| White Hypsizygus marmoreus is also known as seafood mushroom and crab mushroom.At present,the daily output of white Hypsizygus marmoreus in my country has reached 1,000 tons.The products are mainly sold fresh,and the fresh mushrooms are prone to browning and softening after harvesting,which seriously restricts the development of the white Hypsizygus marmoreus industry.White Hypsizygus marmoreus has a high protein content,accounting for about 21.8% of the dry weight,and the umami-flavored amino acid content in the protein accounts for 24.6% of the total amino acid,which has the potential to prepare umami peptides.This thesis conducts the research on the preparation of the flavoring base material of the white Hypsizygus marmoreus,the separation and identification of umami peptides,aiming to explore the feasibility of using the white Hypsizygus marmoreus as raw materials to develop umami peptides,and provide reference for the deep processing of the white Hypsizygus marmoreus and the enhancement of the added value of the white Hypsizygus marmoreus.The thesis studied the effects of high-pressure cooking and compound enzymatic hydrolysis on the release of odorous substances from white Hypsizygus marmoreus.On this basis,ultrafiltration(UF),gel permeation chromatography(GFC)and reversed-phase high-performance liquid chromatography(RP-HPLC)were used.Combining sensory guidance to separate and purify the best components of umami from the water extract of white Hypsizygus marmoreus,and ultra high liquid chromatography-mass spectrometry technology(UPLC-MS/MS)was used to identify umami peptides,and then synthesized the umami peptides,and the flavor characteristics of the umami peptides were studied.The experimental results are as follows:(1)The single factor experiment and orthogonal experiment were used to optimize the preparation methods of high pressure cooking and compound enzymatic hydrolysis of white Hypsizygus marmoreus flavor base material with the total amount of soluble solids and hydrolysis degree as indexes.The results showed that the optimum process of high pressure cooking method was solid-liquid ratio 1?1.5(g/m L),cooking time 2.0 h,cooking pressure 60 k Pa,and the total amount of soluble solids was 15.58 ± 0.11 g.The optimu m hydrolysis conditions were as follows : the ratio of solid to liquid was 1?30(g/m L),cellulase was first used for 1.5 h,and then flavourzyme was used for 1.5 h.The optimum hydrolysis conditions were as follows : the p H of cellulase was 2.5,the hydrolysis temperature was 45 °C,the enzyme dosage was 0.4% of the substrate,the p H of flavourzyme was 6.0,the hydrolysis temperature was 60 °C,and the enzyme dosage was0.5% of the substrate.Under these conditions,the degree of hydrolysis of the hydrolysa te was 25.69 ± 0.23%.(2)Using the reconstituted stock solution as a control,the taste-bearing substances in the high-pressure cooking preparation solution and the compound enzymatic hydrolysis preparation solution were determined.The results showed that: the total amount of free amino acids in the extracts increased after different methods.Among them,the total amount of free amino acids in the high-pressure cooking preparation was the largest,3.63mg/g,and the content of savory amino acids in the high-pressure cooking preparation was significantly higher than The other two extracts(P<0.05);From the perspective of the total amount of flavored nucleotides,the total amount of flavored nucleotides in the composite enzymatic hydrolysis solution was the highest at 1.39 mg/g,followed by the high-pressure cooking preparation solution at 1.08 mg/g,and the reconstituted solution had the lowest content.It was 0.91 mg/g,but the content of 5'-GMP and 5'-IMP two main flavored nucleotides were significantly higher than the other two extracts(P<0.05);THE EUC(equivalent umami concentration)value of the high-pressure cooking liquid is 15.39,which is at the first level.The EUC values of the composite enzymatic hydrolysate and the reconstituted stock solution are 8.50 and 7.68,respectively,which are at the second level,indicating that the high-pressure cooking is compared with the compound enzymatic hydrolysis.It is more suitable for the extraction of taste-producing substances from white Hypsizygus marmoreus.(3)Using UF,GFC,RP-HPLC and UPLC-MS/MS combined with sensory evaluation to purify and identify 6 kinds of umami peptides from the high-pressure cooking liquor of white Hypsizygus marmoreus,namely EAKVY,ELELQ,SLLQPL,NYNGGY,VANGGGFGAA,ELQSGNTY,and the molecular weights are 608.32 Da,630.32 Da,669.41 Da,686.27 Da,819.39 Da,and 910.40 Da.(4)After the identified peptides were synthesized directionally,sensory analysis showed that the 6 synthetic peptides are umami peptides,and the umami taste threshold is between 0.16-0.63 mg/m L.Among them,the umami taste thresholds of ELELQ and ELQSGNTY are lower than the umami taste threshold of MSG.The six synthetic peptides are also umami-enhancing peptides,and the freshness-enhancing threshold is between 0.02 and 0.25 mg/m L.From the dose-response curve in the monosodium glutamate solution,it can be seen that the freshness-enhancing ability of the six synthetic peptides is different.The freshness-enhancing ability of NYNGGY and ELELQ was significantly higher than the other four umami peptides(P<0.05);The six synthetic peptides had the characteristics of umami,salty and sweet taste enhancement in chicken soup,and ELELQ,NYNGGY and ELQSGNTY had the best effect on improving the taste of chicken soup.The taste characteristics of the 6 synthetic peptides and their amino acid mixtures with equal mass ratios are different to different degrees,and the umami tastes of the 6 synthetic peptides are significantly higher than their amino acid mixtures(P<0.05).It shows that the taste of peptide is not formed by the combination of the taste of individual amino acids,but the effect of the combination of amino acids into a specific structure through peptide bonds. |
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