Harvesting yeast (Saccharomyces cerevisiae) at different physiological phases significantly affects its functionality in bread dough fermentation

BACKGROUND AND OBJECTIVES Yeast cells are also partly responsible for bread flavor and may affect dough rheology. Entrance into the diauxic shift is accompanied by an increase in storage molecules such as glycogen and trehalose. As the cells approach the stationary phase, different enzymes and storage carbohydrates accumulate. To this end, yeast was harvested at seven distinct points during growth, characterized and subsequently used in the production of dough.MATERIALS AND METHODSThe effect of harvesting yeast at seven different points, its characteristics on the growth of fermentation performance, metabolite production and the effect on important fermentation indicators were investigated. yeast was harvested at seven distinct points during growth, characterized and subsequently used in the production of dough.the supernatants of fermented growth media were dried in an oven at ۱۰۰ C for ۲۴ h. Total gas production and gas retention are measured with a pressure sensor through direct and indirect cycles, respectively. During the direct cycle,the changes in the gas pressure inside the fermentation tank are being recorded and this leads to the total gas production curve. This gives the total gas retention of dough during the fermentation process.RESULTS AND DISCUSSIONThe first three points showed little succinic acid production while the cells harvested and in the next four points showed up to fourfold higher succinic acid production.This threshold might be variable for different dough samples based on the fermentation speed of yeast.The combination of produced metabolites by the yeast during dough fermentation, and the fermentation rate of yeast at different harvest points might be the key determining factors on gas holding capacity.CONCLUSIONThe results demonstrate the importance of yeast harvest time on the subsequent dough fermentation capacity of yeast, including fermentation rate and metabolite production. Hence, we postulate that differences in production of metabolites such as ethanol, acetic acid and succinic acid by the yeast during dough fermentation might influence dough extensibility, and therefore affect the gas holding capacity of fermenting dough.

کلیدواژه ها:

Saccharomyces Cerevisiae ، Diauxic Shift ، Fermentation Parameter