Process optimization for hot air puffing of black rice

Abstract

Black rice is gaining popularity as a nutrient-rich superfood, offering more antioxidants and health benefits than brown rice. High temperature short time puffing (HTST) is an effective method for processing grains, allowing them to expand quickly using hot air without oil. With more people leading busy urban lifestyles, there is a growing demand for convenient ready-to-eat (RTE) foods. This study investigates the optimization and quality evaluation of hot air puffing for black rice, focusing on key process variables and storage conditions. Optimal puffing parameters were determined as 18 months of aging of paddy, 19 h soaking of paddy in boiled water and 290 °C of puffing temperature (PT) and 6800 g/h feed rate (FR) for processed paddy in a single-pass in a hot air puffing machine. Under these conditions, the final puffed product achieved a moisture content of 3.70% db, expansion ratio (ER) of 2.69, puffing percentage (PP) of 89.0%, and a colour change (ΔE) value of 14.77. Hot air puffing of black rice revealed dry basis reduction of 4.59% in fibre, 10.19% in fat, 11.54% in protein and 23.93% in ash content during puffing, may be due to high temperature exposure of the product. Aging studies showed a significant improvement in puffing performance over 18 months, with Expansion ratio and Puffing Percentage increasing from 1.14 and 4.87% at 0 months to 2.69 and 89.0% at 18 months, respectively, attributed to probable increase in amylose content.