Foam-mat drying is a dehydration method for liquid and semi-liquid foods in which a foaming agent — such as a protein, gum, or emulsifier — is whipped into the liquid to create a stable foam, which is then spread in a thin mat and dried with warm air. The foam structure gives a huge surface area, so water evaporates quickly at relatively low temperatures, protecting flavour, colour, and heat-sensitive nutrients. Once dry, the brittle foam sheet is milled into a free-flowing powder that reconstitutes easily in water. The technique is used for fruit juices, tomato paste, milk, and egg products, and it suits materials that are too sticky or heat-sensitive for spray drying. Careful control of foam stability and drying temperature is essential for a uniform product.