Thermal drying of Lactobacillus delbrueckii subsp. bulgaricus and its efficient use as starter for whey fermentation and unsalted cheese making.

Lactobacillus bulgaricus grown on whey was dried by a simple thermal drying method at the range 35-55 degrees C and its efficiency for lactic acid fermentation of whey was evaluated. Drying of cells in whey suspension in the examined temperature range did not affect significantly their viability (82-87% survival), indicating a protective effect of whey as both growth and drying medium. The kinetics of fermentation of whey and mixtures of whey/molasses using the dried culture were comparable to those of non-dried cells, and only low pH had a detrimental effect on the fermentation ability of the dried cells. Furthermore, dried L. bulgaricus, free or immobilized on casein coagulates, was used as starter for the production of unsalted hard-type cheese. The effects of the amount of starter culture and the immobilization technique, the evolution of microbial counts, and the sensory properties of the produced cheeses were evaluated during ripening at various temperatures.