Enhancing and Maintaining Nutritional Quality and Bioactive Compounds of “Hayward” Kiwifruit: Comparison of the Effectiveness of Different CaCl2 Spraying Times

Abstract

This study was conducted to elucidate the effect of calcium chloride (CaCl2) spraying times and number of sprays on the changes in biochemical compounds of “Hayward” kiwifruit (Actinidia deliciosa) during storage as well as at the shelf life. The vines in two different commercial kiwifruit orchards were sprayed with CaCl2 (15 g/L), one, two and three times in 35, 85 and 125 days after full bloom. Fruits were harvested at maturity stage and then were stored at 0C for 90 days and 5 additional days under simulated marketing conditions. The results showed that orchard location had significant effect on fruit biochemical compounds. With a few exceptions, one-time (early-, mid-, late-season) and twice CaCl2 sprays had no significant effects on kiwifruit quality characteristics. Thrice sprays significantly reduced respiration rate, ethylene production and polygalacturonase activity that lead to delay degradation of vitamin c, phenolic compounds and antioxidant activity, and maintained fruit sensory quality. Overall, thrice sprays of CaCl2 delayed fruit ripening processes and maintained fruit quality of “Hayward” kiwifruit. Practical Applications As the importance of phytochemical content in the health benefits of fruits and vegetables is recognized, interest in the antioxidant activity, enzymes, and polyphenolic and phytochemical contents of kiwifruit has increased significantly in recent years. During cold storage, many physicochemical changes occur that significantly affect fruit quality. Polygalacturonase (PG) is a cell wall-bound enzyme which has been found to play a role in numerous plant developmental processes such as fruit ripening and softening. Considerable attention has been given to calcium (Ca) application to kiwifruit, since maintenance of relatively high Ca concentrations in fruit tissues results in better nutrients balance, maintaining cell wall stabilization and integrity, retards fruit respiration and ripening by lower rates of CO2 and C2H4 production, PG activity, softening, and finally extends storability. It should also be noted that the beneficial effects of preharvest Ca sprays depend on the time and number of treatments and orchard location.