Investigating the effects of crab shell chitosan on fungal mycelial growth and postharvest quality attributes of pomegranate whole fruit and arils

- Antifungal efficacy of chitosan varied against the fungal pathogens.
- Chitosan was most effective as a preventative treatment than as a curative.
- Quality deterioration of pomegranate was effectively delayed by chitosan treatment.
- The biocompatibility of chitosan makes it applicable for use as a green fungicide.

Postharvest disease management for pomegranate fruit remains a critical challenge and the need for effective alternative treatments is essential in order to minimise losses. This study investigated the in-vitro and in-vivo antifungal activities of crab shell chitosan and fludioxonil (a registered postharvest fungicide) as a control against Botrytis sp., Penicillium sp. and Pilidiella granati isolated from pomegranate fruit. Mycelial growth inhibition was evaluated using potato dextrose agar amended with varying concentrations of 0-1 g/L for fludioxonil, and 0-10 g/L of chitosan. Complete mycelial growth inhibition was observed at 0.10 g/L and 10 g/L for fludioxonil and chitosan, respectively. Chitosan concentrations causing a 50% reduction in mycelial growth (EC50) were 0.47, 1.19, and 2.21 g/L for P. granati, Botrytis sp., and Penicillium sp., respectively. The EC50 concentrations for fludioxonil were 0.02, 0.48, and 0.90 mg/L for Penicillium sp., P. granati, and Botrytis sp., respectively. For in-vivo investigation of artificially inoculated pomegranate fruit; chitosan effectively reduced rot incidence by 18-66%, and was most efficient when applied as a preventative treatment regardless of cultivar ('Herskawitz' and 'Wonderful'). Additionally, chitosan treatments (0, 2.5, 7.5 and 15 g/L) were applied on minimally processed pomegranate arils as edible coating prior to packaging and storage at 4 °C for 14 days. The chitosan treated arils best maintained physico-chemical quality attributes and significantly lower microbial counts for mesophilic aerobic bacteria, yeast and moulds. This study showed that crab shell chitosan has a potential as a green fungicide for postharvest disease management of pomegranate.