Effect of variable temperature levels on drying characteristics and quality indices of rice in continuous drying and multi‐stage intermittent drying

Abstract

The aim of this study was to investigate the effect of variable temperature levels on the drying characteristics and quality indices of rice in continuous drying and multistage intermittent drying (MID). The quality indices of rice were assessed in terms of stress crack index, head rice yield (HRY), color, sensory characteristics, and taste value. Moreover, the microstructure of the cross-section of rice was analyzed at different variable temperature levels. In addition, the quality indices evaluation of rice was carried out by principal component analysis. The results showed that drying temperature at the same temperature level was positively correlated with stress cracking index and total color difference, negatively correlated with drying time, HRY, whiteness index, and taste value. The MID with Δ5 (45-50 C) temperature level had the highest comprehensive score of 1.431. The results provide a reference for optimizing the drying process for rice. Practical applicationsDrying is a key control step in relation to the yield and quality of rice. A reasonable and effective variable temperature drying process can improve drying efficiency and solve the problem of the limitations of a single temperature heating method. The quality indices evaluation of rice can provide a reference for the optimization of drying parameters for different variable temperature drying processes. Moreover, the variable temperature drying method in this study can improve the adaptability of the process and provide research ideas and technical references for the industrial production and automatic control of variable temperature in rice. K E Y W O R D S color, head rice yield, microstructure, stress cracking index, taste value 1 | INTRODUCTION China is a large agricultural country and rice production has increased incrementally in recent years, which requires postproduction grain storage to meet the gradually increasing demand for rice production in order to reduce postproduction losses (Sarker et al., 2013). Different regions experience different weather climates during rice harvest, resulting in high moisture content in part of the rice (Wang et al., 2021). The moisture content of harvested rice usually affects the respiration and metabolism of the rice grain during storage and other processes, changing the quality of the rice. Rice with high moisture content requires prompt drying to inhibit the growth of molds. The drying