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

The storage stability and leavening activity of compressed baker's yeast are two of the important quality criteria for baking. It is known that the fraction of budding cells (FBC) is correlated to both of them. This paper deals with the design of a feeding strategy to minimize the FBC and maximize the yeast quality at the end of the fed-batch cultivation. The feeding strategy was obtained by means of a combined metabolic and cell-cycle model for Saccharomyces cerevisiae. The optimal feeding was successfully applied in three experiments, the final FBC values approached a minimum. Further tests on the leavening activity of samples taken from these experiments revealed that after the FBC was minimized, the long-term storage stability of the yeast cells was indeed enhanced, but that the opposite effect could occur if the storage period was very short. Further investigations indicated that the same methods may be applied to control the quality of active dry yeast.