Fermentation Characteristics of Lactobacillus casei LK-1 and Its Application in Pineapple Juice

In order to utilize Lactobacillus casei to prepare fermented pineapple juice beverage, the growth curve, acid production, acid tolerance, and sugar tolerance characteristics of Lactobacillus casei LK-1 (L. casei LK-1) were investigated and analyzed in this research. Moreover, the optimal conditions for the fermentation of pineapple juice by L. casei LK-1 were explored by single-factor test and response surface methodology, with the viable cell count and total acid content as indicators. As revealed by the results, L. casei LK-1 grew and reproduced well in an environment with pH5~7 or containing 0% to 10% glucose. The survival rates of it were 76% and 71%, respectively, after 3 h of incubation in an acidic (pH3) or high sugar (40% glucose) environment. Besides, after 48 h incubation in MRS medium, its acid production was 5.35 g/kg, which was good for the fermentation of the juice. The optimal conditions for fermenting pineapple juice with L. casei LK-1 were: Initial pH of 6.8, fermentation temperature of 37 ℃, inoculum level of 1% (v/v), as well as fermentation time of 30 h. Under this preparation condition, the viable cell count of fermented pineapple juice was 8.99±0.04 lg CFU/mL, the total acid content was 7.16±0.26 g/kg, and the juice was bright in color, sweet and sour with excellent flavor. The results of this research can provide a theoretical and technical basis for the further application of L. casei LK-1 in fermented foods.