食品速冻保鲜过程冰晶生长的相场模拟

针对食品速冻保鲜工艺因大冰晶破坏细胞结构造成品质下降的问题,将细胞溶液视为水和溶质二元系统,采用五重对称强界面能各向异性相场模型,再现冰晶生长演化过程,探讨了冷冻时间对冰晶生长行为的影响。结果表明:冰晶生长模拟结果与实际形貌一致,两者主枝中部具有发达的侧向分支,主枝根部出现缩颈,主枝和侧枝尖端具有棱角。在主枝和侧枝之间扩散通道不畅通,形成半封闭液相区其溶质浓度达到1.76%,冰晶生长受到抑制。固液界面区域的无量纲温度在冰晶主枝根部变化平缓,而在尖端变化急剧。随着冷冻时间延长,无量纲温度和溶质浓度先快速增加后逐渐趋于稳定,尖端生长速率和曲率半径先急剧减小后逐渐趋于稳定,冰晶从初期近似五边形经过5主枝结构向五重对称多分支小平面结构转变。

Phase-field simulation of ice crystal growth on foodquick-freezing preservation process

In view of the reduction of food quality due to the destructs cellular structure by the large ice crystals in quick-freezing preservation process, regarding cell solution as water and solute in binary system, the five-fold symmetric phase-field model with anisotropy of strong interface energy was used to reproducing the evolution process of ice crystal growth, the effect of freezing times on the behavior of ice crystal growth was studied. The results showed that simulation result of ice crystal growth were consistent with the actual morphology, both of which had developed side-branching in the middle of the main branch, the root of the main branch was necked, and the corners were formed at the tips of them. The diffusion channel between the main branch and the side-branch was not smooth, and the solute concentration in the semi-enclosed liquid phase reached 1.76%, the growth of ice crystals was inhibited. The dimensionless temperature of solid liquid interface in the root of the ice crystal main branch changed gently, but changed sharply in the tip. As the freezing time increased, the dimensionless temperature and solute concentration first rapid increased then gradually became stable, and the tip growth rate and curvature radius sharply decreased and then gradually became stable. The ice crystal changed from the initial approximate pentagonal structure through the 5 main stem structure to the five-fold symmetric multi-branch faceted structure.