| This paper studied the differences of soys under two kinds of fermentation conditionswhich included natural fermentation and insulation fermentation. Firstly, the mainmicroorganism and the dynamic variation of physical and chemical compositions such asamino acid nitrogen, total acid, pH, NaCl and the color of samples was studied. Then themain flavor substances such as organic acid, amino acid and volatile sroma composition weredetected and compared. The conclusions were drawn as followed:(1) Under the condition of natural fermentation, the total number of yeast, the totalnumber of lactic acid bacteria and the total number of bacterial colony in the soy sauce wereless at initial stage, along with the fermentation, then it increased gradually and reached thehighest at middle stage, finally it started to decline gradually. The total number of yeast, thetotal number of lactic acid bacteria and the total number of bacterial colony in soy saucereached the maximum value of3.09×10~6cfu/mL,3.02×10~8cfu/mL and7.41×10~6cfu/mLrespectively at the40th day of natural fermentation. Under the condition of insulationfermentation, yeast, lactic acid bacteria and other bacteria were inhibited during the early20days, and reached the highest of2.63×10~5cfu/mL,5.62×10~5cfu/mL and1.05×10~6cfu/mLrespectively at the40th day of fermentation. The total number of mold showed a trend ofgradual decline in the entire fermentation. At early stage, the total number of mold in naturalfermentation of soy sauce declined slowly, but that in the insulation fermentation of soysauce declined quickly. When the post-fermentation of the two kinds of soy sauce came toend, the total number of yeast, lactic acid bacteria, bacterial colony and mold variedconsiderably.(2) The amino nitrogen contents of insulation fermented sauce and natural fermentedsauce were not obviously different：the amino nitrogen content of insulation sauce reachedpeak value after20day’s fermented time, while amino nitrogen content of natural fermentedsauce reached peak value after40day’s fermented time, and both of them were close to0.9g/100mL. The contents of total acids and pH of insulation fermented sauce and naturalfermented sauce were remarkably different: the pH of natural fermented sauce was almost thesame which maintained at4.23after40day’s fermented time, and the content of total acid ofwhich was2.3g/100mL; while the pH of insulation fermented sauce was almost the same which maintained at4.85after20day’s fermented time, and the content of total acid of whichwas1.5g/100mL. The content of NaCl of insulation fermented sauce and natural fermentedsauce were basically not different, the color ratio trends of them were also the same and bothof which increased rapidly in the former fermentation.(3) Tartaric acid, lactic acid, acetic acid and pyroglutamic acid were detected in the sauceproduced under the two processes and, among which, the content of acetic acid and lactic acidwere relatively high. The contents of the acetic acid, lactic acid, tartaric acid and pyroglutamicacid were respectively4.34mg/mL,2.3mg/mL,1.77mg/mL and2.10mg/mL lower ininsulation fermented sauce than in natural fermented sauce. The proportion of glutamate andthreonine in the two kinds of sauce were relatively high and the content of the two aminoacids were17.89%and6.56%, respectively, while the content of arginine was only0.93%which was the lowest. The total contents of amino acids and the contents of each amino acidof naturally fermented sauce and insulation fermented sauce were not significantly different,the total contents of amino acid in the two kinds of sauce were26.46mgm/L and26.59mg/mL,respectively. The contents of three kinds of flavor amino acid in the sauces produced underthe two processes were almost the same. Among the three different flavor amino acids, thekinds of bitter taste amino acids were the most and the proportion of them was slightly high,reaching42.62%; while the proportion of sweet taste amino acids was the least, only reaching10.39%; and the proportion of umani taste amino acids was34.46%.110kinds of aromasubstances were detected using the method of headspace solid phase microextraction-gaschromatography-mass spectrometry, including19kinds of alcohols,30kinds of esters,ketones20kinds of ketones,10kinds of aldehydes,9kinds of acids,16kinds pyrazines,6kinds of phenols. The total relative percentage of alcohol was the highest, followed byaldehydes and esters, while the total relative percentage of acids was the lowest. The relativepercentages of volatile aroma component of natural fermented sauce and insulation fermentedsauce were not very different: among which, the total relative percentages of alcohols in thetwo kinds of sauces were45.55%and45.52%, the total relative percentages of alcohols esterswere11.39%and11.28%, the total relative percentages of acids were3.15%and3.02%; thetotal relative percentages of aldehydes were12.63%and12.69%, the total relative percentages of ketones were10.82%and10.59%, the total relative percentages of pyrazines were4.82%and4.80%, and the total relative percentages of phenolic compounds were6.29%and6.31%,respectively. |
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