Enhancement of Egyptian soft white cheese shelf life using a novel chitosan/carboxymethyl cellulose/zinc oxide bionanocomposite film

Advances in the application of chitosan as a sustainable bioactive material in food preservation

Chitosan is obtained from chitin and considered to be one of the most abundant natural polysaccharides. Due to its functional activity, chitosan has received intense and growing interest in terms of applications for food preservation over the last half-century. Compared with earlier studies, recent research has increasingly focused on the exploration of preservation mechanism as well as the targeted inhibition with higher efficiency, which is fueled by availability of more active composite ingredients and integration of more technologies, and gradually perceived as "chitosan-based biofilm preservation." In this Review, we comprehensively summarize the potential antimicrobial mechanisms or hypotheses of chitosan and its widely compounded ingredients, as well as their impacts on endogenous enzymes, oxidation and/or gas barriers. The strategies used for enhancing active function of the film-forming system and subsequent film fabrication processes including direct coating, bioactive packaging film and layer-by-layer assembly are introduced. Finally, future development of chitosan-based bioactive film is also proposed to broaden its application boundaries. Generally, our goal is that this Review is easily accessible and instructive for whose new to the field, as well as hope to advance to the filed forward.

A journey to the world of fascinating ZnO nanocomposites made of chitosan, starch, cellulose, and other biopolymers: Progress in recent achievements in eco-friendly food packaging, biomedical, and water remediation technologies

Green chemistry or in other words "green world" is referred to a sustainable environment using biocompatible, biodegradable, renewable, economical, and simple materials, and methods. Without any exaggeration, the exceptional chemical and physical properties of ZnO bionanocomposites beside various utilizations, make it vital materials in research and green chemistry field. Biocompatible ZnO nanoparticles with fascinating antimicrobial, physicochemical, as well as photocatalytic performance could be applied as a prominent candidate to reinforce diverse biopolymer matrixes, for instance, chitosan, starch, cellulose, gelatin, alginate, poly(hydroxyalkanoates), carrageenan, and so on. With a combination of advantageous properties of these materials, they could be illustrated specific utilizations in different areas. In this regard, the following context focuses on highlighting the recent achievements of this category of material on three important and widely used scopes: eco-friendly food packaging, biomedical specially wound dressings, and water remediation technologies.

Soluble soybean polysaccharide/nano zinc oxide antimicrobial nanocomposite films reinforced with microfibrillated cellulose

Nanocomposite films of soluble soybean polysaccharide (SSPS)/nano zinc oxide (nZnO) reinforced with microfibrillated cellulose (MFC) were developed by solvent casting method. The structure, optical, barrier, thermal, surface wettability, mechanical properties and antimicrobial activity of the SSPS/MFC, SSPS/nZnO and SSPS/nZnO/MFC nanocomposite films were evaluated. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra indicated interactions between SSPS and the nano-fillers. The nanocomposite films containing MFC showed improved tensile strength, stiffness, ultraviolet (UV) light barrier property, thermal stability and water resistance when compared with the neat SSPS film. The nZnO-incorporated nanocomposite films exhibited good antimicrobial activity against E. coli and B. subtlis. Overall, the MFC-reinforced SSPS/nZnO nanocomposite films possessed desirable characteristics to be considered as potential candidates for antimicrobial packaging and biomedical applications.

Study on Biodegradable Chitosan-Whey Protein-Based Film Containing Bionanocomposite TiO2 and Zataria multiflora Essential Oil

In our research, a composite film of whey protein isolate (WPI)/chitosan incorporated with TiO2 nanoparticles (NPs) and essential oil of Zataria multiflora (ZEO) was developed. The resulting composite films were evaluated by FTIR, SEM, and XRD, and also the physicochemical characteristics including color, mechanical properties, swelling ratio, and water vapor permeability (WVP) were studied. SEM graphs exhibited that the samples had a uniform and homogeneous structure where TiO2 NPs and ZEO were well dispersed. FTIR and XRD findings also show that the hydrogen bonds and hydrophobic interactions are the main interactions between the composite WPI/chitosan and TiO2. The crystalline nature of the composite samples increased with the increase of NP content. Nevertheless, ZEO had an insignificant effect on the functional groups and the crystallinity of composite samples. The film visual characterization revealed that, by adding and increasing the TiO2 and TiO2-ZEO, sample lightness and opacity significantly increased. Additions of TiO2 remarkably (p<0.05) improved the water vapor and mechanical properties of composite samples, although the loading of ZEO, regardless of TiO2 incorporation, led to a considerable decrement of these properties. Furthermore, composite films containing ZEO combined with 2% of TiO2 compared with 1% of NPs blended with ZEO had strong antimicrobial properties against Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes. Generally, the findings proposed that the addition of TiO2 reinforces the properties of composite films with a synergistic effect of ZEO loading on the antibacterial ability, by which the resulting biodegradable composite samples can be used as a food active packaging material.

Antimicrobial activity of chitosan coating containing ZnO nanoparticles against E. coli O157:H7 on the surface of white brined cheese

White brined cheese may serve as an ideal medium for the growth of foodborne pathogens including E. coli O157:H7. The objectives of this study were i) to evaluate the inhibitory effects of zinc oxide (ZnO) nanoparticles against E. coli O157:H7 at 10 or 37 °C using broth dilution; ii) to address the post-process contamination of white brined cheese with E. coli O157:H7 by using chitosan coating with or without ZnO nanoparticles during storage for 28 d at 4 and 10 °C; and iii) to study the physicochemical characteristics of chitosan coating containing ZnO nanoparticles. ZnO nanoparticles at ≥0.0125% inhibited the growth of three E. coli O157:H7 strains at both 37 and 10 °C. The chitosan coating with or without ZnO nanoparticles significantly reduced the initial numbers of E. coli O157:H7 in white brined cheese by 2.5 and 2.8 log CFU/g, respectively, when stored at 4 °C or by 1.9 and 2.1 log CFU/g, respectively, when stored at 10 °C. The chitosan-ZnO nanoparticle coating was not significantly different (p > 0.05) but was slightly better than chitosan alone as an active, smart packaging material in food applications.

Ethylene scavengers for the preservation of fruits and vegetables: A review

The phytohormone ethylene is the main cause of postharvest spoilage of fruit and vegetables (F&V). To address the global challenge of reducing postharvest losses of F&V, effective management of ethylene is of great importance. This review summarizes the various ethylene scavengers/inhibitors and emerging technologies recently developed for the effective removal of ethylene released, paying particular attention to the ethylene scavenger/inhibitors containing catalysts to promote the in-situ oxidation of ethylene without inducing further pollution. Packing ethylene scavengers, such as zeolite, titanium dioxide and transition metals, in a small sachet has been practically used and widely reported. However, incorporating ethylene scavenger into food packaging materials or films along with the in-situ oxidation of ethylene has been rarely reviewed. The current review fills up this gap, covering the latest research progress on ethylene scavengers/inhibitors and discussion on the mechanisms of ethylene elimination and oxidation associated with F&V packaging.

Polysaccharide and Protein Films with Antimicrobial/Antioxidant Activity in the Food Industry: A Review

From an economic point of view, the spoilage of food products during processing and distribution has a negative impact on the food industry. Lipid oxidation and deterioration caused by the growth of microorganisms are the main problems during storage of food products. In order to reduce losses and extend the shelf-life of food products, the food industry has designed active packaging as an alternative to the traditional type. In the review, the benefits of active packaging materials containing biopolymers (polysaccharides and/or proteins) and active compounds (plant extracts, essential oils, nanofillers, etc.) are highlighted. The antioxidant and antimicrobial activity of this type of film has also been highlighted. In addition, the impact of active packaging on the quality and durability of food products during storage has been described.

From waste/residual marine biomass to active biopolymer-based packaging film materials for food industry applications – a review

Waste/residual marine biomass represents a vast and potentially underexplored source of biopolymers chitin/chitosan and alginate. Their isolation and potential application in the development and production of bio-based food packaging are gaining in attractiveness due to a recent increment in plastic pollution awareness. Accordingly, a review of the latest research work was given to cover the pathway from biomass sources to biopolymers isolation and application in the development of active (antimicrobial/antioxidant) film materials intended for food packaging. Screening of the novel eco-friendly isolation processes was followed by an extensive overview of the most recent publications covering the chitosan- and alginate-based films with incorporated active agents.

Efficiency of Novel Antimicrobial Coating Based on Iron Nanoparticles for Dairy Products’ Packaging

The main function of food packaging is to maintain food’s quality and safety. The use of active packaging, including antimicrobial materials, can significantly extend the shelf life of food. Many of these packaging solutions are based on the application of polymer films containing metal nanoparticles (e.g., Ag, Au, Cu) or metal oxides (e.g., TiO2, ZnO, MgO). However, the use of iron nanoparticles is rarely mentioned. In the study, polylactide (PLA) films containing zero-valent iron (ZVI) were made by casting method. Pure PLA films and PLA films with the addition of Fe2O3 were used as comparative materials. The composition and structure of ZVI/PLA films were evaluated with scanning electron microscopy. The XRD spectra performed on ZVI/PLA films confirmed the presence of iron in the packaging material and revealed their oxide form (Fe2O3). The addition of zero-valent iron in the concentration 1%, 3%, or 5% resulted in the formation of crystallographic planes measuring 40.8, 33.6, and 28.6 nm, respectively. The color and gloss of the films, and their antimicrobial activity against bacteria (Bacillus subtilis, Escherichia coli, Staphylococcus epidermidis) and fungi (Geotrichum candidum, Rhodotorula rubra) were also examined. The PLA films with addition of 3% of ZVI (w/w) inhibited the growth of all tested organisms in contrast to PLA and PLA/Fe2O3 films. The addition of ZVI to polymer matrix caused changes in its appearance and optical properties. The ZVI/PLA coating used on polyolefin film allowed to extend the shelf life of goat cheese packed in examined material to 6 weeks. Considering the antimicrobial properties of the ZVI/PLA films and PLA biodegradability the obtained material can be successfully applied in the food industry.

Synthesis and evaluation of eco-friendly carboxymethyl cellulose/polyvinyl alcohol/CuO bionanocomposites and their use in coating processed cheese

In the present study, we formulated and characterized CMC/PVA/CuO bionanocomposites to evaluate their use in coating processed cheese. Copper oxide nanoparticles (CuO-NPs) were prepared and added to a mixed solution of carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA) using compositions of 0.3, 0.6 and 0.9% (w/v). The CMC/PVA/CuO bionanocomposites were prepared by a solution casting method and used for coating processed cheese. The fabricated bionanocomposite films and CuO-NPs were characterized by TEM, SEM, EDEX, XRD, DLS, and FT-IR analysis. Inclusion of CuO-NPs decreased the gas transmission rate (GTR) and water vapor transmission rate (WVTR) of the prepared film. Also, the bionanocomposite suspensions exhibited high but variable inhibitory effects against several pathogenic bacteria and fungi. The impact of coating of processed cheese surfaces with the prepared bionanocomposite films on microbiological, physicochemical, textural and sensory properties of the processed cheese were assessed during 6 months of cold storage. Coating cheese with film containing CuO-NPs eliminated mould growth on the cheese surface and decreased significantly (P < 0.05) the total bacterial count of the cheese. Furthermore, coating of cheese decreased the moisture losses and retarded the increase in the cheese hardness during storage. The highest acceptability at the end of the storage period was given for processed cheese coated with the bionanocomposite containing 0.9% CuO-NPs. Thus, the obtained CMC/PVA/CuO bionanocomposite films could be a promising candidate for cheese packaging applications.

In the present study, we formulated and characterized CMC/PVA/CuO bionanocomposites to evaluate their use in coating processed cheese.

Development of Antibacterial Carboxymethyl Cellulose-Based Nanobiocomposite Films Containing Various Metallic Nanoparticles for Food Packaging Applications

In this study, silver (Ag), zinc oxide (ZnO), and copper oxide (CuO) metallic nanoparticles were used in preparation of carboxymethyl cellulose (CMC) nanobiocomposite films. Scanning electron microscopy (SEM), X-ray diffraction (EDXA), water vapor permeability (WVP), ultraviolet and visible light (UV-Vis) spectroscopy, and mechanical and microbial tests were used to determine the characteristics of the obtained active films. SEM results showed that the CMC nanobiocomposite films had roughness deflection levels and the EDXA test confirmed the presence of Ag, ZnO, and Cuo nanoparticles in the biopolymer tissue. UV-Vis spectroscopy confirmed that with addition of metallic nanoparticles to the pure CMC film, absorption rate increased and WVP decreased. In the mechanical tests, addition of nanoparticles also increased the tensile strength of the films, and the nanobiocomposite films exhibited higher resistance compared to the pure CMC film. Films incorporating metallic nanoparticles showed antibacterial properties against Escherichia coli and Staphylococcus aureus growth. Thus, nanobiocomposite films can be used as active packaging films and could increase the shelf-life of the food.

High-density immobilization of a ginsenoside-transforming β-glucosidase for enhanced food-grade production of minor ginsenosides

Use of recombinant glycosidases is a promising approach for the production of minor ginsenosides, e.g., Compound K (CK) and F₁, which have potential applications in the food industry. However, application of these recombinant enzymes for food-grade preparation of minor ginsenosides are limited by the lack of suitable expression hosts and low productivity. In this study, Corynebacterium glutamicum ATCC13032, a GRAS strain that has been used extensively for the industrial-grade production of additives for foodstuffs, was employed to express a novel β-glucosidase (MT619) from Microbacterium testaceum ATCC 15829 with high ginsenoside-transforming activity. A cellulose-binding module was additionally fused to the N-terminus of MT619 for immobilization on cellulose, which is an abundant and safe material. Via one-step immobilization, the fusion protein in cell lysates was efficiently immobilized on regenerated amorphous cellulose at a high density (maximum 984 mg/g cellulose), increasing the enzyme concentration by 286-fold. The concentrated and immobilized enzyme showed strong conversion activities against protopanaxadiol- and protopanaxatriol-type ginsenosides for the production of CK and F₁. Using gram-scale ginseng extracts as substrates, the immobilized enzyme produced 7.59 g/L CK and 9.42 g/L F₁ in 24 h. To the best of our knowledge, these are the highest reported product concentrations of CK and F₁, and this is the first time that a recombinant enzyme has been immobilized on cellulose for the preparation of minor ginsenosides. This safe, convenient, and efficient production method could also be effectively exploited in the preparation of food-processing recombinant enzymes in the pharmaceutical, functional food, and cosmetics industries.

Utilization of chitosan/Ag bionanocomposites as eco-friendly photocatalytic reactor for Bactericidal effect and heavy metals removal

Chitosan is a nontoxic, eco-friendly, and biocompatible natural polymer which could be used in an extensive range of applications for example in the areas of membranes, biomedicine, hydrogels, wastewater treatment, food packaging. Moreover, chitosan based nanomaterials had high sorption capacities, chelating activities, stability, and versatility, that would be potentially applied as green reactants in various scientific and engineering applications. The current study involved the preparation of silver nanoparticles incorporated into chitosan thin films and used for various purposes including photo-oxidation of organic pollutants, heavy metal removal (Cd, Pb, Cr, and Fe) and antibacterial activity. The fabricated chitosan/silver (CS/Ag) bionanocomposites thin films were characterized by the ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and Fourier transforms infrared (FT-IR) spectroscopy. Furthermore, the prepared CS/Ag bionanocomposites had revealed good photodegradation rate, heavy metals removal and antimicrobial activity against gram-negative bacteria like E. coli, and gram-positive bacteria like G. bacillus, with increasing the loading of different concentrations of chitosan and silver nanoparticles incorporated into the prepared bionanocomposite thin films. Consequently, the prepared CS/Ag bionanocomposites are considered good candidates for wastewater treatment through photo-oxidation of organic pollutants, heavy metal removal as well as respectable antibacterial materials.

Gellan gum incorporating titanium dioxide nanoparticles biofilm as wound dressing: Physicochemical, mechanical, antibacterial properties and wound healing studies

In this work, the potential of titanium dioxide nanoparticles incorporated gellan gum (GG + TiO₂-NPs) biofilm as wound dressing material was investigated. The GG + TiO₂-NPs biofilm was prepared via evaporative casting technique and was characterized using FTIR, XRD, and SEM to study their physiochemical properties. The mechanical properties, swelling and water vapor transmission rate (WVTR) of biofilm was determined to comply with an ideal wound dressing material. In vitro and in vivo wound healing studies was carried out to evaluate the performance of GG + TiO₂-NPs biofilm. In vitro wound healing was studied on 3 T3 mouse fibroblast cells for cell viability, cell proliferation, and scratch assay. The acridine orange/propidium iodide (AO/PI) staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were used to evaluate the viability of cell and cell proliferation. Cell migration assay was analyzed using Essen BioScience IncuCyteTM Zoom system. In vivo wound healing via open excision wounds model on Sprague Dawley rat was studied within 14 days. The FT-IR spectra of GG + TiO₂-NPs biofilm show main bands assigned to OH stretching, OH deformation, and TiO stretching modes. XRD pattern of GG + TiO₂-NPs biofilm suggesting that TiO₂-NPs was successfully incorporated in biofilm and well distributed on the surface as proved by SEM analysis. The GG + TiO₂-NPs biofilm shows higher mechanical strength and swelling (3.76 ± 0.11 MPa and 1061 ± 6%) as compared to pure GG film (3.32 ± 0.08 Mpa and 902 ± 6%), respectively. GG + TiO₂-NPs biofilm shows good antibacterial properties as 9 ± 0.25 mm and 11 ± 0.06 mm exhibition zone was observed against Staphylococcus aureus and Escherichia coli bacteria, respectively. While no exhibition zone was obtained for pure GG biofilm. GG + TiO₂-NPs biofilm also demonstrated better cell-to-cell interaction properties, as it's promoted cell proliferation and cell migration to accelerate open excision wound healing on Sprague Dawley rat. The wound treated with GG + TiO₂-NPs biofilm was healed within 14 days, on the other hand, the wound is still can be seen when it was treated with GG. However, GG and GG + TiO₂-NPs biofilm show no cytotoxicity effects on mouse fibroblast cells.

The Effect of Nanofillers on the Functional Properties of Biopolymer-based Films: A Review

Waste from non-degradable plastics is becoming an increasingly serious problem. Therefore, more and more research focuses on the development of materials with biodegradable properties. Bio-polymers are excellent raw materials for the production of such materials. Bio-based biopolymer films reinforced with nanostructures have become an interesting area of research. Nanocomposite films are a group of materials that mainly consist of bio-based natural (e.g., chitosan, starch) and synthetic (e.g., poly(lactic acid)) polymers and nanofillers (clay, organic, inorganic, or carbon nanostructures), with different properties. The interaction between environmentally friendly biopolymers and nanofillers leads to the improved functionality of nanocomposite materials. Depending on the properties of nanofillers, new or improved properties of nanocomposites can be obtained such as: barrier properties, improved mechanical strength, antimicrobial, and antioxidant properties or thermal stability. This review compiles information about biopolymers used as the matrix for the films with nanofillers as the active agents. Particular emphasis has been placed on the influence of nanofillers on functional properties of biopolymer films and their possible use within the food industry and food packaging systems. The possible applications of those nanocomposite films within other industries (medicine, drug and chemical industry, tissue engineering) is also briefly summarized.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Fracture Mechanics and Oxygen Gas Barrier Properties of Al₂O₃/ZnO Nanolaminates on PET Deposited by Atomic Layer Deposition

Rapid progress in the performance of organic devices has increased the demand for advances in the technology of thin-film permeation barriers and understanding the failure mechanisms of these material systems. Herein, we report the extensive study of mechanical and gas barrier properties of Al₂O₃/ZnO nanolaminate films prepared on organic substrates by atomic layer deposition (ALD). Nanolaminates of Al₂O₃/ZnO and single compound films of around 250 nm thickness were deposited on polyethylene terephthalate (PET) foils by ALD at 90 °C using trimethylaluminium (TMA) and diethylzinc (DEZ) as precursors and H₂O as the co-reactant. STEM analysis of the nanolaminate structure revealed that steady-state film growth on PET is achieved after about 60 ALD cycles. Uniaxial tensile strain experiments revealed superior fracture and adhesive properties of single ZnO films versus the single Al₂O₃ film, as well as versus their nanolaminates. The superior mechanical performance of ZnO was linked to the absence of a roughly 500 to 900 nm thick sub-surface growth observed for single Al₂O₃ films as well as for the nanolaminates starting with an Al₂O₃ initial layer on PET. In contrast, the gas permeability of the nanolaminate coatings on PET was measured to be 9.4 × 10⁻³ O₂ cm³ m⁻² day⁻¹. This is an order of magnitude less than their constituting single oxides, which opens prospects for their applications as gas barrier layers for organic electronics and food and drug packaging industries. Direct interdependency between the gas barrier and the mechanical properties was not established enabling independent tailoring of these properties for mechanically rigid and impermeable thin film coatings.

Highly Transparent, Strong, and Flexible Films with Modified Cellulose Nanofiber Bearing UV Shielding Property

This work investigates multifunctional composite films synthesized with cellulose nanofibers (CNFs) and poly(vinyl alcohol) (PVA). First, TEMPO-oxidized CNFs were modified in the heterogeneous phase with benzophenone, diisocyanate, and epoxidized soybean oil via esterification reactions. A thorough characterization was carried out via elemental analysis as well as FT-IR and X-ray photoelectron spectroscopies and solid-state NMR. Following, the surface-modified CNFs were combined with PVA to endow composite films with UV-absorbing capabilities while increasing their thermomechanical strength and maintaining a high light transmittance. Compared to neat PVF films, the tensile strength, Young modulus, and elongation of the films underwent dramatic increases upon addition of the reinforcing phase (maximum values of ∼96 MPa, ∼ 714 MPa, and ∼350%, respectively). A high UV blocking performance, especially in the UVB region, was observed for the introduced multifunctional PVA films at CNF loadings below 5 wt %. The trade-off between modified nanofibril function as interfacial reinforcement and aggregation leads to an optimum loading. The results indicate promising applications, for example, in active packaging.

Current advancements in chitosan-based film production for food technology; A review

Chitosan is obtained from chitin, which could be considered to be the most abundant polymer after cellulose. Owing to these properties, chitosan alone or chitosan-based composite film production is attaining huge attention in terms of applications from researchers and industrialists coming from divergent fields. To enhance the biological (mainly antimicrobial and antioxidant) and physiological (mainly mechanical, thermal and barrier) attributes of the chitosan-based films, a vast medley of plant extracts and supporting polymers has been blended into chitosan films. Considering the up to date literature reports based on chitosan film production and applications, it can be stated that still, the research ratio is low in this field. Chitosan blend/composite films with specific properties (superhydrophobicity, excellent mechanical strength, acceptable barrier properties) can be produced only for specific applications in food technology. In the current review, we tried to summarize the advancements made in the last 5-7 years in the field of chitosan film technology for its application in the food industry.

Recent Developments in Food Packaging Based on Nanomaterials

The increasing demand for high food quality and safety, and concerns of environment sustainable development have been encouraging researchers in the food industry to exploit the robust and green biodegradable nanocomposites, which provide new opportunities and challenges for the development of nanomaterials in the food industry. This review paper aims at summarizing the recent three years of research findings on the new development of nanomaterials for food packaging. Two categories of nanomaterials (i.e., inorganic and organic) are included. The synthetic methods, physical and chemical properties, biological activity, and applications in food systems and safety assessments of each nanomaterial are presented. This review also highlights the possible mechanisms of antimicrobial activity against bacteria of certain active nanomaterials and their health concerns. It concludes with an outlook of the nanomaterials functionalized in food packaging.

Luminescent and UV-Shielding ZnO Quantum Dots/Carboxymethylcellulose Sodium Nanocomposite Polymer Films

Luminescent and UV-shielding bio-polymers have seldom been reported. Zinc oxide quantum dots (ZnOQD) (~3.2 nm) was synthesized by a short-term sol-gel method. ZnOQD possessed a crystal lattice spacing of 0.28 nm and a hexagonal wurtzite structure. Luminescent and UV-shielding ZnOQD/carboxymethylcellulose sodium (CMC) nanocomposite polymer films were successfully fabricated by incorporating ZnOQD into a CMC matrix through a solution casting method. Thermal analysis demonstrated that the ZnOQD reduce the thermal decomposition rate of CMC, and a large number of ZnOQD can promote the catalytic degradation of ZnOQD/CMC nanocomposites. Furthermore, ZnOQD/CMC hybrid polymer films exhibited photoluminescence with maximum emission wavelength at 525 nm. More significantly, ZnOQD/CMC showed prominent UV-absorbing capability. Such ZnOQD/CMC nanocomposite polymer films are promising in UV-shielding and optical applications.