The suspension of active yeast was prepared according to a reported method (Marie, El-Hamid, El-Khatib, & El-Gamal, 2004). The procedure was adopted as follows.
450 g dry weight of Brewer’s yeast was pasted with 150 g sugar, and then 1 L of warm water (40 C) was added to the paste of yeast while stirring for a period of time until the yeast was brewed. Finally the solution was filtered and frozen.