Effect of protective solutes on leakage from and survival of immobilized Lactobacillus subjected to drying, storage and rehydration

When lactic acid bacteria are used industrially as fermentation starters it is important to obtain stable and highly viable bacterial cultures. Six st rains of Lactobacillus encapsulated in Ca-alginate gel beads were investiga ted to determine whether dehydration, storage and rehydration may inflict i njury. A negative relationship between leakage of lactate dehydrogenase and survival rates was found. Mesophilic lactobacilli showed only negligible l eakage compared with thermophilic strains when dehydrated at 30 degrees C t o a level of 0.11 g H2O (g dry wt)(-1). The choice of an appropriate suspen ding medium to be introduced before drying was therefore very important for thermophilic lactobacilli in order to increase the survival rates during d ehydration, storage and rehydration. The osmoregulatory solutes tested were adonitol, betaine, glycerol and reconstituted non-fat milk solids (NFMS). Less injury was inflected during dehydration for Lactobacillus helveticus w ith adonitol, glycerol and NFMS. Survival rates for the strains subjected t o immobilization, dehydration, storage and rehydration varied with the stra in and the protective solute when fluidized-bed drying was used at 5 degree s C to a level as high as 0.34 g H2O (g dry wt)(-1). Non-fat milk solids ga ve the best protection for thermophilic lactobacilli, while adonitol and NF MS were best for mesophilic lactobacilli.