Effect of Germination and Parboiling on Milling, Physicochemical, and Textural Properties of Medium- and Long-grain Rough Rice

Germinated brown rice is commonly consumed in Asia for its enhanced nutritional properties such as gamma-aminobutyric acid (GABA) and softer cooked texture. However germination decreases milling yield and alters some physicochemical properties, and most germinated rice studies evaluated medium-grain and aromatic rice cultivars. This study compared the effects of germination duration and parboiling on milling, physicochemical, and textural properties of a medium(Jupiter) and a long-grain (Wells) rice cultivars. Rough rice was soaked in water at 25°C for 12 hr, and then incubated at 30-34°C for varying germination durations, or combined with parboiling at 120°C for 20 min prior to drying. Germination resulted in an increase in brokens and a decrease in kernel weight for Wells. Parboiling increased milling yield and GABA content but decreased kernel whiteness and pasting profiles for both cultivars. Jupiter was consistently higher in soluble sugars, ash, and GABA content with germination progression compared with Wells. There were no significant changes in gelatinization temperatures and pasting properties between germination durations for parboiled and nonparboiled rice. Germination decreased cooked rice hardness of Wells and cooked rice stickiness of Jupiter for both non-parboiled and parboiled samples. Parboiling increased GABA content and cooked rice softness for both cultivars. The impacts of germination and subsequent parboiling on milling, physicochemical, and textural properties of rice were affected by grain type and germination duration.