A novel antifungal surface-coating application to limit postharvest decay on coated apples: Molecular, thermal and morphological properties of electrospun zein–nanofiber mats loaded with curcumin

Coating surfaces of fruit with electrospun zein mats with functionalized antimicrobial properties can be a novel strategy to prevent fungal colonization on fruit surfaces. In this study, we tested curcumin-loaded electrospun zein nanofibers (CLZN) in terms of limitation of postharvest decay on CLZN–coated apples infected with Botrytis cinerea and Penicillium expansum. Mixtures of zein and curcumin (the curcumin amounts of 2.5 and 5 wt% based on the weight of zein powder) were electrospun to yield cylindrical and ultrafine (< 350 nm in diameter) polymeric nanofibers. In addition, molecular, thermal, zeta potential and morphological properties of the CLZN as well as their encapsulation efficiency and releasing kinetics were determined, revealing that the developed zein-based scaffolds showed high encapsulation efficiency, molecular interactions with curcumin within nanofibers, alterations in physical states of these components, smooth beadless structure and good thermal (an endothermic peak at 152 °C) and dispersion stability (− 24 mV of ζ potential) properties. In vitro antifungal activity tests conducted at 27 °C for six days showed that CLZN were effective against growth of the tested fungal pathogens, exhibiting almost 40–50% inhibition of mycelial growth of the fungal pathogens; but the antifungal effect against P. expansum was but two-fold higher than that against B. cinerea. In vivo tests conducted at 23 °C with 75% humidity for six days confirmed in vitro test results in terms of both visual inspections on uncoated and coated apples, revealing almost 50% reduction in lesion diameter measured on coated apples infected with Penicillium expansum. Our results suggest that CLZN mats open up new opportunities for a novel application of edible and biodegradable antifungal coating material with the ability to hinder fungal proliferation on coated apples during storage period. Industrial relevance We coated the surfaces of fruits with electrospun mats with functionalized antimicrobial properties to prevent fungal colonization on fruit surface. The coating of apples with curcumin-loaded zein nanoparticles (CLZNs) limited the postharvest decay caused by the fungal pathogens, Penicillium expansum and Botrytis cinerea. This study showed that by encapsulation of curcumin into zein-based nanofibers considerably increased the antifungal effectiveness of curcumin. Our results highlighted the potential use of the CLZN as an effective fungicidal coating material against P. expansum and B. cinerea and suggested that CLZNs can be promising tools to compete with synthetic fungicide counterparts of curcumin. The results of this study should be of great importance to industrial applications in terms of development of natural, but effective preservatives as alternative to synthetic ones.