Anthocyanins and flavonoids from shredded red onion and changes during storage in perforated films

From the edible parts of the Spanish red onion (cultivar 'Morada de Amposta'), the anthocyanins cyanidin 3-glucoside, cyanidin 3-arabinoside, cyanidin 3-malonylglucoside and cyanidin 3-malonylarabinoside and the flavonoids quercetin 3,4'-diglucoside, quercetin 7,4'-diglucoside, quercetin 3-glucoside, dihydroquercetin 3-glucoside and isorhamnetin 4'-glucoside were identified. The amount of anthocyanins reached 233 mg kg(-1) and that of the flavonoids 943 mg kg(-1) fresh weight of onions. The onions were processed minimally to produce fresh 'ready-to-eat' shredded onion, and the stability of the anthocyanin pigments was evaluated during storage in perforated films for 7 days at 8 degrees C. After 1 day of storage, a slight increase in anthocyanins was observed, followed by a decrease, reaching the lower levels after 7 days of storage. In spite of the decrease in anthocyanins, the appearance of the commodity was acceptable after the storage period. The stability of the individual anthocyanins was very different, the malonated anthocyanins being much more stable than the corresponding non-acylated pigments. In addition, the arabinosides were shown to be less stable than the corresponding glucosides. Copyright (C) 1996 Canadian Institiute of Food Science and Technology. Published by Elsevier Science Ltd.