Comparison of nano-calcium and calcium chloride spray on postharvest quality and cell wall enzymes activity in apple cv. Red Delicious

The aim of the experiment was to compare the effects of preharvest nano-calcium and calcium chloride spraying on postharvest quality and the cell wall enzyme activities of the apple fruit (Malus domestica L. cv. Red Delicious) at harvest and during storage (1, 2, 3, 4 month). Sprayings on apple trees were started from 70 d after full-bloom until one month before harvesting. They were sprayed 5 times, intervals of two weeks, with nano-calcium (0, 1.5, 2, and 2.5%), and calcium chloride (0, 1, 1.5, and 2%) solutions. After harvest, some fruit were transported to the laboratory to evaluate the parameters while other fruit were stored at 0 °C and at 90% RH for 4 months. Measurements were performed on fruit firmness, weight loss, titrable acidity (TA), total soluble solids (TSS), total phenolic content (TPC), browning, total antioxidant activity (TAA), and fiber content at 0, 1, 2, 3, and 4 months of storage period. Furthermore, assessments were made regarding enzymes in the cell wall such as polygalacturonase (PG), pectin methylesterase (PME), and β-galactosidase (β-Gal). Results showed that firmness, TA, TPC, TAA, and fiber content increased in fruit that treated with both nano-calcium and calcium chloride as compared to control fruit, however, these parameters decreased by prolonging the storage time. Meanwhile, weight loss, TSS, and internal browning increased during storage time, but, this increase in treated fruit was less than control fruit. Moreover, during storage, lower activities of PG, PME, and β-Gal enzymes were observed in fruit that sprayed with both calcium fertilizers. In addition, In short, it was observed that the quality of apple fruit treated with nano-calcium was better than those treated with calcium chloride in all parameters. So, it can be considered to use nano-calcium fertilizer instead of calcium chloride fertilizer for improving quality and storability of fruit such as apple.