The effect of carboxymethyl cellulose-wax composite edible coating on postharvest quality of tomato fruit harvested at varying maturity

Abstract

Tomato fruit is important due to its high nutrient content which is beneficial for a good health. However, these nutrients are reduced during postharvest value chain due to rapid deterioration as the produce is perishable. This is more pronounced in fruit harvested at red stage owing to increased respiration and water loss leading to reduced postharvest life and quality. The effect of these processes can be minimized by applying coatings such as carboxymethyl cellulose (CMC) and waxes. However, waxes may reduce gas exchange, while CMC has limited moisture retention, compromising its protecting barriers. The use of composite coatings may enhance the barrier properties improving moisture retention and allowing better gas exchange. Thus, we investigated the effect of carboxymethyl cellulose (CMC) and wax composite coating on tomato fruit and further evaluated whether this effect is influenced by harvest maturity. Tomato fruit harvested at mature-green and red stages were dipped in 0.5% CMC, Citrashine® wax, or a composite coating of CMC and wax (CMC+wax). Control fruit were dipped in distilled water. Thereafter, the fruit were stored at ambient temperature (± 24ºC) for 9 days. During the 9-day storage, variables such as weight, firmness, peel colour, total soluble solids (TSS), titratable acidity (TA) and TSS/TA ratio were determined at 3-day intervals. The results showed that coating had a more significant effect on mature green fruit compared to red fruit during ambient storage. The CMC+wax coating significantly (p<0.05) reduced weight loss and firmness loss compared to either coating alone or control. Tomato peel colour changes were significantly (p<0.05) delayed by the combined CMC and wax coating as indicated by lower a*, higher b*, L* and C* compared to control and coatings alone. In terms of chemical quality, CMC+wax coating significantly delayed the increase in TSS, reduced the decline in TA and maintained a balanced TSS/TA ratio compared to control and either coating alone. The study showed that the CMC and wax composite effectively extended the shelf life and maintained the postharvest quality of tomato fruit, particularly green-matured. Therefore, this technique offers an environmentally friendly alternative to synthetic preservatives used to maintain the quality of tomato during postharvest storage.