INVESTIGATIONS ON THE OPTIMAL-CONTROL OF STORAGE STABILITY OF COMPRESSED BAKERS-YEAST SACCHAROMYCES-CEREVISIAE

The storage stability and leavening activity of compressed baker's yea st are two of the important quality criteria for baking. It is known t hat the fraction of budding cells (FBC) is correlated to both of them. This paper deals with the design of a feeding strategy to minimize th e FBC and maximize the yeast quality at the end of the fed-batch culti vation. The feeding strategy was obtained by means of a combined metab olic and cell-cycle model for Saccharomyces cerevisiae. The optimal fe eding was successfully applied in three experiments, the final FBC val ues approached a minimum. Further tests on the leavening activity of s amples taken from these experiments revealed that after the FBC was mi nimized, the long-term storage stability of the yeast cells was indeed enhanced, but that the opposite effect could occur if the storage per iod was very short. Further investigations indicated that the same met hods may be applied to control the quality of active dry yeast.