Preparation And Flavor Characterization Of Seasoning Base Derived From Morchella Sextelata

Morel mushroom(Morchella sextelata),rich in umami components and flavor precursors,is palatable and nutritious,thereby being a potential source of natural food condiment.In this study,umami substances of defective and broken fruiting bodies of morel were extracted through bio-enzymolysis technology,combining Maillard reaction to debitterize and enhance flavor of enzymolysates to prepare palatable morel core seasoning base.Simultaneously,further investigation of effect of Maillard reaction on the flavor of enzymolysates,the reactivity of peptide fractions with different molecular weights in Maillard reaction(MR)as well as their contribution to flavors of Maillard reaction products(MRPs)were carried out after the best usage of flavor substances in morel mushroom.This research could provide theoretical guidance for the development of new morel products.The main results are as follows:1.With the same total addition amounts of enzymes,pysico-chemical indexes and taste attributes of seven morel hydrolysates(MHs)derived from four single-protease groups(SPG)including Neutrase,Papain,Protamex,Flavourzyme and three doubleprotease groups(DPG)including Neutrase/Flavourzyme(NF),Papain/Flavourzyme(PaF),and Protamex/Flavourzyme(PrF)were analyzed to select the most suitable protease combination for hydrolyzing morel.The results of scanning electron microscope(SEM),protein recovery,sugar yield and degree of hydrolysis(DH)showed that the structure of morel was highly damaged by emzymolysis,leading to the release of internal solutes.As to SPG,Flavourzyme could degrade proteins and peptides more effectively.The hydrolysis effect of DPG is better than that of SPG,with NF and PrF being best.The analysis of flavor indexes showed that emzymolysis was an effective method to improve the utilization of umami substances in morel,while the type of protease was crucial to the flavor characteristics of MHs.Due to hydrolysis,the molecular weight distribution(MWD)of peptides of MHs decreased significantly while free amino acids(FAAs)as well as nucleotides increased considerably.Equivalent umami concentration(EUC)of MHs were at the second level.The result of electronic tongue(E-tongue)denoted that the single endo-protease treatment(such as Neutrase and Papain)induced more bitterness while the combined treatment of endo-protease and Flavourzyme could reduce the bitter taste of MHs,preparing hydrolysates with high umami and low bitterness.Among them,NF showed the highest FAAs content and small peptide content as well as the highest EUC level,exhibiting the best comprehensive taste property.With DH being set as an evaluation index,the single factor test,Plackett-Burman test and Box-Behnken test were designed to optimize the hydrolysis conditions of NF.The optimal treatment parameters were established to be morel to water ratio of 1:10,Neutrase to Flavourzyme ratio of 2:1,total enzyme concentration of 4000 U/g,enzymatic temperature of 50?,hydrolysis pH of 6.0 and reaction time of 3 h.In this case,the DH of MH was up to 35.95%.2.MH was used as a substrate material,exogenously adding xylose,glucose and cysteine to induce MR under high temperature conditions.The browning intensity and Friedman classification test were used to preliminary optimize MR conditions.By constructing the relationship between factor set,comment set and weight,a fuzzy mathematics theoretical sensory evaluation mode(FME)was established.An L9(34)orthogonal test using FME was carried out to further optimize MR conditions and a verification test was performed.The optimal conditions for the MR of MH were obtained to be the amount of reducing sugar of 10%,the ratio of xylose and glucose of 2:1,the addition amount of cysteine of 2%,the reaction temperature of 115?.The initial reaction pH of 7.0 and the reaction time of 30 min.The morel seasoning base produced under these conditions had the highest fuzzy evaluation value of 3.636,exhibiting delicious taste,rich meaty flavor,pleasant mushroom flavor,as well as appetizing color.3.The MH was subjected to ultrafiltration treatment,and 5 different peptide fractions(PFs)were separated according to their molecular weight(>10 KDa,5-10 KDa,3-5 KDa,1-3 KDa,and<1 KDa).Five PFs and MH were employed as raw materials to induce MR under the optimal reaction conditions,preparing morel seasoning base(named MPF0)and five MR products of PFs(named MPF1-5).Meanwhile,corresponding native PFs and MH(products named NPF0-5)were set as blank control,and heat-treatment groups(without reducing sugar and cysteine added,products named HPF0-5)were used as negative control.The results showed that the pH values of MPF0 and MPF3-5 decreased significantly,while their content of colorless intermediates,browning intensity and chroma value(C*)increased remarkably,indicating the strong intensity of MR in small peptide groups,which mean they contained more flavor substances and contribute more to the formation of attractive color.Compared with NPFs and HPFs,FAA contents of MPFs,especially MPFs derived from peptide<5 KDa,decreased considerably.Bitter FAAs showed high reactivity in MR.The E-tongue results demonstrated that although both thermal treatment and MR could improve the taste of NPFs to a certain extent,the MPFs showed an obviously stronger taste-enhancing ability than HPFs,which could reduce the addition amount of salt and MSG in food to a certain extent.Besides,MWD of PFs played a great role on the taste characteristics of MPFs.MPFs derived from peptides below 3 KDa were highly correlated with umami and salty taste,showing good tasteenhancing capacity.The analysis of electronic nose and comprehensive twodimensional gas chromatography-time-off-light mass spectrometry(GC×GC-TOF-MS)demonstrated that MR could effectively remove the unpleasant odor of MHs.Morel seasoning base was rich in meaty,roasted,caramel,nutty and fruity volatiles,including aldehydes(30.17%),furan(15.30%),alcohols(14.76%),sulfur containing compounds(11.04%),nitrogen containing compounds(10.22%)and ketones(6.02%).Additionally,the content of volatiles increased as the peptide MWD decreased.It was observed that peptides of 1-3 KDa contributed more nitrogen-containing and sulfur-containing compounds as well as aldehydes,while peptides below 1 KDa contributed more aldehydes,alcohols,and furans.