Respiration and viability of thermally injured Saccharomyces cerevisiae

Abstract

Resting cells of Saccharomyces cerevisiae Y25 were heated at 560C for 0 to 2 min. Respiratory activity of the cells reflected the severity of the heat stress. The endogenous respiration was approximately 50 IlI of 02/mg per h for cells heated for 2 min at 560C as compared with 2 ,ul of 02/mg per h for nonheated cells. There was a distinct decrease in respiration after 1 to 3 h, and after 20 h the respiration rate of heated cells was less than that of nonheated cells. Along with increased rates of endogenous respiration, respiratory quotients of cells were altered after heat stress. Addition of 2,4-dinitrophenol stimulated 02 uptake in nonheated cells but decreased 02 uptake of heated cells. Due to the high rate of endogenous respiration, addition of glucose resulted in no substantial change in the rate of respiration of heated cells. However, addition of glucose prolonged the presence of the high rates of respiration observed in heated cells. t Michigan State Agricultural Experiment Station journal article no. 8965.

Increased sensitivity of heat-stressed Saccharomyces cerevisiae cells to food-grade antioxidants

“…Experimental design did not permit conclusions to be drawn concerning the mechanism of action of antioxidants on injured and healthy cells. However, increased endogenous respiratory activity of heat-injured S. cerevisiae cells, indicating a requirement for increased energy during repair, has been reported by Graumlich and Stevenson (11). In their study, glucose was shown to increase the total oxygen uptake of heat-stressed cells in comparison with unheated cells, and this increased oxygen consumption may have reflected utilization of added glucose to meet increased energy demands of damaged cells.…”

Strain-dependent assessment of dough’s polymer structure and functionality during the baking process

“…The maximum relative volume is then reached at 60°C and retained until the end of the baking process. The initial expansion can be explained by the CO 2 production of yeast cells till the death of yeast cells sets in at ~ 50°C [ 35 – 37 ]. During this initial baking phase, an expansion rate of 0.104 min -1 was determined by a linear model (relative volume–baking time), which is markedly higher compared to the gas production rate during the fermentation phase.…”