Estimation of Postharvest Quality of “Red Delicious†Apple Fruits Based on Fruit Nutrient Elements Composition

Fruit nutrient elements content during harvest could considerably effect on postharvest life of apples. In this study, apple fruits cultivar Red Delicious were harvested at the commercial maturity stage at 20 commercial orchards. Fruits were divided into three groups according to peel color; dark red, medium and light red. The mineral elements nutrient content such as nitrogen, phosphorus, potassium, calcium and magnesium and their ratios were measured in the harvested fruits. Thereafter, fruits were places in the cold storage at 0 °C and relative humidity of 90% for 4 months. The characteristics such as fruits weight loss, firmness, TSS, dry matter, total anthocyanin content, antioxidant activity, respiration rate and ethylene production were measured at the end of storage. The results showed a positive significant correlation between fruit firmness at the end of storage time with N+K-Ca, K+Mg-Ca, K-Ca and Mg-Ca ratios. Furthermore, a negative significant correlation was found between total anthocyanin with Nitrogen content, Mg-Ca and N-Ca ratios. The results also showed a positive significant correlation between fruit respiration rate and Nitrogen, N+K-Ca and N-Ca ratios. The analysis of regression based on mean values of three red apple groups showed a significant negative correlation between total anthocyanin with fruit ethylene production at the storage time and Mg-Ca ratio. The relationship between these two variables and Anthocyanin was expressed by the equation of regression- Anthocyanin = 100.22–1.651 Ethylene–43.963 Mg-Ca. Overall, the results confirm that measurement of fruit mineral composition during harvest time could be a strategy for predicting postharvest behaviors of apple fruits at the cold storage. Also the results showed that a relationship between mineral nutrient composition and the characteristics such as firmness, anthocyanin, respiratory rate in apple fruits.