SPRAY-DRYING AS A METHOD FOR PREPARING CONCENTRATED CULTURES OF LACTOBACILLUS-BULGARICUS

Spray drying and freeze drying as methods for concentration of Lactoba cillus bulgaricus starter cultures were compared in terms of viability , lag phase until onset of pH decrease and total acid production. For the experimental conditions used, no significant differences were dete cted between the methods. The effect of spray drying on the cell membr ane of Lactobacillus bulgaricus was studied. Five separate methods wer e used to study the theory that spray drying causes cell membrane dama ge; three relating to leakage of intracellular components from the cel l into the surrounding environment (260 and 280 nm absorbing materials , potassium ions and proteins); and two relating to increased cell per meability (increased sensitivity to NaCl and increased permeability to o-nitrophenyl-beta-D-galactopyranoside (ONPG). Partial loss of some c ytoplasmic material from the damaged cells was observed. The dried cel ls also became sensitive to NaCl and permeable to ONPG. Heat shock inc reased the survival of exponential cells as compared to controls but d id not result in normal levels found with unshocked stationary phase c ells. Heat shock had no effect on stationary phase cells. Different re hydration methods and media were investigated: slow rehydration increa sed survival.