Figure 5.

Fermentation abilities of baker's yeast strains in doughs after baking-associated stress treatments. (a) Fermentation ability after air-drying stress. After exposure to 42°C for 90 min, baker's yeast strains (WT, PRO1-I150T/MPR1-F65L, and PRO1-I150T/MPR1-F65L/Δput1) were mixed with dough and fermented. The remaining CO₂ gas production after 2 h was measured. The gassing power of WT strain is relatively taken as 100%. The values are the means and standard deviations of results from three independent experiments. Significant difference of PRO1-I150T/MPR1-F65L from WT was confirmed by Student's t test (P < 0.005). (b) Fermentation ability after freeze-thaw stress. The doughs were prefermented for 2 h at 30°C and then frozen at -20°C for 3 weeks. The frozen dough was thawed for 30 min at 30°C, and the remaining CO₂ gas production after 2 h was measured. The gassing power before freezing of each strain was defined as 100%. The values are the means and standard deviations of results from three independent experiments. Significant difference of PRO1-I150T/MPR1-F65L from WT was confirmed by Student's t test (P < 0.05).