Preparation and characterization of multilayer films composed of chitosan, sodium alginate and carboxymethyl chitosan-ZnO nanoparticles

Development and characterization of bilayer chitosan/alginate cling film reinforced with essential oil based nanocomposite for red meat preservation

With a goal to finding suitable alternatives to plastic packaging in the food industry, we developed a multifunctional bio-based active packaging film to enhance the shelf life of red meat. A chitosan/alginate (Chi + Alg) bilayer film was developed through layer-by-layer (LBL) assembly and an active material i.e. lemongrass nanoemulsion with silver nanoparticles-based nanocomposite (NC1) was loaded into the alginate layer to improve the quality of the bio-based film (Chi + Alg + NC1). The Chi + Alg + NC1 film was characterized in terms of its microstructure, mechanical strength, thermal stability, and antimicrobial activity. Scanning electron microscopy (SEM) revealed a film (22.5 ± 1.44 μm thickness) with a smooth and even surface and a cross-sectional structure. The incorporation of NC1 improves the quality of the film by enhancing its mechanical strength and thermal stability. FT-IR spectra showed the successful interaction between chitosan and alginate in the LBL assembly and the incorporation of NC1 in the alginate layer. The red meat preservation test demonstrated that the shelf life improved when the meat was covered with the fabricated bio-based film. The color of the meat was retained for up to 7 days compared to that of the control (Chi alone and Chi + Alg). Additionally, a reduction in the microbial count in the Chi + Alg + NC1 film was observed, corroborating the shelf-life improvement. In addition to its inherent antimicrobial properties, NC1 induced hydrophilic properties to the film, which further aids in its antimicrobial activity against E. coli. These findings suggest that Chi + Alg + NC1 film could be a potent alternative to plastic packaging and can be used as a cling film to prolong the shelf life of red meat.

Conformal immunomodulatory hydrogels for the treatment of otitis media

Otitis media (OM), a condition stemming from the proliferation of various bacteria within the tympanic cavity (TC), is commonly addressed through the administration of ofloxacin (OFL), a fluoroquinolone antibiotic. Nevertheless, the escalating issue of antibiotic resistance and the challenge of drug leakage underscore the exploration of an alternative, more effective treatment modality in clinical practice. Here, we introduce a simple and easily implementable fluid-regulated strategy aimed at delivering immunomodulatory hydrogels into the TC, ensuring conformal contact with the irregular anatomical surfaces of the middle ear cavity to more effectively eliminate bacteria and treat OM. This innovative strategy exhibits expedited therapeutic process of antibiotic-resistant, acute and chronic OM rats, and significant reductions in the severity of tympanic membrane (TM) inflammation, residual bacteria within the TC (0.12 *105 CFU), and the thickness of TM/TC mucosa (17.63/32.43 μm), as compared to conventional OFL treatment (3.6, 0.76 *105 CFU, 48.70/151.26 μm). The broad-spectrum antibacterial and antibiofilm properties of this strategy against a spectrum of OM pathogens are demonstrated. The strategy is validated to bolster the host's innate immune response through the stimulation of antibacterial protein synthesis, macrophage proliferation and activation, thereby accelerating bacterial eradication and inflammation resolution within the TC. This facile, cost-effective and in vivo degradable technology exhibits promising prospects for future clinical implementation.

Factors influencing the antimicrobial mechanism of chitosan action and its derivatives: A review

Chitosan, a versatile amino polysaccharide biopolymer derived from chitin, exhibits broad-spectrum antimicrobial activity against various pathogenic microorganisms, including gram-negative and gram-positive bacteria, as well as fungi. Due to its ubiquitous use in medications, food, cosmetics, chemicals, and crops, it is an effective antibacterial agent. However, the antimicrobial performance of chitosan is influenced by multiple factors, which have been extensively investigated and reported in the literature. The goal of this review paper is to present a thorough grasp of the mechanisms of action and determining variables of chitosan and its derivatives' antibacterial activity. The article begins by providing a brief background on chitosan and its antimicrobial properties, followed by the importance of understanding the mechanism of action and factors influencing its activity".

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 carboxymethylated pullulan/butyric acid-modified chitosan active sustainable bi-layer coatings intended for packaging of cheese slices

Dependence of the food industry on conventional plastic and the generation of enormous amounts of food waste caused by microbiological spoilage have been imposed as inspiration for this work, to develop active sustainable packaging for sliced cheese using the bi-layer design. Pullulan was modified using a green approach to obtain a polyanionic character in the coating formulation. Chitosan, which has a cationic character in an acidic environment, has been modified using a butyric acid to obtain an amphiphilic character. The formed active bi-layer has demonstrated an improved barrier (decreased permeability for moisture vapor 72.2 and 77.7 times) and mechanical properties (increased tensile strength value up to 3.9 and 9.4 times) compared to the monolayer films. A novel approach to microbiological control of sliced cheese has been established, which implies a synergistic effect of Helichrysum italicum essential oil (EO) and corresponding hydrolate (HY) incorporated in separated layers. This design has ensured avoiding surfactants and preserving cheese's sensory properties, prolonging its shelf-life by 50 % at least. Improvements in cheese storage conditions using this packaging lie in the improved barrier, mechanical and antimicrobial properties, the order of lamination, and a good covering of the cheese surface by spraying.

Enhancing biodegradable smart food packaging: Fungal-synthesized nanoparticles for stabilizing biopolymers

The increasing global concern over environmental plastic waste has propelled the progress of biodegradable supplies for food packaging. Biopolymer-based packaging is undergoing modifications to enhance its mechanical properties, aligning with the requirements of smart food packaging. Polymer nanocomposites, incorporating reinforcements such as fibers, platelets, and nanoparticles, demonstrate significantly improved mechanical, thermal, optical, and physicochemical characteristics. Fungi, in particular, have garnered significant interest for producing metallic nanoparticles, offering advantages such as easy scaling up, streamlined downstream handling, economic feasibility, and a large surface area. This review provides an overview of nano-additives utilized in biopackaging, followed by an exploration of the recent advancements in using microbial-resistant metal nanoparticles for food packaging. The mycofabrication process, involving fungi in the extracellular or intracellular synthesis of metal nanoparticles, is introduced. Fungal functionalized nanostructures represent a promising avenue for application across various stages of food processing, packaging, and safety. The integration of fungal-derived nanostructures into food packaging materials presents a sustainable and effective approach to combatting microbial contamination." By harnessing fungal biomass, this research contributes to the development of economical and environmentally friendly methods for enhancing food packaging functionality. The findings underscore the promising role of fungal-based nanotechnologies in advancing the field of active food packaging, addressing both safety and sustainability concerns. The study concludes with an investigation into potential fungal isolates for nanoparticle biosynthesis, highlighting their relevance and potential in advancing sustainable and efficient packaging solutions.

Alginate-modified ZnO anti-planktonic and anti-biofilm nanoparticles for infected wound healing

Bacterial infections is one of the main factors delaying the wound healing, which has become a serious challenge for healthcare systems. Zinc oxide nanoparticles (ZnO NPs), which show broad-spectrum and excellent antibacterial activity, tend to aggregate easily and therefore hardly penetrate into bacterial biofilms, showing limited anti-biofilm properties. Herein，alginate (ALG) modified ZnO NPs (ZnO@ALG) were prepared via the combination of mussel-inspired method and "thiol-Michael" click reaction, which showed excellent dispersion and biocompatibility. Besides, the interactions between ZnO@ALG and bacteria was much better than that of ZnO NPs, and makes the bacteria produced more reactive oxygen species (ROS) than bare ZnO NPs. The anti-planktonic activity of ZnO@ALG (250 μg/mL) could reach almost 100 %, which was 2-3 times higher than that of bare ZnO NPs. In addition, the ZnO@ALG could significantly accelerate the healing of S. aureus infected wounds, and the wound healing rate of ZnO@ALG group was about 79.2 %, which was significantly higher than that of ZnO NPs (~65.8 %). This study demonstrates that the ZnO@ALG holds a great potential in the anti-planktonic and anti-biofilm fields, and the ALG-modification method can be an effective strategy to enhance the antibacterial properties of nanomaterials.

Evaluation of the cytotoxicity and antibacterial activity of nano-selenium prepared via gamma irradiation against cancer cell lines and bacterial species

A recent scientific investigation has shown promising results of selenium nanoparticles (SeNPs) for the anticancer and antimicrobial activities. This study aims to evaluate the effects of PVP SeNPs on bacterial strains, including Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus), Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa). Also, its antitumor activity against the MRC-5 carcinoma cell line. SeNPs were prepared via gamma irradiation using PVP as a capping agent, and their size and morphological structure were determined using HRTEM. The size of the SeNPs ranged from 36 to 66.59 nm. UV-vis spectra confirmed the formation of SeNPs, while FTIR measurement confirmed a change in the PVP structure after adding selenium nanoparticles. The highest effect was reported on HepG2 by an IC50 with a value of 8.87 µg/ml, followed by HeLa, PC3, MCF-7, and Caco2 cell lines, respectively. Furthermore, ZOI reached 36.33 ± 3.05 mm. The best value of the minimum inhibitory concentration (MIC) was 0.313 µg/ml. Scanning electron microscope (SEM) imaging against bacteria showed deformations and distortions in their structures. Transmission electron (TEM) revealed ultrastructure changes in treated bacteria because of the free radicals that made cytotoxicity which confirmed by Electron spin resonance (ESR).

Alginate composite films incorporated with Zn-based inorganic antimicrobials for food packaging: Effects of morphology

Biopolymers-based food packaging materials have drawn attention as potential candidates for substitution of petroleum-based materials. In this study, composite alginate films were developed by incorporating Zn-based antimicrobials to overcome the intrinsic disadvantages of alginates that hinder their wide applications. Antimicrobials with different morphologies (nanoplatelets, nanorods, and nanospheres) were employed to investigate the effects of antimicrobials' morphology on antibacterial, thermal, mechanical, and barrier performance of composite alginate films. Meanwhile, morphological and structural characterizations were carried out to explore the interactions between antimicrobials and alginate matrix. Results indicated that films with nanospheres exhibited superior antibacterial property, while those with one-dimensional nanorods possessed better mechanical and barrier performance. Besides, preliminary test on fresh-cut potatoes and chicken breasts indicated that the composite films showed potential in extending shelf life of foods. By incorporating antimicrobials with three different morphologies, this study provides particular insights into improving properties of composite packaging materials.

Carboxymethyl chitosan and dialdehyde cellulose nanocrystal based injectable self-healing emulsion gel

The study aims to demonstrate a general method for producing emulsion gels with self-healing properties. Specifically, the self-healing emulsion gels were fabricated by crosslinking carboxymethyl chitosan (CMC) stabilized emulsion with dialdehyde cellulose nanocrystal (DACNC). The reversible imine bonds between primary amino groups from CMC and aldehyde groups from DACNC endow the emulsion gel with self-healing properties. The compressive strength of the emulsion gels was greatly increased from 37.43 kPa 83.7 kPa by encapsulating emulsion droplets (φ = 0 %-40 %.) in the gel matrix. Moreover, the emulsion gels exhibited much better self-healing and injectability ability compared to hydrogel because the emulsion droplets interacted with the 3D gel matrix, which were observed by cryo-SEM and CLSM. The emulsion droplets distributed in the gel matrix improved the mobility and interfacial contact area of CMC and DACNC. Water contact measurement confirmed that the CMC/DACNC self-healing emulsion gels showed a hydrophilic surface. The CMC/DACNC emulsion gels could maintain a good structural stability as the oil loss was <1 % after centrifugation. This research provides a method to keep the structural stability of emulsion gels by inducing self-healing ability and modified cellulose nanocrystals, which could extend the shelf life and application area of emulsion gels.

Bioactive composite films with improved antioxidant and barrier properties prepared from sodium alginate and deep eutectic solvent treated distillers' grains

In this work, a straightforward approach utilizing distillers' grains (DG) waste and sodium alginate (SA) was developed to prepare functional and bioactive packaging films. Deep eutectic solvents (DESs) were initially synthesized from choline chloride (CO), betaine (BO), glycerol (GO), and oxalic acid. Composite films were then prepared from DES-treated DG slurry and SA at different ratios. Characterization and analysis revealed that adding 75 % CO-treated DG slurry reduced the water vapor permeability (WVP) by over 66 % compared to that of the SA film. Composite films containing CO/BO-treated DG slurry had an ultraviolet light barrier rate exceeding 99 %, while those with 75 % DES-treated DG slurry demonstrated excellent antioxidant activity, with a 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging rate of 80.14 %-88.35 %, representing a 322.45 %-365.73 % increase compared to that of the pure SA film. These composite films also exhibited favorable mechanical properties (31.58 MPa, 5.53 % EB), thermal stability, and biodegradability, extending the shelf life of grapes by 1.8 times. In conclusion, bioactive composite films derived from DES-treated DG are expected to replace petroleum-based plastics, enhancing sustainable biomass use and environmental responsibility.

Intelligent double-layer film based on gellan gum/modified anthocyanin/curcumin/sodium alginate/zinc oxide for monitoring shrimp freshness

In this study, intelligent double-layer films were prepared using modified black rice anthocyanin (MBRA)-curcumin (CUR)-gellan gum (GG) as the inner indicator layer and sodium alginate (ALG)‑zinc oxide (ZnO) as the outer antimicrobial layer. The bilayer films were successfully prepared, as revealed by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction measurements. The mechanical characteristics, moisture content, and water vapor resistance of GG-MBRA/CUR1@ALG-ZnO, GG-MBRA/CUR2@ALG-ZnO, and GG-MBRA/CUR3@ALG-ZnO films showed significant enhancement compared to GG-MBRA/CUR3 and ALG-ZnO films. The bilayer films exhibited excellent pH responsiveness and reacted effectively to ammonia. The outer layer significantly improved the antioxidant and antibacterial properties of the inner layer. When the films were applied to shrimp, it was found that the double-layer films not only monitored the freshness of the shrimp in real-time but also were influential in extending the shelf life of the shrimp by about 1 d. Therefore, the double-layer film demonstrated potential as a smart packaging material for real-time monitoring of meat product freshness.

Chitosan-based nanocomposite films with carnauba wax, rosin resin, and zinc oxide nanoparticles

This work aimed to develop edible emulsion-based barriers in the form of chitosan composite films, with a focus on assessing the impacts of carnauba wax, rosin resin, and zinc oxide nanoparticles on their properties. Six films were produced by casting using chitosan as polymer base and glycerol as plasticizer. Acetic acid and polysorbate 80 were also used to facilitate the dissolution and mixing of the components. The six filmogenic solutions contained chitosan at 1.2% w/v, wax or resin content with 0 or 0.6% m/v and ZnO with 0 or 0.05% m/v. The dried films were characterized according to their chemical, barrier, mechanical, thermal and optical properties. All treatments resulted in flexible films. Chitosan films appeared smoother and more uniform under SEM imaging, while carnauba wax films displayed roughness due to their hydrophobic nature. Wax and resin films were less transparent and water soluble than the chitosan-only films. On the other hand, the addition of ZnO in the formulations increased the solubility of the films. The sorption degree was in line with the solubility results, i.e., films with ZnO presented higher sorption degree and solubility values. All treatments showed low or non-light UV transmission, indicating that the films provide good barrier to UV light. In the visible light region, films of resin with ZnO showed the lowest transmittance values, hence offering a good barrier to visible light. Among the evaluated films, chitosan, and resin films with ZnO nanoparticles were more rigid and resistant to deformation. Overall, films produced with rosin resin and ZnO nanoparticles showed potential improvements in barrier, mechanical, thermal, and optical properties, mainly due to their low water solubility, good UV protection and low permeability to water vapor and oxygen, which are suitable for using in formulations, intended to produce edible films and coatings.

Shear Flow-Assembled Janus Membrane with Bifunctional Osteogenic and Antibacterial Effects for Guided Bone Regeneration

Guided bone regeneration (GBR) membranes that reside at the interface between the bone and soft tissues for bone repair attract increasing attention, but currently developed GBR membranes suffer from relatively poor osteogenic and antibacterial effects as well as limited mechanical property and biodegradability. We present here the design and fabrication of a bifunctional Janus GBR membrane based on a shear flow-driven layer by a layer self-assembly approach. The Janus GBR membrane comprises a calcium phosphate-collagen/polyethylene glycol (CaP@COL/PEG) layer and a chitosan/poly(acrylic acid) (CHI/PAA) layer on different sides of a collagen membrane to form a sandwich structure. The membrane exhibits good mechanical stability and tailored biodegradability. It is found that the CaP@COL/PEG layer and CHI/PAA layer contribute to the osteogenic differentiation and antibacterial function, respectively. In comparison with the control group, the Janus GBR membrane displays a 2.52-time and 1.84-time enhancement in respective volume and density of newly generated bone. The greatly improved bone repair ability of the Janus GBR membrane is further confirmed through histological analysis, and it has great potential for practical applications in bone tissue engineering.

Metal and Metal Oxides Nanoparticles as Nanofillers for Biodegradable Polymers

Polymeric materials, despite their many undeniable advantages, nowadays are a major environmental challenge. Thus, in recent years biodegradable polymer matrices have been widely used in various sectors, including the medicinal, chemical, and packaging industry. Their widespread use is due to the properties of biodegradable polymer matrices, among which are their adjustable physicochemical and mechanical properties, as well as lower environmental impact. The properties of biodegradable polymers can be modified with various types of nanofillers, among which clays, organic and inorganic nanoparticles, and carbon nanostructures are most commonly used. The performance of the final product depends on the size and uniformity of the used nanofillers, as well as on their distribution and dispersion in the polymer matrix. This literature review aims to highlight new research results on advances and improvements in the synthesis, physicochemical properties and applications of biodegradable polymer matrices modified with metal nanoparticles and metal oxides.

Recoverable and degradable carboxymethyl chitosan polyelectrolyte hydrogel film for ultra stable encapsulation of curcumin

Hydrogels have shown great potential for application in food science due to their diverse functionalities. However, most hydrogels inevitably contain toxic chemical cross-linking agent residues, posing serious food safety concerns. In this paper, a curcumin/sodium alginate/carboxymethyl chitosan hydrogels (CSCH) were prepared by self-assembly of two oppositely charged polysaccharides, carboxymethyl chitosan and sodium alginate, to form a three-dimensional network encapsulating curcumin for extending food shelf life. The network structure of the CSCH film confirmed by FTIR, XRD, and XPS was mainly formed by electrostatic interactions. The chemical stability of CSCH network encapsulated curcumin was 4.2 times greater than that of free curcumin, with excellent gas barrier, antimicrobial, antioxidant, and biosafety properties. It was found that CSCH films reduced dehydration, prevented nutrient loss, inhibited microbial growth, and lowered the respiration rate, which effectively maintained the quality of mango and prolonged its shelf-life up to 11 days. Notably, CSCH films possessed the properties of rapid recycling (10 mins) and biodegradability (53 days). This polysaccharide-based hydrogel film provides a viable strategy for the development of green and sustainable food packaging.

Reducing cherry rain-cracking: Enhanced wetting and barrier properties of chitosan hydrochloride-based coating with dual nanoparticles

The synergistic effects of phosphorylated zein nanoparticles (PZNP) and cellulose nanocrystals (CNC) in enhancing the wetting and barrier properties of chitosan hydrochloride (CHC)-based coating are investigated characterized by Fourier Transform Infrared Spectra (FTIR), X-ray Diffraction (XRD), atomic force microscopy and by investigating the mechanical properties, etc., with the aim of reducing cherry rain cracking. FTIR and XRD showed dual nanoparticles successfully implanted into CHC, CHC-PZNP-CNC combined moderate ductility (elongation at break: 7.8 %), maximum tensile strength (37.5 MPa). The addition of PZNP alone significantly improved wetting performance (Surface Tension, CHC: 55.3 vs. CHC-PZNP: 48.9 mN/m), while the addition of CNC alone led to a notable improvement in the water barrier properties of CHC (water vapor permeability, CHC: 6.75 × 10-10 vs. CHC-CNC: 5.76 × 10-10 gm-1 Pa-1 s-1). The final CHC-PZNP-CNC coating exhibited enhanced wettability (51.2 mN/m) and the strongest water-barrier property (5.32 × 10-10 gm-1 Pa-1 s-1), coupled with heightened surface hydrophobicity (water contact angle: 106.4°). Field testing demonstrated the efficacy of the CHC-PZNP-CNC coating in reducing cherry rain-cracking (Cracking Index, Control, 42.3 % vs. CHC-PZNP-CNC, 19.7 %; Cracking Ratio, Control, 34.6 % vs. CHC-PZNP-CNC, 15.8 %). The CHC-PZNP-CNC coating is a reliable option for preventing rain-induced cherry cracking.

Multi-functional polyvinyl alcohol/tannin acid composite films incorporated with lignin nanoparticles loaded by potassium sorbate

The biocompatible, biodegradable and strong polyvinyl alcohol-based films have been widely investigated and used in the field of active packaging. To endow with diverse function, this paper firstly prepared lignin nanoparticles loaded with potassium sorbate (LNP@PS) as additives to exploit additional antibacterial, UV blocking, oxygen barrier, and water barrier properties. Besides, tannin acid (TA) was incorporated for compensating and further enhancing mechanical properties. Results showed that the PVA-based composite films containing 3 % LNP@PS and 5 % TA could achieve the optimal tensile strength at 74.51 MPa, water vapor permeability at 7.015·10-13·g·cm/cm2·s·Pa and oxygen permeability at 1.93 cm3/m2·24 h MPa, which was an 165 % of increase, 47 % and 112 % of reduction respectively compared to pure PVA films. Additionally, the composite films exhibited apparently superior bacteria and oxygen resistance properties evidenced by microbial infection and free radical scavenging performance. In addition, the slow-release effect of PS assisted the strawberry preservation with an extension of 3 days, which provided a promising novel route to prepare active food packaging material.

Development of carboxymethyl cellulose-based nanocomposite incorporated with ZnO nanoparticles synthesized by cress seed mucilage as green surfactant

This study aimed to enhance carboxymethyl cellulose (CMC)-based films by incorporating zinc oxide nanoparticles (ZnO NPs) and cress seed mucilage (CSM), with a view to augmenting the physical, mechanical, and permeability properties of the resulting nanocomposite films. For the first time, CSM was exploited as a green surfactant to synthetize ZnO NPs using hydrothermal method. Seven distinct film samples were meticulously produced and subjected to a comprehensive array of analyses. The findings revealed that the incorporation of CSM/ZnO-5 % improved the physical properties of the films, demonstrating a significant reduction in moisture content and water vapor permeability (WVP). Increasing the concentration of NPs in conjunction with CSM markedly decreased the solubility of the nanocomposites by up to 56 %. The films containing CSM/ZnO showed higher tensile strength and elongation at the break values. The UV absorption of the films exhibited a substantial rise with the addition of ZnO NPs, particularly with an increased content in the presence of CSM. The thermal stability of nanocomposites containing a high concentration of CSM/ZnO exhibited an improvement compared to the control sample. In light of these results, the CMC/CSM/ZnO-5 % film emerges as a promising candidate for a biocompatible packaging material, exhibiting favorable physical characteristics.

Development of CO2-sensitive antimicrobial bilayer films based on gellan gum and sodium alginate/sodium carboxymethyl cellulose and its application in strawberries

To effectively extend the shelf life of fruits meanwhile facilitating consumers to judge their freshness, in this work, a double-layer multifunctional film combining CO2 sensitivity and antibacterial properties was successfully prepared by adding methyl red (MR), bromothymol blue (BTB) into gellan gum (GG) as the sensing inner layer, and doping tannic acid (TA) into sodium alginate with sodium carboxymethyl cellulose (CMC) as the antimicrobial outer layer, which was applied to the freshness indication of strawberries. Microscopic morphology and spectral analysis demonstrated that the bi-layer films were fabricated successfully. The mechanical characteristics, thermal stability, water vapor resistance, and antibacterial capabilities of the bilayer films improved as TA concentration rose. They exhibited noticeable color changes at pH = 2-10 and different concentrations of CO2. Application of the prepared films to strawberries revealed that the GG-MB@SC-6%TA film performed most favorably under 4 °C storage conditions, not only monitoring strawberry freshness but also retaining high soluble solids and titratable acidity, resulting in a slight decrease in hardness and weight loss. Therefore, taking into account all of the physical-functional characteristics, the GG-MB@6%TA film has a broad application prospect for intelligent food packaging.

Polysaccharide film containing cinnamaldehyde-chitosan nanoparticles, a new eco-packaging material effective in meat preservation

The development of novel eco-friendly materials like chitosan for food storage and preservation has become crucial in eliminating plastic packaging and minimizing waste. In this work, cinnamaldehyde has been encapsulated in chitosan nanoparticles and subsequently incorporated into a 2 % chitosan film. The obtained nanoparticles achieved an average radius size of 89.80 nm, PDI of 0.40, and spherical morphology determined by SEM. Cinnamaldehyde was encapsulated in chitosan nanoparticles achieving values of encapsulation close to 7 %, showing a biphasic release profile with sustained release during 5 days. Films with an average thickness of 0.124 mm and elongation at break of 63.66 % to 76.50 % were obtained. Finally, the antimicrobial properties of the films was tested showing reduction values in total aerobic value of 4.85 log cfu/g, total coliform of 1.26 log cfu/g and grow potential value of < 0.5 log10 for Listeria monocitogenes over 20 days.

The Chemical Modification to Improve Solubility of Chitosan and Its Derivatives Application, Preparation Method, Toxicity as a Nanoparticles

Chitosan is a functional polymer in the pharmaceutical field, including for nanoparticle drug delivery systems. Chitosan-based nanoparticles are a promising carrier for a wide range of therapeutic agents and can be administered in various routes. Solubility is the main problem for its production and utilization in large-scale industries. Chitosan modifications have been employed to enhance its solubility, including chemical modification. Many reviews have reported the chemical modification but have not focused on the specific characteristics obtained. This review focused on the modification to improve chitosan solubility. Additionally, this review also focused on the application of chitosan derivatives in nanoparticle drug delivery systems since very few similar reviews have been reported. The specific method for chitosan derivative-based nanoparticles was also reported and the latest report of chitosan, chitosan derivative, and chitosan toxicity were also described.

A review on versatile applications of biomaterial/polycationic chitosan: An insight into the structure-property relationship

Chitosan is a versatile and generous biopolymer obtained by alkaline deacetylation of naturally occurring chitin, the second most abundant biopolymer after cellulose. The excellent physicochemical properties of polycationic chitosan are attributed to the presence of varied functional groups such as amino, hydroxyl, and acetamido groups enabling researchers to tailor the structure and properties of chitosan by different methods such as crosslinking, grafting, copolymerization, composites, and molecular imprinting techniques. The prepared derivatives have diverse applications in the food industry, water treatment, cosmetics, pharmaceuticals, agriculture, textiles, and biomedical applications. In this review, numerous applications of chitosan and its derivatives in various fields have been discussed in detail with an insight into their structure-property relationship. This review article concludes and explains the chitosan's biocompatibility and efficiency that has been done so far with future usage and applications as well. Moreover, the possible mechanism of chitosan's activity towards several emerging fields such as energy storage, biodegradable packaging, photocatalysis, biorefinery, and environmental bioremediation are also discussed. Overall, this comprehensive review discusses the science and complete information behind chitosan's wonder function to improve our understanding which is much needful as well as will pave the way towards a sustainable future.

Chitosan/konjac glucomannan bilayer films: Physical, structural, and thermal properties

To overcome the limitations of chitosan (CS) and konjac glucomannan (KGM), the bilayer films of CS and KGM were prepared by layer-by-layer (LBL) casting method, and the effects of different mass ratios (i.e., C5: K0, C4:K1, C3:K2, C1:K1, C2:K3, C1:K4, and C0:K5) on the microstructures and physicochemical properties of bilayer films were examined to evaluate their applicability in food packaging. The results revealed that the bilayer films had uniform microstructures. When compared with pure films, the bilayer films displayed lower swelling degrees and water vapor permeability. However, the tensile tests revealed a reduction in the mechanical properties of the bilayer films, which was nonetheless superior to that of the pure KGM film. In addition, the intermolecular interactions between the CS and KGM layers were observed through FTIR and XRD analyses. Finally, TGA and DSC analyses demonstrated a decrease in the thermal stability of the bilayer films. Our cumulative results verified that CS-KGM bilayer films may be a promising material for use in food packaging and further properties of the bilayer films can be supplemented in the future through layer-by-layer modification and the addition of active ingredients.

Comparison of the Properties of Pullulan-Based Active Edible Coatings Implemented for Improving Sliced Cheese Shelf Life

The development of active edible coatings with improved mechanical and barrier properties is a huge challenge. In this study, active edible coatings for sliced cheese have been developed using pullulan (Pull) in combination with two different biopolymers, chitosan (CS) and gelatine (Gel), and a combination of hydrolats as a source of active compounds with antimicrobial effects. In comparison to the monolayer coating, the bilayer coating system demonstrates improved barrier and mechanical properties. A preliminary assessment of the antimicrobial effect of lemongrass and curry plant hydrolats has revealed that both hydrolats exhibited antimicrobial activity against the targeted bacterium Staphylococcus aureus, albeit at different levels. The obtained results suggest that a mixture of 1.56% lemongrass and 12.5% curry plant hydrolats yielded a lower fractional inhibitory concentration (FIC) value. Bilayer coating systems (Pull/CS and Pull/Gel) with an incorporated mixture of hydrolats have demonstrated effectiveness in both cases: artificial contamination before application of the coating system and after application of the coating system. In both contamination scenarios, the coating systems consistently effectively limited bacterial proliferation, indicating the antimicrobial effect of the hydrolat mixture in the coating layers. In the case of artificial contamination before applying the coating system, both coatings demonstrated antimicrobial effectiveness, but the formulation with chitosan had a biocide effect, while the other, with gelatine, had only a bacteriostatic effect in a long-term setting. In the second case, both Pull/CS and Pull/Gel coatings demonstrated effectiveness in inhibiting bacterial growth regardless of the moment of contamination of the sample; the Pull/CS coating showed slightly better antimicrobial activity, achieving complete elimination of bacteria earlier compared with the Pull/Gel coating system.

Antibacterial photodynamic properties of silver nanoparticles-loaded curcumin composite material in chitosan-based films

In order to cope with the increasingly severe food contamination and safety problems, a powerful sterilization of food packaging material is urgently needed. Chitosan (CS) has potential applications in food packaging due to its good film-forming properties, but its antibacterial activity is not sufficient to meet the needs in practical applications. Silver nanoparticles (AgNPs) have the problem of weak immediate antibacterial activity as a broad-spectrum antibacterial agent. Therefore, in this study, AgNPs@GA@Cur-POTS (AGCP) composite antibacterial system was prepared by combining AgNPs with antibacterial photodynamic therapy using gallic acid (GA) as a reducing agent, curcumin (Cur) as a photosensitizer and perfluorosilane (POTS) for surface modification. The results showed that AGCP could produce a large number of reactive oxygen species under blue light irradiation, killing >90 % of E. coli and S. aureus within 2 h. Subsequently, the composite film of CS loaded with AGCP (CS/AGCP) was prepared by the flow-delay method. The CS/AGCP composite film exhibited excellent barrier properties and antioxidant activity, while its antibacterial rates against E. coli and S. aureus reached 98.44 ± 1.27 % and 99.11 ± 0.24 %, respectively, while the OD630 values of the two groups of bacteria treated with it showed no significant increase in incubation for up to 132 h, exhibiting remarkable and sustained antibacterial effects. Taken together, this work will provide a new strategy for antibacterial food packaging.

Development of a chitosan/pectin-based multi-active food packaging with both UV and microbial defense functions for effectively preserving of strawberry

Multi-active food packaging was prepared for strawberry fruit preservation where epigallocatechin gallate (EGCG)-containing pectin matrix and natamycin (NATA)-containing chitosan (CS) matrix were utilized to complete LBL electrostatic self-assembly. The results showed that the physicochemical properties of the multi-active packaging were closely related to the addition of NATA and EGCG. It was found that NATA and EGCG were embedded in the CS/pectin matrix through intermolecular hydrogen bonding interactions. The CN/PE 15 % multi-active films prepared based on the spectral stacking theory formed a barrier to UV light in the outer layer, exhibited excellent NATA protection under UV light exposure conditions at different times, and provided long-lasting and sustained bacterial inhibition in the inner layer. In addition, the CN/PE 15 % multi-active packaging extended the shelf life of strawberry at room temperature compared with the control samples. In conclusion, the developed CN/PE 15 % packaging provided potential applications for multi-active food packaging materials.

Construction of carboxymethyl chitosan/PVA/chitin nanowhiskers multicomponent film activated with Cotylelobium lanceolatum phenolics and in situ SeNP for enhanced packaging application

This work focused on the construction of bioactive packaging films based on carboxymethyl chitosan and poly(vinyl alcohol) (CMP) as polymeric matrix and fortified with chitin nanowhiskers, Cotylelobium lanceolatum phenolic extract (CL) and in situ synthesized nano selenium. Extensive morphological, microstructural, physical and mechanical analysis revealed that the nanofillers were well-dispersed and integrated into CMP matrix. Incorporation of the extract and nano selenium produced excellent UV blocking properties without seriously compromising the transparency of the composite (CMP/CNW/CLNS1) film. Moreover, blending of CMP with the filler materials significantly elevated (p < 0.05) the surface hydrophobicity (WCA by 35.4°), water barrier (by 53.86 %), tensile strength (from 29.35 to 33.09 MPa), elongation at break (from 64.28 to 96.48 %), and thermal properties of the resultant CMP/CNW/CLNS1 film, with concomitant reduction in water solubility and swellability. Furthermore, the CMP/CNW/CLNS films exhibited remarkable improvement in antioxidant properties. When used for packaging of peeled fresh garlic cloves, the CMP/CNW/CLNS1 film pouch, not the plain CMP or CMP/CNW film pouches, inhibited weight loss, oxidative browning, and the emergence of black mold on the packaged cloves. The developed CMP/CNW/CLNS1 film demonstrated enhanced capacity to safeguard the quality of packaged food and improved shelf life. Therefore, the present study suggests that incorporation of CNW/CLNS into carboxymethyl chitosan/PVA films is a suitable and facile strategy for the fabrication of films with improved mechanical, physico-chemical and functional properties with great potential for application as a sustainable active packaging material in the food industry.

Pulp waste extracted reinforced powder incorporated biodegradable chitosan composite film for enhancing red grape shelf-life

Chitosan (CS) is widely used as a natural biopolymer due to its semi-crystalline structure, good film-forming properties, and easy availability. CS-based composite films are widely used in industry, particularly in the food sector as active food packaging. Despite all of these advantages, their wide range of applications are constrained by poor mechanical properties. Therefore, this work introduced refined bamboo cellulose powder (RBCP), a reinforcing material that is extracted from waste bamboo pulp and applied to CS composite films to enhance their mechanical and physicochemical properties. The chemical composition and crystallinity properties of CS composite films with RBCP addition were observed by ATR-FTIR and XRD. The homogeneous and heterogeneous surfaces of the RBCP incorporated films before biodegradation and after biodegradation (20 days) were observed by scanning electron microscopy (SEM). The increase in reinforcing RBCP materials from 0.00 to 5.00 % resulted in an increase in tensile strength for CS/RBCP films from 2.9 to 8.3 MPa. The application of the CS/RBCP/5 composite film as red grapefruit storage was also investigated, which performed much better than commercial plastic and control CS films with 92.8 and 88.6 % viability of S. aureus and E. coli bacteria. Overall achieved properties demonstrated strong potential for usage as active packaging materials to preserve and lengthen the shelf life of red grapefruits.

Carboxymethyl chitosan/sodium alginate hydrogel films with good biocompatibility and reproducibility by in situ ultra-fast crosslinking for efficient preservation of strawberry

Strawberry is a seasonal and regional fruit. Thus, strawberry waste caused by spoilage and decay is an urgent problem that must be solved. Developing hydrogel films (HGF) for multifunctional food packaging can effectively slow down strawberry. Based on the carboxymethyl chitosan/sodium alginate/citric acid with excellent biocompatibility, preservation effect, and ultrafast (10 s) coating on the strawberry surface, HGF specimens were designed and prepared through the electrostatic interaction of opposite charges between polysaccharides. The prepared HGF specimen exhibited excellent low moisture permeability and antibacterial properties. Its lethality rates against both Escherichia coli and Staphylococcus aureus were more than >99 %. The HGF could keep strawberries fresh for up to 8, 19, and 48 days at 25.0, 5.0, and 0 °C, respectively, by delaying the fruits' ripening, dehydration, microbial invasion, and respiration rate. The HGF dissolved and regenerated five times still exhibited good performance. The water vapor transmission rate of the regenerative HGF could reach 98 % of that of the original HGF. The regenerative HGF could maintain the freshness of strawberries for up to 8 days at 25.0 °C. This study provides new insight into an alternative film design for convenient, green, and renewable alternative films to delay perishable fruit spoilage.

Incorporation of Bayberry Tannin into a Locust Bean Gum/Carboxycellulose Nanocrystals/ZnO Coating: Properties and Its Application in Banana Preservation

The application of polysaccharide-based coatings to prolong the shelf-life of fruits has attracted increasing attention. This study aims to develop a fruit coating comprising locust bean gum/carboxycellulose nanocrystals/ZnO (LCZ) blended with bayberry tannins (BT). The results revealed a significant increase from 4.89% and 11.04% to 29.92% and 45.01% in the free radical scavenging rates of 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-di-[3-ethylbenzthiazthiazoline sulfonate] with the percentage of BT increasing from 0% to 5%, respectively. At a 5% of BT, the antibacterial activity against both E.coli and S. aureus exceeded 90% while simultaneously achieving excellent UV shielding (transmittance of 380-200 nm ≤ 0.19%). After 3 days of storage, uncoated bananas showed signs of browning, and their titratable acid and vitamin C (Vc) contents decreased from 0.57% to 0.30% and from 7.37 mg/100 g to 4.77 mg/100 g, respectively. However, bananas coated with LCZ containing 3% BT not only exhibited a better appearance, but also possessed higher titratable acid (0.44%) and Vc content (5.31 mg/100 g). This study provides a sustainable and multifunctional coating for fruit preservation.

Evaluation of Cytotoxicity of Hyaluronic Acid/Chitosan/Bacterial Cellulose-Based Membrane

Novel wound dressing materials are required to non-cytotoxic with a viable cell ratio of above 92%. Herein, the cytotoxicity of hyaluronic acid/chitosan/bacterial cellulose-based (BC(CS/HA)) membranes are evaluated and compared to that of alginate/chitosan/bacterial cellulose-based (BC(CS/Alg)) membranes was investigated. Multilayer membranes with up to ten CS/HA or CS/Alg layers were prepared using the layer-by-layer (LBL) method. Scanning electron microscopy showed that the diameters of the fibers in the BC(CS/Alg) and BC(CS/HA) membranes were larger than those in a BC membrane. The cytotoxicity was analyzed using BALB-3T3 clone A31 cells (mouse fibroblasts, 1 × 10⁴ cells/well). The BC(CS/HA)₅ and BC(CS/HA)₁₀ membranes exhibited high biocompatibility, with the cell viabilities of 94% and 87% at 5 d, respectively, compared to just 82% for the BC(CS/Alg)₅ and BC(CS/Alg)₁₀ membranes with same numbers of layers. These results suggested that BC(CS/HA)₅ is a promising material for wound dressings.

Metal-Based Nanoparticles in Food Packaging and Coating Technologies: A Review

Food security has continued to be a topic of interest in our world due to the increasing demand for food. Many technologies have been adopted to enhance food supply and narrow the demand gap. Thus, the attempt to use nanotechnology to improve food security and increase supply has emerged due to the severe shortcomings of conventional technologies, which have made them insufficient to cater to the continuous demand for food products. Hence, nanoparticles have been identified to play a major role in areas involving food production, protection, and shelf-life extensions. Specifically, metal-based nanoparticles have been singled out to play an important role in manufacturing materials with outstanding properties, which can help increase the shelf-life of different food materials. The physicochemical and biological properties of metal-based nanoparticles, such as the large surface area and antimicrobial properties, have made them suitable and adequately useful, not just as a regular packaging material but as a functional material upon incorporation into biopolymer matrices. These, amongst many other reasons, have led to their wide synthesis and applications, even though their methods of preparation and risk evaluation remain a topic of concern. This review, therefore, briefly explores the available synthetic methods, physicochemical properties, roles, and biological properties of metal-based nanoparticles for food packaging. Furthermore, the associated limitations, alongside quality and safety considerations, of these materials were summarily explored. Although this area of research continues to garner attention, this review showed that metal-based nanoparticles possess great potential to be a leading material for food packaging if the problem of migration and toxicity can be effectively modulated.

Self-assembly fabrication of chitosan-tannic acid/MXene composite film with excellent antibacterial and antioxidant properties for fruit preservation

It is highly urgent to develop a simple and effective strategy to extend the shelf life of time-sensitive fruits, which are very susceptible to spoilage over time, resulting in considerable food waste. Herein, a biopolymer-based composite film with superior antibacterial and antioxidant properties was developed by introducing MXene and tannic acid into a chitosan network via hydrogen bonding and an electrostatic self-assembly method. The results show that the mechanical properties, water and heat resistance, antibacterial and antioxidant capabilities of the obtained Chitosan-Tannic acid/MXene film are significantly increased to meet the use of packaging film scenarios. The fruit preservation experiments also confirmed that the composite film can effectively extend the shelf life of bananas and grapes through its excellent water vapor and oxygen barrier. These desirable performances enable our newly designed composite film to be an effective and competitive packaging material to solve the fresh fruit preservation dilemma.

Developing fisetin-AgNPs incorporated in reinforced chitosan/pullulan composite-film and its application of postharvest storage in litchi fruit

In this study, Toxicodendron vernicifluum fisetin chelated silver nanoparticles (FT-AgNPs) with outstanding antioxidant and antimicrobial activities were constructed via self-assembly. To surprise, 0.6 wt% FT-AgNPs was compatibly dispersed into the 1:1 chitosan/pullulan (CS/PUL, CP) matrix. The hydrogen bonding and electrostatic interaction between FT-AgNPs and CP, slightly increased the CP thermal stability, and greatly enhanced the tensile strength to 61.2 MPa, water vapor permeability below 20 kg/m²•d. Furthermore, after treated with the composite hydrocolloid film (FT-AgNPs/CP), the reactive oxygen species level of the treated Aspergillus niger cells was significantly increased, and the membrane permeability was enhanced. It effectively slowed down the decay of litchi fruit induced by microbial infection under the storage at 25 °C (15 d of the 0.6 % FT-AgNPs/CP treatment vs 9 d of the control). In addition, 0.024 μg/kg Ag⁺ residual in lichi pulp verified the qualified safety of the application of the 0.6 % FT-AgNPs/CP.

Lignin-induced sacrificial conjoined-network enabled strong and tough chitosan membrane for food preservation

As a natural green polymer, chitosan is a promising material for plastic replacement. However, the mutually exclusive strength and toughness severely limit its commercial application, and the improved strength of chitosan-based materials is typically achieved at the expense of elongation or toughness. Herein, inspired by the existed multiple non-covalent interactions in biosynthesized fibers, we successfully fabricated a high-performance lignin/chitosan composite film by constructing sacrificial conjoined-network (hydrogen bonds, electrostatic interaction, etc.), which results in an impressive enhancement in tensile strength (50.2 MPa), elongation (73.6 %), and toughness (2.7 MJ/m³) simultaneously, much superior to the pure chitosan film. In addition, the composite film also demonstrates excellent UV resistance, thermal stability, low oxygen permeability (3.9 cm³/(m²·24h‧0.1 MPa)) and food preservation (with no negligible change for grape, apple, and cherry tomato after 5-10 days). Such developed lignin/chitosan with both components from biomass represents a promising alternative for plastic replacement.

Facile fabrication of robust bilayer film loaded with chitosan active microspheres for potential multifunctional food packing

The utilization of microcarriers is an effective technique to protect and slow down the release of active ingredients, while the combination of microcarriers and film materials is an important way to expand the application scenario of active ingredients. The aim of this study was to develop a simple and facile strategy for designing a multifunctional bilayer bioactive film that combines stable mechanical properties, sustained-release characteristics for active ingredients with good antioxidant and antibacterial properties. The EGCG-loaded chitosan active microspheres were prepared by sol-gel method, and then the carboxymethyl cellulose solution containing the active microspheres was assembled onto the carboxymethyl chitosan gel substrate based on intermolecular hydrogen bonding to construct a film with a stable bilayer structure. The results indicated that the bilayer film had dense microstructure and excellent mechanical strength (37.05 MPa), and exhibited UV-blocking properties and excellent gas barrier performance. Meanwhile, the loading of active ingredients (EGCG) in the microspheres enabled the bilayer film to exhibit excellent antioxidant and antibacterial properties, and the controlled release of EGCG by the film was sustainable and showed pH responsiveness. The results of this work provide a new perspective for the design and development of bio-based active packaging film with tunable functional characteristics.

Characterization of a thermostable PL-31 family alginate lyase from Paenibacillus ehimensis and its application for alginate oligosaccharides bioproduction

Currently, people pay more attention to marine sugars, because of their unique physiological effects. Alginate oligosaccharides (AOS) are the degradation products of alginate and have been used in food, cosmetic, and medicine fields. AOS display good physical characteristics (low relative molecular weight, good solubility, high safety, and high stability) and excellent physiological functions (immunomodulatory, antioxidant, antidiabetic, and prebiotic activities). Alginate lyase plays a key role in the AOS bioproduction. In this study, a novel PL-31 family alginate lyase from Paenibacillus ehimensis (paeh-aly) was identified and characterized. It was extracellularly secreted in E. coli and exhibited a preference for the substrate poly β-D-mannuronate. Using sodium alginate as the substrate, it showed the maximum catalytic activity (125.7 U/mg) at pH 7.5 and 55 °C with 50 mM NaCl. Compared with other alginate lyases, paeh-aly exhibited good stability. About 86.6% and 61.0% residual activity could be maintained after 5 h incubation at 50 and 55 °C respectively, and its T_m value was 61.5 °C. The degradation products were AOS with DP 2-4. Paeh-aly demonstrated strong promise for AOS industrial production because of its excellent thermostability and efficiency.

Recent advances of polymer based nanosystems in cancer management

Cancer is still one of the leading causes of death worldwide. Nanotechnology, particularly nanoparticle-based platforms, is at the leading edge of current cancer management research. Polymer-based nanosystems have piqued the interest of researchers owing to their many benefits over other conventional drug delivery systems. Polymers derived from both natural and synthetic sources have various biomedical applications due to unique qualities like porosity, mechanical strength, biocompatibility, and biodegradability. Polymers such as poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), and polyethylene glycol (PEG) have been approved by the USFDA and are being researched for drug delivery applications. They have been reported to be potential carriers for drug loading and are used in theranostic applications. In this review, we have primarily focused on the aforementioned polymers and their conjugates. In addition, the therapeutic and diagnostic implications of polymer-based nanosystems have been briefly reviewed. Furthermore, the safety of the developed polymeric formulations is crucial, and we have discussed their biocompatibility in detail. This article also discusses recent developments in block co-polymer-based nanosystems for cancer treatment. The review ends with the challenges of clinical translation of polymer-based nanosystems in drug delivery for cancer therapy.

Preparation and characterization of chitosan/whey isolate protein active film containing TiO2 and white pepper essential oil

Active packaging films are designed to improve quality and extend the food shelf life by incorporating functional active ingredients into biopolymer films. This study developed a bioactive film based on chitosan (CS) and whey isolated protein (WPI) incorporated with 0.01 wt% TiO2 and 0.1 wt% white pepper essential oil (WPEO). The physicochemical properties of the prepared film were also evaluated comprehensively. The results showed that water solubility and water vapor permeability of the film incorporated with TiO2 and WPEO were 25.09% and 0.0933 g mm m–2 h–1 KPa–1, respectively, which were significantly higher than those of other films (P &lt; 0.05). In addition, the UV barrier properties of films incorporating TiO2 and WPEO have improved. The films were characterized by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The FTIR results showed interactions between TiO2 and WPEO with CS/WPI compound, and the SEM results indicated a good incorporation of TiO2 into the composite films. The antioxidative and antibacterial properties of films were significantly enhanced by incorporating WPEO. According to results, the developed biocomposite film can be considered as a packaging material.

Fabrication and Characterization of Eco-Friendly Polyelectrolyte Bilayer Films Based on Chitosan and Different Types of Edible Citrus Pectin

The eco-friendly polyelectrolyte bilayer films were prepared by layer-by-layer (LBL) casting method using chitosan (CS) and four types of edible citrus pectin as film substrates. The results showed that the polyelectrolyte bilayer films exhibited excellent comprehensive properties. Furthermore, the interaction between CS and pectin was closely related to the degree of methyl-esterification (DM), molecular weight (Mw), and zeta potential of pectin. The low DM, Mw, and high zeta potential of the low methyl-esterified pectin (LM) resulted in a denser internal structure of the bilayer film, stronger UV shielding performance, and stronger gas barrier ability. The high DM and Mw of the high methyl-esterified pectin (HM) endow the bilayer film with stronger mechanical properties, thermal stability, and antifogging property. The microstructural and spectroscopic analysis showed that there are hydrogen bonds and electrostatic interactions between the layers. Overall, the developed CS-pectin polyelectrolyte bilayer films provided potential applications for food bioactive packaging.