Food dehydration

Food dehydration removes water from food to change its texture or slow spoilage. It can use heat, airflow, sunlight, or reduced pressure.

Water activity: A measure of water available in a material for microbial growth and chemical reactions. Dehydration extends storage life chiefly by lowering water activity, not simply by reducing total water.
Sun drying: A preservation method that dries food through exposure to sunlight and ambient air. It is a low-cost method for drying suitable foods in hot, dry climates.
Food preservation: Methods that slow spoilage and extend the usable life of food. Dehydration is one preservation method among several ways to control spoilage.
Canning: Food preservation by sealing food in containers and applying heat to destroy spoilage organisms. Unlike dehydration, canning preserves food in a moist state inside a sealed container.
Osmosis: The movement of water through a selectively permeable membrane from lower solute concentration toward higher solute concentration. Salting and sugaring draw water from food cells through osmotic movement.
Freeze-drying: A dehydration process that freezes food and removes ice by sublimation under reduced pressure. It preserves porous structure and often rehydrates better than heat-dried food.
Food spoilage: The deterioration of food that makes it undesirable or unsafe to eat. Drying targets moisture-dependent deterioration but cannot prevent every cause of spoilage.
Freezing: Food preservation by lowering temperature until water freezes and microbial activity slows. Freezing limits spoilage without removing water from the food.
Maillard reaction: A set of reactions between reducing sugars and amino compounds that browns food during heating. Heat and reduced moisture can promote browning and flavor changes during drying.
Spray drying: A process that turns liquid feed into dry powder by spraying it into hot gas. It produces powders from foods such as milk, coffee, and fruit juices.

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