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°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°C) than slowly (−20°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.