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BACKGROUND: Our living environment is being increasingly polluted by petroleum‐based plastics and there is an increasing demand for biodegradable food packaging. In this study, the effect of various ultrahigh‐pressure (UHP) treatments (0, 200 and 400 MPa) on the microstructure and thermal, barrier and mechanical properties of poly(lactic acid) (PLA)/ZnO nanocomposite films was studied. RESULTS: The film‐forming solution was processed using UHP technology. The crystallinity, strength and stiffness of the composite film after UHP treatment increased. In addition, barrier property analysis showed that the UHP treatment significantly (P < 0.05) reduced the oxygen permeability and water vapor permeability (WVP) coefficient of the PLA/ZnO nanocomposite film. Furthermore, the WVP value of the film treated at 400 MPa (50 g kg−1 nano‐ZnO content) was the lowest and reduced by 47.3% compared with that of pure PLA film. The improvement in these properties might be due to the interaction between nano‐ZnO and PLA matrix promoted by UHP treatment. CONCLUSIONS: Therefore, the application of UHP technology on the film‐forming solution could improve the crystallinity and functional properties of the nanocomposite film, and has great potential in the production of food packaging films with ideal functions. © 2021 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Effects of high pressure treatment (0, 200 and 400 MPa) on water vapour barrier, microstructure, thermal, and mechanical properties of poly (lactic acid) (PLA)/Ag nanocomposite films were investigated. The migration behavior of nano-Ag from the nanocomposite films in the presence of 50% (v/v) ethanol as a food simulant was also studied. The water vapour barrier properties increased as pressure was applied to film-forming solutions. High pressure treatment enhanced the mutual effect between PLA and nanoparticles, leading to a more compact network structure in PLA/Ag nanocomposite films. Furthermore, PLA/Ag nanocomposite films treated by high pressure were significantly affected by microstructure, thermal, and mechanical properties when, compared with untreated samples. High pressure treatment at 200 to 400 MPa significantly (p < 0.05) reduced the migration of nano-Ag from the films. Overall, high pressure treatment on film-forming solutions showed potential in improving the functional properties of nanocomposite films, especially in relation to water vapour barrier properties. [ABSTRACT FROM AUTHOR]

Different percentages (0%, 1%, 5%, and 10%) of nano-Ag particles were added to polylactic acid (PLA) to make an active nanocomposite packaging film. Strawberries were packaged by the nanocomposite films and stored at 4 ± 1 °C for 10 days. The freshness of strawberries was assessed by regularly measuring the physicochemical properties of the strawberries in each packaging film. The difference in the freshness of strawberries was evaluated by determining the following parameter changes: weight loss, hardness, soluble solids, titratable acid, color, vitamin C, total phenol, free radical scavenging activity, peroxidase activity, and sensory evaluation. The results revealed that the active nanocomposite packaging film has better preservation effect when compared with pure PLA film. Its preservation effect is mainly reflected in the more effective reduction of vitamin C loss, delaying the decline of total phenols and 1-Diphenyl-2-picrylhydrazyl (DPPH) in strawberries. It also showed better physical properties. The results showed that the PLA nanocomposite packaging film could effectively preserve freshness of strawberries. [ABSTRACT FROM AUTHOR]

Highlights • A film was prepared by adding TiO 2 and Ag nanoparticles into PLA matrix. • Weight loss in PLA nanocomposite group was lower than that for PLA and PLA/BEO group. • The PLA nanocomposite films provided better retention in firmness, color, and Vit C. • The PLA nanocomposite films had an obvious inhibition on the microorganism growth. • Mango sample packed by the PLA nanocomposite films achieved a shelf-life of 15 days. Abstract The effects of polylactic acid (PLA) film, PLA/bergamot essential oils (BEO) film, and PLA nanocomposite film (PLA/BEO/nano-TiO 2 film and PLA/BEO/nano-TiO 2 +nano-Ag film) on the physicochemical and microbial quality of mangoes stored at room temperature for 15 days was evaluated. The measured properties of mangoes included weight loss, fruit firmness, color, total soluble solids content, total acidity, vitamin C, microbial property, and sensory quality. The weight loss of mangoes packed by PLA nanocomposite films was significantly (p < 0.05) lower than that for PLA and PLA/BEO groups from day 9 to day 12. The PLA nanocomposite films could effectively delay the loss of mango firmness during the entire storage period. The PLA nanocomposite films could also retard the harmful changes in color, total acidity, vitamin C, and microbial property when compared with PLA and PLA/BEO films. The overall acceptability of mangoes packed by the PLA nanocomposite films was still higher than 5 scores and within limit of marketability at the end of storage period. The result indicated that the PLA nanocomposite films could be used to maintain the quality of fresh mango and extend its postharvest life to 15 days. [ABSTRACT FROM AUTHOR]