| Umami is one of the favorite flavors of consumers,and it is also an important quality of high-quality condiments.In addition to umami substances(refers to the compounds with umami taste,such as MSG,taste nucleotide,etc.),umami-enhancing compounds are another important component of umami condiments,which have synergistic effect with umami compounds,can significantly enhance the intensity of umami,and make prominent contributions to the umami characteristics of condiments.At present,the researches mainly focus on the umami compounds and the researches on the umami-enhancing compounds are relatively few,which limits the development and utilization of the high umami base materials.The soybean meal hydrolysate(SMH)is mainly prepared by enzymatic hydrolysis of defatted soybean meal with protease,and rich in taste peptides.In this paper,SMH is the research object.On the basis of clarifying its taste and umami-enhancing characteristics,the contribution of taste peptides to umami-enhancing properties of SMH was studied by combining taste recombination experiments,separation and identification methods.The possible mechanism of Maillard reaction to enhance the umami properties of SMH was also revealed from the aspects of volatile and non-volatile products.The basic taste and umami-enhancing characteristics of SMH were discussed firstly.After the systematic analysis of the composition of taste compounds,the umami-enhancing contribution of taste peptides to the SMH was compared and analyzed by the taste recombination experiment.The results showed that the SMH had strong kokumi,sour and bitter taste,and weak sweet and umami taste.More importantly,it had good umami-enhancing effect in soy sauce and chicken powder.In order to further clarify the umami-enhancing effect of SMH,it was mixed with different umami agents such as MSG,IMP,GMP,I+G and scellein.And it was found that the SMH had the strongest umami-enhancing effect in I+G.In addition,in order to clarify the material basis of the umami-enhancing properties in SMH,the umami-enhancing properties of SMH and its taste recombination(lack of taste peptides)were compared.It was found that there was a big difference between the taste recombination and SMH.This indicated that taste peptides may contribute to the umami-enhancing properties of SMH.In order to further clarify the material basis of taste peptides with umami-enhancing effect,the SMH was divided into five fractions(20%-F,40%-F,60%-F,80%-F and supernatant)by ethanol fractionation.Then the 40%-F fraction with the strongest umami-enhancing effect was divided into seven fractions(F1,F2,F3,F4,F5,F6 and F7)by Sephadex G-15 gel chromatography.Combined with sensory evaluation,F2 had the strongest umami-enhancing effect in I+G,followed by F1.Therefore,F2 and F1 were separated and identified by UPLC-ESI-QTOF-MS/MS.There were 8 short peptides were identified,which were LE,VE,LP,PE,LD,VD,VPP and GLI.Then sensory evaluation showed that these 8peptides all had an umami-enhancing effect in I+G,and the umami-enhancing thresholds of them were 0.04,0.09,0.06,0.15,0.08,0.07,0.06 and 0.13 m M,respectively.Analyzing characteristics of the primary structure of umami-enhancing peptides reported so far,it was found that more than half of these peptides were short peptides(dipeptides and tripeptides).And the composition of amino acids(umami amino acids)was one of the important factors affecting umami-enhancing characteristics.The optimum reaction conditions of Maillard reaction(MR)of SMH were as follows:reducing sugar xylose,sugar content 3%,concentration 55%,temperature 70?,time 70 min,p H 6.The mechanism of MR is complex,and its volatile and non-volatile products may contribute to the improvement of umami-enhancing property of SMH.The compositions of peptides and amino acids in SMH and its MRPs were determined.Then it was found that peptides less than 500 Da in SMH participated in MR to a large extent.Some peptides participated in the MR and generated derivatives which might contribute to umami-enhancing.In addition,new peptides generated from MR may also be related to the umami-enhancing characteristic.In the complex system of SMH,changes in the types and proportions of peptides may change the umami-enhancing characteristic.GC-MS/MS was used to analyze the changes of volatile substances.The results showed that the contents of alcohols,ketones,pyrazines,furans and sulfur compounds were reduced during the MR,and more esters,aldehydes,acids and pyrroles were formed.2,6-dimethylpyrazine in SMH may contribute to umami-enhancing to a certain extent;phenylacetaldehyde has the characteristics of improving the aftertaste and palatability in umami solutions.2-methylbutanal in the MRPs of SMH can significantly enhance the aftertaste of umami solutions;3-ethyl-2,5-dimethylpyrazine,2,3,5-trimethyl pyrazines and ketones such as 2-heptanone and acetone may also have a certain effect on umami-enhancing. |
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