DIFFERENTIAL-EFFECTS OF ETHEPHON AND SENIPHOS ON COLOR DEVELOPMENT OFSTARKING DELICIOUS APPLE

The differential effects of two color improving products, ethephon an ethylene-releasing compound, and seniphos, a nonethylene-releasing pro duct, were studied on 'Starking Delicious' apples (Malus domestica Bor kh L.). Ethephon and seniphos were applied 2 or 3 weeks before commerc ial harvest. Ethephon- and seniphos-treated fruit showed a significant improvement of peel color associated with a sharp increase in anthocy anin content and chromaticity values. Color improvement in ethephon-tr eated apples occurred during the preharvest period and cold storage. T he seniphos-treated fruit stopped color development in cold conditions . In comparison to the ethephon-treated fruit, the seniphos-treated ap ples showed lower internal ethylene concentrations and a ripening dela y. Both treatments sharply increased the activity of phenylalanine-amm onia-lyase enzyme, which seemed to be the determining factor of color enhancement. The seniphos-treated apples compared to ethephon had high er fruit firmness and lower soluble solids concentrations. Anthocyanin biosynthesis may be enhanced by seniphos treatment, without inducing ethylene production or other ripening associated changes. As a consequ ence, fruit treated with seniphos can be held longer in storage.