Enhancing the freezing-thawing tolerance of frozen dough using ε-poly-L-lysine treated yeast

This study aimed to explore the effectiveness and mechanisms of enhancing the freezing-thawing (F/T) tolerance of frozen dough using epsilon-poly-L-lysine (epsilon-PL) treated industrial yeast. The specific volume, hardness and internal texture changes in steamed bread that added with the epsilon-PL treated yeast after 1-4 times of F/T cycles were investigated. In addition, the growth curves, intracellular trehalose and CO2 production of epsilon-PL treated yeast were further detected. Meanwhile, the protein network of dough was evaluated after F/T cycles. As a result, porous crumb steamed bread with large specific volume and soft texture were obtained in epsilon-PL treated groups (0.1, 0.3 and 0.6 mg/mL) after 4 times of F/T cycles, but the opposite results occurred in the excessive epsilon-PL treated group (0.9 mg/mL) and untreated (0 mg/mL) group. epsilon-PL treated yeast had a longer lag phase and log growth phase, together with higher intracellular trehalose compared with untreated yeast. After F/T cycles, compared with the untreated group, the decrease rates of CO2 production and glutenin macropolymer (GMP) content in epsilon-PL treated groups were lower. Meanwhile, the protein network was more integrity. This study can provide valuable insights into the relationship between epsilon-PL treated yeast and the quality of steamed bread made by frozen dough.