Infrared radiation for food processing

Energy conservation is one of the key factors determining pro tability and success of any unit operation. Heat transfer occurs through one of three methods, conduction, convection, and radiation. Foods and biological materials are heated primarily to extend their shelf life or to enhance taste. In conventional heating, which is achieved by combustion of fuels or by an electric resistive heater, heat is generated outside of the object to be heated and is conveyed to the material by convection of hot air or by thermal conduction. By exposing an object to infrared (IR) radiation (wavelength of 0.78-1000 µm), the heat energy generated can be directly absorbed by food materials. Along with microwave, radiofrequency (RF), and induction, IR radiation transfers thermal energy in the form of electromagnetic (EM) waves and encompasses that portion of the EM spectrum that borders on visible light and microwaves (Figure 5.1). Certain characteristics of IR heating such as ef ciency, wavelength, and re ectivity set it apart from and make it more effective for some applications than others. IR heating is also gaining popularity because of its higher thermal ef ciency and fast heating rate/response time in comparison to conventional heating. Recently, IR radiation has been widely applied to various thermal processing operations in the food industry such as dehydration, frying, and pasteurization [1].