Lower Water Vapor Permeability Research Articles

Antimicrobial multi-crosslinking tamarind xyloglucan/protein-chitosan coating packaging films with self-recovery and biocompatible properties

Natural and high-quality biomass-based coating films are considered promising packaging to consumers. However, the poor mechanical properties and weak antimicrobial activity of biomass materials have limited their practical application. A cleaner and low-cost strategy is used to prepare antimicrobial, self-recovery, and biocompatible coating films using tamarind kernel powder (TKP) and chitosan (CS). The TKP protein and chitosan chains were covalently cross-linked with tetrakis(hydroxymethyl)phosphonium chloride (THPC) to form a three-dimensional network based on THPC-amine dynamic bonds, and act as a sacrificial bond. Then, the hydrogen bond forms an interpenetrating network to build a strong multi-network film. Thus, the THPC multi-crosslinking TKP based films showed enhanced stretchable property (increased from 3.23 % to 77.54 %), and self-recovery after 30 min of recovery. Additionally, the film has been found to exhibit low water vapor permeability, low oxygen transmittance rate, and excellent antimicrobial efficiency (maximum inhibition zones: 24.39 mm). Moreover, the prepared films were demonstrated to be biocompatible and non-hemolytic based on cell viability and hemolytic activity assays. The method described herein could broaden the scope of biomass-based materials in the realm of antimicrobial coating films.

Development of Functional Composite Edible Films or Coatings for Fruits Preservation with Addition of Pomace Oil-Based Nanoemulsion for Enhanced Barrier Properties and Caffeine for Enhanced Antioxidant Activity.

The aim of this study was to develop functional composite edible films or coatings for fruit preservation by the addition of bioactive components in combinations that have not yet been thoroughly studied, according to the relevant literature. Edible films were initially composed of (i) chitosan (CH), cellulose nanocrystals (CNC) and beta-cyclodextrin (CD) (50%-37.5%-12.5% ratio), and (ii) hydroxypropyl methylcellulose (HPMC), cellulose nanocrystals (CNC) and beta-cyclodextrin (CD) (50%-37.5%-12.5% ratio). The bioactive components incorporated (5, 10 and 15% v/v) were as follows: (i) pomace oil-based nanoemulsion (NE) aiming to enhance barrier properties, and (ii) caffeine (C), aiming to enhance the antioxidant activity of films, respectively. Indeed, NE addition led to very high barrier properties (low oxygen and water vapor permeability), increased flexibility and reduced color. Furthermore, the contribution of these coatings to fresh strawberries' preservation under cold storage was investigated, with very promising results concerning weight loss, color difference, and preservation of fruit moisture and quantity of O2 and CO2 inside the packages. Additionally, C addition led to very high antioxidant activity, reduced color and improved barrier properties. Finally, the contribution of these coatings to avocado's preservation under cold storage was investigated, with very encouraging results for color difference, hardness and peroxide value of the fruit samples.

Anthocyanin modified by chondroitin sulphate and tannic acid improved the quality-indicating properties of gelatin-based intelligent film

A highly pH-responsive gelatin film incorporating purple cabbage anthocyanin (PCA) and chondroitin sulphate (CS)/tannic acid (TA) was developed. Co-pigmentation of PCA via CS/TA improved its photothermal stability and visibility of color change in gelatin film. The morphological and structural properties of CS-PCA and TA-PCA films revealed that a more stable network was formed as new hydrogen bonds were generated by the co-pigmentation. Meanwhile, the co-pigmentation improved film's mechanical and hydrophobic properties, expressed as higher tensile strength (16.65 and 17.97 Mpa) and lower water vapor permeability (1.45 and 1.41) in CS-PCA and TA-PCA films, compared to PCA film. CS-PCA and TA-PCA films showed distinct color transitions for chilled fish fillets during storage. Total color difference (ΔE) of CS-PCA and TA-PCA films correlated well with the deterioration indexes of total volatile base nitrogen (TVB-N). All the results provided a novel pH-sensitive intelligent packaging strategy by co-pigmenting CS/TA with PCA for freshness monitoring.

A high-strength collagen-based antimicrobial film grafted with ε-polylysine fabrication by riboflavin-mediated ultraviolet irradiation for pork preservation

In this study, a UV-cured collagen-based film (C-P-H film) with high mechanical strength and antimicrobial properties was developed by riboflavin-mediated ultraviolet irradiation of collagen solution containing histidine-modified ε-polylysine. Fourier transform infrared analysis indicated that covalent cross-linking was formed between the collagen molecule and the histidine-grafted ε-polylysine. Compared with the pure collagen film, the C-P-H film containing 5 wt% histidine-modified ε-polylysine showed higher tensile strength (145.98 MPa), higher thermal denaturation temperature (76.5 °C), lower water vapor permeability (5.54 × 10−11 g m−1 s−1 Pa) and excellent antimicrobial activities against Escherichia coli and Staphylococcus aureus. In addition, the wrapping of the C-P-H film effectively inhibited bacterial growth of pork during storage time, successfully prolonging the shelf-life of pork by approximately 4 days compared to that of plastic wrap. These results suggested that collagen-based film grafted with histidine-modified ε-polylysine via riboflavin-mediated ultraviolet irradiation process had a great potential for pork preservation.

Effect of ultrasonically stimulated potato germination during soaking on the physicochemical properties of starch and its use in edible films

The aim of this work was to investigate the effects of ultrasonic treatment during soaking of potatoes on the physicochemical properties of starches obtained after 16 weeks of germination. The ultrasonic treatment showed a direct correlation between sprout length and ultrasonic time. The protein content decreased from 0.63 to 0.38 % and the fat content decreased significantly from 0.31 to 0.01 % after germination. The amylose content changed depending on the ultrasonic treatment, and increased from 36.27 to 40.92 % after 16 weeks of germination, which was related to the amylopectin debranching and the duration of the ultrasonic treatment. X-ray diffraction showed that the nanocrystals with hexagonal structure were not affected by the germination and the duration of ultrasonic treatment. Scanning electron microscopy showed that the surface of the starch granules was not affected by the enzymatic treatment.The sprouted potato starch resulted in films with better tensile strength and lower water vapor permeability (WVP) compared to the native potato starch films. In addition, the films produced with ultrasound stimulated potato starch exhibited better properties (high strength and low permeability), which is desirable when it comes to controlling moisture exchange between a food product and the surrounding atmosphere.

Self-Powered Sensors Utilizing Single Pillar Thermocells with Pyrolytic Graphite Sheet Electrodes: Harvesting Body Heat and Solar Thermal Energy

This study investigates the development of self-powered sensors employing single pillar thermocells to harness body heat and solar thermal energy. A pyrolytic graphite sheet was selected for its low water vapor permeability, and its surface was modified to be hydrophilic to minimize interfacial resistance. Two types of DC–DC converters, Asahi Kasei Microdevices AP4473 and Matrix Mercury, underwent evaluation for compatibility with these thermocells. The compact 1.5 cm3 (1 cm × 1 cm × 1.5 cm) device effectively powered the AP4473 converter, illuminating a light-emitting diode. A larger device (2.5 cm × 2.5 cm × 1.5 cm) efficiently drove the Matrix Mercury converter, enabling the operation of Bluetooth low-power sensors. These self-powered sensors wirelessly provided humidity and temperature data using solar thermal energy for approximately 4 h per day during peak temperature differences in January. This study showcases the potential of thermocells for sustainable energy harvesting and suggests avenues for future research, such as exploring alternative heat sources like geothermal energy to power these sensors.

Preparation, characterization, and application of gallic acid-mediated photodynamic chitosan-nanocellulose-based films

In this study, an active film composed of gallic acid (GA), chitosan (CS), and cellulose nanocrystals (CNC) was prepared using a solution casting method and synergistic photodynamic inactivation (PDI) technology. Characterization of the film showed that the CS-CNC-GA composite film had high transparency and UV-blocking ability. The addition of GA (0.2 %–1.0 %) significantly enhanced the mechanical properties, water resistance, and thermal stability of the film. The tensile strength increased up to 46.30 MPa, and the lowest water vapor permeability was 1.16 × e−12 g/(cm·s·Pa). The PDI-treated CS-CNC-GA1.0 composite film exhibited significantly enhanced antibacterial activity, with inhibition zone diameters of 31.83 mm against Staphylococcus aureus and 21.82 mm against Escherichia coli. The CS-CNC-GA composite film also showed good antioxidant activity. Additionally, the CS-CNC-GA1.0 composite film generated a large amount of singlet oxygen under UV-C light irradiation. It was found that using the CS-CNC-GA1.0 composite film for packaging and storage of oysters at 4 °C effectively delayed the increase in pH, total colony count, and lipid oxidation in oysters. In conclusion, the CS-CNC-GA composite film based on PDI technology has great potential for applications in the preservation of aquatic products.

The Shelf Life of Yellow Passion Fruit with an Edible Biocomposite Coating Based on Chitosan, Graphene Oxide Nanoparticles, and Beeswax

Yellow or sour passion fruit is a climacteric fruit with a high rate of respiration and ethylene production, and postharvest technology is needed to extend its shelf life. This study investigated the properties of a biocomposite film with chitosan (CH) incorporated with beeswax (BW) and graphene oxide (GO) nanoparticles for use as an edible coating to extend the shelf life of yellow passion fruit at 22 °C and 70% RH for eight days. CH films associated with BW showed lower water vapor permeability (WVP) than films with CH alone. However, adding GO to the CH + BW biopolymer matrix improved the WVP, decreased the solubility (12.8%), and increased the opacity of the film by 9% compared to those of the CH film. Fruits coated with CH + BW or CH + BW + GO exhibited a reduction in respiration rate, a slower ripening process by approximately 3 days, and a significant decrease in weight loss. This also resulted in a higher soluble solids content and increased antioxidative capacity of the pulp. The incorporation of GO into the CH + BW matrix resulted in a more pronounced delay of fruit ripening, as evidenced by the lower depigmentation of the peel at eight days, with a lightness approximately 10.7% lower at 54.92, a chroma value 16.5% lower at 49.33, a hue angle 7.2% higher at 92.56, a soluble solid (SS) content 16.7% higher at 11.32°Brix, and an acidity 31.9% higher at 4.18% compared to the control. Furthermore, the biopolymer packaging led to a higher consumer acceptance score for the fruit.

Development of multifunctional chitosan-based composite film loaded with tea polyphenol nanoparticles for strawberry preservation

Incorporating polysaccharide-based composite films with nanobiotechnology offers a new strategy for food preservation. This study initially focuses on the preparation of tea polyphenol nanoparticles (TPNP), novel and derived from natural antibacterial agents, which serve to improve stability. Afterwards chitosan-based composite films loaded with TPNP (CTN film) were developed using solution casting method. The incorporation of TPNP significantly improved the UV/water/oxygen barrier properties, mechanical properties and thermal stability, alongside notable physical properties including water contact angle (93.65 ± 0.04°), low water vapor permeability (33.72 ± 3.32 g/m2h) and oxygen permeability (0.11 ± 0.02 g/m2h), tensile strength (61.83 ± 0.70 %), and elongation at break (31.60 ± 6.12 %). The CTN film not only exhibited exceptional biodegradability and nontoxicity, but also demonstrated remarkable antimicrobial efficacy against Escherichia coli and Bacillus subtilis. Additionally, it showcased potent antioxidant activity, boasting DPPH and ABTS radical scavenging rates up to 89.25 ± 0.18 % and 93.84 ± 0.42 %. The CTN film was successfully formed on the surface of strawberries through dip-coating process and their shelf life was extended from 4 to 6 days at 20 °C without side-effect on the weight loss, harness, pH and total soluble solids, illustrating its potential for enhancing food preservation.

Effect of Ultrasound and Freeze‐Drying to Enhance the Extraction of Phenolic Compounds in Dragon Fruit Peels and Apply Them in Edible Starch‐Based Films

ABSTRACTIn this study, dragon fruit peels were subjected to different times (5, 10, 15, 20 and 25 min) of ultrasound pretreatment (4.870 W m−2/25°C) and then freeze‐drying (FD) (−56°C/48 h) to obtain powder particles, which underwent physical–chemical, functional and structural characterisation. Additionally, the extraction of total phenolic compound (TPC) was evaluated through ultrasound‐assisted kinetics and mechanical agitation. Finally, films based on black rice starch were developed with the addition (0.5, 1.5 and 2.5%) of dragon fruit peel powder particles, and their physical, barrier, antioxidant, structural and mechanical properties were evaluated. The results obtained showed that all particles had low water content (4.21%–6.58%) and high solubility (84.62%–88.73%) with a reduction in particle size (23.21–39.32 μm). In the extraction of TPC, the synergistic effect of the tested conditions increased efficiency, reaching 686.66 mg GAE/100 g for pretreated dragon fruit peel powder particles (25 min) in 180 min of extraction. Furthermore, the type ‘A’ crystallinity structure did not change significantly with pretreatment, but there was a reduction in peak area, reflecting on relative crystallinity, with a maximum decrease of 29.04%. The starch‐based films produced with 2.5% dragon fruit peel powder particles showed low solubility (28.72%) and low water vapour permeability (5.03 × 10−8 g mm s−1 m2 Pa), however, they contained higher levels of TPC (31.78 mg GAE/100 g film) and antioxidant activity (8.17 μmol TE/g film) that were easily migrated in aqueous medium. Furthermore, they also presented low values of tensile strength at break (3.41 MPa) and Young's modulus (4.18 MPa), as well as a high value of elongation at break (45.82%). Finally, our results highlight the potential of ultrasound as a pretreatment for FD of dragon fruit peels, paving the way for the development of rice starch‐based food packaging.

Biodegradable monolayer film based on the collagen extracted from Oreochromis sp. processing byproducts blended with chitosan and assembled with PCL and PLA monolayers to form bilayers films

AbstractThe objective of the study is to develop and characterize biodegradable monolayer and bilayer films using collagen extracted from tilapia skin and scales (Oreochromis sp.) with chitosan in combination with biodegradable polyester; polylactic acid (PLA) or polycaprolactone (PCL). Collagen extraction was conducted with acetic acid (0.5 M). Monolayer films based on collagen and chitosan were formed by the casting process with a solution of chitosan (2% w/w) in 1.5% acetic acid, followed by the addition of skin collagen at concentrations of 0.5%, 1%, or 2% w/w, and dried at 45–50°C. The PLA and PCL films were made by compression molding. The films were characterized according to their appearance, structure, morphology, interaction with water, thermal stability, and mechanical and barrier properties. The results indicated that collagen from tilapia skin and scales yielded 36.5% and 2.57%, respectively. The results showed that adding chitosan increased the tensile strength but decreased the elongation of the films. An improvement in thermal stability was observed by increasing the proportion of collagen or chitosan, and it also influenced water solubility and water vapor permeability. Microscopy showed a crack‐free interface between collagen and chitosan. The color of the films varied depending on the composition, highlighting the influence of chitosan in yellow and reddish tones. The bilayers with PLA had lower water vapor permeability and higher gloss compared to those with PCL. Finally, the developed films showed promising properties for their application in food packaging and promote the use of fishery waste.Practical applicationsThe study aims to develop and characterize biodegradable monolayer and bilayer films using collagen extracted from tilapia skin and scales (Oreochromis sp.) combined with chitosan and biodegradable polyester such as polylactic acid or polycaprolactone. The practical applications of this research span a wide range of industrial fields. For instance, monolayer films could be used as sustainable food packaging, offering enhanced barrier properties and biodegradability, thus reducing the environmental impact of conventional packaging. Furthermore, bilayer films could find applications in the healthcare industry, such as controlled‐release drug patches or dressings leveraging the antimicrobial properties of chitosan. This research also provides valuable insights into improving the mechanical, thermal, and barrier properties of biodegradable films, potentially leading to the production of more efficient and versatile materials for a variety of industrial applications.

Isolation of taro peel cellulose nanofibers and its application in improving functional properties of taro starch nanocomposites films

The current work focuses on developing nanocomposite films using taro starch and cellulose nanofibers extracted from the root's peel. Films were prepared using mixtures of starch, cellulose nanofibers (0 %, 5 %, 10 %, and 15 % w/w), glycerol, and water. Results showed that the addition of cellulose nanofibers increased film thickness, opacity, UV-light barrier capacity, and water swelling percentage. All films showed a typical B-type X-ray diffraction pattern characteristic of semicrystalline materials. FTIR analysis confirmed chemical interactions between the starch chains and the nanofibers, which probably interact through hydrogen bonds. Nanocomposite films exhibited increased tensile strength and reduced strain at break compared to control materials. Films with cellulose nanofibers showed an increase in Young's modulus compared to control ones, with no differences observed between films with cellulose nanofibers at 10 % and 15 %. Furthermore, films with cellulose nanofibers at 5 % and 10 % exhibited lower water vapor permeability than control samples, while those with cellulose nanofibers at 15 % showed an increase in this parameter compared to other materials. These results suggest that incorporating taro cellulose nanofibers is a promising alternative for obtaining taro starch nanocomposites films with improved properties.

Development of dual-channel starch-based film incorporated with betanin@β-cyclodextrin inclusion complex and berberine for indicating shrimp freshness

In this study, the β-cyclodextrin encapsulated betanin (BET@β-CD) with improved thermal stability and retention as well as the berberine (BBR) with aggregate induced luminescence effect were incorporated into corn amylose (CA) biomatrix to develop colorimetric/fluorescent dual-channel smart film. Results shown that the added functional components were uniformly distributed in the film matrix. The high tensile strength (78.87%), low water solubility (31.15%) and water vapor permeability (1.24 × 10−10 g Pa−1 s−1 m−1) of the film predicted its acceptable stability. It was worth mentioning that the film displayed excellent responsiveness to volatile ammonia (0.025–25 mg/mL) with at least 4 times recyclability. Application experiment demonstrated that the film can achieve macroscopic dynamic monitoring of the freshness of shrimps stored at 25 °C, 4 °C, −20 °C under daylight (red to yellow) and UV light (yellow-green to blue-green). Thus, the study suggests an attractive and effective strategy for constructing dual-mode smart packaging materials for food freshness detection.

Attempts to Obtain Material Based on Polyvinyl Alcohol with Barrier Properties against Water Vapor

The purpose of this study was to obtain a biodegradable film based on polyvinyl alcohol with reduced water vapor permeability. The hydrophobic character of the films was achieved by incorporating beeswax, vegetable bio-surfactant, citric acid as a cross-linking agent, and glycerol to provide elasticity, along with the application of thermal treatment. Water vapor permeability was determined gravimetrically. The results indicated that all films produced had lower water vapor permeability compared to unmodified or untreated polyvinyl alcohol films. The barrier to water vapor varied directly with the mass of beeswax used, and the homogeneous dispersion of beeswax in the polyvinyl alcohol matrix was essential for achieving an efficient hydrophobic film. The best performing-material exhibited a water vapor permeability 5.15 times lower than that of the neat polyvinyl alcohol and 15 times higher than that of polyethylene. Considering the fact that the water vapor barrier property of neat polyvinyl alcohol was 78 times lower than that of polyethylene, the combination of beeswax, citric acid, and vegetable bio-surfactant—along with thermal treatment—can be a viable solution to reduce the hygroscopicity of polyvinyl alcohol-based films.

Preparation of films based on reticulated fish gelatin containing garlic essential oil

Agro-industrial co-products, such as fish gelatin, stand out for their capacity in forming biopolymeric films, being biocompatible and non-toxic; however, its hydrophilicity poses a challenge. Essential oils, rich in bioactives, attract research interest aiming to enhance the protective barrier of films and enable their application in packaging. This study produced films based on cross-linked Nile tilapia skin gelatin, incorporating garlic essential oil. Gelatin obtained through partial collagen hydrolysis from the fish skin and cross-linked with gallic acid had hydroxyproline content of 10.02 g 100 g−1 and gel strength of 287 g, which were consistent with other studies. Oil extraction used supercritical CO2 as a solvent and ethanol as a cosolvent, following a factorial experimental design, evaluating the extraction temperature (40 °C and 70 °C) and cosolvent ratio (1:1 and 1:3), with three central points. Extraction was successful, with higher yields on a dry basis at 70 °C (88.35 %), using a 1:1 cosolvent ratio. Films incorporated with oil exhibited lower water vapor permeability (WVP) than those with only cross-linked gelatin (1.59 (g m−1 s−1 Pa−1) 1011). The film with the most suitable tensile strength (19.07 MPa), elongation (120.91 %), and WVP (1.09 (g m−1 s−1 Pa−1) 1011) properties contained garlic oil extracted at the central point (55 °C and 1:2). Thermal analysis indicated increased melting temperatures in films with added oil, suggesting low thermal degradation. These results suggest that garlic oil addition can improve the properties of fish gelatin-based films, making them promising for biodegradable packaging.

Effect of Soybean Oil on the Improvement of the Functionality of Edible Membrane-Type Food Packaging Films Based on Caseinate-Carboxymethyl Chitosan Compositions.

Edible film biopolymers are gaining attention to tackle problems of plastic waste and food safety to alleviate environmental problems associated with plastic products in food packaging. In this study, caseinate-carboxymethyl chitosan (CA-CMCH) composite films were made with the incorporation of soybean oil (SO) using a casting technique. The influence of different soybean oil concentrations at 0, 0.5, and 1% (w/w) on physical, mechanical, barrier, and surface characteristics of films composed of caseinate-carboxymethyl chitosan (CA-CMCH) was evaluated. The brightest film (L* value of 95.95 ± 0.30) was obtained with the edible film made from the control group of samples with sodium caseinate (NaCA-100; 100% NaCA). The results also indicated that samples with 1% SO in NaCA-75 and CaCA-75 had lower water vapor permeability (WVP), while those with NaCA-50 and CaCA-50 showed higher values of WVP. For mechanical properties, this study found that incorporating soybean oil into the caseinate-carboxymethyl (CA-CMCH) composite films led to an enhancement of both tensile strength and elongation at break. The morphological structures, determined using SEM, of control and composite films showed compact and homogenous surfaces. Overall, the addition of soybean oil contributed to the improvement of the functional properties of the edible films, offering potential solutions to the environmental issues associated with plastic packaging and enhancing the safety and performance of food packaging.

Structure and properties of starch - BaSO4 composite obtained using mechanical activation techniques

The aim of this study is to obtain and characterize starch films structurally modified by in situ precipitation of BaSO4 combined with mechanical activation of casting dispersion in a rotor-stator device. By the rheological method, it was found that the modification causes a decrease in the ability of casting dispersions to structure over time. Composite films with a filler content of 0 %–15 % (w/w) were characterized using optical and SEM microscopy, FT-IR spectroscopy, and tensile and moisture resistance testing data. The maximum increase in strength (by 70 %) and elongation at break (by 870 %) is achieved with a filler content of 5 % and 15 %, respectively. An increase in the filler content to 5 % causes an increase in starch recrystallization rate, but at concentrations above 5 % of BaSO4, it inhibits retrogradation. The films obtained by mechanical activation with optimized parameters were uniformly translucent, had lower water vapor permeability than films made from starch alone, had high flexibility, and did not warp or shrink. The developed high-performance, environmentally friendly method can be recommended for the large-scale production of starch-based composite materials.

Properties of an active film based on chitosan/silk fibroin loaded with an essential oil microemulsion and its application in preservation of strawberries

This study aimed to enhance the weak antibacterial activity of silk fibroin (SF) by creating a composite edible coating film. The film was composed of chitosan (CS), SF, and a 3% (v/v) cinnamon essential oil microemulsion (CEOM), which showed excellent inhibition rates of over 99% against two bacteria and four fungi. The resulting film had a transparency of 84.6% and a contact angle of 61.85° on hydrophobic surfaces. In addition, it exhibited a low water vapor permeability of 1.09 × 10−12 g·cm−1·s−1·Pa−1. These properties make it ideal for use in food coating applications. To assess the preservation capabilities of the composite films, strawberries were coated with different films: CS, SF, SF-CEOM, and SF-CS-CEOM. The results showed that the SF-CS-CEOM film had a similar effect to the SF-CEOM film in suppressing the deterioration of strawberries, when compared to the untreated group, and the shelf life of the strawberries was extended from 2 days to 8 days. The SF-CS-CEOM film inhibits oxidation and metabolism by reducing gas exchange, thereby protecting the integrity of cell membranes, maintaining firmness, and reducing weight loss, while delaying the onset of spoilage by inhibiting microbial growth.

Flexible cellulose nanofibers/MXene composite films for UV-shielding packaging

Cellulose nanofibers (CNF) based films are promising packaging materials, but the lack of special functions (especially UV-shielding property) usually restrict their further applications. In this work, MXene was incorporated into the CNF film by a direct solvent volatilization induced film forming method to study its UV-shielding property for the first time, which avoided the using of a vacuum filtration equipment. The composite films containing glycerin could be folded repeatedly without breaking, showing good flexibility. The structure and properties of MXene/CNF composite films (CMF) were characterized systematically. The results showed that MXene distributed uniformly in the CNF film matrix and there was strong hydrogen bonding interaction between CNF and MXene. The tensile strength and Young's modulus of the composite films could reach 117.5 MPa and 2.23 GPa, which was 54.1 % and 59.2 % higher than those of pure CNF film, respectively. With the increase of MXene content, both the UVA and UVB shielding percentages increased significantly from 17.2 % and 25.5 % to 100.0 %, showing excellent UV-shielding property. Moreover, CMF exhibited a low oxygen permeability (OP) value of 0.39 cc μm d−1 m−2 kPa−1, a low water vapor permeability (WVP) value of 5.13 × 10−11 g−1s−1Pa−1 and a high antibacterial rate against E. coli (94.1 % at 24 h), showing potential application in the packaging field.

Sodium-alginate-based indicator film containing a hydrophobic nanosilica layer for monitoring fish freshness

In this study, hydrophobic sodium alginate/anthocyanin/cellulose nanocrystal indicator films were fabricated by incorporating nanosilica (NS) as a waterproofing layer. The concentrations and formation methods (spraying (S), coating (C), and impregnation (I)) of the NS layer (denoted as NSS, NSC, NSI, respectively) were optimized. The results indicated that the optimum concentration of the NS layer was 5 % at a water contact angle (WCA) 110.5°. Further, Fourier transform infrared spectra showed the presence of SiOSi and SiCH3 groups in the NSS, NSC, and NSI films, and X-ray diffraction spectra indicated that original structures of these films were disordered. Moreover, the surface morphology, mechanical properties, and light transmission were affected by the NS layer, and the optimal layer was found to be NSI. After 10 days of storage at 100 % humidity, the NSI film exhibited low water vapor adsorption (37.22 g) and permeability (0.1484 g/m·s·Pa·10−11) and a high WCA (110.2°). In addition, the NSI film exhibited a visible color shift with an increasing pH of the buffer solution. A monitoring test of fish freshness showed that the NSI film displayed a distinctive color change corresponding to fish spoilage during 14 days of storage. This indicates that NSI has high potential in indicator film applications.