Abstract: Considering the different applications of freezing methods (commonly used in households, traditional industrial production, and research laboratories), three freezing methods were selected to freeze non-fermented dough, namely cryogenic refrigerator freezing (RF), spiral tunnel freezing (SF) and liquid nitrogen spray freezing (LF). This study compared the effects of the freezing methods on the various characteristics of non-fermented dough, including water state, texture characteristics, rheological characteristics and microstructure. The results showed that there were significant differences in the freezing rates of the three different freezing methods, showing a decreasing order of LF (1.33 ℃/min) > SF (0.31 ℃/min) > RF (0.08 ℃/min). Furthermore, with the decrease in freezing rate, the water loss rate after dough freezing showed an upward trend, the proportion of A21 (peak area of strongly bound water) and A22 (peak area of weakly bound water) showed a downward trend, and the texture quality and rheological properties of the thawed dough deteriorated. In particular, we observed an increase in hardness. The microstructural observation showed that as the freezing rate slowed down, the pores in dough became larger and the structural compactness became poorer. In conclusion, the quality of the thawed dough treated by LF was the closest to that of fresh dough, followed by SF and RF. Therefore, LF, an emerging technology to be developed, is superior to SF, while RF is not conducive to maintaining the quality of flour-based foods.

Key words: non-fermented dough; liquid nitrogen spray freezing; rheological properties; texture properties; microstructure