30D-15 |
Optical properties of food under near and mid-infrared |
M. F. ALMEIDA, Food Science, Cornell University, 175 Riley Robb Hall, Ithaca, NY 14853 and A. K. Datta. As faster and efficient heating mechanisms of food are always being investigated, near and mid-infrared are good alternatives for faster heating of foods. Although they have the advantages of easy control, reduced equipment space and instant on and off, food processing has not benefited from infrared heating mainly due to the lack of information about infrared absorption and penetration properties in food. The objective of this study is to measure optical properties of potato slices under irradiation of two different infrared sources over a range of wavelength of the near and mid-infrared and a range of moisture content of potato. Samples with different thickness, from 0.2 mm to 2 cm, are placed in a spectroradiometer comprised of infrared source, monochromator, integrating sphere and detectors. They are weighted before and after the measurements and their moisture content is determined. The spectral dependence of the reflection and transmission properties is measured in the wavelength range of 700-2500 nm. Dependence of the properties on moisture content is also measured. From transmission measurements for different thickness, penetration depth is calculated. Results showed that there is greater penetration of near-infrared radiation for the halogen lamp irradiation compared with the ceramic rod, all in the range below 1500 nm. The penetration depth is comparable to microwave penetration depth for potato (3 mm). Reflection of infrared from surface decreased with moisture content that can be explained by the reduced scattering of radiation. As moisture content is reduced, transmission of infrared decreases reaching a minimum after which it increases. These findings will help the food processing industry to use near-infrared as a heating source either by itself or as a complement to other heating modes, such as microwave or convective heating.
Session 30D, Food Engineering: Physical and chemical properties
|