Effect of starch multi-scale structure alteration on japonica rice flour functionality under infrared radiation drying and storage

Abstract

Infrared radiation drying (IRD) is a novel technique that can effectively dry paddy rice and well maintain the milling yield and storage qualities. The objective of this research was to investigate the mechanism of IRD to improve the qualities of stored rice from the aspect of starch multi-scale structure. The rice flour functionality and multi-scale structure of rice starch treated by IRD and ambient air drying (AAD) during 8 months of storage were determined. Compared to AAD, IRD significantly increased the peak viscosity, final viscosity, gelatinization enthalpy, G′ and G″ moduli of stored paddy rice flour (p < 0.05). IRD shows stabilization on rice starch multi-scale structure by improving the degree of short-range order structure, increasing the relative crystallinity in the range of 25.2%–26.8% and compacting the double helix in the crystalline regions. Fractures and aggregation were observed on the IRD-treated rice starch granules, which might cause the increase in pasting viscosities and gelatinization enthalpy. In addition, the functionality and multi-scale structure of IRD-treated rice starch showed slighter changes during storage. Therefore, IRD is an effective method to improve the rice flour functionality and storage stability by altering the multi-level structure of rice starch molecules.