The effect of extraction conditions on antioxidant activities and total phenolic contents of different processed Thai Jasmine rice

Abstract

© All Rights Reserved. Germination and parboiling process are techniques for enhancing nutrients and phytochemicals in rice. The objective of this research was to optimize extraction conditions (ethanol concentrations, extraction temperatures and extraction times) in relatedness to antioxidant activities and total phenolic contents (TPCs) using rice samples that passed through different processes. According to the results, rice extracted with 40% (v/v) aqueous ethanol under 50°C of extraction temperature exhibited the highest antioxidant activities and TPCs. However, varied extraction times (1-16 hours) could not differentiate antioxidant activities and TPCs. Under the optimized extraction conditions, parboiled germinated brown rice significantly exhibited the highest TPC (72±2 mg GAE/100 g dry weight) and antioxidant activities measured by ORAC (3343±137 μmole TE/100 g dry weight), DPPH radical inhibition (71% inhibition) and FRAP (420±41 μmole TE/100 g dry weight) assays, followed by those of germinated brown rice, brown rice and white rice, respectively. These results suggested that bioactive compounds and phenolics could be lost due to rice polishing process, while significant amount of nutrients were promoted during parboiling process.