds are calculated based on the composition and content of the identified volatile compounds.

[0037] 7. Sensory evaluation Ten professional evaluators were selected to conduct evaluations under natural light and in an odor-free environment. Color: Observe and describe the powder's uniformity and color (pale yellow to golden yellow), with no impurities being preferred; Aroma: Smell the aroma intensity and harmony, evaluating for a strong egg yolk aroma, added flavor, and any off-odors; Bitterness: Take an appropriate amount of sample, mix it with warm water, taste it, and evaluate the presence and intensity of bitterness. Combine this with the overall taste assessment to give a comprehensive score, and record the evaluation results.

[0038] Neutral protease: purchased from Upco Biotechnology Co., Ltd., with an enzyme activity of 70,000 U / g; Papain: Purchased from UPK Biotechnology Co., Ltd., with an enzyme activity of 300,000 U / g; Cysteine ​​endonuclease: purchased from Upco Biotechnology Co., Ltd., with an enzyme activity of 100,000 U / g.

[0039] Example 1 A method for enhancing the flavor of egg yolk hydrolysate using the Maillard reaction, the method comprising the following steps: (1) Preparation of egg yolk protein hydrolysate Take 100g of fresh egg yolks, homogenize at 9000r / min for 2min, add 2000mL of deionized water, adjust the pH to 7.2 with NaOH, add 0.4g of neutral protease and 0.3g of papain, and enzymatically hydrolyze at 50℃ for 2h. Then add 0.3g of cysteine ​​endonuclease and continue enzymatic hydrolysis for 3h. After the enzymatic hydrolysis is completed, heat at 95℃ for 12min to inactivate the enzyme, centrifuge at 4500r / min for 18min, and take the supernatant to obtain egg yolk protein hydrolysate EPH. (2) Add xylose (2% of the mass of EPH) to the egg yolk protein hydrolysate EPH obtained in step (1), then adjust the initial pH to 7.2 with citric acid solution (concentration 5%), stir evenly and then homogenize using a high-pressure homogenizer; (3) The homogenized system of step (2) is spray-dried into powder, placed in a sealed container, and subjected to constant temperature dry heat reaction at 80°C for 3 days to obtain the flavored egg yolk hydrolysate product EPH-X-Cys.

[0040] Example 2 The only difference from Example 1 is that the amount of xylose added in step (2) is 0.2%, 0.5%, 1%, 3%, and 4%, respectively. All other parameters and conditions are the same as in Example 1.

[0041] Example 3 The only difference from Example 1 is that the dry heat reaction temperature in step (3) is 70℃, 90℃, 100℃ and 110℃ respectively, and the dry heat reaction time is 3 days. Other parameters and conditions are the same as in Example 1.

[0042] Comparative Example 1 The only difference from Example 1 is that the neutral protease and papain enzymatic hydrolysis process is omitted in step (1), and only cysteine ​​endonuclease is used for enzymatic hydrolysis. Other parameters and conditions are the same as in Example 1; the sample obtained is numbered DPH-X-Cys.

[0043] Comparative Example 2 The only difference from Example 1 is that step (2) is omitted. All other parameters and conditions are the same as in Example 1, and the obtained sample number is EPH.

[0044] Comparative Example 3 100g of fresh egg yolks are dried and placed in a sealed container. The mixture is then subjected to a constant dry heat reaction at 80℃ for 3 days to obtain non-hydrolyzed dried egg yolk powder, which is DPH.

[0045] Comparative Example 4 The only difference from Example 1 is that step (1) is omitted, while the other parameters and conditions are the same as in Example 1, and the obtained sample number is DPH-X.

[0046] Comparative Example 5 The only difference from Example 1 is that step (1) omits the cysteine ​​endonuclease digestion process and only uses cysteine ​​endonuclease for digestion. Other parameters and conditions are the same as in Example 1. The sample obtained is numbered EPH-X.

[0047] Comparative Example 6 The difference from Example 1 is that step (1) omits the addition of cysteine ​​endonuclease; in step (2), 0.5% cysteine ​​(0.5% of EPH mass) is added at the same time as xylose, and other parameters and conditions are the same as in Example 1.

[0048] Results Analysis 1. The effect of different xylose addition amounts on the properties of egg yolk hydrolysates is shown in Table 1. Table 1. Effects of different xylose addition amounts on product properties

[0049] Table 1 shows the results of browning intensity (A420), DPPH radical scavenging rate, and characteristic volatile compound (2-pentylfuran) content of the products. It is evident that within the xylose addition range of 0.5-3%, the products exhibit higher browning intensity, higher DPPH radical scavenging rate, and higher 2-pentylfuran content. Flavor enhancement and functionality show a clear xylose addition dependence. Further increasing the xylose addition to 4% did not significantly improve the Maillard reaction degree, DPPH radical scavenging rate, or 2-pentylfuran content.

[0050] 2. The effect of different reaction temperatures on the hydrolysis performance of egg yolk is shown in Table 2. Table 2. Effect of different reaction temperatures on the volatile compounds in the products.

[0051] As shown in Table 2, 80-100℃ is the optimal thermal reaction temperature. At this temperature, the product has the richest variety of volatile compounds and the highest content of characteristic flavor substances such as pyrazines. Too high a temperature will cause some volatile compounds to decompose, while too low a temperature will result in insufficient Maillard reaction and less flavor substances generated.

[0052] 3. The products of Example 1, Comparative Example 1 and Comparative Example 2 were tested for performance, with egg yolk hydrolysate (EPH) without xylose added as a control. The results are shown in Table 3. Table 3. Main performance indicators of the product

[0053] Table 3 shows that the product prepared by this invention has a moderate pH, a significantly improved L* value, and effectively controlled browning degree; its antioxidant properties and the proportion of low molecular weight components are much higher than the control, it has a rich variety of volatile compounds, a high GMP taste activity value, and a significant synergistic flavor-enhancing effect of amino acids and nucleotides. The comparative data indicate that cysteine ​​endonuclease hydrolysis and the addition of xylose to induce the Maillard reaction are both necessary steps for enhancing the flavor of hydrolyzed egg yolk powder.

[0054] 4. Sensory rating and electronic nose test Electronic nose tests were conducted on Example 1 and Comparative Examples 1-5, and the results are as follows: Figure 1 As shown, in terms of flavor enhancement, enzymatic hydrolysis (preparation of egg yolk protein hydrolysate EPH) provided sufficient substrate for the xylose-induced Maillard reaction. The cysteine ​​active sites released by the complex enzymatic hydrolysis and the xylose complex system acted as key inducing factors, significantly regulating the volatile flavor profile. Electronic nose PCA analysis showed that the first and second principal components contributed a total of 99.179%, effectively distinguishing all samples. The boundary between EPH that had not undergone the Maillard reaction and EPH-X-Cys (Maillard reaction products) generated by xylose induction was clear and non-overlapping, indicating that the addition of xylose can significantly change the volatile flavor composition of egg yolk hydrolysate. At the same time, there were significant differences in overall odor among different MRPs (DPH-X, DPH-X-Cys, EPH-X, EPH-X-Cys), indicating that the synergistic effect of the type of enzymatic hydrolysis product (determined by the enzyme combination scheme involving egg yolk hydrolysis) and xylose can achieve differentiated flavor enhancement, providing a foundation for subsequent targeted aroma enhancement.

[0055] In terms of flavor regulation and enhancement, enzymatic hydrolysis lays the foundation for the basic taste characteristics of egg yolk hydrolysates, while xylose-induced Maillard reactions further optimize the taste profile. Electronic tongue analysis eliminated the subjectivity of human sensory evaluation. The results showed that the enzymatic hydrolysis product EPH had a higher flavor richness than the unenzymatically hydrolyzed DPH (p<0.05), while there was no significant difference in bitterness and bitter aftertaste between the two. Although the xylose-induced EPH-X-Cys did not show a better potential for enhancing umami and saltiness than DPH-X-Cys, it can be inferred from relevant studies that this phenomenon is related to the higher reactivity of xylose and the decrease in the concentration of low molecular weight peptides in the Maillard reaction, rather than a negative effect of xylose induction. Furthermore, the electronic tongue PCA analysis (cumulative variance contribution of 97.2%) showed that the taste characteristics of all samples could be effectively distinguished. The basic taste differences between DPH and EPH were significant, while the corresponding MRPs of the two partially overlapped within the 95% confidence interval, reflecting the synergistic regulatory effect of xylose induction on the taste characteristics of different enzymatic hydrolysis products, making the taste profile of MRPs more reasonable.

[0056] In summary, enzymatic hydrolysis degrades egg yolk protein to generate small peptides and amino acids, releasing more cysteine ​​active sites that can undergo Maillard reactions, providing necessary substrates for the generation of flavor compounds, and laying the foundation for the basic taste characteristics of the hydrolysate. Xylose, as an inducing factor, significantly alters the volatile flavor composition of egg yolk hydrolysate by initiating Maillard reactions, achieving differentiated flavor enhancement and optimizing the taste profile. The synergistic effect of these two processes effectively improves the flavor and taste quality of egg yolk hydrolysate, providing theoretical support for the targeted flavor enhancement and food industry applications of egg yolk hydrolysate.

[0057] 5. Sensory evaluation Based on the evaluations from invited volunteers, the evaluation results of Example 1, Comparative Example 1, and Comparative Example 6 were summarized. Example 1: The color is uniform, golden yellow, and free of impurities; the aroma is rich and harmonious, with a pure egg yolk fragrance and a clear flavor enhancer, and no off-flavors; it has no bitter taste after being mixed with warm water, and has a mellow taste.

[0058] Comparative Example 1: The color is relatively uniform, pale yellow, with occasional slight impurities; the aroma is moderate, with a weak egg yolk aroma and flavor enhancement, no obvious off-flavor, and the taste is acceptable. The main reason for the overall weak aroma is that the first enzymatic hydrolysis step only used cysteine ​​endonuclease hydrolysis, which could not fully release the cysteine ​​sites, resulting in a low degree of Maillard reaction in subsequent steps.

[0059] Comparative Example 6: Uneven color with many discolorations; weak aroma; noticeable bitterness and rough texture after mixing. This is mainly because the process of directly adding cysteine ​​to replace the release of endogenous cysteine ​​and small molecule peptides by a complex enzyme results in the Maillard reaction of the entire system being limited to a single cysteine-xylose reaction. The reaction efficiency is low and the product is singular, failing to generate sufficient characteristic flavoring substances. At the same time, single cysteine ​​is easily oxidized and degraded to produce bitter substances, and the lack of endogenous peptides leads to a decrease in system stability. The color also shows discoloration and color difference due to uneven reaction.

[0060] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for enhancing the flavor of egg yolk hydrolysate using the Maillard reaction, characterized in that, The method includes the following steps: (1) Take fresh egg yolks, homogenize them, add water and adjust the pH to 7-8, add protease and cysteine ​​endopeptidase respectively to react, inactivate the enzymes after the reaction, centrifuge, take the supernatant, and obtain the flavor-enhanced egg yolk protein hydrolysate. (2) Add xylose to the flavored egg yolk protein hydrolysate obtained in step (1), then adjust the initial pH to 7.0~7.5 with citric acid solution, stir evenly and then homogenize using a high-pressure homogenizer; (3) The homogenized system in step (2) is prepared into powder by spray drying, placed in a sealed container, and subjected to dry heat reaction to obtain the flavored egg yolk hydrolysate.

2. The method according to claim 1, characterized in that, The ratio of water to fresh egg yolk in step (1) is 10~20:1, mL / g.

3. The method according to claim 1, characterized in that, The homogenization conditions in step (1) are 8000~12000 r / min and 2~5 min.

4. The method according to claim 1, characterized in that, Step (1) The protease includes one or more combinations of papain, flavor protease, and serine endonuclease; preferably a combination of papain and neutral protease.

5. The method according to claim 1, characterized in that, The amount of protease added in step (1) is 0.2~1.0g / 100g egg yolk, and the total enzyme activity is 1000-4000 U / g.

6. The method according to claim 1, characterized in that, The amount of cysteine ​​endonuclease added in step (1) is 0.1~0.4g / 100g egg yolk.

7. The method according to claim 1, characterized in that, The amount of xylose added in step (2) is 0.5%-3% of the mass of the hydrolysate of egg yolk protein.

8. The method according to claim 1, characterized in that, The conditions for the dry heat reaction in step (3) are: 80~100℃, and the time is 2~4 days.

9. The flavored egg yolk protein hydrolysate obtained by the method according to any one of claims 1 to 8.

10. The application of the flavor-enhancing egg yolk protein hydrolysate according to claim 9 in food processing.

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