Effects of soaking and sprouting on bioactive compounds of black and red pigmented rice cultivars
Mohammad Zahirul Islam, Minjung Shim, Suyeon Jeong, Young‐Tack Lee
Abstract
Summary This study was conducted to investigate the effects of steeping and sprouting on bioactive compounds of five pigmented rice, including two black and three red rice cultivars, and one ordinary rice. Dehulled rice samples were soaked in distilled water at 25 °C for different durations (0, 3, 6, 12, 24 and 48 h) and allowed to germinate under the dark condition at 25 °C and 95% humidity for 3 days. As the steeping time progressed up to 24 h, the germination rate and sprout growth of pigmented rice increased, and decreased at 48 h. During the soaking process, a gradual decrease in L* value (lightness) of soaking water was observed, with the highest reduction observed in Bosukheugchal (waxy black rice cultivar), indicating a considerable loss of anthocyanin during soaking. Black rice cultivars had the highest level of anthocyanin content, which was significantly reduced after germination. γ‐Aminobutyric acid (GABA) content (6.68–74.58 µg g −1 ) of pigmented rice cultivars increased significantly (226.36–339.91 µg g −1 ) ( P ≤ 0.05) after germination. Germinated rice had 3.55 to 33.88 ‐times higher GABA content than non‐germinated rice. Total phenolic and flavonoid content in pigmented rice cultivars also increased after germination.