Dual regulation strategy to enhance polysaccharide coating adhesion and tangerine fruits preservation: Mechanistic insights and effect evaluation

Abstract

To address the instability of polysaccharide-based coatings on fruit surfaces caused by weak interfacial bonding, this study investigated the use of small-molecule wetting agents for the dual regulation of fruit surface free energy and coating solution surface tension. Through systematic screening of four wetting agents, triglyceride monostearate (TGMS) was selected as the optimal wetting agent, based on its ability to minimize the contact angle of chitosan (CS) and pullulan (PU) coating solutions on red tangerine fruit (Citrus reticulata Blanco) surfaces. Mechanism studies revealed that TGMS treatment raised fruit surface free energy to 41.44 mN/m by enhancing polar group availability on fruit surfaces, while its incorporation into CS and PU coatings lowered surface tension to ∼40 mN/m through reduced intermolecular interactions. This achieved precise energy matching between coating solutions and fruits surface, reducing the contact angle from > 90° to 54° and increasing the spreading coefficient by 70 %. In postharvest storage trials, the optimized dual-treatment coatings (0.4 T-CS/20 T and 0.6 T-PU/20 T) reduced the decay rate of tangerine fruit by 45 % and 55 %, respectively, and extended shelf life by about 4 – 8 days compared with the uncoated control. The coated fruits also retained higher firmness and nutrient content (total soluble solids, ascorbic acid, and titratable acidity). This dual regulation strategy, using TGMS to simultaneously enhance fruit surface free energy and reduce coating surface tension, offers a novel approach to boost edible coating adhesion and preservation, offering a viable pathway to extend fresh fruit shelf life and mitigate postharvest losses.