Effect of canning and storage on carotenoids (vitamin A activity) and vitamin C in Spanish and Turkish oranges

Canning caused a small reduction in the vitamin C content of orange purée of both Spanish and Turkish varieties; subsequent storage for 24 months at 10°C caused complete loss of vitamin C. Carotenoids, however, were retained to a limited extent after storage and similar amounts were present at both room temperature and at 10°C. Most of the vitamin C in the flavedo was retained after 24 months' storage at ‐ 20°C but there was a considerable fall when the frozen material was thawed and stored at room temperature for 4 days. Thirteen carotenoids were present in both varieties of purée, with three additional ones in the Spanish variety and one additional one in the Turkish variety. Despite the heating in acid conditions involved in the canning process, only two of the pigments, violaxanthin and flavoxanthin, isomerised from the all‐trans to cis‐trans isomers.