Physical Integrity of Long-Grain Hybrid, Pureline, and Medium-Grain Rice Kernels as Affected by Storage Conditions

Abstract

Highlights Rice kernel physical integrity diminished at higher storage temperature and moisture content. Variation in rice kernel physical integrity was noticeable among rice cultivars. Fungal attack lessened rice kernel physical integrity. Abstract . Rice kernel physical integrity directly correlates with rice milling yield and quality. In this study, the impact of storage conditions on rice kernel physical integrity was examined by assessing changes in head rice yield (HRY) and kernel microstructure. Long-grain hybrid (XL753), long-grain pureline (Roy J), and medium-grain (Titan) rice were stored at different storage moisture contents (16% and 21% MCs, wet basis), storage temperatures (20°C, 30°C, and 40°C), and storage durations (4, 8, 12, and 16 weeks); the samples were also treated with antifungals, sodium chloride, and natamycin. Results show that kernel physical integrity was highly dependent on the rice storage environment. At the same storage conditions, the physical integrity of medium-grain cultivar was significantly higher than that for the two long-grains. Generally, the long-grain hybrid rice exhibited more resilience to breakage than pureline under the same storage conditions. An average of 4% reduction in HRY was seen for the three cultivars when 16% MC rice was stored at 40°C compared to at 20°C; however, the HRY reduction was 12% for rice stored at the highest MC (21%). Decreases in kernel physical integrity were also associated with unique microstructural changes in rice kernels. Sodium chloride treatment of rice kernels significantly and negatively impacted their physical integrity during storage compared to natamycin treatment and untreated control samples. Multiple regression models, developed for each cultivar were applicable for predicting changes in rice kernel physical integrity as a function of studied storage conditions and antifungal treatments. Keywords: Antifungal treatment, Head rice yield, Microstructure, Milled rice quality, Storage, Rice kernel physical integrity.