Effective strategies to enhance ultraviolet barrier ability in biodegradable polymer-based films/coatings for fruit and vegetable packaging

The limitation of preservation technology causes great losses on fresh fruits and vegetables (F&V) during postharvest. Ultraviolet (UV) as a secondary catalyst can trigger the photooxidation chain reaction in F&V, and induce them rapid oxidation, senescence, and rot. Many studies have shown that adding UV barrier ingredients to film/coating packaging can effectively delay the deterioration of F&V food. This work reviews the strategies used to enhance the UV barrier properties in films/coatings over the past five years, focusing on their application in F&V quality maintenance. Then, UV induction effect on F&V deterioration and potential mechanism are discussed. In addition, the UV barrier mechanism and the future trends were summarized. UV can cause the disintegration of endogenous photosensitizers of F&V through reactive oxygen species and seriously affects their physiological and metabolic balance. The enhancement strategies for enhancing the film/coating UV barrier properties mainly include the addition of UV barrier components and the improvement of film structure. The UV barrier components can absorb UV through electronic transition in chromogenic groups, electron hole pairs, sp2 hybridization of central atoms, as well as surface plasmon resonance, or barrier UV via light reflection, refraction, and scattering. In addition, enhancing the film/coating structure can adjust the surface roughness, internal crosslinking state, and UV barrier ingredients’ retention thus improving UV barrier performance. However, most of present studies only focus on the improvement of UV barrier films/coatings on F&V quality and pay less attention to the physiological state.