Experimental and Simulation Study on Freezing Process of Trepang

海参因其较高的食疗和药用价值得到消费者的广泛认可，即食海参作为食用方便的深加工海参制品具有很高的经济价值和广阔的市场前景。然而其在运输，冻藏过程中易发生自溶现象造成品质严重劣变。因此研究其冻结过程对于优化冻结工艺，提高产品品质，减少能耗有重要意义。本文建立海参冻结过程数值模型，考虑了海参的多孔介质基体，采用变物性参数与等效比热容法预测冻结过程中温度场与水分含量的变化。结果表明：海参中心温度的模拟与实验值的均方差和为1.24，冻结时间的相对误差为4.35%，冻结速率的相对误差为7.06%，冻结后平均含水率相对误差为0.75%，说明数值模型与计算方法合理。随后讨论了海参冻结品质的工艺参数(冷冻环境温度，表面传热系数)的优化，筛选得到优选工艺参数区间为(−40℃, 58.35 W/(m2∙℃)~−26℃, 108.35 W/(m2∙℃))，此时海参能在30 min内通过最大冰晶生成带的同时具有大于50 mm/h的冻结速率。Trepang is widely recognized by consumers for its high therapeutic and medicinal value, and instant trepang as a convenient and deep-processed trepang product has high economic value and broad market prospect. However, it is prone to autolysis during the transportation and freezing process, causing serious quality deterioration. Therefore, it is important to study the freezing process to optimize the freezing process, improve the product quality and reduce energy consumption. In this paper, we establish a numerical model of the freezing process of trepang, consider the porous medium matrix of trepang, and predict the changes of temperature field and moisture content during the freezing process by using variable physical parameters and equivalent specific heat capacity method. Experimental validation showed that the mean sum of squared differences between the simulated and experimental values of trepang central temperature was 1.24, the relative error of freezing time was 4.35%, the relative error of freezing rate was 7.06%, and the relative error of average moisture content after freezing was 0.75%, indicating that the numerical model matched the calculation method. The optimization of the process parameters (freezing environment temperature, surface heat transfer coefficient) for the freezing quality of trepangs was then discussed, and the preferred process parameters were selected in the range of (−40˚C, 58.35 W/(m2∙˚C) to −26˚C, 108.35 W/(m2∙˚C)), when the trepangs could pass the maximum ice crystal generation zone within 30 min and had a freezing rate of more than 50 mm/h.