小米挤压膨化产品的吸湿动力学研究

Research on moisture absorption kinetics of millet extruded products

挤压膨化食品极易从周围环境中吸收水分,导致脆性丧失;对吸湿动力学过程的了解有助于选定合适的包装材料和存储环境。将4种形态的小米挤压膨化产品在不同温度、相对湿度下吸湿,并对吸湿过程进行模拟分析。与扩散模型、Peleg模型相比,Weibull模型最能预测小米挤压膨化产品的吸湿行为。根据Weibull模型,同一温度下,初始吸湿速率随相对湿度增大而近似线性增大。同一相对湿度下,总体吸湿速率随温度升高呈近似线性增大。温度越低、相对湿度越高,平衡水分越高。不同样品间的平衡水分差异较小,而吸湿速度差异明显,尤其在低温—低相对湿度条件时。外层气孔结构的差异可能是样品间初始吸湿速率差异的主要原因。

Extruded-puffed foods absorb moisture extremely easily from environment to cause losing their unique texture characteristic of crispness.The knowledge of the moisture absorption kinetics can help to select proper package materials and storage conditions.Four kinds shape of millet extruded-puffed foods were allowed to absorb moisture from air with different relative humidity levels at different temperatures,and the processes were simulated.Compared with the Peleg and diffusion models,the Weibull model was more suitable for predicting water absorption behavior of millet extruded-puffed foods.At the same temperature,the initial water-absorbing rate approximately linearly increased with the relative humidity of air.At the same relative humidity,the general water-absorbing rate approximately linearly increased with temperature.The lower the temperature was,the higher the relative humidity and equilibrium moisture were.There were little differences in equilibrium moisture between the four samples,while significant differences in water-absorbing rates especially at lower temperature combined with lower relative humidity.The different external layer with pore structure of each sample were possibly the main reason of the various initial water-absorbing rates