油茶籽的吸附等温线及热力学性质

Adsorption isotherms and thermodynamic properties of camellia oleiferaseeds

为充分了解油茶籽水分含量与水分活度、温度之间的复杂关系,运用吸附原理,通过静态调整环境湿度法,研究了油茶籽不同温度下的吸附等温线,选择5种常用数学模型进行拟合,并在此基础上分析油茶籽的热力学性质.结果表明,修正Henderson模型的拟合度最高(R2=0.999 9,RMSE=0.007 1),根据该模型获知油茶籽在20,30,40℃下的相对安全水分含量和绝对安全水分含量分别为9.48%与8.00%,8.96%与7.57%,8.51%与7.19%.热力学性质显示,油茶籽的等量吸附热、吸附结合能均随平衡含水率的增加而不断下降,当平衡含水率一定时,吸附结合能随温度的升高而增大.

In order to reveal the complex relationships among the moisture content,the water activity and the temperature of camellia oleiferaseeds,and to provide fundamental data for storage and processing,the adsorption isotherms of camellia oleiferaseeds at different temperatures were determined by statically adjusting the ambient humidity based on the adsorption theory.The obtained isotherms were fitted to five commonly-used mathematical models.The thermodynamic properties of camellia oleiferaseeds were analyzed.The results indicate that the modified Henderson model is most suitable for fitting the isotherms（R2=0.999 9,RMSE=0.007 1）.The absolutely-safe and the relatively-safe storage moisture contents of camellia oleiferaseeds were calculated according to the fitted isotherm model,which reached to 9.48% and 8.00% at 20 ℃,8.96% and 7.57% at 30 ℃,8.51% and 7.19% at 40 ℃,respectively.The thermodynamic properties of camellia oleiferaseeds show that both the isosteric heat and the adsorbing energyof the seeds gradually decrease with the equilibrium moisture content,and the adsorbing energy increases with the temperature at a constant equilibrium moisture content.