ABSTRACT
Infrared (IR) radiation is one of the oldest ways to heat-treat foods. A traditional drying method for food products by exposure to intensive sunlight, it was aimed at reducing water activity and allowing longer periods of storage with minimal packaging requirements. It is known that IR radiation has some advantages over convective heating. Heat transfer coefficients are high, the process time is short, and the cost of energy is low. Since air is transparent to IR radiation, the process can be done at ambient air temperature. Equipment can be compact and automated with a high degree of control over process parameters (Nowak and Lewicki, 2004). Similar to other electromagnetic waves such as microwaves and radio frequencies, IR rays attain their unique radiative characteristics. Two key radiative aspects of interest for designing the IR heater are its spectral distribution and energy intensity. The spectral region of IR radiation can be controlled by the use of appropriate optical filters and the surface temperature of its heating elements. According to Jun and Irudayaraj (2004), the differential energy absorption of protein among several key components in the food complex can be found when the IR ray emits light in the narrow spectral region between 6 and 11 μm. Also, the radiation properties of food materials vary with decreasing water content; consequently, its reflectivity increases and the
1.1 Introduction ......................................................................................................1 1.2 Basic Laws of Radiative Heat Transfer .............................................................2
