Preparation Of Suanyu By Fermentation With Lactobacillus Plantarum EH06 And Alcohol Active Dry Yeast

Carp have a delicate meat,there are more intermuscular spines,and the rate of picking meat is low,restricting the healthy development of its breeding industry.Suanyu is a kind of traditional fermented fish products with rich nutrition and strong flavor.It is popular among consumers because of its storage at room temperature and ready-to-eat with bone.It is an effective processing way to increase the added value of carp.Suanyu is mostly natural fermentation,fermentation time of Suanyu is long and product quality is difficult to control,the product difference is large,industrial production is the development direction of Suanyu.Artificial controlled fermentation using the dominant microorganisms in Suanyu is a hot research topic at present,but there is a lack of systematic research on the fermentation characteristics of single and complex strains and the effects on the quality of Suanyu.In this paper,corn meal was used as auxiliary material,Lactobacillus plantarum EH06 and Alcohol Active Dry Yeast were used as starter cultures for temperature-controlled fermentation.On the basis of studying the fermentation characteristics of different strains of Suanyu,the suitable ratio of composite strains of Suanyu was explored.The research results are expected to provide basic data and theoretical basis for the industrial production of Suanyu.(1)Different strains had different effects on the quality of Suanyu.After the fermentation of Lactobacillus plantarum EH06,the p H of the samples decreased to 4.76 at 7 d,4.33 at 14 d,and then slowly decreased to 4.12.amino acid nitrogen increased rapidly in the first three weeks,and then slowed down,reaching(0.31±0.07)g/100 g at the end of fermentation,which was significantly higher than that in Alcohol Active Dry Yeast group and natural fermentation group.The volatile base nitrogen was the lowest(24.990±0.07 mg/100 g),and the hardness and elasticity of the samples were improved.Before fermentation,Arg,Phe and His were the most abundant amino acids.After fermentation,except for Arg and His,the contents of other amino acids increased,especially Asp and Glu.The contents of various amino acids in the samples fermented by Lactobacillus plantarum EH06 were higher than that of Alcohol Active Dry Yeast.(2)The quality improvement of Suanyu was different with different strain ratio.Compared with a single strain,the number of viable bacteria increased significantly,the amino acid content of umami increased,but the growth of total acid slowed down.The hardness of fresh carp increased from 311.10 g to 399.35 g.The aroma components of Suanyu in complex fermentation increased from 21 at the beginning of fermentation to 38 at fermentation maturity.At the later stage of fermentation,the aroma of ethyl acetate,hexyl acetate,isobutyl caproate and acetic acid increased,and the odor of 1-octene-3-ol and hexal decreased significantly.Another odor substance,isovaleric acid,was produced on the 7th day and disappeared on the 28th day.The AAN,amino acid and volatile base nitrogen indices of Suanyu fermented with 2:1 and 1:1 were better than those of the 1:2 fermentation group.Combined with sensory evaluation and aroma analysis,Suanyu fermented with ratio of 1:1had softer smell,better palatability and the highest score.(3)According to the relative odor activity values,the typical aroma components of Suanyu were identified as 1-octene-3-ol,ethyl acetate,isoamyl acetate,nonal,octyal,heptal,etc.Pearson correlation analysis showed that there was a certain correlation between microorganisms and volatile flavor compounds,natural fermentation had a significant positive correlation with 1-octene-3-ol,and Lactobacillus plantarum EH06 and Alcohol Active Dry Yeast had a significant negative correlation with 1-octene-3-ol,indicating that inoculation of microbial fermentation could effectively reduce or eliminate the odor represented by 1-octene-3-ol.Alcohol Active Dry Yeast in particular.(4)The determined processing technology of Suanyu is:adding 2%sugar and 3%salt according to the quality of fish block,curing for 24 h,drying for 4 h at 50℃until the water content of fish is about 65%～68%.50%of the mass of dried fish was added with corn meal and the ratio of strains was 1:1.After inoculation,the cell concentration of strains was 4.9×10~6cfu/g,and the sealed fermentation was conducted at 25℃for 35 days.At this time,p H was4.21,TA reached 25.26g/kg,amino acid nitrogen content was(0.32±0.05)g/100 g,volatile base nitrogen was(22.24±0.07 mg/100 g),ethyl acetate,hexyl acetate,isoamyl acetate,nonaldehyde,octyl aldehyde and other typical aroma was prominent.The highest sensory score was 87.5.