Effect of varied calcium formulations and time of application on postharvest quality and organoleptic acceptability of mango fruits

Abstract

Mango (Mangifera indica L.) is a highly perishable fruit with a short shelf life at ambient conditions, which may lead to post-harvest losses approximated to be 40-45%. This reduces returns to farmers significantly. The problem is compounded by the fact that most farmers do not have access to cold storage facilities. Nutrient management has been shown to affect postharvest characteristics of fruits. Calcium particularly plays a critical role in cell membrane integrity, tissue firmness and delays lipid catabolism. Previous studies have indicated a deficiency of calcium in some mango growing regions in Kenya. A field study was carried out to determine the effect of varied calcium formulations applied at various stages of growth on mango fruits post-harvest quality and organoleptic acceptability. The study was carried out in Embu County Eastern Kenya during seasons 2017/2018 and 2018 /2019 using “Van Dyke” cultivar, aged approximately 10 years. The experiment was set up in a randomized complete block design with a split-split plot arrangement, three trees per replication, replicated thrice. Three calcium formulations: calcium chloride, calcium nitrate and Easygro™ were applied at rates of 0%,1.0%, 1.5% and 2.0% at fruit set, 30 days after fruit set and 30 days to physiological maturity. The calcium sources formed the main plots, the timing of application formed the subplots while the rates of application formed the sub-sub plots. Total soluble solids (TSS) and percentage titratable acidity (TA) were assessed at harvest and after 12 days of storage under ambient conditions (25±2ºC, 70±5% relative humidity) using standard procedures. Selected fruits’ sensory attributes were also evaluated after storage using a hedonic scale. Analysis of data was done using the 14th Edition of the Genstat software. The differences among the means of the treatments were compared using Fisher’s Protected LSD test at 5% probability level. Fruits sprayed with calcium chloride, 2.0% at fruit set had higher TSS (6.8 º brix and 6.3º brix) (10.47 º brix and 9.10 º brix), TA (1.29% and 1.27%), (0.77% and 0.675%) than other treatments at maturity and after storage in both seasons, respectively. Calcium chloride at 2.0% level of application led to a superior peel color appearance contrary to calcium nitrate and Easygro™ also applied at 2.0%, which led to an inferior peel color appearance and an inferior taste of fruits. Therefore, calcium nitrate and easy gro should be sprayed at concentration of 1.5% for good taste and peel colour appearance.