文档介绍：Chapter 6 Drying of fruits and vegetables
Introduction
drying干燥或dehydration脱水, The term dehydration has taken the meaning in the food industry as that process of artificial drying.
Definition
一、Principle of drying
(一)水分的external diffusing外扩散作用
At the beginning, surface water of fruits and vegetables was vaporized.
(二) internal diffusing内扩散作用
Because of humidity grads, water and vapor existed the interior were moved out.
The first section Principle of drying and changes of drying products
二、Process of drying果蔬的干燥过程
1、constant drying phase恒速干燥阶段
2、 decelerating drying phase降速干燥阶段
在两个阶段交界点的水分称为critical water临界水分
The first section Principle of drying and changes of drying products
三、Dry substances of fruits and vegetables果蔬中的干物质
1. soluble substances可溶性物质
anic acid有机酸、pectin果胶、tannin单宁、enzyme酶、some matter containing nitrogen含氮物质、water-soluble vitamin部分水溶性维生素、part pigments部分色素和some anic salt无机盐类等。
2. indissolvable substances 不溶性物质
不溶性物质在果蔬中组成了固形物,这些包括cellulose纤维素、hemi-cellulose半纤维素、original pectin原果胶、starch淀粉、不溶于水的含氮物质,某些pigments色素、fat脂肪、fat-soluble vitamin部分脂溶性维生素。
The first section Principle of drying and changes of drying products
四、factors affecting drying影响干燥的因子
of medium 干燥介质的温度
2. humidity of medium干燥介质的湿度
speed风速
4. kinds and condition of fruits and vegetables果蔬的种类和状态
5. Thickness of material原料的厚度
The first section Principle of drying and changes of drying products
五、Changes of drying products果蔬在干燥过程中的变化
1. Reducing the volume and lightening the weight体积缩小、质量减轻。
2. Changes of color and lustre色泽变化
①Enzymic brown酶褐变
②non-enzymic brown非酶褐变
3. Changes of transparence透明度的改变
The first section Principle of drying and changes of drying products
4. Changes of nutrition营养成分的变化
①Changes of water水分的变化。果蔬在干制中水分大量蒸发。
②Changes of sugar糖分的变化
③Changes of vitamins维生素的变化
The first section Principle of drying and changes of drying products
5. Case hardening表面硬化
If the temperature of the air is high and the relative humidity of the air is low, th