Mannitol-enhanced survival of Lactococcus lactis subjected to drying

Survival of Lactococcus lactis subjected to different drying conditions was investigated. Mannitol most remarkably enhanced the survival of dried cell s to a level almost equalling that of viable cells [log(10) (cfu ml(-1)) = 9.42] as was found prior to the drying process (log(10) = 9.6). In the abse nce of mannitol, a survival was reduced by a factor of 10(4). Drying of cel ls at 20 degrees C led to higher survival rates than drying at 30 degrees C . Mannitol enhanced the survival rate at both temperatures, and at both 20 degrees C and 30 degrees C the highest reduction in survival occurred when cells were dried at a water activity of 0.76. In the presence of mannitol, differences in survival after drying at different water activities were les s pronounced. Rehydration of cells dried in the presence of mannitol result ed in an extended lag phase of 4 h compared to fresh cells. No growth or ac idification of the culture medium was observed for 12 h in the case of rehy drated cells dried in the absence of mannitol. It was hypothesized that a r adical scavenging activity of mannitol could partly explain these observati ons.