Impacts of selected infrared wavelength treatments on the pasting properties and discoloration of Rice

Abstract

This study sought to understand the effects of selected IR wavelength, including tempering, on rice pasting properties and discoloration. Rough rice was treated with different IR heat intensities (from 0.73 to 15.71 kW/m2), generated at different wavelengths (3.2, 4.5, and 5.8 μm), for 10, 20, and 30 s. For tempering, IR-treated samples were tempered at 60oC for 4 h. After the IR treatment, the samples pasting properties and color were determined. Treatment at the highest IR heat intensity (15.71 kW/m2) and heating duration (30 s) reduced the peak viscosity of rice from 2511.67 to 1998.33 centipoise (cP); reduced final viscosity from 2902 to 2592.5 cP. However, this treatment combination did not cause rice discoloration. After tempering was added, rice treated at IR heat intensity of 15.71 and 10.08 kW/m2 for 30 s had lower peak, final, and breakdown viscosities; higher yellowness, and lower whiteness when compared with untreated sample (control). Novelty Impact Statement The outcome of this study provides a strong understanding of how different IR heat intensities generated at different wavelengths affect the pasting properties and color of rice. These two properties are strong indicators of rice quality and hence, are of great economic importance to the rice industry. The selected IR wavelength technology can easily be scaled up and employed by rice processing industry to produce safe and high-quality rice.