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Abstract
Thai jasmine rice (Oryza sativa L. cv. KDML105) is highly valued due to its subtle aroma, robust seed characteristics and high nutritional quality. Low-energy ion-beam bombardment was chosen to improve the quality of jasmine rice by mutation induction. One mutated variety, named BKOS, was found to exhibit a deep purple colour due to an increased accumulation of anthocyanin. The total phenolic content and antioxidant activities of cooked and uncooked rice extracts were compared with KDML105, BKOS and other rice mutants created by a low-energy ion beam. The BKOS extracts showed the highest total phenol content (0.140 and 0.096 mg of gallic acid equivalent (GAE) g−1 dry extract from uncooked and cooked rice, respectively). The BKOS extracts also had improved antioxidant activities, determined using three standard methods: 2,2′-diphenyl-1-picrylhdrazyl (DPPH) free radical scavenging, ABTS radical cation (ABTS•+) decolourisation and ferric-reducing antioxidant power assays. BKOS extracts showed 2–2.5-fold increased levels for each method. Interestingly, there was no significant difference between the antioxidant activities of the cooked and uncooked BKOS rice extracts. The increased quantity of antioxidants in this anthocyanin-based natural product could allow antioxidants to be consumed by a wider population than what is currently possible.
Acknowledgements
The authors thank the National Research Council of Thailand, the Office of the Higher Education Commission and the Thailand Research Fund for financial support. Miss Nuananong Semsang was also supported by a grant under the Strategic Scholarships for Frontier Research Network for the Joint Ph.D. Program Thai Doctoral degree and by funding from the Office of the Higher Education Commission, Thailand.