Drying of Yeasts-Factors Affecting Inactivation During Drying

The inactivation behavior of baker's yeasts during low-temperature hot air drying and freeze drying was investigated. The activity was determined by measuring the fermentative abilities. Inactivation was observed during the falling drying rate period even at low temperature (30 degrees C). As their fermentation activities in suspensions at 30 degrees C are maintained up to a few hours, this decrease was found to be due to dehydration inactivation. Similar dehydration inactivation was also observed during freeze drying. The dehydration inactivation became more significant when the drying rate was increased. The stability of dried yeasts increased with decreasing water content. The addition of sorbitol before drying further improved the stability of dried yeasts.