Charoenrein S, Reid D S
Department of Food Science and Technology, University of California, Davis 95616.
Adv Exp Med Biol. 1991;302:687-701. doi: 10.1007/978-1-4899-0664-9_38.
Quality changes in food frozen by different conditions and at different storage temperatures were demonstrated using a model system. A frozen starch gel represents a frozen food matrix, and ions in the external medium represent the reactant molecules. We determined the effective diffusion rates of Zn+2 ions into frozen starch gel cylinders that were frozen at different freezing rates. The diffusion was performed at -8 degrees and -15 degrees C. The amounts of ion diffused were determined by atomic absorption, whilst the structure of the frozen samples could be simultaneously determined by scanning electron microscopy. The effective diffusion rates were found to correlate with the amount of unfrozen portion of the samples. This suggests that ions move mainly through the unfrozen portion around the ice crystals. Fast- and slow-frozen samples exhibited significantly different effective diffusion rates at -15 degrees C, which might be due to differences in size and orientation of ice crystals. Zn+2 ions moved slower at -15 degrees C than at -8 degrees C.
使用一个模型系统展示了在不同条件和不同储存温度下冷冻食品的质量变化。冷冻淀粉凝胶代表冷冻食品基质，外部介质中的离子代表反应物分子。我们测定了Zn+2离子向以不同冷冻速率冷冻的冷冻淀粉凝胶圆柱体中的有效扩散速率。扩散在-8℃和-15℃下进行。通过原子吸收测定扩散的离子量，同时通过扫描电子显微镜可以同时测定冷冻样品的结构。发现有效扩散速率与样品未冷冻部分的量相关。这表明离子主要通过冰晶周围的未冷冻部分移动。快速冷冻和缓慢冷冻的样品在-15℃下表现出显著不同的有效扩散速率，这可能是由于冰晶大小和取向的差异。Zn+2离子在-15℃下的移动速度比在-8℃下慢。
