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Effects of storage conditions and cooking on colour and antioxidant activities of organic pigmented rice


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Influences of the conditions of raw rice storage and cooking on parameters related to colour and antioxidant activities of organic hulled red fragrant rice were investigated. Raw rice samples were vacuum-packed in oriented polypropylene/aluminium/linear low-density polyethylene or nylon/linear low-density polyethylene pouches and stored at ambient temperature or 15 °C up to 12 months. Cooked samples were prepared from aged raw samples. Kernel colour, total anthocyanin content (TAC) of acidic methanolic extracts as well as total phenolic content (TPC), reducing power (RP) and radical scavenging activity (RSA) of methanolic extracts and enzymatically digested samples were maintained during 12-month storage, regardless of packaging materials and storage temperatures. Cooked kernels had larger L value, lower a and b values, and greater TAC (dry basis), comparing with the raw rice. Cooking caused drastic decrease in TPC, RP and RSA of methanolic extracts. Nevertheless, less negative impacts of cooking were found for enzymatically digested samples.