Oxidizing enzymes and vitamin C in tomatoes

Abstract

Oxidising enzymes occur in highest concentration in the skin, ripe or unripe. The flesh and seeds contain less and the juice practically none. The pH of the ripe and unripe skin is 8.0-9.6, of the juice 3.9-5.0 and of the flesh 8.4-9.0 when unripe and 4.6-5.5 when ripe. When oxidase is set free by disruption of the tissues it destroys vit. C most rapidly in the skin (67% in 1 rain.), less rapidly in the flesh and slowest in the juice. The conc. of vit. C is 2 or 3 times as high in the skin as in the flesh or juice, and about 10 times as high as in the seeds. Because of the higher proportion of skin, very small tomatoes may contain higher concs. of vit. C, but the differences observed were not large enough to discredit the findings of Sansome and Zilva on polyploidy. Exposure to sunshine during ripening increases the vit. C content, but this is also affected by the oxidase, which may destroy much of the vit. under certain conditions.