Zhang Luo, Yang Wei, Xu Kai, Long Linshuang, Ye Hong
Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei 230027, China.
Foods. 2025 May 7;14(9):1649. doi: 10.3390/foods14091649.
Moisture phase change (MPC), a key process in bread baking, significantly impacts heat and mass transfer, as confirmed by experiments. However, existing models poorly characterize this phenomenon, and its quantitative impact on baking needs systematic study. This research develops a coupled multiphase model for heat and mass transfer with large deformation, employing both equilibrium and nonequilibrium approaches to describe MPC in closed and open pores, respectively. Experimentally calibrated pore-opening functions and viscosity variations revealed that pore-opening primarily occurs at 71-81 °C, whereas dough solidification occurs at 50-110 °C. Model-based analysis indicates that in closed pores, evaporation-diffusion-condensation is the primary mode of moisture transport and heat transfer with contributing approximately 60% of the total effective thermal conductivity, and when pores open, water vapor evaporates or condenses on pore walls, forming an 'evaporation front' and 'condensation front'. The content of liquid water increases at the 'condensation front' and decreases at the 'evaporation front'. Bread deformation is predominantly governed by pressure differentials between closed pores and the ambient environment, with the partial pressure of water vapor emerging as the principal driver because its average content exceeds 70% within closed pores. These findings demonstrate that MPC governs heat and mass transfer and deformation during bread baking.
水分相变（MPC）是面包烘焙中的一个关键过程，实验证实它对传热传质有显著影响。然而，现有模型对这一现象的描述欠佳，其对烘焙的定量影响需要系统研究。本研究开发了一个用于大变形传热传质的耦合多相模型，分别采用平衡和非平衡方法来描述封闭孔隙和开放孔隙中的MPC。通过实验校准的孔隙开口函数和粘度变化表明，孔隙开口主要发生在71-81°C，而面团固化发生在50-110°C。基于模型的分析表明，在封闭孔隙中，蒸发-扩散-冷凝是水分传输和传热的主要模式，约占总有效热导率的60%，当孔隙打开时，水蒸气在孔隙壁上蒸发或冷凝，形成“蒸发前沿”和“冷凝前沿”。液态水含量在“冷凝前沿”增加，在“蒸发前沿”减少。面包变形主要受封闭孔隙与周围环境之间的压力差控制，水蒸气分压成为主要驱动力，因为其在封闭孔隙中的平均含量超过70%。这些发现表明，MPC控制着面包烘焙过程中的传热传质和变形。
