Preparation, characterization and food packaging application of nano ZnO@Xylan/quaternized xylan/polyvinyl alcohol composite films

Preparation, characterization, antimicrobial evaluation, and grape preservation applications of polyvinyl alcohol/gelatin composite films containing zinc oxide@quaternized chitosan nanoparticles

This study employed a precipitation method to synthesize zinc oxide@quaternised chitosan nanoparticles (ZnO@QAC NPs) containing different concentrations of zinc oxide, namely ZnO@QAC-2, ZnO@QAC-4, and ZnO@QAC-6. Subsequently, these nanoparticles were incorporated into matrices consisting of gelatine (Gn) and polyvinyl alcohol (PVA) separately, which were prepared by casting to form a biodegradable film. We assessed the physicochemical properties of ZnO@QAC NPs and physicochemical characteristics, antioxidant properties, antimicrobial activity and grape preservation efficacy of the film. Compared to the control group, the films showed a reduction in water vapor permeability by >9.38 %, an increase in tensile strength by over 51.95 %, over 70 % scavenging of ABTS free radicals, and good biocompatibility. Additionally, the antimicrobial activity of the films containing ZnO@QAC-6 increased by 37.6 %. In the grape preservation experiment, the weight loss of grapes wrapped in ZnO@QAC-2 film was reduced by 40.13 % on day 15 compared to unwrapped grapes. These results demonstrate that ZnO@QAC/PVA/Gn films have considerable potential for food packaging applications.

Preparation and characterization of polyvinyl alcohol/pullulan/ZnO-Nps composite film and its effect on the postharvest quality of Allium mongolicum Regel

Allium mongolicum Regel is prone to rapid senescence and quality deterioration during postharvest storage. Herein, polyvinyl alcohol/pullulan/ZnO nanoparticles (PVA/PUL/ZnO-Nps) composite films were prepared via solution casting and studied to analyze the effects of ZnO-Nps on the PVA/PUL film matrix. Results revealed that the incorporation of suitable ZnO-Nps effectively reduced the light transmittance, improved water contact angle, water vapor permeability, and mechanical properties of the composite films, as well as enhanced their antimicrobial activity. The composite films were used for the postharvest preservation of A. mongolicum Regel. Results revealed that the PVA/PUL/ZnO-Nps film effectively reduced malondialdehyde accumulation content, superoxide radical generation rate, hydrogen peroxide content, improve the activity of related enzymes, and extend the storage time compared with that of polyethylene films. Therefore, the PVA/PUL/ZnO-Nps film can be used as a novel packaging material for the postharvest preservation of A. mongolicum Regel.

Advances in sustainable food packaging applications of chitosan/polyvinyl alcohol blend films

Researchers are addressing environmental concerns related to petroleum-based plastic packaging by exploring biopolymers from natural sources, chemical synthesis, and microbial fermentation. Despite the potential of individual biopolymers, they often exhibit limitations like low water resistance and poor mechanical properties. Blending polymers emerges as a promising strategy to overcome these challenges, creating films with enhanced performance. This review focuses on recent advancements in chitosan/polyvinyl alcohol (PVA) blend food packaging films. It covers molecular structure, properties, strategies for performance improvement, and applications in food preservation. The blend's excellent compatibility and intermolecular interactions make it a promising candidate for biodegradable films. Future research should explore large-scale thermoplastic technologies and investigate the incorporation of additives like natural extracts and nanoparticles to enhance film properties. Chitosan/PVA blend films offer a sustainable alternative to petroleum-based plastic packaging, with potential applications in practical food preservation.

Z-scheme heterojunction g-C3N4-TiO2 reinforced chitosan/poly(vinyl alcohol) film: Efficient and recyclable for fruit packaging

Nanoparticles-loaded bio-based polymers have emerged as a sustainable substitute to traditional oil-based packaging materials, addressing the challenges of limited recyclability and significant environmental impact. However, the functionality and efficiency of nanoparticles have a significant impact on the application of bio-based composite films. Herein, graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) coupled photocatalyst (g-C3N4-TiO2) was prepared by one-step calcination and introduced into chitosan (CS) and polyvinyl alcohol (PVA) solution to fabricate g-C3N4-TiO2/CS/PVA green renewable composite film via solution casting method. The results demonstrated the successful preparation of a Z-scheme heterojunction g-C3N4-TiO2 with exceptional photocatalytic activity. Furthermore, the incorporation of heterojunction enhanced mechanical properties, water barrier, and ultraviolet (UV) resistance properties of the fresh-keeping film. The g-C3N4-TiO2/CS/PVA composite film exhibited superior photocatalytic antibacterial preservation efficacy on strawberries under LED light, with a prolonged preservation time of up to 120 h, when compared to other films such as polyethylene (PE), CS/PVA, g-C3N4/CS/PVA, and TiO2/CS/PVA. In addition, the composite film has good recyclability and renewability. This work is expected to have great potential for low-cost fruit preservation and sustainable packaging, which also contributes to environmental protection.

Studies on the degradation pattern of wheat malt endo-1,4-β-xylanase on wheat-derived arabinoxylans

BACKGROUND

Wheat malt endo-1,4-β-xylanase is a key enzyme for arabinoxylan degradation, but its wheat-derived arabinoxylan degradation pattern is unclear.

RESULTS

Water-extractable arabinoxylan (WEAX) of 300-750 kDa and 30-100 kDa were the two components with the highest degradation efficiency of wheat malt endo-1,4-β-xylanase, followed by > 1000 kDa WEAX, but 100-300 kDa WEAX showed the lowest degradation efficiency. The main enzymatic products were the 5-30 kDa WEAX, which accounted for 57.57%, 68.15%, and 52.28% of WAXH, WAXM, and WAXL products, respectively. The enzymatic efficiency of wheat malt endo-1,4-β-xylanase was relatively high, and the continuity of enzymatic efficiency was good, especially since the enzymatic reaction was the most intense in 1-3 h. WEAX of > 300 kDa was highly significant and positively correlated with viscosity. In comparison, WEAX of < 30 kDa was highly significant and negatively correlated with viscosity. As the enzymatic degradation proceeded, there were fewer and fewer macromolecular components but more and more small molecule components, and the system viscosity became smaller and smaller.

CONCLUSION

In this study, it was found that wheat malt endo-1,4-β-xylanase degraded preferentially 300-750 kDa and 30-100 kDa WEAX, not in the order of substrate size in a sequential enzymatic degradation. Wheat malt endo-1,4-β-xylanase was most efficient within 3 h, primarily generating < 30 kDa WEAX ultimately. The main products were highly significantly negatively correlated with the system viscosity, so that the system viscosity gradually decreased as the enzymatic hydrolysis proceeded. © 2024 Society of Chemical Industry.

Synthesis and antitumor activity of bagasse xylan derivatives modified by graft-esterification and cross-linking

A crucial aspect in achieving sustainable development of biomass materials is the modification of renewable polysaccharides to create various high-value functional materials. In this paper, bagasse xylan (BX) was used as a raw material to introduce benzyl methacrylate (BMA) through graft copolymerization reaction to generate the intermediate product BX-g-BMA. Subsequently, the target product (CA-BX-g-BMA) was synthesized by catalytic esterification of BX-g-BMA with citric acid (CA) in AmimCl ionic liquid. Meanwhile, the characterization and bioactivity studies of CA-BX-g-BMA were carried out. The graft copolymerization and esterification reactions induced significant changes in the morphological structure of BX and obviously improved its thermal stability and crystallinity. The application of density functional theory (DFT), molecular electrostatic potential (MEP) and molecular docking has revealed that CA-BX-g-BMA possesses multiple active sites, strong biological activity and a strong binding affinity to 6RCF tumor protein with a binding energy of -32.26 kJ/mol. The in vitro antitumor activity of this novel derivative was tested by MTT assay, and the results showed that CA-BX-g-BMA was non-toxic to normal cells and inhibited MDA-MB-231 (breast cancer cells) by up to 32.16 % ± 4.89 %, which is approximately 11 times higher than that of BX. The exploration of these properties is essential to promote future multidisciplinary applications of BX derivatives.

Synergistic Microbial Inhibition and Quality Preservation for Grapes through High-Voltage Electric Field Cold Plasma and Nano-ZnO Antimicrobial Film Treatment

To ensure their quality and safety, harvested grapes should be protected from microbial contamination before reaching consumers. For the first time, this study combined high-voltage electric field cold plasma (HVEF-CP) and nano-ZnO antimicrobial film to inhibit microbial growth on grapes. Using the response surface method, the optimal processing parameters of HVEF-CP (a voltage of 78 kV, a frequency of 110 Hz, and a time of 116 s) were identified to achieve 96.29% sterilization. The effects of co-processing with HVEF-CP and nano-ZnO antimicrobial film on the quality and safety of grapes during storage were explored. When stored at 4 °C and 20 °C, the co-processing extended the shelf life of grapes to 14 and 10 days, respectively. The co-processing increased the sterilization rate to 99.34%, demonstrating a synergistic effect between the two methods to ensure not only the safety of grapes but also their nutrient retention during storage. This novel approach is promising for the efficient, safe, and scalable preservation of grapes as well as other foods.

Highly Hydrophobic Gelatin Nanocomposite Film Assisted by Nano-ZnO/(3-Aminopropyl) Triethoxysilane/Stearic Acid Coating for Liquid Food Packaging

Biodegradable gelatin (G) food packaging films are in increasing demand as the substitution of petroleum-based preservative materials. However, G packaging films universally suffer from weak hydrophobicity in practical applications. Constructing a hydrophobic micro/nanocoating with low surface energy is an effective countermeasure. However, the poor compatibility with the hydrophilic G substrate often leads to the weak interfacial adhesion and poor durability of the hydrophobic coating. To overcome this obstacle, we used (3-aminopropyl) triethoxysilane (APS) as an interfacial bridging agent to prepare a highly hydrophobic, versatile G nanocomposite film. Specifically, tannic acid (TA)-modified nanohydroxyapatite (n-HA) particles (THA) were introduced in G matrix (G-THA) to improve the mechanical properties. Micro/nanostructure with low surface energy composed of nanozinc oxide (Nano-ZnO)/APS/stearic acid (SA) (NAS) was constructed on the surface of G-THA film (G-THA/NAS) through one-step spray treatment. Consequently, as-prepared G-THA/NAS film presented excellent mechanics (tensile strength: 7.6 MPa, elongation at break: 292.7%), water resistance ability (water contact angle: 150.4°), high UV-shielding (0% transmittance at 200 nm), degradability (100% degradation rate after buried in the natural soil for 15 days), antioxidant (78.8% of 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity), and antimicrobial (inhibition zone against Escherichia coli: 15.0 mm and Staphylococcus aureus: 16.5 mm) properties. It should be emphasized that the bridging function of APS significantly improves the interfacial adhesion ability of the NAS coating with more than 95% remaining area after the cross-cut adhesion test. Meanwhile, the G-THA/NAS film could maintain stable and long-lasting hydrophobic surfaces against UV radiation, high temperature, and abrasion. Based on these multifunctional properties, the G-THA/NAS film was successfully applied as a liquid packaging material. To sum up, we provide a feasible and effective method to prepare high-performance green packaging films.

Enhancing Hydrophobicity and Oxygen Barrier of Xylan/PVOH Composite Film by 1,2,3,4-Butane Tetracarboxylic Acid Crosslinking

Hemicellulose has potential advantages in food packaging because of its abundant reserves, degradability and regeneration. However, compared with fossil-derived plastic films, hemicellulose-based films show inferior hydrophobicity and barrier properties because of their low degree of polymerization and strong hydrophilicity. Focusing on such issues, this work covers the modification of a xylan/polyvinyl alcohol (PVOH) film using 1,2,3,4-butane tetracarboxylic acid (BTCA) as esterifying agent. The thus prepared composite film was more compact owing to the esterification reaction with xylan and PVOH forming a crosslinked network structure and reducing the distance between molecular chains. The results showed that BTCA had a positive effect on the oxygen barrier, hydrophobicity and mechanical properties of the composite film. The tensile strength of the xylan/PVOH composite film with 10% BTCA content increased from 11.19 MPa to 13.99 MPa. A 20% BTCA loading resulted in an increase in the contact angle of the composite film from 87.1° to 108.2°, and a decrease in the oxygen permeability from 2.11 to 0.43 (cm³·µm)/(m²·d·kPa), corresponding to increase in the contact angle by 24% and a decrease in oxygen permeability by 80%. The overall performance enhancement indicates the potential application of such composites as food packaging.

Metal-Polymer Nanocomposites: A Promising Approach to Antibacterial Materials

There has been a new approach in the development of antibacterials in order to enhance the antibacterial potential. The nanoparticles are tagged on to the surface of other metals or metal oxides and polymers to achieve nanocomposites. These have shown significant antibacterial properties when compared to nanoparticles. In this article we explore the antibacterial potentials of metal-based and metal-polymer-based nanocomposites, various techniques which are involved in the synthesis of the metal-polymer, nanocomposites, mechanisms of action, and their advantages, disadvantages, and applications.

Recent trends in nanocomposite packaging films utilising waste generated biopolymers: Industrial symbiosis and its implication in sustainability

Uncontrolled waste generation and management difficulties are causing chaos in the ecosystem. Although it is vital to ease environmental pressures, right now there is no such practical strategy available for the treatment or utilisation of waste material. Because the Earth's resources are limited, a long-term, sustainable, and sensible solution is necessary. Currently waste material has drawn a lot of attention as a renewable resource. Utilisation of residual biomass leftovers appears as a green and sustainable approach to lessen the waste burden on Earth while meeting the demand for bio-based goods. Several biopolymers are available from renewable waste sources that have the potential to be used in a variety of industries for a wide range of applications. Natural and synthetic biopolymers have significant advantages over petroleum-based polymers in terms of cost-effectiveness, environmental friendliness, and user-friendliness. Using waste as a raw material through industrial symbiosis should be taken into account as one of the strategies to achieve more economic and environmental value through inter-firm collaboration on the path to a near-zero waste society. This review extensively explores the different biopolymers which can be extracted from several waste material sources and that further have potential applications in food packaging industries to enhance the shelf life of perishables. This review-based study also provides key insights into the different strategies and techniques that have been developed recently to extract biopolymers from different waste byproducts and their feasibility in practical applications for the food packaging business.

Silver Nanoparticles Modified with Polygonatum sibiricum Polysaccharide Improve Biocompatibility and Infected Wound Bacteriostasis

Silver nanoparticles (AgNPs) exhibit strong antibacterial activity and do not easily induce drug resistance; however, the poor stability and biocompatibility in solution limit their widespread application. In this study, AgNPs were modified with Polygonatum sibiricum Polysaccharide (PSP) to synthesize PSP@AgNPs with good stability, biocompatibility, and antibacterial activity. When PSP@AgNP synthesis was performed under a reaction time of 70 min, a reaction temperature of 35 °C, and an AgNO₃-to-PSP volume ratio of 1:1, the synthesized PSP@AgNPs were more regular and uniform than AgNPs, and their particle size was around 10 nm. PSP@AgNPs exhibited lower cytotoxicity and hemolysis, and stronger bacteriostatic activity. PSP@AgNPs damage the integrity and internal structure of cells, resulting in the leakage of intracellular nucleic acids and proteins. The rate of cell membrane damage in Escherichia coli and Staphylococcus aureus treated with PSP@AgNPs increased by 38.52% and 43.75%, respectively, compared with that of AgNPs. PSP@AgNPs inhibit the activities of key enzymes related to antioxidant, energy and substance metabolism in cells. The inhibitory effects on the activities of superoxide dismutase (SOD), catalase (CAT), adenosine triphosphate enzyme (ATPase), malate dehydrogenase (MDH), and succinate dehydrogenase (SDH) in E. coli and S. aureus cells were significantly higher than those of AgNPs. In addition, compared with AgNPs, PSP@AgNPs promote faster healing of infected wounds. Therefore, PSP@AgNPs represent potential antibacterial agents against wound infections.

Green and recyclable graphitic carbon nitride/chitosan/polyvinyl alcohol photocatalytic films with efficient antibacterial activity for fruit packaging

Chitosan (CS) is an excellent raw material for the preparation of food packaging films due to its good film-forming properties, non-toxicity, and biodegradability. However, pure chitosan films have drawbacks such as weak mechanical properties and limited antimicrobial activity. In this work, novel food packaging films containing chitosan, polyvinyl alcohol (PVA) and porous graphitic carbon nitride (g-C₃N₄) were successfully prepared. The PVA served to improve the mechanical properties of the chitosan-based films, whilst the porous g-C₃N₄ acted as a photocatalytically-active antibacterial agent. The tensile strength (TS) and elongation at break (EAB) of the g-C₃N₄/CS/PVA films both increased by ~4 times compared to the pristine CS/PVA films at the optimum g-C₃N₄ loading of ~10 wt%. The addition of g-C₃N₄ increase the water contact angle (WCA) of the films from 38° to 50°, whilst decreasing the water vapor permeability (WVP) from 160 × 10^-12 to 135 × 10^-12 g∙Pa^-1 s^-1 m^-1. The shelf life of strawberries covered with g-C₃N₄/CS/PVA films at room temperature could be extended up to 96 h, compared to 48 h and 72 h for strawberries covered with polyethylene (PE) films or CS/PVA films, respectively. The g-C₃N₄/CS/PVA films offered good antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Further, the composite films could be easily recycled with the regenerated films offering almost identical mechanical properties and activities as the original films. The prepared g-C₃N₄/CS/PVA films thus offer promise for low-cost antimicrobial packaging applications.