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High costs and low performance have constrained the application of bio-based materials in food packaging. Herein, a series of ultra-thin poly(L-lactic acid-iconic acid N-diol) (P(LA-NI)) copolymer films were developed using a "one-step" polycondensation process with integrated toughness, barrier properties, gas selectivity, and quality control features. The massive branched structure and gg conformers in P(LA-NI) act as "internal chain expansion" and "internal plasticization". Meanwhile, P(LA-NI) contains numerous polar groups and unique nanoscale microphase structures to realize excellent CO 2 , O 2 barrier, CO 2 /O 2 selectivity, anti-fogging, and UV shielding functions. The atmosphere within the package spontaneously achieves the desirable low O 2 and high CO 2 levels when packaging button mushrooms with high respiratory metabolism. Eventually, the shelf life of button mushrooms reached 24 days, >3-fold extended. This PLLA-based film meets "dual carbon" and "food safety" goals and has vast potential for fresh food preservation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

An atmosphere within a package affects the metabolic process of food and the microbial growth of fresh products and has a vital role in preserving food. It depends on the membrane's specific gas permeability and selectivity to generate a desirable atmosphere for storage. In this study, triblock poly(l-lactic acid‑ d -ɛ-caprolactone) (PLDC) copolymers and three-arm poly(l-lactic acid- g -ɛ-caprolactone) (PLGC) star copolymers were synthesized, in which a microphase-separated morphology of sea-island structure was established in PLGC membrane as a gas "fast permeation channel" for regulating CO 2 and O 2 permeability and CO 2 /O 2 selectivity. AFM observation revealed different well-defined micro phase-separated structures of PLGC with size ranges of 200– 300 nm. Comparing PLGC membrane with PLLA, CO 2 and O 2 transmission rates increased by 416.9 % and 132.7 %, while H 2 O transport rates increased by 245.6 %. Mechanical testing shows that the PLGC membrane exhibits 40.8-fold elongation at break compared to PLLA, showing excellent flexibility. Moreover, okra's equilibrium-modified atmosphere packaging was designed based on a theoretically derived model. Preservation results suggested that the PLGC packaging membrane could generate an ideal high 8.7– 9.2 % CO 2 and low 2.3– 2.7 % O 2 atmosphere for okra preservation, delaying the discoloring and rotting of okra. [Display omitted] • A three-arm star poly (l-lactic acid- g - ɛ -caprolactone) membrane has been prepared. • Construction of a sea-island structure to regulate membrane gas permeability. • An ideal atmosphere with high CO 2 and low O 2 can be generated in the package. • Poly (l-lactic acid- g - ɛ -caprolactone) membranes can extend the shelf life of okra. [ABSTRACT FROM AUTHOR]

To improve the film-forming ability and gas permeability of chitosan (CS), cross-linked CS was prepared via cross-linking reaction with diepoxy-poly (ethylene glycol) (PEG) and used for coating preservation of vibration damaged Nanguo pears. Results showed that the elongations at break of cross-linked CS films increased from 10.4 to 31.5 cm/100 cm with PEG insertion. Meanwhile, the carbon dioxide/oxygen (CO 2 /O 2) perm-selective ratio increased from 3.48 to 6.02 with 37.5 g/100 mL PEG addition, which is beneficial for the formation of a low O 2 and high CO 2 microenvironment. Both disc diffusion assay and in vivo antimicrobial activity assay on pears revealed that the CS-PEG coating can effectively inhibit the growth of spoilage organisms. CS-PEG coated pears also have lower respiration rates and malondialdehyde content. Principal component analysis displayed that CS-PEG coating has a significant effect on hardness and sensory quality of pears. The CS-PEG coated vibration damaged pears maintained a better physical appearance and remarkable hardness for 25 days. [Display omitted] • Cross-linked CS-PEG films were prepared via the epoxy-amine and crosslinking reaction.. • The elongation at break of Cross-linked CS film was increased by triple with PEG.. • CO 2 /O 2 perm-selective ratio of CS-PEG films increased from 3.48 to 6.02. • CS-PEG film had better antimicrobial activity than CS.. • CS-PEG coated vibration damaged pears maintain better quality by 25th day.. [ABSTRACT FROM AUTHOR]

The irreconcilable paradox between barrier performance and ductility is a "stumbling block" restricting the development of poly(L-lactic acid) (PLLA) films in the packaging industry. In this work, we reported the fabrication of an ultra-thin PLLA-based film with barrier properties and ductility by adjusting the polarity and conformational behavior of the polymer chains. Firstly, a novel unsaturated poly(L-lactic acid- co -butyrate itaconate) P(LA-BI) copolymer containing C C double bonds was synthesized using melt polycondensation. The results reveal that the addition of 60 % of P(LA-BI) enables PLLA film to achieve an elongation at a break of 83.6 % due to P(LA-BI) containing partially branched structures, which resulted in the polymer chains being arranged more in a high-energy gg conformer. Meanwhile, because of the large number of C O polar groups in P(LA-BI), PLLA/P(LA-BI) 60 film show CO 2 and O 2 permeability coefficients (CDP and OP) of 1.8 and 0.45 × 10−8 g·m·m−2·h−1·Pa−1 respectively, which means that it has excellent gas barrier properties. Moreover, PLLA/P(LA-BI) 60 film shows a 33.3 % increase in CO 2 /O 2 ratio and an excellent ultraviolet (UV) barrier performance compared to neat PLLA. Preservation results suggested that the CO 2 and O 2 levels within the package could be regulated by varying the amount of P(LA-BI) added. Among them, PLLA/P(LA-BI) 40 film generated a more desirable CO 2 and O 2 atmosphere for cherry tomatoes preservation, which was reflected by the delaying of senescence, discoloration, and decay, inhibition of oxidative cell damage through reduced malondialdehyde production, and maintenance of nutritional and flavor substances in cherry tomatoes. This PLLA-based film offers the advantages of operational simplicity, environmental friendliness, and inexpensive cost, making it great promising for food preservation and other applications requiring barrier properties and ductility. [Display omitted] • A poly(L-lactic acid- co -butyrate itaconate) copolymer was synthesized for the first time. • An ultra-thin PLLA film with ductility and barrier properties was prepared. • Improve film ductility by regulating conformational behavior of the chains • Establishment of a desirable CO 2 and O 2 atmosphere for cherry tomatoes storage • Maintains the overall quality and extends the shelf life of cherry tomatoes [ABSTRACT FROM AUTHOR]