The effect of storage conditions on antioxidant activities and total phenolic contents of parboiled germinated brown rice (Khao Dok Mali 105)

Abstract

Rice (Oryza sativa) is a staple crop that has supplied over half of the world's population. Our preliminary data suggested that parboiled germinated brown rice exhibited higher antioxidant activities and total phenolic contents than germinated brown rice, brown rice and white rice, respectively. Nevertheless, the information on the stability of the antioxidant capacities and total phenolic contents in parboiled germinated brown rice is unavailable. Therefore, this research aimed to investigate the effects of storage conditions of parboiled germinated brown Thai Jasmine rice (Khao Dok Mali 105) regarding its antioxidant capacities and total phenolic contents. The determination of antioxidant capacities was employed using ferric reducing antioxidant power (FRAP), oxygen radical antioxidant (ORAC) assays and DPPH (1,1-diphenyl-2-picrylhydrazyl)-radical scavenging assays, while total phenolic content was determined using Folin-Ciocalteu reagent. The results found that the antioxidant activities (FRAP values of 348-371 μmol TE/100 g and ORAC values of 2475-2812 μmol TE/100 g, DPPH values of 62-66 %) and total phenolic contents (62-64 mg GAE/g) had no statistically significant difference under the storage temperatures of 30 and 40°C for 6 months. Since these temperatures are average temperatures in Thailand (30-40°C), rice can be kept for consumption for half a year without any significant changes in anti-oxidative agents and total phenolic contents.