Dehydration

Dehydration is another term for drying: the removal of water from foods by heat, moving air or other means. It ranks among humanity’s oldest preservation methods, because lowering water activity below microbial growth thresholds makes foods shelf-stable without refrigeration while concentrating flavour. Today’s plants use hot-air tunnels, freeze dryers, spray dryers and vacuum chambers, each matched to the product. Skilful control of temperature and humidity through the process protects colour, texture and vitamins in the finished dried food. Rehydration behaviour is also tested, since consumers judge dried foods by how well they plump back.