Control of citrus postharvest green and blue molds by avocado stone extract

Postharvest fungal decay represents a major cause of economic losses for the citrus industry worldwide. This study investigated ultrasound-assisted extracts from avocado seeds (AVS), almond hulls (AMH), and olive pomace (ALP), agri-food by-products rich in phenolic compounds, as natural antifungal alternatives to synthetic fungicides for the control of citrus postharvest green and blue molds, caused respectively by Penicillium digitatum and Penicillium italicum . Extracts were chemically characterized for total phenolic content and antioxidant capacity. In vitro assays revealed that AVS inhibited 99.9%, while AMH and ALP showed moderate inhibition of P. digitatum and P. italicum . AVS disrupted fungal membranes, leading to leakage of cellular content, and impeded fungal mycelial growth. Interestingly, concentration–response assays indicated a reduction in antifungal activity against P. digitatum at higher AVS concentrations. AVS dip treatments at 8.0 mg mL −1 applied to previously wound inoculated oranges reduced the incidence of green and blue molds by 70 and 64% after incubation at room temperature (20 °C) for 8 days, and 70 and 24% after 4 weeks of cold storage at 5 ºC plus 7 days of shelf life at 20 ºC, respectively. Importantly, AVS dip treatment did not adversely affect postharvest key fruit quality parameters, including weight loss, firmness, color, and sensory flavor parameters, and improved fruit visual appearance and rind gloss. Overall, these findings demonstrate the strong antifungal potential and quality-preserving capacity of AVS, supporting its potential use as a sustainable, bio-based alternative to synthetic fungicides for citrus postharvest disease management within a circular bioeconomy framework.