Study On Fermentation Technology Of Lactic Acid Bacteria In Litchi Juice

Litchi juice has the characteristics of high level of sugars content, low level of fruityfragrance, strong heat-sensitivity, and also browning and flavor deterioration is easy tooccur during traditional thermal processing. In this paper, in order to slove the problems ofhigh level of sugars content and low level of fruity fragrance, the fermentation of lacticacid bacteria was implemented. Moreover, in order to slove the problems of strongheat-sensitivity, browning and flavor deterioration, the traditional thermal processing wasreplaced by high hydrostatic pressure processing in litchi juice before fermentation. In theend, we developed an functional fermented litchi juice beverage product. The mainconclusions are as follows:1.The changes of lactic acid bacterial number, pH, total titratable acidity, total sugar,reducing sugar, total phenolics, DPPH scavenging and color in pasteurised litchi juiceswere studied when fermented with various lactic acid bacteria (Lactobacillus casei,Leuconostoc mesenteroides, Streptococcus lactis, Lactobacillus plantarum, Lactobacillusbulgaricus and Streptococcus thermophilus). The results showed that the nutrient of litchijuice was rich for growth of lactic acid bacteria, and the growth rate of Leuconostocmesenteroides in logarithmic growth phase was slightly higher than other5strains. Ascompared with other5strains, sugar transformation ability of Leuconostoc mesenteroideswas the highest, which was almost78%. Moreover, Leuconostoc mesenteroides was alsosuperior to other5strains in reserve of total polyphenol and color.2. In this study, fermentation of litchi juice using probiotic Lactobacillus casei,Lactobacillus bulgaricus and Leuconstoc mesenteroides was carried out at30°C, and thechanges of microbial population and quality of fermented litchi juice during storage at4°Cwere also investigated. Results found three lactic acid bacteria can grow rapidly in litchijuice, and received the highest number of lactic acid bacteria (9.0lg CFU/mL). And threelactic acid bacteria showed obvious difference in utilizing the sugar and organic acid oflitchi juice, and Lactobacillus casei and Lactobacillus bulgaricus produced more than37.5g/L exopolysaccharides. Moreover, after12h fermentation, the content of phenolics andVc showed no significant changes (p>0.05), L*values were significantly decrease(p<0.05), and the color is more white in all fermented litchi juice. During storage of4weeks at4°C, no further fermentation was found in all fermented litchi juice, but thenumber of Leuconostoc mesenteroides dropped to less than7log, and Lactobacillus caseiand Lactobacillus bulgaricus only decreased0.5log.3. The aim of this study was to evaluate the use of litchi juice treated by highhydrostatic pressure (HHP) as substrates for producing a probiotic beverage byLactobacillus casei. The quality attributes and products stability of fermented heat-and HHP-treated litchi juice by L. casei was compared. Compared with fermented heat-treatedlitchi juice, fermented HHP-treated litchi juice showed a better color, flavor and overallacceptance, and also retained more total phenolics and antioxidant capacity. Both viabilitycounts of L. casei were more8.0lg CFU/mL in heat-and HHP-treated litchi juice after4weeks of storage at4°C. Besides, some quality attributes in fermented heat-andHHP-treated litchi juice showed the tendency to slow decrease during storage at4°C, butboth scores of overall acceptance of fermented heat-and HHP-treated litchi juice showedno reduction after the storage of4weeks at4°C. Overall, the application of HHP treatmentcould be an ideal alternative of heat treatment to ensure the microbial safety, consistentsensory and nutritional quality of fermented litchi juice prior to fermentation.