Pigmented rice, consisting of black rice and red rice, is known to contain antioxidant compounds in its bran that tend to leach out into the water during cooking. As the rice is usually cooked in excess water which is discarded after cooking, the purpose of this study is therefore, to evaluate the rice cooking water as an antioxidant drink in terms of its antioxidant properties, storage stability and anthocyanin degradation kinetics. The results showed that the percentages of antioxidant extractability from pigmented rice into the cooking water were 88.42 and 103.26%, respectively for red rice and black rice, respectively. However, red rice drink possessed significantly (p<0.05) higher antioxidant activity than black rice drink, except for its total monomeric anthocyanin content. The drinks showed good microbiological stability throughout 12 weeks of storage when kept at 4°C, while those stored at 25°C lasted for 4 weeks. There was a significant decrease of antioxidant content, chroma and pH and increase in L value and hue angle, while less significant changes were observed for total soluble solids and viscosity of the drinks during the storage stability study. The degradation of anthocyanins in both drinks kept at different temperatures followed first-order reaction kinetics. According to the findings of this study, black rice and red rice cooking water have the potential of being new antioxidant drinks.

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Pigmented rice can be categorized as a functional food due to its various health benefits, mainly from its polar antioxidant content which consists of anthocyanins in black rice and proanthocyanidins in red rice. This rice is usually cooked in excess water and removal of the water will be a waste as it can be further utilized as a base for antioxidant drink. Therefore, the objective of this study was to determine the optimum processing conditions (extraction temperature, time, and water/rice (W/R) ratio) for minimum 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity IC 50 , maximum total flavonoid (TFC), and Maximum Total Phenolic Content (TPC) in the pigmented rice extracts using response surface methodology (RSM). The optimum hot water extraction conditions for black rice were W/R ratio of 20 ml/g at 95.6°C for 40 minutes, while that for red rice are W/R ratio of 20 ml/g at 97°C for 30 minutes. It can be concluded that RSM is a useful method in optimizing the processing conditions for production of antioxidant drink from pigmented rice and hot water extraction showed great potential in extracting antioxidants from pigmented rice.