Study On Main Indicators In The Fermentation Brine Of Stinky Tofu By Three Inoculation Methods

Southern stinky tofu is known as its unique smell,and brine is the main source of special flavor for stinky tofu.In this paper,three kinds of inoculation of fermented brine A,B,C as the object,the changes of amino acid,pH value,amino acid nitrogen and volatile components during 12-month fermentation were analyzed.The results are as follows:(1)The changes of Amino acids,p H value and amino acid nitrogen in the fermentation brine of stinky tofu by three inoculation methods were analyzed.The results showed that the total amount of A,B and C amino acids in stinky tofu brine is obviously increased,and the variation range was 0.06-0.545 g,0.166-0.335 g and 0.106-0.365 g per 100 g respectively.The pH value increased from 4.13 to 8.89,and the amino acid is shown a rising trend,and the three indexes showed positive correlation.(2)SPME-GC-MS was used to detect the volatile substances in three samples.The main volatile components in the A and C were the phenols and heterocycles.The relative content of phenols and heterocycles in brine A reached 47.92% and 59.22%,respectively.The relative contents of phenols and heterocycles in brine C were 38.98% and 52.93% respectively.The main volatile components in sample B are acids and alcohols,the highest relative content of 73.71%,respectively,66.64%.The common substances in the three brines were 4-methylphenol,indole,3-methylindole.The phenols showed an upward trend in the first nine months of the three brine fermentation processes,the latter basically stabilized.The heterocyclics in the first ten months of fermentation was on the rise,the latter basically stabilized.(3)The tendency of 4-methylphenol,indole and 3-methylindole have special flavor components were analyzed in the fermentation processing by three inoculation methods.The results showed that during the fermentation process,The relative content of 4-methylphenol increased from 7.34 to 7 in brine,and increased from 10.24% to 38.11% in brine A,and in brine B 0.19% to 26.40%,brine C from 0.01% to 29.14%,when pH> 7,4-methylphenol content decreased,brine A decreased to 22.17%,brine B decreased to 15.85%,brine C dropped to 21.40%.The content of 3-methylindole and indole in the fermentation process showed different trend.The relative content of indole in brine A decreased from 31.53% to 0.95%,and the relative content of 3-methylindole increased from 5.16% to 55.15 %,The relative content of indole in brine B decreased from 5.72% to 0.07%,the relative content of 3-methylindole increased from 0.15% to 7.08%,the relative content of indole in brine C decreased from 6.09% to 0.84% The relative content of 3-methylindole increased from 0.02% to 52.33%.The relative content of 3-methylindole was lower than that of indole when pH 4.13 was increased to 6.5.When pH> 6.5,the relative content of indole was lower than that of 3-methylindole.The formation of phenol and indole may be related to the change of microbial community in the fermentation broth.