A low-cost in situ nanoparticle coating with high encapsulation efficiency and continuous release capability for inhibiting flesh lignification and enhancing antioxidant capacity and cold tolerance of loquat fruit

Loquat fruit is vulnerable to postharvest chilling lignification. Fumigation with methyl jasmonate (MeJA) could inhibit the lignification, but is inefficient. The present study developed nanoparticles encapsulated with MeJA (MeJA@NPs) with high encapsulation efficiency (94.83 %) and 30 d sustained release capability. Then, a transparent, edible, in situ coating was prepared by blending a gelatin/pullulan solution with MeJA@NPs. The coating could continuously inhibit chilling lignification of loquat fruit, where the firmness increase and lignin accumulation were reduced by 82.7 % and 52.3 % respectively after 6 d of storage. Further analysis of the inhibition mechanism showed that the coating suppressed the peroxidase activity, thereby blocking lignin polymerization. Besides, the coating could also enhance the antioxidant capacity of fruits via activating cinnamate 4-hydroxylase and 4-coumarate: CoA ligase and upregulating the superoxide dismutase, catalase, and ascorbate peroxidase activities. In conclusion, our work provides a novel approach of in situ nanoparticle coating on fruits for postharvest preservation.