Physicochemical and fermentation properties of pre-fermented frozen dough: Comparative study of frozen storage and freeze–thaw cycles

This study compared the deterioration of pre-fermented frozen dough in 1–90 days frozen storage (FS) and 1–4 times of freeze–thaw cycles (FT) by analysing the characteristics of steamed bread, its dynamic rheology and rheofermentation properties, gluten aggregation, yeast viability, cell microstructure and yeast metabolites. The results showed that the specific volume and hardness of steamed bread after 25 days of FS and 1 FT were unacceptable. The decrease in the elasticity modulus and the increase in the viscosity modulus caused by FT were more obvious than those caused by FS. The rheofermentation results indicated that both FS and FT decreased the gas retention and gas production ability, but more significant negative effect was observed during FT than during FS. Further investigation of the gluten aggregation showed that the glutenin macropolymer decreased during FS and FT whether yeast was added or not to the dough, and the yeast increased the decline rate from 0.24 to 0.52 when FT was conducted, which indicated that the yeast had a negative effect on gluten aggregation. The yeast viability and microstructure showed no significant difference during FS and FT, whereas the yeast metabolites results demonstrated that the glucose and fructose contents increased during FS but decreased during FT, which indicate a difference in yeast metabolism. Fructose and glucose could be the indicators of the difference in the deterioration mechanism of FS and FT based on the factor analyses. This study provided novel insights on the deterioration mechanism of pre-fermented frozen dough.