Fresh flavor peptide sourced from soybean dregs as well as preparation method and application thereof

Abstract

The invention belongs to the field of soybean residue resource utilization and food flavor chemistry, and particularly relates to a soybean residue sourced umami peptide as well as a preparation method and application thereof. In order to promote comprehensive utilization of the soybean dregs, oligopeptide with delicate flavor is developed, the soybean dregs are used as raw materials, the FAPEFLEH delicate flavor peptide is obtained through separation and purification, and the molecular weight is 989.4729 Da. The umami peptide sourced from soybean dregs prepared by the invention has the advantages of high purity, good activity, artificial synthesis, safety and no toxicity. Through sensory evaluation and threshold determination, it is found that the umami peptide has good umami and freshness increasing characteristics, the umami threshold is 0.18 mmoL / L, the synergistic freshness increasing threshold with MSG is 0.07 mmoL / L, and the umami peptide can be applied to preparation of functional flavor base materials and facilitates high-value utilization of soybean by-products, namely soybean residues.

Description

Technical Field

[0001] The invention belongs to the field of soybean residue resource utilization and food flavor chemistry, and particularly relates to an umami peptide derived from soybean residue and a preparation method and application thereof. Background Art

[0002] Okara is a byproduct of the production of soy milk or tofu. my country's traditional tofu and soy products require about 6 million tons of soybean raw materials each year. Therefore, my country produces a large amount of okara byproducts every year. Due to the fact that okara is easy to rot, has poor flavor and rough taste, it is usually used to make fertilizers, feed or even directly discarded. This will not only cause more and more serious environmental problems, but also make the okara lose the opportunity to be used for value-added purposes. Although okara is a loose substance, it contains rich nutrients, including protein, dietary fiber and oligosaccharides. Therefore, it is of great significance to process and utilize okara.

[0003] Patent document CN108929892A discloses a method for extracting soluble dregs protein and polypeptides from dregs. The method uses dregs, a byproduct produced during the processing of soy products, as raw materials, mixes the dregs with water, heats and stirs to dissolve the protein in the dregs; after the system is cooled, enzyme complex I is added to the system for primary extraction, centrifuged, and the supernatant is taken; the solid phase obtained from the primary extraction is crushed and dissolved, and enzyme complex II is added again for secondary extraction, centrifuged, and the supernatant is taken; the supernatants obtained twice are mixed, the enzyme is inactivated, the pH is adjusted to precipitate soluble proteins and polypeptides, centrifuged, the solid phase is taken, and dried to obtain soluble dregs protein and polypeptide finished products. The method adopts a process of multiple extractions by complex enzymes, utilizes the mutual promotion between alkaline protease, papain and cellulase, and simultaneously extracts soluble proteins and polypeptides from dregs, thereby improving the utilization rate and economic added value of dregs and reducing the pollution of dregs to the environment.

[0004] Patent document CN115868603A discloses an enzymatic hydrolysis bean dregs powder and a preparation method thereof. The preparation method comprises the following steps: (S1), taking bean dregs, adding cellulase and protease for enzymatic hydrolysis to obtain an enzymatic hydrolysis product; (S2), adding 2-5% amino acids by weight of bean dregs, 2-5% reducing sugar by weight of bean dregs and 1-2% garlic extract by weight of bean dregs to the enzymatic hydrolysis product, mixing them evenly, and then carrying out browning reaction to obtain a reactant; (S3), removing water from the reactant by filter pressing, and drying by microwave until the water content of the reactant is less than 8wt%, to obtain a dried product; (S4), crushing the dried product, and using a graded sieve to screen out enzymatic hydrolysis bean dregs powder of different particle sizes at different levels, wherein the obtained enzymatic hydrolysis bean dregs powder effectively removes the beany smell, has a better taste, has excellent antioxidant and antibacterial properties, and can also provide certain flavor substances.

[0005] At present, the research on okara is generally focused on the optimization process of enzymatic hydrolysis of okara protein and peptides, and there is less research on umami peptides. Umami is one of the five tastes of human beings. Umami substances mainly include free amino acids, nucleotides, organic acids, organic bases, peptides, etc., which can make the taste of food softer, more coordinated and mellow. Umami peptides are compounds formed by amino acids connected by peptide chains. They have outstanding umami properties and are one of the most important sources of umami in food besides volatile and non-volatile flavor substances. Compared with some traditional umami ingredients, umami peptides not only have umami properties, but also have the function of synergizing with other substances to enhance freshness and weaken the intensity of bitterness, while also reducing some adverse reactions. Therefore, it is of great market value to fully tap and utilize high-quality plant protein resources such as okara to carry out research on umami peptides. Summary of the invention

[0006] In order to broaden the comprehensive utilization value of soybean residue, the present invention provides an umami peptide derived from soybean residue, specifically, fresh soybean residue is used as a matrix, the fungus "Neurospora crassa" is inoculated and fermented to make red fungus tofu, and then the umami peptide is separated and purified from the red fungus tofu. The red fungus tofu fermented from soybean residue of the present invention contains rich protein, and the proportion of umami amino acids in the protein is relatively high, from which umami peptides with high purity and high activity can be separated and purified.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] The invention provides an umami peptide derived from soybean residues. The amino acid sequence of the umami peptide is: Phe-Ala-Pro-Glu-Phe-Leu-Glu-His (FAPEFLEH).

[0009] The soybean residue-derived umami peptide provided by the invention is prepared by inoculating Neurospora crassa with fresh soybean residue as raw material to make red mushroom tofu through fermentation; then the red mushroom tofu is crushed, extracted, ultrafiltered, and separated by chromatography on a dextran gel permeation chromatography column, and the main umami parts of the red mushroom tofu are obtained with sensory umami as the guide, the polypeptide structure is analyzed by nano-liquid chromatography-tandem mass spectrometry (NanoLC-MS / MS), computer simulation and molecular docking technology are used to screen potential umami peptides, and in vitro chemical synthesis of umami peptide monomers is performed for sensory verification, so as to obtain an oligopeptide with strong umami taste, wherein the amino acid sequence of the oligopeptide is: Phe-Ala-Pro-Glu-Phe-Leu-Glu-His (FAPEFLEH), and the molecular weight is 989.4729Da.

[0010] Sensory evaluation and threshold determination revealed that the FAPEFLEH umami peptide had good umami and umami enhancement properties, with an umami threshold of 0.18 mmoL / L, and a synergistic umami enhancement threshold of 0.07 mmoL / L with monosodium glutamate. At the same time, the functional activity of the FAPEFLEH umami peptide was predicted using the BIOPEP-UWM database, and it was found that the FAPEFLEH umami peptide had ACE inhibitory activity, DPP-IV inhibitory activity, α-glucosidase inhibitory activity, and renin inhibitory activity, indicating that the umami peptide derived from soybean residue provided by the present invention has the effect of lowering blood pressure and blood sugar.

[0011] Furthermore, the specific preparation method of the soybean residue-derived umami peptide comprises the following steps:

[0012] Step S1, preparation of red mushroom tofu:

[0013] The fresh soybean residue is crushed, sieved, sterilized, cooled, and inoculated with Neurospora crassa for fermentation to obtain red fungus tofu;

[0014] Step S2, polypeptide extraction:

[0015] The red fungus tofu prepared in step S1 is crushed and sieved to obtain red fungus tofu fine powder, and the red fungus tofu fine powder is added into deionized water to dissolve to obtain a suspension, and then the suspension is placed in a 100° C. water bath for 100 to 120 minutes, filtered, and the filtrate is taken. After the filtrate is cooled to room temperature, it is centrifuged and the supernatant is taken to obtain a crude polypeptide extract;

[0016] Step S3, polypeptide separation, purification and identification:

[0017] The crude polypeptide extract obtained in step S2 is subjected to ultrafiltration separation, the separated components are subjected to umami evaluation, the component with the strongest umami taste is selected for gel chromatography separation and purification, the component with the strongest umami taste is selected through sensory evaluation, and then separated and identified by liquid chromatography-mass spectrometry to obtain the product.

[0018] Furthermore, in step S1, the inoculation amount of Neurospora crassa is 0.1-0.2% (w / w), and the fermentation conditions are: fermentation for 24-48 hours at a temperature of 28-32° C. and a humidity of 70-80%.

[0019] Furthermore, the centrifugation conditions in step S2 are: centrifugation at a temperature of 4° C. and a rotation speed of 7000 to 10000 r / min for 10 to 15 min.

[0020] Furthermore, the ultrafiltration separation conditions in step S3 are as follows: filtering the crude polypeptide extract with a 0.45 μm aqueous filter membrane, taking the filtrate, and then passing the filtrate through 10 kDa, 5 kDa, 3 kDa, and 1 kDa ultrafiltration membranes in sequence at 4°C.

[0021] Furthermore, the conditions for gel chromatography separation and purification in step S3 are: the specification of the dextran gel is G-15, the injection concentration is 20 mg / mL, ultrapure water is used as the eluent, the flow rate is 1.0 mL / min, and the wavelength is 220 nm.

[0022] Furthermore, in step S3, the liquid chromatography-mass spectrometry instrument uses a C18 reverse phase analytical chromatographic column for liquid phase separation.

[0023] Furthermore, in the C18 reverse phase analytical chromatographic column: mobile phase A is 0.1% formic acid solution, mobile phase B is a mixed solution of 80% acetonitrile and 0.1% formic acid, the flow rate is 600nL / min, and the time is 66min; liquid chromatography elution gradient: 0-2min, 4%-8% mobile phase B; 2-45min, 8%-28% mobile phase B; 45-55min, 28%-40% mobile phase B; 55-56min, 40%-95% mobile phase B; 56-66min, 95% mobile phase B.

[0024] In addition, the present invention also provides the use of the umami peptide derived from soybean residues in the preparation of food seasonings or food additives.

[0025] Furthermore, the present invention also provides the use of the umami peptide derived from soybean residue in the preparation of health food for improving hypertension or hyperglycemia.

[0026] At the same time, the present invention also provides an umami peptide preparation, including the above-mentioned umami peptide. Of course, in order to improve the application scope of the preparation, it can also include other auxiliary materials that can be applied to the field of food additives. The preparation can be prepared in the form of granules, pastes and powders.

[0027] In summary, compared with the prior art, the umami peptide derived from soybean residue provided by the present invention has high purity, good activity, can be artificially synthesized, is safe and non-toxic. Sensory evaluation and threshold measurement show that the umami peptide has a strong umami taste, can be used in the field of food additives to enhance flavor, and is beneficial to the resource utilization of soybean waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a graph showing the umami taste of the four components (H1-H4) separated from the crude polypeptide extract by ultrafiltration.

[0029] Figure 2 Figure 3 shows the gel chromatography separation and purification of the H4 component with the strongest umami taste and the collection of components (F1-F4).

[0030] Figure 3 It is the umami evaluation graph of the subfractions (F1-F4) separated by gel chromatography.

[0031] Figure 4This is the total ion current chromatogram of the F2 component polypeptide.

[0032] Figure 5 This is the result of qualitative identification of polypeptides in the F2 component.

[0033] Figure 6 This is the umami evaluation diagram of FAPEFLEH, the peptide with the strongest umami taste synthesized in vitro. DETAILED DESCRIPTION

[0034] The present invention is further described below by describing specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the scope of the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0035] Example 1. Preparation of umami peptides from soybean residues

[0036] Step S1, preparation of red mushroom tofu:

[0037] (1) Material preparation: Fresh soybean residue from Panlong Market in Guangdong; Neurospora crassa was obtained from the Provincial Key Laboratory of Lingnan Specialty Food Science and Technology of Guangdong Province.

[0038] (2) Fermentation of soybean residue: fresh soybean residue is crushed, passed through a 60-mesh sieve, and sterilized in an autoclave (121° C., 30 min). After sterilization, it is spread out and cooled to room temperature. After cooling, it is inoculated with 0.1% (w / w) Neurospora crassa and mixed evenly to obtain a mixture. The mixture is placed in a tofu frame for shaping, and fermented in an artificial climate incubator at a temperature of 30° C. and a humidity of 75% for 36 h to obtain red fungus tofu, which is then frozen in a -20° C. refrigerator for later use.

[0039] Step S2, polypeptide extraction:

[0040] The red mushroom tofu prepared in step S1 was crushed and passed through a 40-mesh sieve to obtain red mushroom tofu fine powder, and the red mushroom tofu fine powder was added into deionized water to dissolve, the solid-liquid ratio of the red mushroom tofu fine powder to deionized water was 1 g:20 mL, and a suspension was obtained. The suspension was then placed in a 100° C. pot water bath for 120 min, filtered with gauze, and the filtrate was taken. After the filtrate was cooled to room temperature, the filtrate was centrifuged at a temperature of 4° C. and a rotation speed of 8000 r / min for 15 min, and the supernatant was taken to obtain a crude polypeptide extract.

[0041] Step S3, polypeptide separation, purification and identification:

[0042] 1. Sensory evaluation method:

[0043] The researchers recruited 10 healthy panelists (5 females and 5 males, aged 23-28 years) with experience in sensory assessment. Panelists were screened and trained to conduct sensory assessments for 2 weeks and were asked to write sensory descriptions including sweetness (sucrose), sourness (citric acid), saltiness (sodium chloride), bitterness (L-isoleucine), and umami (monosodium glutamate). All samples were dissolved in deionized water and sensory tests were performed at room temperature. Panelists were asked to rest for 5 minutes between two different samples to avoid aftertaste and sensory fatigue effects during the experiment. Taste characteristics used a 10-point intensity scale (0 means no taste; 10 means the strongest taste).

[0044] (II) Ultrafiltration separation of polypeptide crude extract:

[0045] (1) Ultrafiltration separation:

[0046] The crude polypeptide extract obtained in step S2 was subjected to ultrafiltration separation. The crude polypeptide extract was filtered with a 0.45 μm aqueous phase filter membrane, and the filtrate was taken. The filtrate was passed through a 10 kDa ultrafiltration membrane at a temperature of 4°C, and then passed through 5 kDa, 3 kDa, and 1 kDa ultrafiltration membranes in sequence. After classification, four components were obtained, which were named H1 (5 kDa < molecular mass < 10 kDa), H2 (3 kDa < molecular mass < 5 kDa), H3 (1 kDa < molecular mass < 3 kDa), and H4 (molecular mass < 1 kDa), respectively. After rotary evaporation, they were freeze-dried into polypeptide powders and stored at -20°C for later use.

[0047] (2) Sensory evaluation:

[0048] The sensory evaluation of the four components (H1-H4) separated by ultrafiltration of the polypeptide crude extract was carried out using the sensory evaluation method (I). The umami evaluation results of the four components (H1-H4) separated by ultrafiltration of the polypeptide crude extract are as follows: Figure 1 In order to screen out the main umami substances in red mushroom tofu, the red mushroom tofu water extract - the polypeptide crude extract was separated by ultrafiltration technology to obtain four components named H1, H2, H3, and H4, and the four components were subjected to sensory evaluation. Figure 1 It can be seen that all separated components can perceive umami, sweetness and sourness, with basically no bitterness and saltiness. Among them, H4 has the highest umami value and sweetness value and a lower sourness value, which is higher than the umami value of the unseparated component (HJDF component). This indicates that H4 has a more significant umami taste among the four separated components and may contain a large amount of umami peptides.

[0049] (III) Gel chromatography separation of H4 component:

[0050] (1) Gel chromatography separation:

[0051] The H4 component with the strongest umami taste was selected for gel chromatography separation and purification. Sephadex G-15 was used to separate and purify the H4 component with the strongest umami taste. According to the gel properties of this specification and the amount required for the test, an appropriate amount of gel powder Sephadex G-15 was soaked in excessively heated ultrapure water for 24 hours for swelling, and the fully swollen filler was poured into the chromatography column (diameter 1.6 cm, length 80 cm) at one time. The mobile phase was ultrapure water. In order to make the column evenly and firmly filled with dextran gel, it was first naturally deposited for 2 hours, and then the gel filtration chromatography column was flushed with ultrapure water at a flow rate of 2 mL / min for 4 hours. The H4 component with the strongest umami taste after ultrafiltration was prepared into a solution with a concentration of 20 mg / mL with ultrapure water, and passed through a 0.22 μm aqueous phase filter membrane before pouring into the sample. Ultrapure water was used as the eluent at a flow rate of 1.0 mL / min, and a tube of eluent was collected every 3 minutes. After detection by 220 nm UV absorption spectrum, all components corresponding to one peak were mixed and freeze-dried for the next sensory evaluation.

[0052] (2) Gel chromatography separation and sensory evaluation:

[0053] (a) Gel chromatography separation and purification of the H4 component with the strongest umami taste, and the collection of components (F1-F4) Figure 2 As shown. Gel chromatography separation and purification relies on the molecular size difference of sample molecules in the gel filler to achieve separation, and can remove large and small molecular impurities at the same time. The ultrafiltration component H4 (<1kDa) is separated by gel chromatography on a Sephadex G-15 column. According to the separation characteristics of the column, the molecular weight decreases as the component flows out. Figure 2 As shown, four separated components were obtained within the elution time of 30 to 150 min, namely F1, F2, F3 and F4.

[0054] (b) The umami taste of the sub-fractions (F1-F4) separated by gel chromatography was evaluated by the sensory evaluation method (i). The umami taste evaluation results of the sub-fractions (F1-F4) separated by gel chromatography were as follows: Figure 3 As shown. Figure 3It can be seen that the umami taste of the F2 component is the strongest, and it has sweetness and slight bitterness. Umami is dominant among them, which is much greater than the sourness and saltiness in this component. The sourness and saltiness have basically no intensity. Compared with the other three components, the taste of the F2 component is richer, with both umami, sweetness and slight bitterness. Although the peptide content of the F3 component is the highest, the umami intensity is medium. It is speculated that the umami peptide content in the F3 component is not as good as that of the F2 component. The F4 component has the lowest peptide content and the lowest umami value. It can be speculated that F4 basically does not contain umami peptides. All components have no obvious saltiness and sourness, indicating that gel chromatography can well separate and purify umami components and play a desalting role. Based on this result, we speculate that most of the umami substances in red fungus tofu are concentrated in the peptides of the F2 component.

[0055] (IV) Peptide identification of F2 component:

[0056] (1) LC-MS / MS identification of peptides:

[0057] (a) Sample pretreatment: Take an appropriate amount of F2 component sample and add dithiothreitol (DTT) solution to make the final concentration of 10mmol / L, and reduce it in a 56℃ water bath for 1h. Add iodoacetamide (IAM) solution to make the final concentration of 55mmol / L, and react for 40min in the dark. Desalt using a self-filled desalting column and evaporate the solvent in a vacuum centrifugal concentrator at 45℃.

[0058] (b) Injection: Take 5 μL of sample and inject it into a C18 reverse phase analytical column (150 μm id×150 mm, packed with Acclaim PepMap RPLC C18, 1.9 μm, ), mobile phase A is 0.1% formic acid solution, mobile phase B is a mixed solution of 80% acetonitrile and 0.1% formic acid, the flow rate is 600nL / min; the time is 66min; the liquid chromatography elution gradient is: 0-2min, 4%-8% mobile phase B; 2-45min, 8%-28% mobile phase B; 45-55min, 28%-40% mobile phase B; 55-56min, 40%-95% mobile phase B; 56-66min, 95% mobile phase B.

[0059] (c) Primary mass spectrometry parameters: resolution 70000; automatic gain control (AGC) target 3e6; maximum fill time 100ms; mass scan range 100-1500 m / z. Secondary mass spectrometry parameters: resolution 17500; AGC target 1e5; maximum fill time 50ms; TopN 20; normalized collision energy (NCE) 28. The peptide sequence analysis was performed using the Byonic search target protein database. The parameters were set as follows: protein modifications were carbamidomethylation (C) (fixed), oxidation (M) (variable), acetyl (protein N-terminus) (variable); enzyme specificity was set to nonspecific; maximum missed excision was set to 3; precursor ion mass tolerance was set to 20ppm, and MS / MS tolerance was 0.02Da.

[0060] (2) Peptide identification results:

[0061] (a) To clarify the composition of umami substances in red mushroom tofu, LC-MS / MS was used to identify the amino acid sequence of the umami peptide of the strongest umami component F2. The total ion current chromatogram contains the sum of the intensities of all ions in the mass spectrum at each time point and the retention time in the chromatogram. The total ion current chromatogram of the F2 component peptide is shown in Figure 1. Figure 4 shown.

[0062] (b) Qualitative identification results of peptides in F2 component Figure 5 In this study, a total of 1540 effective peptides were identified from the F2 fraction, most of which were peptides with a molecular mass of less than 1 kDa. Due to the large number of peptides identified by mass spectrometry, it is necessary to quickly screen the target umami peptides through preliminary screening of umami peptides and machine learning. The length of the umami peptide chain is usually a peptide with a molecular mass of less than 1kDa, so peptides less than 1kDa were selected for the next step of machine learning to screen potential umami peptides. Among them, there were 9 tripeptides less than 1kDa, accounting for 0.58% of the total, 67 tetrapeptides accounting for 4.35% of the total, 208 pentapeptides accounting for 13.51% of the total, 115 hexapeptides accounting for 7.47% of the total, 96 heptapeptides accounting for 6.23% of the total, 111 octapeptides accounting for 7.21% of the total, 133 nonapeptides accounting for 8.64% of the total, and 159 decapeptides accounting for 10.32% of the total. The number of peptides below decapeptides accounted for 58.31% in total, and the number of peptides above undine peptides accounted for 41.69%.

[0063] (V) Prediction of umami peptide activity:

[0064] The iUmami-SCM database was used to predict the flavor activity of umami peptides, and the peptide sequence with the strongest umami taste was predicted by computer simulation of molecular docking. The identified amino acid sequence was input into the "sensory peptides and amino acids" module to predict the frequency of occurrence of umami fragments, and the five peptides with the highest frequency of umami active fragments among the nine were screened out, among which FAPEFLEH was the peptide with the strongest umami taste. The results are shown in Table 1:

[0065] Table 1 Five peptide sequences with the strongest umami taste predicted by computer simulation molecular docking

[0066]

[0067] Example 2: Artificial synthesis verification and sensory evaluation of FAPEFLEH umami peptide

[0068] In order to verify the FAPEFLEH umami peptide, the umami peptide was synthesized by chemical synthesis and sensory evaluation was performed.

[0069] (1) Synthesis of umami peptides by solid phase synthesis:

[0070] According to the molecular docking results, the peptide with the lowest binding energy was selected for solid phase synthesis. According to the known amino acid sequence Phe-Ala-Pro-Glu-Phe-Leu-Glu-His (FAPEFLEH), the peptide chain was connected by the condensation reaction of amino acids, Fmoc was used as the protecting group of α-amino group, and benzyl alcohol was used for side chain protection. During the synthesis, an Fmoc-amino acid derivative was covalently cross-linked to the resin, Fmoc was removed with alkali, and the free amino terminal was neutralized with triethylamine, and then activated and coupled with the next amino acid by DCC. Beijing Biotech Biotechnology Co., Ltd. was commissioned to carry out solid phase synthesis of peptides. The molecular weight of the synthetic peptide was determined by mass spectrometry, and the purity of the peptide was determined by high performance liquid chromatography.

[0071] (2) Determination of the umami threshold of FAPEFLEH synthetic peptide:

[0072] The umami threshold of synthetic peptides was determined by taste dilution analysis. At room temperature, deionized water was used as the experimental solvent, and the synthetic peptides were diluted stepwise with deionized water at a ratio of 1:1 (v / v). The samples at each dilution level were tested using the trigonometric method. When the panelists could only distinguish the previous sample and two blank controls (ultrapure water), but could not distinguish the next concentration sample from the blank control, the average of the last two concentrations of the synthetic peptide was taken as the umami recognition threshold. The results are shown in Table 2.

[0073] Table 2 Taste description, umami threshold, umami threshold and umami enhancement value of FAPEFLEH with NaCl

[0074]

[0075] According to the results in Table 2, it can be seen that the FAPEFLEH umami peptide separated by the present invention has a strong umami taste, which is verified by artificial synthesis. This umami peptide is expected to be applied in the field of food flavor chemistry, laying a foundation for the application of food-derived umami peptides in the future.

[0076] (3) Evaluation of the umami taste of FAPEFLEH synthetic peptide:

[0077] The sensory evaluation of FAPEFLEH synthetic peptide was conducted using the sensory evaluation method (I). The sensory evaluation results of FAPEFLEH synthetic peptide are as follows: Figure 6 As shown. Figure 6 It can be seen that FAPEFLEH synthetic peptide exhibits a strong umami taste accompanied by sweetness, while other flavors are weaker. Compared with the traditional umami substance MSG (monosodium glutamate), FAPEFLEH synthetic peptide has a stronger umami taste.

[0078] Example 3: Prediction of the functional activity of FAPEFLEH umami peptide

[0079] The functional activity of FAPEFLEH was predicted using the BIOPEP-UWM database. The amino acid sequences were compared with the database and the frequencies of active fragments were calculated to predict the functional activity of peptides with potential umami taste. The computer simulation prediction results of the health activity of FAPEFLEH umami peptide are shown in Table 3.

[0080] Table 3 Computer simulation prediction results of FAPEFLEH umami peptide health activity

[0081]

[0082] As shown in Table 3, FAPEFLEH umami peptide has ACE inhibitory activity, DPP-IV inhibitory activity, α-glucosidase inhibitory activity and renin inhibitory activity. According to the composition characteristics of the oligopeptide amino structure, it is shown that FAPEFLEH umami peptide has the effect of lowering blood pressure and blood sugar.

Claims

1. An umami peptide derived from soybean residue, characterized in that: The amino acid sequence of the umami peptide is: Phe-Ala-Pro-Glu-Phe-Leu-Glu-His.

2. The method for preparing umami peptides derived from soybean residues according to claim 1, characterized in that: The following steps are involved: Step S1, preparation of red mushroom tofu: The fresh soybean residue is crushed, sieved, sterilized, cooled, and inoculated with Neurospora crassa for fermentation to obtain red fungus tofu; Step S2, polypeptide extraction: The red fungus tofu prepared in step S1 is crushed and sieved to obtain red fungus tofu fine powder, and the red fungus tofu fine powder is added into deionized water to dissolve to obtain a suspension, and then the suspension is placed in a 100° C. water bath for 100 to 120 minutes, filtered, and the filtrate is taken. After the filtrate is cooled to room temperature, it is centrifuged and the supernatant is taken to obtain a crude polypeptide extract; Step S3, polypeptide separation, purification and identification: The crude polypeptide extract obtained in step S2 is subjected to ultrafiltration separation, the separated components are subjected to umami evaluation, the component with the strongest umami taste is selected for gel chromatography separation and purification, the component with the strongest umami taste is selected through sensory evaluation, and then separated and identified by liquid chromatography-mass spectrometry to obtain the product.

3. The method for preparing umami peptides derived from soybean residues according to claim 2, characterized in that: In the step S1, the inoculation amount of Neurospora crassa is 0.1-0.2%, and the fermentation conditions are: fermentation for 24-48 hours at a temperature of 28-32° C. and a humidity of 70-80%.

4. The method for preparing umami peptides derived from soybean residues according to claim 2, characterized in that: The centrifugation conditions in step S2 are: centrifugation at a temperature of 4° C. and a rotation speed of 7000 to 10000 r / min for 10 to 15 minutes.

5. The method for preparing okara-derived umami peptide according to claim 2, characterized in that: The ultrafiltration separation conditions in step S3 are as follows: filtering the polypeptide crude extract with a 0.45 μm aqueous filter membrane, taking the filtrate, and then passing the filtrate through 10 kDa, 5 kDa, 3 kDa, and 1 kDa ultrafiltration membranes in sequence at 4°C.

6. The method for preparing umami peptides derived from soybean residues according to claim 2, characterized in that: The conditions for gel chromatography separation and purification in step S3 are: the specification of the dextran gel is G-15, the injection concentration is 20 mg / mL, ultrapure water is used as the eluent, the flow rate is 1.0 mL / min, and the wavelength is 220 nm.

7. The method for preparing umami peptides derived from soybean residues according to claim 2, characterized in that: In step S3, the liquid chromatography-mass spectrometry instrument uses a C18 reverse phase analytical chromatographic column for liquid phase separation.

8. The method for preparing umami peptides derived from soybean residues according to claim 7, characterized in that: In the C18 reverse phase analytical chromatographic column: mobile phase A is 0.1% formic acid solution, mobile phase B is a mixed solution of 80% acetonitrile and 0.1% formic acid, the flow rate is 600nL / min, and the time is 66min; liquid chromatography elution gradient: 0-2min, 4%-8% mobile phase B; 2-45min, 8%-28% mobile phase B; 45-55min, 28%-40% mobile phase B; 55-56min, 40%-95% mobile phase B; 56-66min, 95% mobile phase B.

9. Use of the soybean residue-derived umami peptide according to claim 1 in preparing food seasonings or food additives.

10. Use of the umami peptide derived from soybean residues as claimed in claim 1 in preparing health food for improving hypertension or hyperglycemia.

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