Predicting Fruit Tissue Firmness in Kiwifruit cv.  Hayward at the End of Storage Time Using Mathematical Modeling

Mineral composition in harvested fruits can influenced fruit tissue firmness and postharvest life. In this study fruits were harvested from 70 different commercial kiwifruit orchards on 10 weeks after full bloom and the commercial maturity stage. After harvest, fruit mineral composition such as nitrogen, potassium, phosphorus, calcium, magnesium and dry matter were measured. Tissue firmness was also measured on mature fruits. Thereafter, mature fruits were transferred to storage at 0 ºC and 90-95% relative humidity and after 105 days fruit tissue firmness was evaluated. The regression model showed that, positive correlation existed among fruit tissue firmness at the end of storage with tissue firmness and dry matter of mature fruit at harvest time but a negative correlation with N+K/Ca ratio, phosphor and nitrogen content of mature fruit. Also cluster analysis was divided studied orchards into two main groups. Based on t test fruit tissue firmness at the end of storage in first group orchard was less than second group. In addition, In first group concentration of potassium, phosphorus, nitrogen, N/Ca, N+K/Ca, K/Ca and K+Mg/Ca ratios was higher than the second group, but dry matter in fruitlets and fruits, calcium concentration of mature fruits and fruit tissue firmness at harvest was lower. The discriminate function analysis showed that variables of tissue firmness at the end of storage, ratio of N+K/Ca, K/Ca, N/Ca, K+Mg/Ca had the highest correlation with the discriminant function. In conclusion, mathematical models can be used for prediction of postharvest behavior and storage quality in kiwifruit.