Impact of Flour Protein Content and Freezing Conditions on the Quality of Frozen Dough and Corresponding Steamed Bread

Abstract

Frozen dough made using flour of higher protein content (9.5–11 %) had better resistance to freezing damage than those made using flour of lower protein content and resulted in steamed bread whose specific volume, form ratio and texture were closer to those of bread made from fresh dough. The effects of flour protein content and freezing conditions (freezing air temperature and air speed) on dough and steamed bread quality were investigated in this study. Compared to nonfrozen control, the freezing process caused a deterioration to gluten network as well as a decrease in yeast activity, which resulted in lower maximum dough height and less total gas production, leading to steamed bread of lower specific volume and form ratios, and increased hardness. Faster freezing rates resulted in dough with higher extensibility and a less damaged dough microstructure but led to a decrease in total gas production as yeast activity was compromised. The extreme freezing conditions of −20 °C and air speed of 0 m/s and −40 °C and air speed of 6 m/s had the poorest dough and steamed bread quality. Samples frozen at −30 °C had better form ratio of steamed bread than those frozen at −20 °C and −40 °C, while those frozen at −40 °C had the lowest specific volume. A moderate air speed of 3 m/s resulted in higher volume of total gas production and dough height, as well as better steamed bread texture.