油炸挂糊肉片在贮藏过程中水分的动态变化

Dynamic Moisture Change of Battered and Fried Pork Slices during Storage

采用最小二乘法进行非线性回归分析,通过对拟合系数R^2的评价分别确定贮藏过程中油炸挂糊肉片水分迁移及解吸等温模型。结果表明,在0~40℃时水分传质方式4 h前以表层蒸发为主,内部交换为辅,4 h后主要以内部交换为主。温度与水分散失速率正相关,4 h前为增速期。解吸等温线模型显示为S型属于Ⅱ型等温线。0~40℃水分活度相同时,平衡含水量受温度影响显著(P<0.05)。在动力学模型及解吸模型的基础上,利用低场核磁共振技术分析水分的动态变化。4 h前,水分散失的主要部分为自由水,此时t_(22)、t_(23)变化较小,水分的散失形式为表层扩散。温度对水分迁移的动态变化影响更为显著(P<0.05),30~40℃时t_(22)减小,P_(23)增加明显,说明部分不易流动水向自由水转换,水分散失主要为不易流动水。

The aim of this study was to determine moisture migration and desorption isotherm models for battered and friedpork slices. The experimental data were applied for nonlinear regression analysis carried out by the least square method, andthe fitting coefficient R2 was evaluated. The results showed that moisture diffusion during 0–4 h of storage was given priorityto the surface evaporation at 0–40 ℃, while moisture transfer was mainly through internal exchange later. Temperature andmoisture loss rate were positively correlated with each other, and moisture loss rate was slowed down after the fourth hourof storage. The desorption isotherm model displayed an S-type curve and belonged to type II isotherm. The equilibriummoisture content was significantly affected by temperature in the range of 0–40 ℃ at the same water activity （P 〈 0.05）.Furthermore, the dynamic moisture changes were assessed by low-field nuclear magnetic resonance （LF-NMR）. It wasshown that the main moisture loss was derived from free water during the first 4 h storage. No obvious changes in t22 or t23were found. Moisture loss was mainly due to surface diffusion, while moisture mass transfer was mainly through internalexchange from the fourth hour of storage onwards. The dynamic changes of moisture migration was influenced by temperaturemore significant （P 〈 0.05）. When temperature increased from 30 to 40 ℃, t22 decreased and P23 significantly increased, indicatingthat immobile water is converted to free water and that the main moisture loss is derived from immobile water.