VIS-NIR radiation properties of starchy and protein foods and their impacts on radiant heating effects

Infrared heating has been widely used in food processing; however, there are few studies on the VIS-NIR radiation properties of food. We measured the radiation properties of starchy foods (potato, Chinese yam and sweet potato) and protein foods (beef tenderloin, pork tenderloin and chicken breast) and dispersions of starches and proteins before and after heat treatment in the 0.38–2.5 μm band. The results show that the radiation penetration depths (RPDs) of all tested foods are relatively high in the 0.6–1.3 μm band, with maximum values in the range of 4–8 mm. After heat treatment, the RPDs of starchy foods slightly increase, while those of protein foods decrease to approximately 1/2 of the original values. Comparative heating experiments of potato, Chinese yam and sweet potato heated by a halogen lamp (1.04 μm) and a carbon fiber lamp (1.76 μm) with peak wavelengths in and out of the 0.6–1.3 μm band, respectively, show that the foods heated by the halogen lamp have faster heating rates and more uniform temperature distributions. Because starchy and protein foods have high RPDs in the 0.6–1.3 μm band, the VIS-NIR radiation containing this band is expected to achieve rapid heating.