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Study on the Transport Phenomena and Quality Determination of Agiricultural Products Based on Noueguilibrium Thermodynamics

基于新平衡热力学的农产品输运现象及品质判定研究

基本信息

批准号：
04806035
负责人：
KAMEOKA Takaharu
金额：
$ 1.15万
依托单位：
Mie University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

The attempt at a statistical treatment of water sorption by foods of low moisturre content was made, based on the approximate method for deriving the Dubinin-Astakhov (DA) equation from Weibull distribution function of adsorption energies. A modified DA equation suitable for foods was also derived by changing the meaning of the three parameters theoretically. A new expression of equilibrium moisture content equation for rice was shown by the use of modified DA equation.Interactions between water and saccharide in food are very important. The Water activity cefficient in saccharide-water systems was measured by freesing point depression. Glucose-water systems were used, being ideal solutions. Freezing point depression in these systems was proportional to mole fraction and the accuracy of the experimental data was confirmed. Maltose-water systems behaved as ideal solutions. For tow systems, water activity coefficient decreased from 1.0 at mole fractions above 0.02 in sucrose-water systems.Sorption data of crystalline saccharides and a corn starch were obtained using static method at 10 ﾟC.Each crystalline saccharide sorbed a negligible amount of water at water activity below each saturation point. Amorphous data of sucrose were on the smooth curve expolarated by the sucrose-water solution curve. DA equation showed good agreement with the amorphous data in the range of water activity from 0 to saturation point. As a result, it was shown that DA equation is also applied successfully to the non-porous foods.Based on the above-mentioned water sorption of highly moistened food and nonequilibrium thermodynamics, an equation was derived for the water movement coefficient in vegetable. the quality of vegetable was discussed by the friction coefficient inside this equation. A modefied Arrhenius-type equation was also derived for the diffusivity of water in low moistened food. the activation energy was expressed as a function of temperature and moisture content.

基于由吸附能的威布尔分布函数推导Dubininin-Astakhov（DA）方程的近似方法，尝试对低水分食品的吸水性进行统计处理。通过改变这三个参数的意义，从理论上推导出适用于食品的DA方程。利用修正的DA方程给出了大米平衡含水率方程的一个新的表达式。用自由点下降法测定了糖-水体系的水活度系数。使用葡萄糖-水系统，这是理想的溶液。在这些系统中的凝固点下降成正比的摩尔分数和实验数据的准确性得到了证实。麦芽糖-水体系表现为理想溶液。在蔗糖-水体系中，当摩尔分数大于0.02时，水活度系数从1.0开始下降，结晶糖和玉米淀粉在10 ℃下的吸附数据用静态法得到，在水活度低于饱和点时，每种结晶糖吸附的水可以忽略不计。蔗糖的无定形数据在蔗糖-水溶液曲线拟合的光滑曲线上。在水活度从0到饱和点的范围内，DA方程与无定形数据吻合较好。结果表明，DA方程同样适用于非多孔性食品，根据上述高湿食品的吸水性和非平衡热力学，导出了蔬菜水分运动系数的计算公式。用该方程中的摩擦系数讨论了蔬菜的品质。本文还导出了一个修正的Arkenius型方程，用于描述水分在低湿食品中的扩散系数。活化能表示为温度和水分含量的函数。