Fundamentals of Infrared Heating and Its Application in Drying of Food Materials: A Review

Drying is an energy-intensive unit operation in chemical, food and allied industries. It is always desired to have low energy consumption for drying operation without compromising the quality of products. In this review, fundamental aspects of infrared heating are described in detail with the focus on its application to the drying of food materials. The modeling techniques are explained in detail to get emphasis on the design of large-scale infrared dryers. This review also contains the investigations carried out by several researchers by experimentation and/or modeling to describe the infrared drying, infrared–convective drying, infrared–microwave drying and infrared–freeze drying. The present work describes the author's views regarding the capability and applicability of infrared source for drying of food materials. After going through a literature survey, it can be seen that infrared source especially in the far-IR range has been widely used in convective hot air dryer than other types of dryers. Practical Applications The energy loss in convective air drying is found to be very large in chemical and allied food industries. Air, the drying medium, needs to be heated using air heaters, which generally have low thermal efficiency. On the contrary, as the infrared radiation is recognized as surface heater, it can be very suitable for drying of food materials whose drying is generally carried out in thin slices. Moreover, use of infrared heaters in other dryers is very beneficial to lower the drying time without significantly affecting the quality of the final products. Lowering the drying time can increase the productivity and decrease the cost of operation practically.