Quality improvement of fresh extruded rice-shaped kernels by microwave-aided puffing technology

Microwave treatment was applied in order to solve the issues of hard texture and poor digestibility of fresh extruded rice-shaped kernels (FER), and the effects of microwave power (140–700 W) on physical properties and digestibility of FER were studied. Results showed that microwave treatment significantly (p <.05) reduced the hardness of FER (from 1,361 to 425 g), whereas the vitro digestibility of cooked FER was improved effectively (from 56.15% to 73.83%). Moreover, significant changes had occurred in the expansion index, color, microstructure, thermal stability, and water absorption index compared to the control (CK). Low-field nuclear magnetic resonance (LF-NMR) analysis showed that the T relaxation time curve moved to the right and both the peak amplitude and area increased, which indicated that water entered the FER grains much more easily after microwave treatment. Taking all the parameters into consideration, 420 W emerged as the best microwave power. Practical applications: Recently, fresh extruded rice-shaped kernels (FER) based on naked oat, rice flour, and defatted flaxseed meal have been developed in order to meet the need for a healthy staple food; however, FER tend to exhibit hard texture and poor digestibility. In this study, we treated FER by microwave-aided puffing technology and obtained a high-quality FER, which expressed moderate hardness, springiness, and better water absorption index and digestibility. These characteristics were more in line with the needs of East Asians regarding rice and its substitute.