Research Of Technology Of Direct Vat Set Suansun Fermented

Fermented vegetables are very popular because of their diverse raw materials,unique processes,different flavors and rich tastes.In China,among which fermented Suansun are especially unique because of their raw materials and fermentation conditions,mainly distributed in the southwest coastal areas of China(Guangxi,Guangdong,Yunnan,etc.).In recent years,with the development of traditional Chinese cuisine,Suansun,an important supplement to the traditional snack snail noodles,have become widely known for their unique sour taste.However,traditional Suansun are mostly spontaneously fermented at home,which not only cannot guarantee product quality and safety,but also have limited production to meet the market demand,which greatly limits the theoretical research on Suansun and the development of Suansun industry in China.The screening of lactic acid bacteria with good performance from the fermentation process of kefir to prepare direct-injection fermenters can effectively shorten the fermentation time,stabilize the quality of fermented products,and facilitate large-scale industrial production.Therefore,the purpose of this paper is to screen lactic acid bacteria with excellent fermentation performance from each stage of spontaneous fermentation fermentation of asparagus,explore the technology of high-density culture of strains,so as to prepare direct-injection ferments with high bacterial concentration and high vitality,and provide a theoretical basis and reference scheme for the production of direct-injection ferments for asparagus and industrial production of asparagus.The results of this research are as follows.(1)Isolation and identification of strains from each stage of spontaneous fermentation of Suansun.61 single strains were isolated from the spontaneous fermentation of Suansun,and 60 strains were identified by molecular biology as lactic acid bacteria,among which edible strains included 12 strains of Lactococcus lactis subsp.lactis in the pre-fermentation stage,5 strains of Lactobacillus fermentum in the middle stage of fermentation,and 23 strains of Lactobacillus plantarum in the late stage of fermentation.(2)Determination of fermentation performance of strains.A total of 40 strains of lactic acid bacteria in each stage were measured for acid resistance,and 2 strains with the highest survival rate of acid resistance were selected in each stage,among which 1strain in the early stage and 2 strains in the late stage had survival rates greater than70%,namely:Lactococcus lactis subsp.lactis NCU077004,Lactococcus lactis subsp.lactis NCU077013,Lactobacillus fermentum NCU003090,Lactobacillus fermentum NCU003093,Lactobacillus plantarum NCU001318,Lactobacillus plantarum NCU001330.The acidity,salt tolerance,nitrite degradation and bacterial inhibition of the six strains of Lactobacillus were further determined,and the acidity of the six strains ranged from 6.9 to 14.3 g/Kg,the bacterial concentration was greater than 10⁵ CFU/m L at different salt concentrations,and the nitrite degradation capacity ranged from 13.53to 74.44%,and the supernatant of the mixed culture had good growth inhibition ability against seven common pathogenic bacteria,and the inhibition circle diameter was greater than 20 mm.Lactococcus lactis subsp.lactis NCU077004,Lactobacillus fermentum NCU003090,Lactobacillus plantarum NCU001318 were selected as direct injection fermenters based on the results.(3)Optimization of high-density culture process for Lactobacillus fermentum NCU003090.Lactobacillus fermentum NCU003090 plays a dominant role in the middle of fermentation,so it was optimized for high-density culture process.The optimized results were:medium formulation sucrose 39.6 g/L,yeast extract powder4.76 g/L,peptone from casein 14.28 g/L,anhydrous K₂HPO₄5.07 g/L,C₂H₃Na O₂ 4.80g/L,C₆H₅Na₃O₇ 8.58 g/L,L(+)-Asparagine monohydrate 500 mg/L;The static culture condition was 37?,the initial p H was 7.0,and the inoculum was 3%;the high-density condition was constant p H 6.5,the gas environment was N₂,and the neutralizer was25%NH₃·H₂O.The bacterial concentration reached 12.2×10⁹ CFU/m L after 22 h of high density incubation,which was 5.48 times higher than that obtained by ordinary MRS medium.(4)Optimization of freeze-drying process of Lactobacillus fermentum NCU003090.Lactobacillus fermentum NCU003090 was optimized for vacuum freeze-drying process,and the optimized results were centrifugal force of 8000 r/min,centrifugal time of 10 min,compound freeze-drying protectant formulation of skim milk powder 10%,sodium glutamate 4%,sucrose 8%,and the ratio of bacterium to protectant was 2:1,then the freeze-drying survival rate was up to The lyophilization survival rate was 94.28%,and the concentration of bacteriophage was 5.8×10¹¹ CFU/g.(5)Comparison of the quality of spontaneously fermented Suansun and direct-fed fermented Suansun.The results showed that,compared with spontaneously fermented Suansun,using Lactococcus lactis subsp.lactis NCU077004,Lactobacillus fermentum NCU003090 and Lactobacillus plantarum NCU001318 prepared as the direct fermentation of Suansun with mixed bacteria was carried out,and the maturation time of Suansun was significantly shortened by 13 d.After maturation,p H increased to 3.76,acidity decreased to 7.35 g/L,lactic acid content increased to 2.73 g/L,and total free amino acid content increased to 19.984 mg/100g.The data of volatile flavor substances showed that the content of esters increased to 54.53%,alcohols increased,aldehydes increased and their content increased to 7.07%,and the content of p-methyl phenol,the main odor contributor,decreased significantly to 17.24?g/Kg.