1. 6.2 Food Drying
1.1. low H2O, low Aw
1.2. Traditional
1.2.1. Sun drying
1.2.1.1. Require large space, easy to contaminate
1.2.2. Smoking
1.2.3. Wind drying
1.3. Commercial
1.3.1. Freeze drying
1.3.1.1. Performed by
1.3.1.1.1. pre-treatment (blanching, pre-cooking)
1.3.1.1.2. quick freezing
1.3.1.1.3. reduce pressure
1.3.1.1.4. sublimation
1.3.2. Hot air drying
1.3.2.1. High temperature, faster diffusion of H2O
1.3.2.2. crust formation/case hardening
1.3.3. Hot vacuum drying
1.3.3.1. used for hygroscopic and heat sensitive food
1.3.3.2. supplied by conduction/radiation
2. 6.1 Introduction
2.1. Low moisture content, reduce food spoilage
2.2. Inhibit the m/o growth
2.3. Preserve the food- DRYING
2.4. Types of food
2.4.1. Normal
2.4.1.1. MC:>50%, Aw:>0.85, eg: milk,juices
2.4.2. Intermediate (IM)
2.4.2.1. MC: 15-50%, Aw:0.6-0.85, eg: dried fruits, jams
2.4.3. Low(LM)
2.4.3.1. MC:<15%, Aw:<0.6, eg: crackers, keropok
2.5. Humectants: hygroscopic-able to attract water
2.6. Absorption: Permeation of H2O into the matter
2.7. Adsorption: Adhesion of H2O onto the suraface
3. 6.3 Food Concentrating
3.1. adding solute (low Aw)
3.1.1. salt
3.1.1.1. osmosis
3.1.2. sugar
3.1.2.1. water binding
3.2. Fish salting
3.2.1. high [salt]-kill most m/o (cellular dehydration)