Consumers are increasingly aware of the importance of regular consumption of fresh fruit in their diet. Since fresh fruit are highly sensitive to postharvest decay, several investigations focused on the study natural compounds alternative to synthetic fungicides, to extend their shelf life. A long list of studies reported the effectiveness of the natural biopolymer chitosan in control of postharvest diseases of fresh fruit. However, these findings remain controversial, with many mixed claims in the literature. In this work, we used random‐effects meta‐analysis to investigate the effects of 1% chitosan on (a) postharvest decay incidence; (b) mycelium growth of fungal pathogens Botrytis cinerea, Penicillium spp., Colletotrichum spp. and Alternaria spp.; and (c) phenylalanine ammonia‐lyase, chitinase and β‐1,3‐glucanase activities. Chitosan significantly reduced postharvest disease incidence (mean difference [MD], −30.22; p < 0.00001) and in vitro mycelium growth (MD, −54.32; p  < 0.00001). For host defense responses, there were significantly increased activities of β‐1,3‐glucanase (MD, 115.06; p = 0.003) and chitinase (MD, 75.95; p < 0.0002). This systematic review contributes to confirm the multiple mechanisms of mechanisms of action of chitosan, which has unique properties in the natural compound panorama. Chitosan thus represents a model plant protection biopolymer for sustainable control of postharvest decay of fresh fruit.

Strawberry is a perishable fruit with a limited shelf life after harvest due to deterioration of quality and the development of gray mold, Rhizopus rot and other minor diseases. In this study, the effectiveness of commercial compounds based on chitosan, phosphoric acid plus micronutrients, and sweet orange essential oil (EO) in reducing decay and optimizing the quality of strawberries was analyzed. The plant canopy of a greenhouse crop was sprayed once and strawberry fruit were harvested three days later. Gray mold infections were evaluated after chilled storage for seven days at 4 ± 0.5 °C followed by five days shelf life. The qualitative parameters were recorded at harvest (initial day) and after three days of storage at room temperature (RT, 20 °C) or after cold storage and shelf life (CS, 4 °C). The application of sweet orange EO increased the antioxidant and flavonoid content at harvest, while a decrease was reported following three days of storage at RT. At the same time, increased ethylene production and weight loss were observed during CS three days after harvesting. Chitosan treatment maintained the harvest fruit quality and was effective in the control of postharvest decay. Our results suggest that the investigated natural compounds could improve strawberry quality after harvest. Since chitosan performed best in terms of maintaining quality and reducing postharvest decay, it could be considered as a good substitute for chemical-synthetic fungicides for the preservation of strawberry postharvest gray mold.