Analysis Of The Flavor Characteristics Of Radish Pickles With Different Fermentation Methods And Selection Of The Starter Cultures

Chinese pickle,one of the typical representatives of Chinese traditional fermented foods,is widely consumed in China over centuries.To date,the production of Chinese pickle is mostly based on spontaneous fermentation However,the microorganisms in naturally fermented pickle are complex and diverse,so the quality of pickle is not stable for industrial production.At present,the demand for pickle starter is increasing.The use of starter cultures was reported to help standardize the fermentation by controlling the microbial flora.Firstly,the metabolomic method based GC-MS was combined with sensory evaluation and electronic tongue to analyze the flavor characteristics,sensory characteristics and taste characteristics of 16 kinds of commercial pickles(CP).The results showed that there were differences in pH,acidity,salinity and total sugar content among the different commercial pickles.The pickle CP13,CP14 and CP15 had a higher overall preference,which was positively correlated with the fermented aroma preference and sweetness preference.The sweetness taste and umami aftertaste of PC13,PC14 and PC15 were more prominent,and the sourness taste was relatively weak.The contents of fructose,glucose,tagatose,malic acid,and glycine mainly affected the taste preference.?-Terpinene,?-myrcene,linalool,geraniol,dimethyl trisulfide and ethyl octanoate were the main aroma compounds that could increase the overall preference and the fermentation aroma preference.Secondly,according to the fermentation characteristics in radish juice,a total of 10strains were selected from 30 strains of Lactobacillus plantarum,Leuconostoc mesenteroides and Pediococcus ethanolidurans.The physical and chemical characteristics,sensory characteristics,taste characteristics and flavor components were determined and analyzed.L.mesenteroides SCCDZN2,L.plantarum VHuNHHMY10-L1,and P.ethanolidurans VCQWZ3-L7 showed excellent fermentation characteristics in the fermentation.They could produce acid faster and maintain a higher level of viable counts.And they also had higher sensory preferences.The sourness and sweetness characteristics of pickle fermented by L.plantarum were prominent,and the umami taste of pickle fermented with L.mesenteroides and P.ethanolidurans was obvious.However,the acidity of pickle fermented by different strains was quite different.The content of glycine and malic acid was significantly lower than that of commercial pickle.Then,the pickles were co-fermented by L.mesenteroides and L.plantarum,L.mesenteroides and P.ethanolidurans,the ratio was 1:1,1:2 and 2:1,respectively.When the ratio of L.mesenteroides to L.plantarum was 1:2 and L.mesenteroides to P.ethanolidurans was 1:1,the acid production rate was faster,the synergy was the strongest,and each strain maintained a high number of counts.The result of flavor substances showed that the combination of different strains could adjust the content of metabolites in pickles.When the ratio of L.mesenteroides to L.plantarum was 1:2 and the L.mesenteroides to P.ethanolidurans was 1:1,the sugars and organic acids in pickles could be kept at an appropriate level,and the types and contents of volatile composition were relatively high,giving pickles a good flavor.Next,according to the results of the double-strain fermentation,L.mesenteroides,L.plantarum and P.ethanolidurans were fermented at the ratio of 1:2:1.It could significantly shorten the fermentation period to 60 h,and the sensory preference was high.In terms of flavor composition,the results showed that this compound method combined the fermentation aroma of the pickle of double-strains fermentation.Finally,the composition and formula of the pickle starter was finally determined with three combinations.The ratio of L.mesenteroides and L.plantarum was 1:2 for combination A.The ratio of L.mesenteroides and P.ethanolidurans was 1:1 for combination B.The ratio of L.mesenteroides,L.plantarum and P.ethanolidurans was 1:2:1 for combination C.The total number of lactic acid bacteria was controlled at about 10~7 CFU/mL.For the three combinations,0.10 g/kg glycine and 0.23 g/kg malic acid were added in the pickles.The pickles were fermented at room temperature for 60 h?72 h for the combination A and B,and the pickle was fermented at room temperature for 48 h?60 h for the combination C.