Effect of CaCl2 Sprays at Different Fruit Development Stages on Postharvest Keeping Quality of “Hayward” Kiwifruit

Abstract

The postharvest quality attributes of “Hayward” kiwifruit were investigated to find the optimum times and frequencies of calcium chloride (CaCl2) spray. The vines in two different commercial kiwifruit orchards were sprayed with CaCl2 (1.5%) one, two and three times in 35, 85 and 125 days after full bloom (DAFB). Fruits were harvested at the maturity stage and thereafter stored at 0C for 90 days and five additional days under marketing conditions as shelf life. The results showed that with a few exceptions, one time and two times CaCl2 sprays had no significant effect on kiwifruit postharvest quality. Thrice CaCl2 sprays (35 + 85 + 125 DAFB) significantly enhanced fruit Ca concentration and improved fruit quality such as firmness, total soluble solid, titratable acidity, total chlorophyll and carotenoid content, and reduced fruit weight loss and decay incidence during cold storage and shelf life. Overall, it is proposed that thrice CaCl2 (1.5%) spray in “Hayward” kiwifruit orchards could be more appropriate to improve fruit quality and storability. Practical Applications Consumer's acceptance for ripe “Hayward” kiwifruits is influenced by sugar content, sugar-to-acid ratio, green pulp color and the sensory properties such as texture and appearance. During cold storage, many physicochemical changes will occur in kiwifruits such as weight loss, increase in soluble solid contents, decline in ascorbic acid and cell wall degradation, which significantly affect fruit qualities. Softening plays an important role in textural qualities, consumer acceptability, shelf life and postharvest disease resistance. It is significantly influenced by different preharvest factors. Foliar application of CaCl2 has very important role in improving fruit quality. Calcium participates in cross-linking negative charges, especially on the carboxylic residues of pectin, imparting significant structural rigidity to the wall. Therefore, finding the optimum preharvest CaCl2 spraying time and frequency is very important for orchard management.