关键词: 动力学, 解吸等温线, 水分, 模型, 低场核磁共振

Abstract:

The aim of this study was to determine moisture migration and desorption isotherm models for battered and fried
pork slices. The experimental data were applied for nonlinear regression analysis carried out by the least square method, and
the fitting coefficient R2 was evaluated. The results showed that moisture diffusion during 0–4 h of storage was given priority
to the surface evaporation at 0–40 ℃, while moisture transfer was mainly through internal exchange later. Temperature and
moisture loss rate were positively correlated with each other, and moisture loss rate was slowed down after the fourth hour
of storage. The desorption isotherm model displayed an S-type curve and belonged to type II isotherm. The equilibrium
moisture 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 was
shown that the main moisture loss was derived from free water during the first 4 h storage. No obvious changes in t22 or t23
were found. Moisture loss was mainly due to surface diffusion, while moisture mass transfer was mainly through internal
exchange from the fourth hour of storage onwards. The dynamic changes of moisture migration was influenced by temperature
more significant (P < 0.05). When temperature increased from 30 to 40 ℃, t22 decreased and P23 significantly increased, indicating
that immobile water is converted to free water and that the main moisture loss is derived from immobile water.

Key words: kinetics, desorption isotherms, moisture content, model, low-field nuclear magnetic resonance (LF-NMR)