Effect of storage temperature on the stability of fat‐soluble micronutrients in rice varieties

Storage condition can substantially influence the contents of micronutrients in rice. This study determined the stability of carotenoids, α‐ & γ‐tocopherols, α‐ & γ‐tocotrienols, and γ‐ oryzanols in four rice varieties (white, sweet, orange and brown) over 16 weeks in different storage temperatures (room, 4ºC, and − 80ºC). Rice varieties were extracted using methanol/tetrahydrofuran and analyzed by a reverse phase HPLC system. In 100 g of rice, the contents of lutein (5–244 μg), trans‐β‐ carotene (0–25 μg), γ‐oryzanol (45–115 mg), tocopherols (α‐, 0.8–1.5 mg; γ‐, 0.1–0.7 mg) and tocotrienols (α‐, 0.04–0.07 mg; γ‐, 0.1–0.14 mg) were variable among rice varieties. Carotenoids, tocopherols, and tocotrienols decreased significantly within two weeks at room temperature, and at four weeks at 4ºC (p<0.05). No significant difference was observed in these components up to 16 weeks at −80ºC. Gamma oryzanols were stable up to 16 weeks at all storage temperatures (p<0.01). The stability of fat‐soluble micronutrients were found to be different among rice varieties. Low storage temperature is recommended to reduce the loss of fat‐soluble micronutrients, specially carotenoids and vitamin E isomers, in rice varieties. [Supported in part by the USDA 58–1950‐7–707, USA, RDA ( PJ008755 ), Korea, and CAPES BEX 5547/11–3, Brazil]