Chitosan coating for the preparation of multilayer coated paper for food-contact packaging: Wettability, mechanical properties, and overall migration

Improving the performance of kraft paper by cinnamon essential oil/soybean protein isolate microcapsules and konjac glucomannan for citrus preservation

In order to reduce the quality loss of citrus and extend its storage time after harvest, it is essential to develop coated kraft papers with antibacterial and fresh-keeping properties. In this study, cinnamon essential oil (CEO)/soybean protein isolate (SPI) microcapsules were prepared by the coagulation method, and their properties were optimized. Then, the microcapsules were added to konjac glucomannan (KGM) as a coating solution to enhance the physical, and chemical properties of kraft paper by a coating method. The release behavior of CEO, tensile properties, antibacterial properties and preservation effects of the paper were investigated. The results show that when the ratio of wall to core was 7:3, the highest encapsulation rate was 92.20 ± 0.43 %. The coating treatment significantly reduced the oxygen and water vapor transmission rates of kraft paper. The shelf life of citrus treated with coated Kraft was extended by >10 days. Thus, the CEO/SPI microencapsulation and KGM coating could improve the properties of kraft paper and have the potential for citrus preservation.

Preparation of multi-barrier and multi-functional paper-based materials by chitosan, ethyl cellulose and green walnut husk biorefinery products for sustainable food packaging

The growing interest in paper-based materials for packaging is driven by their renewable and eco-friendly characteristics. However, their poor barrier performance against water, oil, and gas limits their application in the food packaging industry. In this study, we developed a simple dual-layer coating method to create water- and oil-repellent, gas barrier, antioxidant, and antibacterial paper-based materials using naturally-derived materials, including chitosan (CS), ethyl cellulose (EC), and cascade biorefinery products from green walnut husk (GWHE and CNC). The bottom CS/CNC oil-resistant coating and the top EC/GWHE water-resistant coating were applied to the paper surface. The synergistic effect of these coatings enhances the gas barrier and imparts functional properties to the paper. Compared to uncoated paper, the dual-layer-coated paper demonstrated a 239.1 % increase in tensile index, a higher kit rating value of 12/12, a lower Cobb 60 value of 3.21 mg/m2, a 44.0 % decrease in water vapor permeability (WVP), and a 90.7 % reduction in air permeability (AP). Additionally, this coated paper exhibited good antioxidant and antibacterial properties and favorable biodegradability. This study provides novel insights into the valorization of GWH waste and presents a sustainable strategy for producing high-performance paper-based materials for food packaging applications.

In vitro and in silico approach towards antimicrobial and antioxidant behaviour of water-soluble chitosan dialdehyde biopolymers

Chitosan dialdehyde (ChDA) was prepared from a three-step process initiated by thermal organic acid hydrolysis, periodate oxidization, and precipitation from native chitosan (NCh). The developed ChDA resulted in an aldehydic content of about 82 % with increased solubility (89 %) and maximum yield (97 %). The functional alteration of the aldehydic (-CHO) group in ChDA was established using vibrational stretching at 1744 cm-1. The increase in the zone of inhibition of ChDA compared to NCh has confirmed the inherent antimicrobial effect against bacterial and fungal species. ChDA showed better antioxidant activity of about 97.4 % (DPPH) and 31.1 % (ABTS) compared to NCh, measuring 45.3 % (DPPH) and 15.9 % (ABTS), respectively. The novel insilico predictions of the ChDA's biocidal activity were confirmed through molecular docking studies. The amino acid moiety such as ARG 110 (A), ASN 206 (A), SER 208 (A), THR 117 (B), ASN 118 (B), and LYS 198 (B) residues of 7B53 peptide from E. coli represents the binding pockets responsible for interaction with aldehyde group of ChDA. Whereas PHE 115 (E), ALA 127 (H), TYR 119 (C), GLN 125 (H), ASN 175 (E), ARG 116 (E), LYS 101 (H), and LYS 129 (H) of 1IYL A peptide from Candida albicans makes possible for binding with ChDA. Hence, the synergistic effect of ChDA as a biocidal compound is found to be plausible in the drug delivery system for therapeutic applications.

Development of high barrier-coated white cardboard for fruit preservation

Environment-friendly and biodegradable packaging materials have attracted widespread attention. Development of green solutions to extend the fruit shelf life and address fruit preservation thus has a far-reaching impact. In this study, high-barrier white cardboard (WC) was prepared by a facile coating method. Compared with the WC substrate, the WVP value of the polyvinylidene chloride (PVDC) emulsion-coated WC (3.46 × 10-11 g m m-2 s-1 kPa-1) decreased 73.8% and the OP value (14.8 cm3 m-2 day-1·Pa-1) decreased 61.9%. In addition, the mechanical properties of the PVDC emulsion-coated WC increased significantly. The weight loss rate and decay rate of the stored fruits packaged with PVDC emulsion-coated WC decreased by about 5%. The high barrier PVDC emulsion-coated WC with excellent mechanical properties, good barrier effect, and preservation function was successfully prepared. Benefitting from these investigated characteristics, the obtained coated WC can be used to package fruits to reduce water loss and delay ripening, and thus extend their shelf life, exhibiting a favorable effect on blueberry and grape storage. Overall, the fabricated eco-friendly coated white cardboard has shown great potential for biodegradable packaging applications. We believe the current work presents an approach to address perishable fruit preservation and provide a supplement alternative.

Exploring chitosan-plant extract bilayer coatings: Advancements in active food packaging via polypropylene modification

UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.

Synthesis of novel chitosan/sodium hyaluronate/iridium hydrogel nanocomposite for wound healing application

A novel chitosan/sodium hyaluronate/iridium (CHI/SH/Ir) hydrogel nanocomposite with a unique microstructure containing vertically aligned pores is fabricated via an electrophoresis technique. The formation of orderly vertical pores in CHI/SH/Ir hydrogel nanocomposite is due to the confinement of hydrogen bubbles produced from the water electrolysis during electrophoresis that limits their lateral movement and coalescence. In a wet state, the diameter for the vertical pores is 600-700 μm. With a thickness of 500 μm, the CHI/SH/Ir hydrogel nanocomposite exhibits a porosity of 76.7 % and a water uptake of 350 %. Its tensile strength is almost doubled to 8.7 MPa, as compared to that of counterpart without the addition of iridium. In CHI/SH/Ir hydrogel nanocomposite, the iridium nanoparticles are homogeneously distributed with an average size of 3 nm. The CHI/SH/Ir electrophoresis suspension exhibits a negligible cytotoxicity. In cell migration test using the human keratinocytes HaCaT cells, the CHI/SH/Ir hydrogel nanocomposite reveals a relative migration of 122.15 ± 9.02 % (p < 0.001) as compared to the blank sample. The presence of vertically aligned pores with the use of SH and iridium nanoparticles indicates a promising opportunity in wound healing application.

Degradable chitosan-based bioplastic packaging: Design, preparation and applications

Food packaging is an essential part of food transportation, storage and preservation. Biodegradable biopolymers are a significant direction for the future development of food packaging materials. As a natural biological polysaccharide, chitosan has been widely concerned by researchers in the field of food packaging due to its excellent film-forming property, good antibacterial property and designability. Thus, the application research of chitosan-based food packaging films, coatings and aerogels has been greatly developed. In this review, recent advances on chitosan-based food packaging materials are summarized. Firstly, the development background of chitosan-based packaging materials was described, and then chitosan itself was introduced. In addition, the design, preparation and applications of films, coatings and aerogels in chitosan-based packaging for food preservation were discussed, and the advantages and disadvantages of each research in the development of chitosan-based packaging materials were analyzed. Finally, the application prospects, challenges and suggestions for solving the problems of chitosan-based packaging are summarized and prospected.

Eco-friendly food packaging based on paper coated with a bio-based antibacterial coating composed of carbamate starch, calcium lignosulfonate, cellulose nanofibrils, and silver nanoparticles

Traditional paper-based packaging commonly needs to be coated to achieve sufficient mechanical and barrier performances. In this research, a bio-based coating for paper was developed from carbamate starch (Sc), calcium lignosulfonate (CL), and cellulose nanofibrils (CNF). Controlling the electrostatic and hydrogen-bonding interactions among the components of the coating was conducive to tailoring the structure and performance of the coated paper. When the degree of substitution (Ds) of Sc was 0.10, the amount of CL was 1.00 g, and the amount of CNF was 0.65 % of the weight of Sc, the paper coated with the resulting 0.10Sc-1.00CL-0.65CNF coating exhibited increased hydrophobicity and excellent mechanical, air-barrier, and UV-light-barrier properties. After the addition of 0.10 % of silver nano-particles (AgNPs) to the 0.10Sc-1.00CL-0.65CNF coating, the paper coated with the resulting 0.10Sc-1.00CL-0.65CNF-0.10AgNPs coating exhibited good antibacterial activity against Escherichia coli and Staphylococcus aureus. The coated paper was used as the packaging for cherry tomatoes stored under ambient conditions. Due to the synergistic preservation effects of the Sc-CL-CNF coating and AgNPs, the shelf life of the cherry tomatoes was at least 7 days. The coated paper described herein has the potential for applications in the food packaging sector.

Effect of chitosan-based bio coating on mechanical, structural and physical characteristics of microfiber based paper packaging: An alternative to wood pulp/plastic packaging

Limnocharis flava is a noxious aquatic weed that poses a threat to paddy cultivation. The high cellulose and low lignin contents in this plant make it a potential raw material for papermaking. Against this backdrop, this study was taken up to develop Limnocharis flava (LF) based sheets containing natural fibres from Banana (B), Pineapple (P), and Rice Straw (RS) as reinforcing agents. The influence of carboxymethyl cellulose (CMC) as a binder on the LF-based sheets was also studied. To enhance the mechanical and moisture resistance properties, a chitosan coating was provided to the sheets. Analytical tests for mechanical properties, water barrier properties, functional groups, structure and microstructure, thermal properties and biodegradability were performed. Among the samples, LF + B showed the highest tensile strength (34.86 Mpa) and bursting strength (13.055 kg/cm2), while LF + R had higher puncture and tearing strengths. Chitosan coating was found to enhance the sheets and improve the water barrier properties mechanically. The contact angle of LF + B increased from 91.6° to 110.65°, while the water vapour transmission rate of LF reduced from 532.18 to 404.47 on providing chitosan coating. The significant interactions of reinforcing agents were confirmed by the results of FTIR and that of the coating by the SEM micrographs. The LF-based sheets were also found to have decent thermal stability. The high value of the crystallinity index in LF + R samples supported their remarkable mechanical properties. This study proclaims the notable suitability of Limnocharis flava in manufacturing paper for packaging applications.

One-step fabrication of eco-friendly multi-functional amphiphobic coatings for cellulose-based food packaging

Plastic and fluorine-containing oil and water resistant packaging materials have been gradually replaced by non-toxic and harmless bio-based materials because of their hazard to environment and human health. In this study, chitosan/carnauba wax emulsions (CS/CWs) were firstly prepared by one-step and used as oil and water resistant coating for cellulose-based food packaging paper. The impacts of emulsion components on stability of the emulsions and barrier performance of the coated paper were investigated. The results showed that the viscosity, particle size and polydispersity index of the emulsions were greatly dependent on the concentration of CS and CW, and the coated paper had the best comprehensive performance in water and oil resistance when the concentration of CS was 3 % and the amount of CW was 90 % of the total solid content (CS3/CW90). The particle size of CS3/CW90 was in the range of 0.5-0.7 μm, and the Cobb60 value, water contact angle and the kit ratings of paper coated with CS3/CW90 achieved 7.5 g/m2, 130.9° and 12/12, respectively, and the coated paper also exhibited excellent thermal stability and high antibacterial rate of 99.1 %, demonstrating its great potential for application in multi-functional food packaging.

Development of chitin nanofiber coatings for prolonging shelf life and inhibiting bacterial growth on fresh cucumbers

The widespread usage of petroleum-based polymers as single-use packaging has had harmful effects on the environment. Herein, we developed sustainable chitin nanofiber (ChNF) coatings that prolong the shelf life of fresh cucumbers and delay the growth of pathogenic bacteria on their surfaces. ChNFs with varying degrees of acetylation were successfully prepared via deacetylation using NaOH with treatment times of 0-480 min and defibrillated using mechanical blending. With longer deacetylation reaction times, more acetamido groups (-NHCOCH3) in chitin molecules were converted to amino groups (-NH2), which imparted antibacterial properties to the ChNFs. The ChNF morphologies were affected by deacetylation reaction time. ChNFs deacetylated for 240 min had an average width of 9.0 nm and lengths of up to several μm, whereas rod-like structured ChNFs with a mean width of 7.3 nm and an average length of 222.3 nm were obtained with the reaction time of 480 min. Furthermore, we demonstrated a standalone ChNF coating to extend the shelf life of cucumbers. In comparison to the rod-like structured ChNFs, the 120 and 240-min deacetylated ChNFs exhibited a fibril-like structure, which considerably retarded the moisture loss of cucumbers and the growth rate of bacteria on their outer surfaces during storage. Cucumbers coated with these 120 and 240-min deacetylated ChNFs demonstrated a lower weight loss rate of ⁓ 3.9% day-1 compared to the uncoated cucumbers, which exhibited a weight loss rate of 4.6% day-1. This protective effect provided by these renewable ChNFs holds promising potential to reduce food waste and the use of petroleum-based packaging materials.

Extensive Characterization of Alginate, Chitosan and Microfibrillated Cellulose Cast Films to Assess their Suitability as Barrier Coating for Paper and Board

The vast amount of synthetic polymers used in packaging is putting a strain on the environment and is depleting finite, non-renewable raw materials. Abundantly available biopolymers such as alginate, chitosan and microfibrillated cellulose (MFC) have frequently been suggested in the literature to replace synthetic polymers and their barrier properties have been investigated in detail. Many studies aim to improve the properties of standalone biopolymer films. Some studies apply these biopolymers as barrier coatings on paper, but the solids content in most of these studies is quite low, which in turn would result in a high energy demand in industrial drying processes. The aim of this study is to suggest a laboratory procedure to investigate the suitability of these biopolymers at higher and such more industrially relevant solids content as potential coating materials for paper and board in order to improve their barrier properties. First, biopolymer solutions are prepared at a high solids content at which the viscosity at industrially relevant higher shear rates of 50,000 s-1 (1000 s-1 for MFC) is in the same range as a synthetic reference material (in this case ethylene vinyl alcohol EVOH) at 10 wt%. These solutions are analyzed regarding properties such as rheology and surface tension that are relevant for their coatability in industrial coating processes. Then, free-standing films are cast, and the films are characterized regarding important properties for packaging applications such as different surface, mechanical and barrier properties. Based on these results suitable biopolymers for future coating trials can be easily identified.

Active Cellulose Acetate/Chitosan Composite Films Prepared Using Solution Blow Spinning: Structure and Electrokinetic Properties

Cellulose acetate (CA), a very promising derivative of cellulose, has come into the focus of research due to its highly desired good film-forming ability for food packaging applications. Frequently, this derivative is used in combination with other compounds (polymers, nanoparticles) in order to obtain active materials. Here, we report the preparation of thin films made of cellulose acetate loaded with chitosan (CS) using the solution blow spinning (SBS) method. Films are prepared by SBS processing of the polymers mixture solution, considering the following variables: (i) the concentration of cellulose acetate and chitosan in the solution and (ii) the solvent system consisting of acetic or formic acid. The prepared materials are characterized in terms of physical properties, roughness (optical profilometer), porosity, wettability (contact angle measurements), chemical structure (Fourier transform infrared spectrometry), and electrokinetic properties (zeta potential). SBS enables the preparation of CA/CS films with high water vapor permeability, high porosity, and also higher water contact angle compared with pure CA films. The electrokinetic properties of composites are influenced by the inclusion of chitosan, which causes a shift of the isoelectric point (IEP) towards higher pH values, but the magnitude of the shift is not in correlation with chitosan concentration. Adsorption kinetic studies using bovine serum albumin (BSA) as a model protein reveal that chitosan modified cellulose acetate films manifest low affinity towards proteins that suggests prevention of biofilm formation on its surface.

Properties of Paperboard Coated with Natural Polymers and Polymer Blends: Effect of the Number of Coating Layers

Paper is one of the packaging materials that presents a biodegradable character, being used in several areas; however, its barrier properties (gases and fat) and mechanics are reduced, which limits its application. Coating papers with synthetic polymers improve these properties, reducing their biodegradability and recyclability. The objective of this work was to develop and characterize coated paperboard, using the tape casting technique, with different ratios of film form agar-agar/chitosan (AA:CHI, 100:0, 50:50, and 0:100) and different numbers of coating layers (operating times for application of 14.25 min and 28.5 min for one and two layers, respectively). A significant reduction in water absorption capacity was found by applying a 0:100 coating (approximately 15%). Considering all coating formulations, the water vapor permeability reduced by 10 to 60% compared to uncoated paperboard, except for two layers coated with 0:100. The tensile index (independent of AA:CHI) was higher in the machine direction (22.59 to 24.99 MPa) than in the cross-section (11.87-13.01 MPa). Paperboard coated only with chitosan showed superior properties compared to the other formulation coatings evaluated.

Environmentally friendly strategy to access self-healable, reprocessable and recyclable chitin, chitosan, and sodium alginate based polysaccharide-vitrimer hybrid materials

Natural polysaccharides show enviable advantages for preparation of sustainable hybrid materials. However, in most cases, complex chemical modifications of natural polysaccharides are required, which not only causes changes of the inherent properties of polysaccharides, but also increases the manufacturing costs of the final materials. Therefore, it is highly desired to develop efficient and low-cost ways to access polysaccharides-containing hybrid materials. In this work, we report the environmentally friendly preparation of a new kind of polysaccharide-based materials, called polysaccharide-vitrimer hybrid materials, for the first time. The vitrimer synthesis and hybridization with polysaccharides can be achieved via a convenient one-pot method in absence of solvent and catalyst. In addition, time-consuming and labor-intensive physical/chemical modifications of natural polysaccharides are completely avoided. The resultant hybrid materials show good mechanical performance (tensile toughness is up to 13.7 MJ/m³), high thermal stability (T_d,max is up to 457 °C), fast self-healing ability (self-healing efficiency is up to 99 % within 20s at 80 °C) and excellent reprocessability and recyclability (at least three cycles). Especially, conductive polysaccharide-vitrimer hybrid materials could be readily prepared from the resultant materials, exhibiting novel applications as flexible sensors and electromagnetic shielding materials (the EMI SE is up to 24.93 dB).

Development of water-resistant paper using chitosan and plant-based wax extracted from banana leaves

On being exposed to water, cellulose paper swells and its mechanical properties become weak. In this study, natural wax with an average particle size of 12.3 μm extracted from banana leaves was mixed with chitosan to prepare coatings applied on paper surfaces. Chitosan efficiently dispersed banana leaf-extracted wax on paper surfaces. The mixed chitosan and wax coatings considerably influenced paper properties, including yellowness, whiteness, thickness, wettability, water and oil sorption, and mechanical properties. The coating induced hydrophobicity in the paper, resulting in a significant increase in the water contact angle from 65.1 ± 7.7° (uncoated paper) to 123.2 ± 2.1°, and a decrease in water absorption by ⁓64 % to 52.6 ± 1.9 %. The coated paper demonstrated an oil sorption capacity of 212.2 ± 2.8 %, which was ⁓43 % greater than that of the uncoated paper, and the tensile strength of the coated paper improved by 43 % under wet conditions compared to the uncoated paper. Additionally, a separation of oil in water was observed for the chitosan/wax coated paper. Based on these promising results, the paper coated with chitosan and wax could be used for direct-contact packaging applications.

Processing, Characterization and Disintegration Properties of Biopolymers Based on Mater-Bi® and Ellagic Acid/Chitosan Coating

Among the most promising synthetic biopolymers to replace conventional plastics in numerous applications is MaterBi^® (MB), a commercial biodegradable polymer based on modified starch and synthetic polymers. Actually, MB has important commercial applications as it shows interesting mechanical properties, thermal stability, processability and biodegradability. On the other hand, research has also focused on the incorporation of natural, efficient and low-cost active compounds into various materials with the aim of incorporating antimicrobial and/or antioxidant capacities into matrix polymers to extend the shelf life of foods. Among these is ellagic acid (EA), a polyphenolic compound abundant in some fruits, nuts and seeds, but also in agroforestry and industrial residues, which seems to be a promising biomolecule with interesting biological activities, including antioxidant activity, antibacterial activity and UV-barrier properties. The objective of this research is to develop a film based on commercial biopolymer Mater-Bi^® (MB) EF51L, incorporating active coating from chitosan with a natural active compound (EA) at two concentrations (2.5 and 5 wt.%). The formulations obtained complete characterization and were carried out in order to evaluate whether the incorporation of the coating significantly affects thermal, mechanical, structural, water-vapor barrier and disintegration properties. From the results, FTIR analysis yielded identification, through characteristic peaks, that the type of MB used is constituted by three polymers, namely PLA, TPS and PBAT. With respect to the mechanical properties, the values of tensile modulus and tensile strength of the MB-CHI film were between 15 and 23% lower than the values obtained for the MB film. The addition of 2.5 wt.% EA to the CHI layer did not generate changes in the mechanical properties of the system, whereas a 5 wt.% increase in ellagic acid improved the mechanical properties of the CHI film through the addition of natural phenolic compounds at high concentrations. Finally, the disintegration process was mainly affected by the PBAT biopolymer, causing the material to not disintegrate within the times indicated by ISO 20200.

Enhancement of water barrier and antimicrobial properties of chitosan/gelatin films by hydrophobic deep eutectic solvent

Biodegradable chitosan/gelatin (CS/GEL) films have attracted attention as food packaging, but the poor water sensitivity and functional limitations of these films should be addressed. In this study, the hydrophobic deep eutectic solvent (DES, 0-15 %) consisting of thymol and octanoic acid was used to improve the water resistance and antibacterial performance of the CS/GEL composite films. FTIR and SEM analyses revealed a strong interaction between the CS/GEL matrix and DES. The films blended with DES showed increased water contact angle values and thermal stability. Furthermore, the addition of DES resulted in a significant increase in the elasticity and decrease water vapor transmission rate (WVTR). The CS/GEL films blended with 9% DES showed a 38.5% decrease in WVTR compared to those without DES. Additionally, the DES-containing film displayed good antibacterial activity against Staphylococcus aureus and Escherichia coli. Overall, the CS/GEL-DES composite films are expected to contribute an improvement to food packaging.

A facile strategy to fabricate antibacterial hydrophobic, high-barrier, cellulose papersheets for food packaging

As a traditionally used packaging material, natural cellulose-based paper has poor barrier properties to water and oxygen, which severely limits its wide application in food packaging. In this study, we report a new sustainable approach to producing hydrophobic, high-barrier, and antibacterial packaging materials from cellulose paper. In this process, commercially available microcrystalline cellulose was first modified by long-chain stearic acid to form hydrophobic microcrystalline cellulose ester and then mixed with stearic acid as filler in the subsequent surface coating of bagasse fibre paper. The microcrystalline cellulose ester/stearic acid-coated paper (MSP) exhibited good water repellency and oxygen barrier activity due to a continuous hydrophobic film that formed, which completely covered the pores of the original bagasse fibre paper. The coated MSP sample also showed excellent dimensional stability in water and a good wet tensile strength of 16 MPa. In addition, poly(hexamethylene guanidine) (PHMG) was chemically grafted onto the free carboxyl groups of the MSP surface layer, and the resulting MSP-g-PHMG samples exhibited excellent antibacterial activity against Escherichia coli and Listeria monocytogenes. The biodegradable cellulose-based MSP-g-PHMG sample significantly delayed the decay of raspberry during storage, indicating its potential application in food packaging.

Recyclable, UV-shielding, and biodegradable chitosan-based cardanol glycidyl ether as excellent water and oil resistance as well as gas barrier coating for paper

Developing a feasible and low-cost approach to fabricate recyclable, UV-shielding, biodegradable as well as water- and oil-resistant coating for paper substance is still a challenge. Herein, novel full-biobased chitosan-derived cardanol glycidyl ether (CS-xCGE, x = 1/8, 1/4, 1/2, and 1) coatings with different contents of cardanol glycidyl ether (CGE) were developed for paper substance via the ethoxylation of cardanol and sequent addition with chitosan in a one-pot process. Benefiting from the hydrophobicity and ultraviolet resistance of CGE, the resultant CS-CGE (x = 1) coated paper exhibited not only remarkable oil resistance (kit rating value of 11/12), but also water resistance (Cobb 60 value of 5.78 g/m²), UV shielding and excellent recyclability. Compared with the uncoated paper, the mechanical properties of CS-CGE coated paper including tensile strength, folding strength, and resistance of water vapor permeability were improved 25 %, 63 %, and 73.4 %, respectively, which could be ascribed to the flexible long-alkyl chain in the structure of CS-CGE and the continuous and homogeneous CS-CGE derived film covered in paper substance. Most importantly, CS-CGE film is biodegradable when it is only buried in soil. This study affords a feasible and sustainable strategy for large-scale fabrication of full-biobased, recyclable, UV-shielding, water and oil resistant, as well as biodegradable coating for green paper-derived packaging.

Sustainable Coating Paperboard Packaging Material Based on Chitosan, Palmitic Acid, and Activated Carbon: Water Vapor and Fat Barrier Performance

Synthetic polymer coatings impact the biodegradable behavior of cellulosic packaging material. The environmental consequences of food packaging disposal have increased consumer concern. The present study aimed to use natural polymer coatings incorporating palmitic acid and activated carbon applied to paperboard surfaces as a sustainable alternative to improve cellulosic packaging material's moisture and fat barrier properties, minimizing the environmental impact. The coating formulation was defined using a Factorial Experimental Design with independent variables: chitosan, palmitic acid, activated carbon concentrations, and the number of coating layers. The highest concentration of chitosan (2.0% w/w) filled the pores of the cellulosic paperboard network, supporting the compounds incorporated into the filmogenic matrix and improving the fat resistance. The water vapor permeability of the coated paperboard material (range: 101 ± 43 to 221 ± 13 g·d^-1·m^-2) was influenced by the hydrophobicity effect of palmitic acid, the non-polar characteristic of activated carbon, and the number of applied layers. The coating formulation selected was a chitosan concentration of 2.0% (w/w), a palmitic acid concentration of 1.8% (w/w), an activated carbon concentration of 1.2% (w/w), and an application of three layers. The coating provides the potential for a paperboard surface application, improving the cellulosic packaging material's fat and moisture barrier properties and maintaining biodegradability and recyclability.

Potential effects of nano-cellulose and nano-silica/polyvinyl alcohol nanocomposites in the strengthening of dyed paper manuscripts with madder: an experimental study

In the present work, the composite cross-linked were used to consolidate the dyed paper manuscripts. Nanocomposites of mesoporous silica nanoparticle (MPSNP)/polyvinyl alcohol (PVA) and cellulose nanofiber (CNF)/PVA, which have never been used before, have been evaluated for the consolidation process of the dyed paper manuscripts with madder extract. Three concentrations 1%, 3%, and 5% have been prepared. Analysis and investigation methods like scanning electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering analysis (DLS), X-Ray diffraction Analysis (XRD), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and total color difference (ΔE) by spectrophotometer have been used in order to characterize the prepared nano-sized composites and evaluate the treated dyed paper samples before and after the aging process. The results of surface morphology by SEM revealed the effectiveness of MPSNP/PVA core-shell nanocomposite at 5% in the consolidation process, where the improvement of properties of the aged dyed paper samples. The fibers of the treated paper became strong and appeared clearly. The result of ΔE measurements showed that the treated sample with MPSNP/PVA nanocomposite at 5% gave the lowest ΔE (5.22), while, the treated sample with CNF/PVA nanocomposite at 5% gave the highest ΔE value (11.66). Mechanical measurements (tensile strength and elongation) revealed the efficiency of MPSNP/PVA nanocomposite at 5% in the treatment of the aged dyed paper samples. The treated sample with the mentioned material gave tensile strength and elongation values of 84.8 N/nm² and 1.736%, respectively. In contrast, the treated sample with CNF/PVA nanocomposite at 1% gave the lowest tensile strength and elongation values 38.2 N/nm², and 1.166%, respectively. FTIR analysis revealed an increase was noticed in the CH₂ stretching band (refers to the crystallinity of cellulose), where the intensity of the treated sample with MPSNP/PVA nanocomposite was at a 5% increase compared to the control sample. The FTIR results supported the results of mechanical measurements. The intensity of the CH₂ stretching band, which refers to the crystallinity index of cellulose, was increased with the use of MPSNP/PVA nanocomposite at 3% and 5%, which explains the improvement in mechanical properties. This may be due to the nano-mineral particles, which improve the mechanical properties. Additionally, they reduce the effect of accelerated thermal aging on the cellulosic fibers and give them stability. The detailed analysis of analytical methods used for evaluation revealed the novelty of MPSNP/PVA nanocomposite, especially at 5%. It has a potential role in strengthening and improving different properties of the dyed paper manuscripts with madder extract.

Production and Characterization of Biocomposite Films of Bacterial Cellulose from Kombucha and Coated with Chitosan

The purpose of this research is to produce and characterize bacterial cellulose (BC) films coated with chitosan (BC-CH). BC films were produced in a fermentation medium based on Camellia sinensis tea and dextrose (12 days at 25 °C) and subsequently treated with coating-forming solutions (CFSs) based on chitosan (BC-CH 0.5%, BC-CH 1.0%, and BC-CH 1.5%). As a result, the FTIR spectra of BC and BC-CH 1.5% showed the main characteristic bands of cellulose and chitosan. In the physicochemical characterization of the films, it was found that the incorporation of the chitosan coatings did not affect the thickness; however, it decreased the luminosity (L*) and increased redness (a*), yellowness (b*), and opacity (75.24%). Additionally, the light absorption properties in the UV-Vis range were improved. Furthermore, the application of the CFSs increased: the solubility (64.91%), the antimicrobial activity against S. aureus (6.55 mm) and E. coli (8.25 mm), as well as the antioxidant activity (57.71% and 24.57% free radical scavenging activity), and the content of total phenols (2.45 mg GAE/g). Finally, our results suggest that the BC-CH films developed in the present study show a potential application as active packaging material for food.

Chitosan: Sources, Processing and Modification Techniques

Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (M_w) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications.