Effects of a Sodium Alginate Coating Enriched with Isodon serra and Plinia cauliflora Leaf Extracts on Postharvest Quality and Anthracnose Control in Banana

Banana is a typical climacteric fruit that rapidly undergoes ripening, peel browning, softening, moisture loss, and fungal decay during postharvest storage, leading to severe quality deterioration and a shortened shelf life. In this study, a sodium alginate (SA)-based edible coating enriched with Isodon serra extract (IE) and Plinia cauliflora (jaboticaba) leaf extract (JE) was developed and evaluated for its antioxidant, antifungal, and preservation effects on banana fruit. The two extracts exhibited distinct functional properties: IE showed strong inhibitory activity against Colletotrichum musae, whereas JE displayed superior radical scavenging capacity. When incorporated into the coating system, this functional complementarity translated into improved preservation performance. The composite coating (SA-IE-JE) effectively suppressed anthracnose development, reduced peel browning, and delayed ripening progression, as evidenced by an 11.8% reduction in fruit weight loss (11.48% vs. 13.01%), an 11.6% decrease in MDA accumulation (89.96 vs. 101.75), a 51.3% reduction in PPO activity (526 U/g vs. 1080 U/g), sustained TPC, and a slower increase in total soluble solids after 5 days of storage. All coating treatments improved postharvest quality compared with the uncoated control, while SA-IE and SA-IE-JE generally showed stronger preservation effects than SA alone. In particular, SA-IE-JE was more effective in reducing peel browning, delaying the increase in PPO activity, and suppressing anthracnose lesion expansion. These findings highlight that SA coating supplemented with IE and JE can serve as a promising, environmentally friendly strategy for maintaining banana quality and reducing postharvest disease. Our study provides a potential basis for the development of plant-extract-enriched edible coatings for banana preservation.