Drying and Freeze-drying
Food dehydration and preservation methods
Dehydration is one of the oldest and most effective preservation methods. It removes water (to below 20%, ideally 10-15%), stopping bacteria, mold, and yeast. Properly dried foods can last for years without losing nutrition.
Benefits of dehydration
- • Weight reduction by 70-90% (saves space and eases transport)
- • Retains most nutrients (B vitamins, minerals, fiber)
- • Long shelf life without preservatives (1-10 years depending on product)
- • No need for refrigeration
Drying methods
1. Sun drying
Traditional method, needs hot and dry climate (30-35°C, humidity < 60%). Time: 2-4 days. Best for sugary fruits (apricots, plums, grapes).
2. Electric dehydrators
Most controlled method. Temperature 50-70°C, time 4-24 hours. Provides even drying and temperature control.
3. Oven drying
Accessible but less efficient. Temperature 50-60°C, oven door cracked. Risk of uneven drying or overdrying.
Optimal drying temperatures
- • Herbs: 35-40°C (keep essential oils)
- • Vegetables: 50-55°C
- • Fruits: 55-60°C
- • Meat (dried, not smoked): 65-70°C (food safety)
Preparing food
- • Wash and dry thoroughly
- • Slice evenly (3-6 mm) for even drying
- • Blanch vegetables (1-3 minutes) to preserve color and vitamins
- • Soak fruits in ascorbic acid solution to prevent browning
Storing dried foods
- • Cool completely before packing (avoid condensation)
- • Pack airtight: vacuum bags, jars with gasket
- • Add oxygen absorbers for high-fat foods
- • Store in dark, cool (<20°C), dry place
Rehydration
Most foods need soaking before eating: vegetables 20-60 min in warm water, fruits 30-120 min. Dried meat can be eaten without rehydration (jerky-style).