Heat Pump Dehydrator

Working Principle

A heat pump dehydrator is an electrical device that extracts heat from one place and transfers it to another. A compressor pumps the refrigerant between two heat exchanger coils. In one coil, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings.

Dehydration process

Dehydration means the process of removing moisture by the application of artificial heat under controlled conditions of temperature, humidity, and air flow. Dehydration is a complex mechanism as it involves the simultaneous exchange of moisture and heat. The relationship between the moisture content and temperature of the air during the drying process is referred to as the 'psychometric' relation.

Drying or dehydration removes biologically active water, thus stopping the growth of microorganisms. This also results in a reduced rate of enzyme activity and chemical reactions. The processing should be done in such a way that the food value, natural flavor, and characteristic cooking quality of the fresh material are retained after drying. Fruits are considered to be dry when they show no sign of moisture or stickiness when held firmly in the hands. Vegetables is considered to be dry when they become brittle. The residual moisture in the vegetables should not be more than 6 to 8 percent, and in fruits, 10 to 20 percent.