Carboxymethyl cellulose coating regulates cell wall polysaccharides disassembly and delays ripening of harvested banana fruit

Banana is a perishable fruit that ripens and deteriorates quickly after harvest. In this work, we investigated the impact of a dip in carboxymethyl cellulose (CMC) at concentrations of 0.5%, 1.0% and 1.5% on the quality of harvested bananas during storage at ambient conditions of 20 +/- 1 degrees C for a 15-d period. It was noted that 1.5% CMC markedly delayed the occurrence of decay incidence (9%) and suppressed physiological weight loss (6%). The 1.5% CMC treatment suppressed the activities of chlorophyllase, pheophytinase, Mg-dechelatase and chlorophyll (Chl)-degrading peroxidase (POD), which ultimately delayed banana peel color changes by conserving higher total Chl contents and reducing the accumulation of carotenoids. This subsequently resulted in higher L* and a* along with a lower increase in b* values as compared with control. Banana fruit coated with 1.5% CMC exhibited delayed ethylene and respiration peaks in comparison with control. In the same way, 1.5% coating maintained higher firmness and showed higher contents of protopectin, chelate-soluble pectin, sodium carbonate soluble pectin, cellulose and hemicellulose along with lower water-soluble pectin due to reduced activities of cellulase, pectin methylesterase, polygalacturonase and beta-glucosidase. In the same way, postharvest application of 1.5% CMC coating suppressed the increase in total soluble solids (TSS) and showed higher titratable acidity (TA) along with a lower ripening index (TSS/TA ratio) in flesh of banana fruit compared with control. In conclusion, 1.5% CMC application could be an appropriate coating concentration to delay the ripening and rapid softening of harvested bananas stored in ambient conditions.