Effect of protective agents, freezing temperature, rehydration media on viability of malolactic bacteria subjected to freeze-drying

Abstract

Aims: The effects of protective agents, rehydration media and freezing temperature on the viabilities of Lactobacillus brevis and Oenococcus oeni H-2 when subjected to freeze-drying were investigated.

Methods and results: Several protectants and rehydration media were tested to improve the survival after freeze-drying. The cells were also frozen at -65 and -20 degrees C to check the effect of freezing temperature on the viability.

Conclusions: The best protectant and rehydration medium to obtain the highest viability after freeze-drying varied with the species of bacteria. Yeast extract (4.0%) and sodium glutamate (2.5% ) gave maximum viability of L. brevis and O. oeni (67.8% and 53.6% respectively). The highest survival of L. brevis and O. oeni were obtained when rehydrated with 10% sucrose and MGY medium respectively. When the bacterial cells were frozen quickly (-65 degrees C) than slowly (-20 degrees C), L. brevis and O. oeni both showed increased viability after freeze-drying.

Significance and impact of the study: The viabilities of L. brevis and O. oeni after freeze-drying were shown to be strain specific and dependent on protective agents, rehydration media and freezing temperature.