Review on low-temperature heat pump drying applications in food industry: Cooling with dehumidification drying method

Moisture content of food material is a key factor influencing the quality of storage and extending the quality of a food product. Manufacturers develop new technologies to process sensitive food materials to supply new products with improved properties and high quality. The process in which the air is cooled sensibly while the moisture is removed from food is called cooling with dehumidification process. The system fundamentally acts as a heat pump, which pumps the heat from the dehumidified air to a different air stream in another area, with the aid of a refrigerant gas to carry the heat. This article reviews the potential of low-temperature heat pump dehumidifier drying used in the food industry. Moreover, this describes the principle of cooling with dehumidification (CWD) process, the importance of studying psychrometric charts to understand CWD process, measures used in identify energy efficiency, comparison of this method over common dryers, applications, advantages and limitations of the CWD drying method. Practical applications: Multiple measures have been taken to increase the drying efficiency of convection drying, especially by the application of cooling with dehumidified techniques. This drying technique has comparably higher energy efficiency, better and consistent product quality and the ability to control drying temperature and humidity over other conventional methods. Low-temperature heat pump dryers are used increasingly applications in the food industry for the drying of grains, fruits, vegetables, herbs, spices, fish, meat, pet foods, and other heat-sensitive food products in several countries.