The Effect of Rehydration on Leaching of Cellular Phosphate in Active Dry Yeast

Abstract

Summary Active dry yeast cells were rehydrated at different temperatures, using solutions the water activity of which was regulated either by sucrose or glycerol. The temperature of the rehydration solutions ranged from 4–40°C, while their levels of water activity ranged from 1.00–0.92. It has been found that the leached cellular phosphate decreased, while the cell viability increased with the decrease of the water activity of the rehydration solutions. Rehydration at 30–40°C showed the highest protection for the yeast cells at almost all the levels of water activity. However, the deleterious effect of rehydrating the cells at 4°C (cold shock effect) could be overcome by rehydration with solutions having lower levels of water activity. The results indicated that slow rehydration of the cell membrane at lower levels of water activity may be responsible for their protective effect on the yeast cells. Sucrose was found to be superior to glycerol for cell protection, especially at lower levels of water activity.