Preparation and characterization of cellulose nanocrystals films incorporated with essential oil loaded β-chitosan beads

Preparation and characterization of chitosan and polyvinyl alcohol active film incorporated with Syzygium guineense plant extract as active packaging materials

The advancement of active packaging for food conservation has attracted considerable interest over time. In the present study, we aims to create and examine active films composed of chitosan (CS), poly(vinyl alcohol) (PVA), and syzygium guineense plant extract (SYZ) for potential use in food preservation. We examined the impact of ethanol extracts from the SYZ plant on the films' tensile strength, physical, antibacterial, and anti-oxidant properties. Scanning electron microscopy showed that the fabricated films have an even, uniform exterior morphology as well as superior UV-blocking capabilities. FTIR and X-ray diffraction analyses indicated that SYZ interacts with the CS/PVA blend through H-bonding. The addition of SYZ plant extract significantly increases the tensile strength of the films, reaching up to 88.61 ± 3.17 MPa. Furthermore, the water vapor transmission rate decreases to (0.34 ± 0.35 g·s-1m-1Pa-1) × 10-10 with the inclusion of SYZ plant extracts. All fabricated films maintain in general migration rate within permissible limits (<10 mg/dm2). Additionally, CS/PVA films with SYZ plant extract exhibit better anti-bacterial assay against S. aureus and E. coli. All samples containing SYZ plant extracts shows improved antioxidant activity based on DPPH and ABTS radical inhibition. These findings suggest that fabricated films with SYZ plant extract are promising for food wrapping.

Isobavachalcone-loaded electrospun polycaprolactone/gelatin nanofibers for antibacterial and antioxidant applications

Antibacterial nanofibers have been widely used in the fields of biomedicine and food packaging fields. To overcome existing antibiotic resistance, this study utilized isobavachalcone (IBC), a natural compound with antibacterial and antioxidant properties, combined with polycaprolactone (PCL) and gelatin (GEL) to develop an electrospun nanofibrous antibacterial membrane. Scanning electron microscopy (SEM) analysis revealed a uniform and smooth surface structure of the nanofiber. Fourier transform infrared spectroscopy and x-ray diffraction confirmed the interactions among the components of the nanofibrous membrane PCL/GEL/IBC (PGI). Thermogravimetric analysis and contact angle measurements demonstrated the thermal stability and hydrophilic nature. Additionally, the mechanical properties of PGI membrane were that the elongation at break increased to 19.9% and the tensile strength to 2.9 MPa.In vitrorelease studies indicated at least 48% release rate of IBC from the PGI nanofibrous membrane in 12 h, and release period up to 14 d. Antioxidant results revealed PGI membranes had fine abilities for scavenging free radical. The elimination of over 99% ofStaphylococcus aureusand elimination of 54%Candida albicansdemonstrated the antibacterial capacities of the PGI membrane, indicating its potential as antibacterial and antioxidant materials. Subsequent faster wound healing, lower oxidative damage for 4-HNE and 8-OHdG, further demonstrated that PGI can reduce oxidative damage at the wound and promote wound healing. These findings also suggest the potential of PGI in the field of tissue engineering.

Anti-bacterial films developed by incorporating shikonin extracted from radix lithospermi and nano-ZnO into chitosan/polyvinyl alcohol for visual monitoring of shrimp freshness

In recent years, the utilization of smart colorimetric packaging films for monitoring food freshness has garnered significant concentration. However, their limited tensile strength, hydrophobicity, antioxidant, and antibacterial properties have been substantial barriers to widespread adoption. In this study, we harnessed the potential of biodegradable materials, specifically chitosan/polyvinyl alcohol, alongside shikonin extracted from Radix Lithospermi and ZnO nanoparticles, to create a novel colorimetric sensing film. This film boasts an impressive tensile strength of 82.36 ± 2.13 MPa, enhanced hydrophobic characteristics (exemplified by a final contact angle of 99.81°), and outstanding antioxidant and antibacterial properties. It is designed for real-time monitoring of shrimp freshness. Additionally, we verified the effectiveness of this sensing film in detecting shrimp freshness across varying temperature conditions, namely 25 °C and 4 °C was validated through the measurement of total volatile basic nitrogen (TVB-N). Visual inspection unequivocally revealed a transition in color from dark red to purple-light blue and finally to dark bluish providing a clear indication of shrimp spoilage, which demonstrated a strong correlation with the TVB-N content in shrimp measured through standard laboratory procedures. The colorimetric sensing film developed in this study holds great promise for creating smart labels with exceptional antioxidant and antibacterial properties, tailored for visual freshness monitoring of shrimp.

Revolution of nanotechnology in food packaging: Harnessing electrospun zein nanofibers for improved preservation - A review

Zein, a protein-based biopolymer derived from corn, has garnered attention as a promising and eco-friendly choice for packaging food due to its favorable physical attributes. The introduction of electrospinning technology has significantly advanced the production of zein-based nanomaterials. This cutting-edge technique enables the creation of nanofibers with customizable structures, offering high surface area and adjustable mechanical and thermal attributes. Moreover, the electrospinning process allows for integrating various additives, such as antioxidants, antimicrobial agents, and flavoring compounds, into the zein nanofibers, enhancing their functionalities for food preservation. In this comprehensive review, the various electrospinning techniques employed for crafting zein-based nanofibers, and we delve into their enhanced properties. Furthermore, the review illuminates the potential applications of zein nanofibers in active and intelligent packaging materials by incorporating diverse constituents. Altogether, this review highlights the considerable prospects of zein-based nanocomposites in the realm of food packaging, offering sustainable and innovative solutions for food industry.

Formulation and stabilization of high internal phase emulsions: Stabilization by cellulose nanocrystals and gelatinized soluble starch

In this work, high internal phase emulsions (HIPEs) stabilized by naturally derived cellulose nanocrystals (CNC) and gelatinized soluble starch (GSS) were fabricated to stabilize oregano essential oil (OEO) in the absence of surfactant. The physical properties, microstructures, rheological properties, and storage stability of HIPEs were investigated by adjusting CNC contents (0.2, 0.3, 0.4 and 0.5 wt%) and starch concentration (4.5 wt%). The results revealed that CNC-GSS stabilized HIPEs exhibited good storage stability within one month and the smallest droplets size at a CNC concentration of 0.4 wt%. The emulsion volume fractions of 0.2, 0.3, 0.4 and 0.5 wt% CNC-GSS stabilized HIPEs after centrifugation reached 77.58, 82.05, 94.22, and 91.41 %, respectively. The effect of native CNC and GSS were analyzed to understand the stability mechanisms of HIPEs. The results revealed that CNC could be used as an effective stabilizer and emulsifier to fabricate the stable and gel-like HIPEs with tunable microstructure and rheological properties.

Biopolymer Food Packaging Films Incorporated with Essential Oils

Petroleum-based packaging materials are typically nonbiodegradable, which leads to significant adverse environmental and health issues. Therefore, developing novel efficient, biodegradable, and nontoxic food packaging film materials has attracted increasing attention from researchers. Due to significant research and advanced technology, synthetic additives in packaging materials are progressively replaced with natural substances such as essential oils (EOs). EOs demonstrate favorable antioxidant and antibacterial properties, which would be an economical and effective alternative to synthetic additives. This review summarized the possible antioxidant and antimicrobial mechanisms of various EOs. We analyzed the properties and performance of food packaging films based on various biopolymers incorporated with EOs. The progress in intelligent packaging materials has been discussed as a prospect of food packaging materials. Finally, the current challenges regarding the practical application of EOs-containing biopolymer films in food packaging and areas of future research have been summarized.

Preparation, Characterization and Antibacterial Property Analysis of Cellulose Nanocrystals (CNC) and Chitosan Nanoparticles Fine-Tuned Starch Film

To improve the mechanical and antibacterial properties of traditional starch-based film, herein, cellulose nanocrystals (CNCs) and chitosan nanoparticles (CS NPs) were introduced to potato starch (PS, film-forming matrix) for the preparation of nanocomposite film without incorporation of additional antibacterial agents. CNCs with varied concentrations were added to PS and CS NPs composite system to evaluate the optimal film performance. The results showed that tensile strength (TS) of nanocomposite film with 0, 0.01, 0.05, and 0.1% (w/w) CNCs incorporation were 41, 46, 47 and 41 MPa, respectively. The elongation at break (EAB) reached 12.5, 10.2, 7.1 and 13.3%, respectively. Due to the reinforcing effect of CNCs, surface morphology and structural properties of nanocomposite film were altered. TGA analysis confirmed the existence of hydrogen bondings and electrostatic attractions between components in the film-forming matrix. The prepared nanocomposite films showed good antibacterial properties against both E. coli and S. aureus. The nanocomposite film, consist of three most abundant biodegradable polymers, could potentially serve as antibacterial packaging films with strong mechanical properties for food and allied industries.

Electrospinning of PLA Nanofibers: Recent Advances and Its Potential Application for Food Packaging

Poly(lactic acid), also abbreviated as PLA, is a promising biopolymer for food packaging owing to its environmental-friendly characteristic and desirable physical properties. Electrospinning technology makes the production of PLA-based nanomaterials available with expected structures and enhanced barrier, mechanical, and thermal properties; especially, the facile process produces a high encapsulation efficiency and controlled release of bioactive agents for the purpose of extending the shelf life and promoting the quality of foodstuffs. In this study, different types of electrospinning techniques used for the preparation of PLA-based nanofibers are summarized, and the enhanced properties of which are also described. Moreover, its application in active and intelligent packaging materials by introducing different components into nanofibers is highlighted. In all, the review establishes the promising prospects of PLA-based nanocomposites for food packaging application.

Effect of cellulose nanocrystal-stabilized cinnamon essential oil Pickering emulsions on structure and properties of chitosan composite films

The low water-resistance and limited antibacterial activity of chitosan (CS) film hinder its practical applications in food preservation field. To solve these issues, we have facilely and effectively fabricated cinnamon essential oil (CEO)-loaded composite films via incorporating cellulose nanocrystal (CNC)-stabilized CEO Pickering emulsions into CS-based film-forming matrix. Research results show the well distribution of emulsion droplets in film matrix. The insertion of CEO emulsions can improve film water-resistance and antibacterial activity, but reduces its mechanical strength. Concretely, the water contact angle and inhibition zone of composite films can increase by about 12.3° and 2 times compared with CS control film. Compared with tween-80, CNCs can increase film tensile strength by about 3.52 MPa and observably offset the decline of film mechanical property by CEO. Moreover, the film prepared with 3 w/v% CNC stabilized 30 v/v% CEO Pickering emulsion not only enhances pork preservation, but also maintain its structural stability. The fabricated antimicrobial films have considerable potential for packaging application.

Effect of Chitosan Coatings with Cinnamon Essential Oil on Postharvest Quality of Mangoes

Mango (Mangifera indica Linn.) is a famous climacteric fruit containing abundant flavor and nutrients in the tropics, but it is prone to decay without suitable postharvest preservation measures. In this study, the chitosan (CH)-cinnamon essential oil (CEO) Pickering emulsion (CH-PE) coating was prepared, with cellulose nanocrystals as the emulsifier, and applied to harvested mangoes at the green stage of maturity. It was compared with a pure CH coating and a CH-CEO emulsion (CH-E) coating, prepared with the emulsifier Tween 80. Results showed that the CH-PE coating had a lower water solubility and water vapor permeability than the other coatings, which was mainly due to electrostatic interactions, and had a better sustained-release performance for CEO than the CH-E coating. During mango storage, the CH-PE coating effectively improved the appearance of mangoes at 25 °C for 12 d by reducing yellowing and dark spots, and delayed water loss. Hardness was maintained and membrane lipid peroxidation was reduced by regulating the activities of pectin methyl esterase, polygalacturonase, and peroxidase. In addition, the nutrient quality was improved by the CH-PE coating, with higher contents of total soluble solid, titratable acid, and ascorbic acid. Therefore, the CH-PE coating is promising to comprehensively maintain the postharvest quality of mangoes, due to its enhanced physical and sustained-release properties.

Enhanced antibacterial activity of lysozyme loaded quaternary ammonium chitosan nanoparticles functionalized with cellulose nanocrystals

In this study, cellulose nanocrystals (CNC) as functional cross-linker and Pickering emulsifier was used to stabilize Lysozyme (Lys) encapsulated in quaternary ammonium chitosan nanoparticles (QC NPs) via ionic gelation method. Physicochemical, structural, and antibacterial properties of the CNC stabilized Lys loaded QC NPs were also evaluated. Particle size, particle size distribution, Zeta potential (ZP), and spectroscopic analyses showed the successful encapsulation of Lys. Antibacterial activity of NPs against Staphylococcus aureus and Vibrio parahaemolyticus was investigated on the basis of inhibition zone (IZ), minimum inhibitory concentration (MIC), and minimum bacterial concentration (MBC). MIC and MBC of CNC stabilized Lys loaded HQC NPs against S. aureus were 0.094 and 0.188 while corresponding values for CNC stabilized Lys loaded LQC NPs V. parahaemolyticus were 0.156 and 0.312 mg/mL, respectively. Therefore, CNC stabilized Lys loaded QC NPs have potential implications in the food industry for food preservation and packaging.

Sustainable Chitosan-Dialdehyde Cellulose Nanocrystal Film

In this study, we incorporated 2,3-dialdehyde nanocrystalline cellulose (DANC) into chitosan as a reinforcing agent and manufactured biodegradable films with enhanced gas barrier properties. DANC generated via periodate oxidation of cellulose nanocrystal (CNC) was blended at various concentrations with chitosan, and bionanocomposite films were prepared via casting and characterized systematically. The results showed that DANC developed Schiff based bond with chitosan that improved its properties significantly. The addition of DANC dramatically improved the gas barrier performance of the composite film, with water vapor permeability (WVP) value decreasing from 62.94 g·mm·m-2·atm-1·day-1 to 27.97 g·mm·m-2·atm-1·day-1 and oxygen permeability (OP) value decreasing from 0.14 cm3·mm·m-2·day-1·atm-1 to 0.026 cm3·mm·m-2·day-1·atm-1. Meanwhile, the maximum decomposition temperature (Tdmax) of the film increased from 286 °C to 354 °C, and the tensile strength of the film was increased from 23.60 MPa to 41.12 MPa when incorporating 25 wt.% of DANC. In addition, the chitosan/DANC (75/25, wt/wt) films exhibited superior thermal stability, gas barrier, and mechanical strength compared to the chitosan/CNC (75/25, wt/wt) film. These results confirm that the DANC and chitosan induced films with improved gas barrier, mechanical, and thermal properties for possible use in film packaging.

Preparation and Characterization of Ginger Essential Oil Microcapsule Composite Films

New food packaging has shown research significance in the face of increasing demand for high-quality foods and growing attention paid to food safety. In this study, ginger essential oil microcapsule composite films were prepared by combining microcapsules prepared by a complex coacervation method with gelatin films, and the mechanical properties and active functions of the composite films were analyzed. Fourier-transform infrared spectroscopy and differential scanning calorimetry confirmed the successful encapsulation of ginger essential oil. The scanning electron microscopy of the composite films showed the microcapsules and gelatin film matrix were highly compatible. During the entire storage period, the antioxidant capacity of the ginger essential oil microcapsule films weakened more slowly than ginger essential oil microcapsules and could be maintained at a relatively high level for a long time. The microcapsule films had excellent inhibitory effects on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. Therefore, the direct addition of microcapsules to a film matrix can broaden the application range of microcapsules and increase the duration of the release of active ingredients. Ginger essential oil microcapsule films are potential biodegradable food packaging films with long-lasting activity.

Development of novel collagen hydrolysate bio-nanocomposite films extracted from hide trimming wastes reinforced with chitosan nanoparticles

The wide availability of pollutant by-products from the leather industries has been a key factor in driving the research into converting these low-cost by-products into high value-added collagen-based products. In this study, collagen hydrolysate (CH) was extracted from hide trimming waste from the tanneries and used to prepare biodegradable films with chitosan nanoparticles (CNPs) with different concentrations to develop an alternative product to non-biodegradable plastics. The effects of CNPs concentration on the thickness, mechanical, water barrier, thermal, light transmittance, color properties, and opacity of CH-based films were investigated. The results clearly show that the tensile strength and elastic modulus values of CH/CNPs films increase significantly as the concentration of CNPs increases, while the elongation at break, water solubility, and water vapor permeability values decrease. In addition, scanning electron microscopy (SEM) showed uniform distributions of CNPs in the CH-based films. Based on the results obtained, the extraction of CH from hide trimming wastes and reuse in the production of biodegradable films will both prevent these valuable wastes from being dispose into the landfills and will be an alternative to fossil-derived plastics in the future.

Investigating the properties of PLA-nanochitosan composite films containing Ziziphora Clinopodioides essential oil and their impacts on oxidative spoilage of Oncorhynchus mykiss fillets

The present study aimed to investigate the impact of polylactic acid (PLA) integrated with nanochitosan (NC) composite film and Ziziphora Clinopodioides essential oil (ZCEO) on oxidative spoilage of rainbow trout fillets during a 9-day refrigeration period. For this purpose, first, six degradable films including T1: PLA, T2: PLA + NC, T3: PLA + NC + 1% ZCEO, T4: PLA + NC + 1.5% ZCEO, T5: PLA + 1% ZCEO, and T6: PLA + 1.5% ZCEO were prepared. Next, the properties of the films were investigated. The results of the mechanical tests showed that ZCEO decreased the tensile strength and increased the elongation at the break of the PLA films. However, adding NC improved the mechanical characteristics of the PLA film. The outcomes of physical tests including moisture content (14.02%), solubility (17.41%), water vapor permeability (1.14 × 10-7 g s-1 m-1 Pa-1), and oxygen transmission rate (21.54 cm3.mm/m2.24 hr) showed that adding 1% ZCEO improved the film physical characteristics. Nevertheless, by adding 1.5% concentration EO to the PLA film, the values of water vapor permeability, porosity (according to the scanning electron microscopy), and turbidity increased and cross-sectional pores were observed. Moreover, the films had high antioxidant properties (84.33%). In the next step, the effects of the mentioned films on the oxidative spoilage of rainbow trout fillets were investigated. The results of the chemical analysis in PLA film with the EO compared with the control treatment revealed the increasing trend of oxidation indices, in general. Moreover, increasing the concentration yielded better results such that all treatments containing EO showed satisfactory results up until the storage period ends. In most cases, adding NC affected the mentioned characteristics positively, and the best results were observed in T4 and then in T3. However, based on economics and the better mechanical and physical properties of T3, the film can be applied as an active packaging in fishery products.

Microdesigned Nanocellulose-Based Flexible Antibacterial Aerogel Architectures Impregnated with Bioactive Cinnamomum cassia

This work is strategically premeditated to study the potential of a herbal medicinal product as a natural bioactive ingredient to generate nanocellulose-based antibacterial architectures. In situ fibrillation of purified cellulose was done in cinnamon extract (ciE) to obtain microfibrillated cellulose (MFC). To this MFC suspension, carboxylated cellulose nanocrystals (cCNCs) were homogeneously mixed and the viscous gel thus obtained was freeze-dried to obtain lightweight and flexible composite aerogel architectures impregnated with ciE, namely, ciMFC/cCNCs. At an optimal concentration of 0.3 wt % cCNCs (i.e., for ciMFC/cCNCs_0.3), an improvement of around 106% in compressive strength and 175% increment in modulus were achieved as compared to pristine MFC architecture. The efficient loading and interaction of ciE components, specifically cinnamaldehyde, with MFC and cCNCs resulted in developing competent antibacterial surfaces with dense and uniform microstructures. Excellent and long-term antimicrobial activity of the optimized architectures (ciMFC/cCNCs_0.3) was confirmed through various antibacterial assays like the zone inhibition method, bacterial growth observation at OD₆₀₀, minimum inhibitory concentration (MIC, here 1 mg/mL), minimum bactericidal concentration (MBC, here 3-5 mg/mL), and Live/Dead BacLight viability tests. The changes in the bacterial morphology with a disrupted membrane were further confirmed through various imaging techniques like confocal laser scanning microscopy, FESEM, AFM, and 3D digital microscopy. The dry composite architecture showed the persuasive capability of suppressing the growth of airborne bacteria, which in combination with antibacterial efficiency in the wet state is considered as an imperative aspect for a material to act as the novel biomaterial. Furthermore, these architectures demonstrated excellent antibacterial performance under real "in use" contamination prone conditions. Hence, this work provides avenues for the application of crude natural extracts in developing novel forms of advanced functional biomaterials that can be used for assorted biological/healthcare applications such as wound care and antimicrobial filtering units.

Developed Chitosan/Oregano Essential Oil Biocomposite Packaging Film Enhanced by Cellulose Nanofibril

The use of advanced and eco-friendly materials has become a trend in the field of food packaging. Cellulose nanofibrils (CNFs) were prepared from bleached bagasse pulp board by a mechanical grinding method and were used to enhance the properties of a chitosan/oregano essential oil (OEO) biocomposite packaging film. The growth inhibition rate of the developed films with 2% (w/w) OEO against E. coli and L. monocytogenes reached 99%. With the increased levels of added CNFs, the fibrous network structure of the films became more obvious, as was determined by SEM and the formation of strong hydrogen bonds between CNFs and chitosan was observed in FTIR spectra, while the XRD pattern suggested that the strength of diffraction peaks and crystallinity of the films slightly increased. The addition of 20% CNFs contributed to an oxygen-transmission rate reduction of 5.96 cc/m2·day and water vapor transmission rate reduction of 741.49 g/m2·day. However, the increase in CNFs contents did not significantly improve the barrier properties of the film. The addition of 60% CNFs significantly improved the barrier properties of the film to light and exhibited the lowest light transmittance (28.53%) at 600 nm. Addition of CNFs to the chitosan/OEO film significantly improved tensile strength and the addition of 60% CNFs contributed to an increase of 16.80 MPa in tensile strength. The developed chitosan/oregano essential oil/CNFs biocomposite film with favorable properties and antibacterial activity can be used as a green, functional material in the food-packaging field. It has the potential to improve food quality and extend food shelf life.

Chitosan Beads Incorporated with Essential Oil of Thymus capitatus: Stability Studies on Red Tilapia Fillets

Red Tilapia is one of the most consumed but perishable fish in the world. As a result, it requires preservation methods for safe consumption without affecting its organoleptic characteristics. Chitosan encapsulating essential oils have shown to be an excellent food conservation method. For that reason, we carried out the study of the protective effect on red Tilapia fillets with chitosan beads (CB) incorporated with Thymus capitatus (TCEO) essential oil at 500, 1000, and 2000 mg/L to assess the conservation of the fillets. The TCEO composition was characterized by gas chromatography-mass spectrometry (CG-MS). For the other side, CB was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), and Scanning electron microscopy (SEM). The protective effect of the beads was tested against the Gram-positive and Gram-negative bacteria growth for four weeks. The results showed an inhibition effect in Gram-positive bacteria at higher TCEO concentration (1000 and 2000 mg/L). Besides that, the pH, total volatile basic nitrogen (T-BNV-N), color, and fillet texture were evaluated as quality attributes. The results suggested that the incorporation of the CB-TCEO allowed a higher contact of the active compounds with the food surface, which reflected more excellent stability. The quality attributes of the fillets were preserved for 26 days, suggesting its uses for the treatment for perishable food.

A review on versatile applications of blends and composites of CNC with natural and synthetic polymers with mathematical modeling

Cellulose is world's most abundant, renewable and recyclable polysaccharide on earth. Cellulose is composed of both amorphous and crystalline regions. Cellulose nanocrystals (CNCs) are extracted from crystalline region of cellulose. The most attractive feature of CNC is that it can be used as nanofiller to reinforce several synthetic and natural polymers. In this article, a comprehensive overview of modification of several natural and synthetic polymers using CNCs as reinforcer in respective polymer matrix is given. The immense activities of CNCs are successfully utilized to enhance the mechanical properties and to broaden the field of application of respective polymer. All the technical scientific issues have been discussed highlighting the recent advancement in biomedical and packaging field.

Inverse Thermoreversible Mechanical Stiffening and Birefringence in a Methylcellulose/Cellulose Nanocrystal Hydrogel

We show that composite hydrogels comprising methyl cellulose (MC) and cellulose nanocrystal (CNC) colloidal rods display a reversible and enhanced rheological storage modulus and optical birefringence upon heating, i.e., inverse thermoreversibility. Dynamic rheology, quantitative polarized optical microscopy, isothermal titration calorimetry (ITC), circular dichroism (CD), and scanning and transmission electron microscopy (SEM and TEM) were used for characterization. The concentration of CNCs in aqueous media was varied up to 3.5 wt % (i.e, keeping the concentration below the critical aq concentration) while maintaining the MC aq concentration at 1.0 wt %. At 20 °C, MC/CNC underwent gelation upon passing the CNC concentration of 1.5 wt %. At this point, the storage modulus ( G') reached a plateau, and the birefringence underwent a stepwise increase, thus suggesting a percolative phenomenon. The storage modulus ( G') of the composite gels was an order of magnitude higher at 60 °C compared to that at 20 °C. ITC results suggested that, at 60 °C, the CNC rods were entropically driven to interact with MC chains, which according to recent studies collapse at this temperature into ring-like, colloidal-scale persistent fibrils with hollow cross-sections. Consequently, the tendency of the MC to form more persistent aggregates promotes the interactions between the CNC chiral aggregates towards enhanced storage modulus and birefringence. At room temperature, ITC shows enthalpic binding between CNCs and MC with the latter comprising aqueous, molecularly dispersed polymer chains that lead to looser and less birefringent material. TEM, SEM, and CD indicate CNC chiral fragments within a MC/CNC composite gel. Thus, MC/CNC hybrid networks offer materials with tunable rheological properties and access to liquid crystalline properties at low CNC concentrations.

Development of Poly(lactic acid)/Chitosan Fibers Loaded with Essential Oil for Antimicrobial Applications

Cinnamon essential oil (CEO) was successfully encapsulated into chitosan (CS) nanoparticles at different loading amounts (1%, 1.5%, 2%, and 2.5% v/v) using oil-in-water (o/w) emulsion and ionic-gelation methods. In order to form active packaging, poly(lactic acid) (PLA) was used to fabricate PLA/CS-CEO composite fibers using a simple electrospinning method. The shape, size, zeta potential, and encapsulation efficacy of the CS-CEO nanoparticles were investigated. The composition, morphology, and release behavior of the composite fibers were investigated. PLA/CS-CEO-1.5 showed good stability and favorable sustained release of CEO, resulting in improved antimicrobial activity compared to the other blends. The PLA/CS-CEO fibers showed high long-term inactivation rates against Escherichia coli and Staphylococcus aureus due to the sustained release of CEO, indicating that the developed PLA/CS-CEO fibers have great potential for active food packaging applications.