The Formation Of Ammonium Salt In Soy Sauce Brewing And Its Effect On Quality

Ammonium salt in soy sauce is mainly produced by over-decomposition of protein.The way is that the protease secreted by Aspergillus oryzae decomposes soy protein into polypeptide and amino acid.Ammonia is produced by amino acid deaminase produced by other microorganisms.Ammonia is combined with hydrogen ion to form ammonium ion.At present,the research on ammonium salt in soy sauce mainly includes the source and its effect on protease activity.However,little research has been done on the relationship between brewing conditions and the formation of ammonium salt,and the relationship between ammonium salt and soy sauce quality.In this paper,the relationship between the brewing conditions and the production of ammonium salts was systematically studied,and the influence of ammonium salts content on volatile aroma components was analyzed.Combining with the difference of the types and contents of free amino acids in soy sauce,the formation pathway of ammonium salts was preliminarily discussed.This study has important guiding significance and theoretical value for further optimizing the brewing technology of high salt and dilute soy sauce in China and improving the nutritional value of soy sauce.The specific conclusions are summarized as follows.1.The effects of starter-making and fermentation conditions on the formation of ammonium salt in soy sauce were studied.The results showed that there was a significant negative correlation between the amount of ammonium salt and the concentration of fermented brine(10% ~25%)(Correlation coefficient was-0.532,p < 0.01);there was a negative correlation between the amount of ammonium salt and the fermentation temperature of soy sauce(Correlation coefficient was-0.346).The correlation between ammonium salt and koji-making temperature(29~39 ℃)and the addition of fermented brine(1.5~2.5 times the weight of koji)was weak(Correlation coefficients were 0.049 and-0.037).The range analysis of starter-making and fermentation conditions and the content of ammonium salt in soy sauce showed that the order of the range was salt water concentration > fermentation temperature > salt water addition > starter-making temperature,which indicated that salt water concentration and fermentation temperature had greater influence on the formation of ammonium salt in soy sauce.At the same time,the effects of three strains mixed with Aspergillus oryzae on ammonium salt production in soy sauce were studied.The results showed that the inoculation amounts of Saccharomyces cervisiae YB,Weissella confuse RC,Bacillus subtili KD were positively correlated with ammonium salt content in soy sauce.Compared with the control group,the content of glutamic acid in YB,RC and KD groups increased by 3.18%~10.13%,the content of aspartic acid decreased by 9.88%~16.40%,and the content of lysine decreased by 3.78%~7.55%.2.The effect of initial ammonium salt content in soy mash on the main quality indexes of soy sauce was studied.The results showed that when the content of ammonium salt was too high,the content of reducing sugar in soy sauce decreased significantly.Compared with group A-1,the content of reducing sugar decreased by 5.32% in group A-5.With the increase of ammonium salt content,the content of total phenol decreased,the content of total flavonoids and amino acid nitrogen increased gradually.The antioxidant capacity of soy sauce in group A-4 increased first and then decreased.DPPH radical scavenging capacity and FRAP of soy sauce in group A-4 were the strongest,reaching 7.04 μmol TE/mL and 11.21 μmol FE/mL,respectively.The total reducing power of group A-2 was the strongest,which was 16.55% higher than that of group A-1 with the weakest total reducing power.The antioxidant ability of soy sauce can be improved by the presence of appropriate ammonium salt.Compared with group A-1,the contents of aspartic acid,alanine and cysteine in group A-2 and group A-5 decreased by 3.35% and 6.53%,5.93% and 5.93%,10.14% and 14.49%,respectively,while glutamic acid,threonine,serine and histidine increased by 11.32% and 10.63%,6.28% and 9.42%,18.33% and 8.33%,5.41% and 12.84%,respectively.It can be concluded that the content of aspartic acid,cysteine and alanine in soy sauce will be significantly reduced with the increase of ammonium salt content,while the content of glutamic acid,threonine and serine will also be increased.3.The effects of ammonium salt on volatile aroma components in mash were studied by electronic nose and HS-SPME-GC-MS.From group A-1 to group A-5,22,18,25,19 and 25 kinds of volatile compounds were detected respectively.The electronic nose analysis showed that there were significant differences in the flavor of soy sauce among the five groups.The flavor quality of soy sauce was evaluated by principal component analysis..The results showed that the comprehensive scores of group A-1 and group A-2 with lower ammonium salt content were the highest.Except group A-5,the contents of 1-octene-3-alcohol and phenylethanol in the remaining four groups decreased with the increase of ammonium salt content,from 133.98 ng/mL and 94.24 ng/mL to 83.15 ng/mL and 14.73 ng/mL,respectively.The contents of these two substances of soy sauce in group A-5 were also 30.12% and 76.64% lower than those in group A-1,respectively.It is inferred that the presence of ammonium salt is not conducive to the formation and accumulation of 1-octene-3-alcohol and phenylethanol in soy sauce.The content of benzaldehyde and 4-vinyl-2-methoxyphenol in soy sauce of A-3,A-4 and A-5 groups were lower than those of A-1 and A2 groups.The increase of ammonium salt content is not conducive to the formation of overall flavor in soy sauce.