Properties and antimicrobial activity of fish protein isolate/fish skin gelatin film containing basil leaf essential oil and zinc oxide nanoparticles

Current Trends in the Utilization of Essential Oils for Polysaccharide- and Protein-Derived Food Packaging Materials

Essential oils (EOs) have received attention in the food industry for developing biopolymer-derived food packaging materials. EOs are an excellent choice to replace petroleum-derived additives in food packaging materials due to their abundance in nature, eco-friendliness, and superior antimicrobial and antioxidant attributes. Thus far, EOs have been used in cellulose-, starch-, chitosan-, and protein-based food packaging materials. Biopolymer-based materials have lower antioxidant and antibacterial properties in comparison with their counterparts, and are not suitable for food packaging applications. Various synthetic-based compounds are being used to improve the antimicrobial and antioxidant properties of biopolymers. However, natural essential oils are sustainable and non-harmful alternatives to synthetic antimicrobial and antioxidant agents for use in biopolymer-derived food packaging materials. The incorporation of EOs into the polymeric matrix affects their physicochemical properties, particularly improving their antimicrobial and antioxidant properties. EOs in the food packaging materials increase the shelf life of the packaged food, inhibit the growth of microorganisms, and provide protection against oxidation. Essential oils also influence other properties, such as tensile, barrier, and optical properties of the biopolymers. This review article gives a detailed overview of the use of EOs in biopolymer-derived food packaging materials. The innovative ways of incorporating of EOs into food packaging materials are also highlighted, and future perspectives are discussed.

Functional Properties of Gelatin/Polyvinyl Alcohol Films Containing Black Cumin Cake Extract and Zinc Oxide Nanoparticles Produced via Casting Technique

This study aimed to develop and characterize gelatin/polyvinyl alcohol (G/PVA) films loaded with black cumin cake extract (BCCE) and zinc oxide nanoparticles (ZnONPs). The BCCE was also applied for the green synthesis of ZnONPs with an average size of less than 100 nm. The active films were produced by a solvent-casting technique, and their physicochemical and antibacterial properties were investigated. Supplementation of G/PVA film in ZnONPs decreased the tensile strength (TS) from 2.97 MPa to 1.69 MPa. The addition of BCCE and ZnONPs increased the elongation at the break (EAB) of the enriched film by about 3%. The G/PVA/BCCE/ZnONPs film revealed the lowest water vapor permeability (WVP = 1.14 × 10-9 g·mm·Pa-1·h-1·mm-2) and the highest opacity (3.41 mm-1). The QUick, Easy, New, CHEap and Reproducible (QUENCHER) methodologies using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) and cupric ion reducing antioxidant capacity (CUPRAC) were applied to measure antioxidant capacity (AC) of the prepared films. The incorporation of BCCE and ZnONPs into G/PVA films enhanced the AC by 8-144%. The films containing ZnONPs and a mixture of BCCE and ZnONPs inhibited the growth of three Gram-positive bacterial strains. These nanocomposite films with desired functional properties can be recommended to inhibit microbial spoilage and oxidative rancidity of packaged food.

Flavor, antimicrobial activity and physical properties of gelatin film incorporated with of ginger essential oil

Adding essential oil into the gelatin-based film can enhance the antibacterial activity of the film, but excessive amounts of addition will bring the film an unpleasant flavor and reduce its mechanical performance. Hence, we prepared functional gelatin-based films by incorporating low content of ginger essential oil (GEO). The flavor of GEO was not detected from the films containing less than 1% GEO. The antimicrobial activity of films was found to be proportional to GEO content. As GEO content increased from 0 to 1%, the value of water vapor permeability (WVP) and elongation at break (EAB) increased, whereas the value of tensile strength (TS) of film decreased. The Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy analysis revealed the vibration of gelatin film was affected by adding low content of essential oil. Surface morphologies demonstrated oil droplets and a discontinuous structure, and cross-section morphologies proved the formation of a loose structure as GEO was incorporated in the film through SEM. Sensory evaluation revealed that composite films incorporated with 0.5% GEO exhibited the best performance. The resulting films can be used as antimicrobial packaging materials with good physical properties and sensory performance.

Antibacterial, Antioxidation, UV-Blocking, and Biodegradable Soy Protein Isolate Food Packaging Film with Mangosteen Peel Extract and ZnO Nanoparticles

The objective of this study was to prepare a functional biodegradable soy protein isolate (SPI) food packaging film by introducing a natural antimicrobial agent, mangosteen peel extract (MPE, 10 wt% based on SPI), and different concentrations of functional modifiers, ZnO NPs, into the natural polymer SPI by solution casting method. The physical, antioxidant, antibacterial properties and chemical structures were also investigated. The composite film with 5% ZnO NPs had the maximum tensile strength of 8.84 MPa and the lowest water vapor transmission rate of 9.23 g mm/m² h Pa. The composite film also exhibited excellent UV-blocking, antioxidant, and antibacterial properties against Escherichia coli and Staphylococcus aureus. The TGA results showed that the introduction of MPE and ZnO NPs improved the thermal stability of SPI films. The microstructure of the films was analyzed by SEM to determine the smooth surface of the composite films. ATR-FTIR and XPS analyses demonstrated the strong hydrogen bonding of SPI, MPE, and ZnO NPs in the films. The presence of ZnO NPs in the composite films was also proved by EDX and XRD. These results suggest that SPI/MPE/ZnO composite film is promising for food-active packaging to extend the shelf life of food products.

Recent insights into carrageenan-based bio-nanocomposite polymers in food applications: A review

Nanotechnology has proven as progressive technology that enables to contribute, develop several effective and sustainable changes in food products. Incorporating nanomaterials like TiO₂, SiO₂, Halloysite nano clay, Copper sulfide, Bentonite nano clay, in carrageenan to develop innovative packaging materials with augmented mechanical and antimicrobial properties along with moisture and gas barrier properties that can produce safe and healthy foods. Intervention of carrageenan-based bio-nanocomposites as food packaging constituents has shown promising results in increasing the shelf stability and food quality by arresting the microbial growth. Nanomaterials can be incorporated within the carrageenan for developing active packaging systems for continuous protection of food products under different storage environments from farm to the fork to ensure quality and safety of foods. Carrageenan based bio nanocomposite packaging materials can be helpful to reduce the environmental concerns due to their high biodegradability index. This review gives insight about the current trends in the applications of carrageenan-based bio nanocomposites for different food packaging applications.

Physical, Mechanical, and Water Vapor Barrier Properties of Starch/Cellulose Nanofiber/Thymol Bionanocomposite Films

The application of starch films, such as food packaging materials, has been restricted due to poor mechanical and barrier properties. However, the addition of a reinforcing agent, cellulose nanofibers (CNF) and also thymol, into the films, may improve the properties of films. This work investigates the effects of incorporating different concentrations of thymol (3, 5, 7, and 10 wt.%) on physical, mechanical, water vapor barrier, and antibacterial properties of corn starch films, containing 1.5 wt.% CNF produced using the solvent casting method. The addition of thymol does not significantly affect the color and opacity of the films. It is found that the tensile strength and Young’s modulus of the films decreases from 10.6 to 6.3 MPa and from 436.9 to 209.8 MPa, respectively, and the elongation at break increased from 110.6% to 123.5% with the incorporation of 10 wt.% thymol into the films. Furthermore, the addition of thymol at higher concentrations (7 and 10 wt.%) improved the water vapor barrier of the films by approximately 60.0%, from 4.98 × 10^—9 to 2.01 × 10^—9 g/d.m.Pa. Starch/CNF/thymol bionanocomposite films are also found to exhibit antibacterial activity against Escherichia coli. In conclusion, the produced starch/CNF/thymol bionanocomposite films have the potential to be used as antibacterial food packaging materials.

The effects of zinc oxide nanoparticles on the physical, mechanical and antimicrobial properties of chicken skin gelatin/tapioca starch composite films in food packaging

The aim of this study was to characterize chicken skin gelatin/tapioca starch composite films with varying concentrations (0-5%) of zinc oxide nanoparticles using the casting technique. The incorporation of 5% zinc oxide nanoparticles increased the water vapor permeation (1.52-1.93 × 10-7 gmm/cm2hPa) and melting temperature of the films. The tensile strength (22.96-50.43 MPa) was increased, while elongation at break decreased with increasing concentrations of zinc oxide nanoparticles. The structures of the films were also investigated via Fourier transform infrared spectroscopy. The inhibitory zones for both the gram-positive (Staphylococcus aureus) (16-20 mm) and gram-negative (Escherichia coli) (15-20 mm) bacteria were larger in the film with 5% zinc oxide. Overall, chicken skin gelatin-tapioca starch composite films with 3% zinc oxide nanoparticles were found to have the optimal formulation, demonstrating good physical, mechanical and antibacterial properties. Gelatin-based composite films with nanoparticle incorporation show strong potential for use in biodegradable food packaging materials.

Whey Proteins-Zinc Oxide Bionanocomposite as Antibacterial Films

The use of toxic crosslinking agents and reagents in the fabrication of hydrogels is a frequent issue which is particularly concerning for biomedical or food packaging applications. In this study, novel antibacterial bionanocomposite films were obtained through a simple solvent casting technique without using any crosslinking substance. Films were made from a flexible and transparent whey protein matrix containing zinc oxide nanoparticles synthesised via a wet chemical precipitation route. The physicochemical and functional properties of the ZnO nanoparticles and of the composite films were characterised, and their antibacterial activity was tested against S. epidermidis and E. coli. The synthesised ZnO nanoparticles had an average size of about 30 nm and a specific surface area of 49.5 m2/g. The swelling ratio of the bionanocomposite films increased at basic pH, which is an appealing feature in relation to the absorption of chronic wound exudate. A n-ZnO concentration-dependent antibacterial effect was observed for composite films. In particular, marked antibacterial activity was observed against S. epidermidis. Overall, these findings suggest that this novel material can be a promising and sustainable alternative in the design of advanced solutions for wound dressing or food packaging.

Advances in biopolymeric active films incorporated with emulsified lipophilic compounds: a review

The attention towards active films has increased due to consumer demand for high-quality foods without chemical additives. Active biopolymer-based films have shown great potential for active films by impacting food safety, acting as the carriers of various natural antioxidant and antimicrobial compounds, and decreasing environmental pollution from petrol-derived packaging materials. However, there is a wide range of challenges concerning the different characteristics of biopolymers and plasticizers, often hygroscopic/hydrophilic, compared to numerous lipophilic bioactive compounds. Therefore, recent studies have focused on applying oil-in-water emulsion-based systems to enhance the lipophilic bioactive compounds' dispersibility into the film matrix, improving their performance. It is worth emphasizing that resulting complex systems give rise to new challenges such as (i) dispersion technology of the bioactive compounds with minimum adverse effects on its bioactivities, (ii) interactions between different components of the active films, giving rise to new physicochemical properties, and (iii) the change of the diffusion properties of bioactive compounds into the active films, resulting in different release properties. These challenges are profound and critically discussed in this review, as well as the encapsulation techniques employed in preparing emulsions loaded with lipophilic bioactive compounds for the active film development. An outlook of future directions in the research, development, and application of these active films are given.

Antimicrobial biodegradable film based on corn starch/Satureja khuzestanicaessential oil/Ag-TiO2nanocomposites

Biosynthesis of nanoparticles (NPs) using plant extract is an eco-friendly method, in which natural materials are used and is a simple, non-toxic, and environmentally friendly green synthesis. In this study, corn starch (CS) film containingSatureja khuzestanicaessential oil (SEO) and Ag-TiO₂nanocomposites (size: nearly 30-60 nm) were prepared and its antimicrobial, morphological, physical, and mechanical characteristics were investigated. Ag-TiO₂nanocomposites with different molar percentages were synthesized byS. khuzestanicaextract and based on the best antibacterial results against Gram-negative bacteria (Escherichia coliATCC 25922 andSalmonella typhimuriumATCC 14028) and Gram-positive bacteria (Staphylococcus aureusATCC 25923), were chosen to prepare the films. Four types of biodegradable films were provided: simple CS film, the film incorporated with SEO (essence film), the film incorporated with Ag-TiO₂nanocomposites (nanofilm), and nano/essence film. The scanning electron microscopy (SEM) was employed for investigating the morphology of the films. The combined energy-dispersive x-ray spectroscopy with SEM was applied to analyze the near-surface elements. Physical characteristics of the films containing water vapor permeability (%) and their moisture content, mechanical tests, and antibacterial properties were examined. Antimicrobial evaluation of the films revealed a 3-4 log and 6-7 log (CFU ml^-1) reduction inS. aureusandE. colispecies respectively, compared to the control group. The bio-polymer film incorporated with extracted essential oil ofS. khuzestanicaand Ag-TiO₂nanocomposites are effective to package foods and can delay chemical, physical, and microbial spoilage.

Effects of cinnamon essential oil on the physical, mechanical, structural and thermal properties of cassava starch-based edible films

The edible films were mainly made from oxidized hydroxypropyl cassava starch incorporated with cinnamon essential oil (CEO). The effects of CEO amount on the physical and mechanical properties of films were studied, and the structures of films with and without CEO were characterized. The results showed that the elongation at break, water resistance, water vapor transmission coefficient, as well as oxygen and ultraviolet barrier properties of the films (p < 0.05) significantly increased with addition of CEO, while the tensile strength of the films decreased. The field emission scanning electron microscopic (FE-SEM) images and infrared (IR) spectra showed that the CEO had good compatibility with other components and could be evenly dispersed in the film, which was conducive to the stable release of the active components. X-ray diffraction (XRD) patterns showed that the addition of CEO increased the crystallinity of the film, indicating that the compatibility and structural stability of the crystal structure of the film were improved. The thermogravimetric analysis results showed that CEO was beneficial to improve the thermal stability of the films. This study provided a potential to develop edible films from modified cassava starch with CEO.

Prospects of Polymeric Nanofibers Loaded with Essential Oils for Biomedical and Food-Packaging Applications

Essential oils prevent superbug formation, which is mainly caused by the continuous use of synthetic drugs. This is a significant threat to health, the environment, and food safety. Plant extracts in the form of essential oils are good enough to destroy pests and fight bacterial infections in animals and humans. In this review article, different essential oils containing polymeric nanofibers fabricated by electrospinning are reviewed. These nanofibers containing essential oils have shown applications in biomedical applications and as food-packaging materials. This approach of delivering essential oils in nanoformulations has attracted considerable attention in the scientific community due to its low price, a considerable ratio of surface area to volume, versatility, and high yield. It is observed that the resulting nanofibers possess antimicrobial, anti-inflammatory, and antioxidant properties. Therefore, they can reduce the use of toxic synthetic drugs that are utilized in the cosmetics, medicine, and food industries. These nanofibers increase barrier properties against light, oxygen, and heat, thereby protecting and preserving the food from oxidative damage. Moreover, the nanofibers discussed are introduced with naturally derived chemical compounds in a controlled manner, which simultaneously prevents their degradation. The nanofibers loaded with different essential oils demonstrate an ability to increase the shelf-life of various food products while using them as active packaging materials.

Plant-Mediated Biosynthesis and Photocatalysis Activities of Zinc Oxide Nanoparticles: A Prospect towards Dyes Mineralization

In recent years, nanoparticles synthesis by green synthesis has gained extensive attention as a facile, inexpensive, and environmentally friendly method compared with chemical and physical synthesis methods. This review covered the biosynthesis of zinc oxide nanoparticles (ZnO NPs), including the procedure and mechanism. Factors affecting the formation of ZnO NPs are discussed. The presence of active bioorganic molecules in plant extract played a vital role in the formation of ZnO NPs as a natural green medium in the metallic ion reduction processes. ZnO NPs exhibit attractive photocatalysis properties due to electrochemical stability, high electron mobility, and large surface area. In this review, the procedure and mechanism of the ZnO photocatalysis process are studied. The effects of dyes amount, catalysts, and light on photodegradation efficiency are also considered. This review provides useful information for researchers who are dealing with green synthesis of ZnO NPs. Moreover, it can provide investigators with different perceptions towards the efficiency of biosynthesized ZnO NPs on dyes degradation and its restrictions.

Investigation of Functionalized Surface Charges of Thermoplastic Starch/Zinc Oxide Nanocomposite Films Using Polyaniline: The Potential of Improved Antibacterial Properties

Improving the antibacterial activity of biodegradable materials is crucial for combatting widespread drug-resistant bacteria and plastic pollutants. In this work, we studied polyaniline (PANI)-functionalized zinc oxide nanoparticles (ZnO NPs) to improve surface charges. A PANI-functionalized ZnO NP surface was prepared using a simple impregnation technique. The PANI functionalization of ZnO successfully increased the positive surface charge of the ZnO NPs. In addition, PANI-functionalized ZnO improved mechanical properties and thermal stability. Besides those properties, the water permeability of the bionanocomposite films was decreased due to their increased hydrophobicity. PANI-functionalized ZnO NPs were applied to thermoplastic starch (TPS) films for physical properties and antibacterial studies using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The PANI-functionalized ZnO bionanocomposite films exhibited excellent antibacterial activity for both E. coli (76%) and S. aureus (72%). This result suggests that PANI-functionalized ZnO NPs can improve the antibacterial activity of TPS-based bionanocomposite films.

Functional biocompatible nanocomposite films consisting of selenium and zinc oxide nanoparticles embedded in gelatin/cellulose nanofiber matrices

In recent decades, environmental concerns and increasing consumer demand for healthy and nutritious food products with prolonged shelf life have made the food packaging industry pay more attention to the preparation of multifunctional biodegradable packaging films based on biopolymers containing active components such as antioxidant and antimicrobial agents. In this study, bio-nanocomposite films were fabricated from gelatin (G) and cellulose nanofibers (CNFs), and different concentrations of zinc oxide (ZnO) and/or Selenium (Se) nanoparticles (NPs) by the casting method. The mechanical, barrier, optical, and structural (FTIR, XRD, and SEM) properties of the films were investigated along with their antibacterial and antioxidant features. The incorporation of ZnO and Se NPs improved the physicomechanical and water resistance of G/CNF films. In this regard, the maximum tensile strength value was obtained for the G/CNF containing 5% w/w ZnO NPs (G/CNF/ZnO3) and G/CNF containing 0.1% w/w Se NPs (G/CNF/Se2) films (~2.20-fold and ~2.13-fold higher than the G/CNF film, respectively). Also, G/CNF with 3% w/w ZnO NPs (G/CNF/ZnO₂) film had the lowest water vapor permeability and water solubility among all films. Results of the disc diffusion assay showed a stronger antibacterial effect of ZnO NPs compared with Se NPs. The bacterial susceptibility to the antibacterial films was as follows: Listeria monocytogenes > Escherichia coli > Staphylococcus aureus > Pseudomonas fluorescens. The G/CNF films incorporated with Se nanoparticles possessed the higher property of scavenging free radicals in comparison films containing ZnO nanoparticles. Also, the combination of Se NPs and ZnO NPs enhanced the antioxidant effect of the films. In conclusion, gelatin-based edible films containing CNFs, ZnO NPs, and Se NPs can be used in the development of active food packaging products.

Development of an active packaging system containing zinc oxide nanoparticles for the extension of chicken fillet shelf life

The casting method was employed to prepare gelatin-based nanocomposite films containing different concentrations of cellulose nanofiber (CNF) as a reinforcement filler (2.5%, 5%, and 7.5% w/w of gelatin) as well as zinc oxide nanoparticles (ZnO NPs) as an antimicrobial agent (1%, 3%, 5%, and 7% w/w of gelatin). The results showed that the incorporation of 5% CNFs (optimum concentration) significantly boosted the films' stiffness (YM; by 47%) and strength (TS; by 72%) but decreased its flexibility (EAB; by 28%), water vapor permeability, and moisture absorption. The best G/CNF film antibacterial activity was provided by the 5% concentration of ZnO NPs according to the disk diffusion assay; Gram-positive bacteria were inhibited significantly more than Gram-negative bacteria. The antimicrobial efficacy of the G/CNF/ZnO NPs film as a food packaging material was assessed via counts of Staphylococcus aureus and Pseudomonas fluorescens inoculated on chicken fillets (as a food model) in the treatment (G/5% CNF/5% ZnO) and control groups (plastic bag). The antibacterial film led to a significant reduction in the bacterial load of the chicken fillets (p < .05), especially against the Gram-positive strain. This study illustrated that G/CNF/ZnO NPs films can be utilized as active packaging to prolong the shelf life of different perishable foods such as meat.

Preparation and Properties of Microcrystalline Cellulose/Fish Gelatin Composite Film

As a natural macromolecule-based biomaterial, fish gelatin is used in medical materials for its low pathogen infection risk. However, because of poor mechanical properties, its application has been limited. In this study, microcrystalline cellulose-reinforced fish gelatin (FG/MCC) composite films were prepared with a biological cross-linking agent (genipin) under ultrasonic treatment. SEM micrographs showed that the smooth microstructure of FG film became increasingly disordered with the addition of MCC. The infrared spectrum analysis (FTIR) demonstrated the existence of hydrogen bond interaction between MCC and FG. Compared with the pure FG film, the tensile strength (TS) and modulus of elasticity (MOE) of composite films with MCC were improved, and the elongation at break (EAB) and swelling ratios (SR) were decreased. Ultrasonic treatment could further improve TS, MOE, and SR. When the composite film was prepared with 15% MCC and treated with ultrasound, the TS and MOE increased by 115% and 227%, respectively, while the EAB decreased by 35% and the SR decreased by 4% in comparison with pure FG films. Thermo-gravimetric analysis (TGA) showed that the FG/MCC composite films were stable below 100 °C. The above results indicate that the FG/MCC films have optimistic application prospects in the biomedical field.

Nanocomposite films consisting of functional nanoparticles (TiO2 and ZnO) embedded in 4A-Zeolite and mixed polymer matrices (gelatin and polyvinyl alcohol)

In this study, nanocomposite films with enhanced functional properties were prepared by loading titanium dioxide (TiO₂) and/or zinc oxide (ZnO) nanoparticles within 4A zeolite (4AZ) particles, and then incorporating these nanocomposites into a poly (vinyl alcohol) (PVA) and gelatin matrix. The composition and morphology of the films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The thermal behavior of the films was established using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). SEM showed the nanoparticles were dispersed throughout the films when used at these levels. FTIR indicated that the inorganic nanoparticles interacted with the PVA/gelatin polymer network through hydrogen bonding. XRD confirmed that the nanoparticles were in a crystalline state within the films. DSC and TGA showed that introduction of the nanoparticles modified the nanocomposite's thermal behavior. Nanoparticle addition had a number of effects: (i) it decreased film transparency from 78.7% to 69.4% 72.0% and 69.7%; (ii) it decreased film water vapor permeability (WVP) from 8.20 × 10^-9 to 5.13 × 10^-9, 5.71 × 10^-9 and 5.24 × 10^-9 g/Pa.h.m; (iii) it reduced film oxygen permeability from 4.57 to 3.29, 3.10 and 3.00 mEq/g; and (i) it increased film tensile strength (TS) from 14.6 to 22.0, 20.3 and 18.0 MPa, for PVA/gelatin films containing 0%, 1.5% ZnO, 1.5% TiO₂ and 1% (ZnO + TiO₂) nanoparticles, respectively (with the nanoparticles being trapped within 4AZ). Moreover, active nanocomposite films exhibited significant antimicrobial effects especially against gram-negative bacteria. Overall, our results show that nanoparticle-loaded PVA/gelatin nanocomposites may be useful as active biodegradable nanocomposite films for application in the packaging industry and that their properties can be modulated by controlling the nature and level of nanoparticles incorporated.

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

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

Effects of Ultrasonication Time on the Properties of Polyvinyl Alcohol/Sodium Carboxymethyl Cellulose/Nano-ZnO/Multilayer Graphene Nanoplatelet Composite Films

Ultrasonication-assisted solution casting was used to prepare polyvinyl alcohol (PVA)/sodium carboxymethyl cellulose (CMC)/nano-ZnO/multilayer graphene nanoplatelet (xGnP) composite films; the performances (mechanical properties, water vapor permeability (WVP), biodegradability and antibacterial activity) of these films were investigated as a function of the ZnO NPs:xGnP mass ratio and ultrasonication time. Intermolecular interactions among ZnO NPs, xGnP and the PVA/CMC matrix were shown to improve WVP, while X-ray diffraction and scanning electron microscopy analyses revealed that the internal reticular structure of ultrasound-treated PVA/CMC/ZnO NPs/xGnP composite films was in a fluffier state than that of the untreated composite films and the PVA/CMC film. The incorporation of ZnO NPs and xGnP into the composite film reduced its tensile strength and elongation at break, and increased antibacterial activity and biodegradability. In addition, we carried out the experiment of strawberry preservation and measured weight loss ratio, firmness, content of total soluble solids and titration acid. Finally, the composite film of 7:3 had the best preservation effect on strawberries. Thus, the obtained results paved the way to develop novel biodegradable composite films with antimicrobial activity for a wide range of applications.

Long-Term Antibacterial Effect of Electrospun Polyvinyl Alcohol/Polyacrylate Sodium Nanofiber Containing Nisin-Loaded Nanoparticles

Response Surface Methodology (RSM) was used to assess the optimal conditions for a Water/Oil/Water (W/O/W) emulsion for encapsulated nisin (EN). Nano-encapsulated nisin had high encapsulation efficiencies (EE) (86.66 ± 1.59%), small particle size (320 ± 20 nm), and low polydispersity index (0.27). Biodegradable polyvinyl alcohol (PVA) and polyacrylate sodium (PAAS) were blended with EN and prepared by electrospinning. Scanning electron microscopy (SEM) revealed PVA/PAAS/EN nanofibers with good morphology, and that their EN activity and mechanical properties were enhanced. When the ultrasonication time was 15 min and 15% EN was added, the nanofibers had optimal mechanical, light transmittance, and barrier properties. Besides, the release behavior of nisin from the nanofibers fit the Korsemeyer–Peppas (KP) model, a maximum nisin release rate of 85.28 ± 2.38% was achieved over 16 days. At 4 °C, the growth of Escherichia coli and Staphylococcus aureus was inhibited for 16 days in nanofibers under different ultrasonic times. The application of the fiber in food packaging can effectively inhibit the activity of food microorganisms and prolong the shelf life of strawberries, displaying a great potential application for food preservation.

Characterization and Antimicrobial Activity of Biodegradable Active Packaging Enriched with Clove and Thyme Essential Oil for Food Packaging Application

Bioactive packaging contains natural antimicrobial agents, which inhibit the growth of microorganisms and increase the food shelf life. Solvent casting method was used to prepare the Poly (lactide)-Poly (butylene adipate-co-terephthalate) (PLA-PBAT) film incorporated with the thyme oil and clove oil in various concentrations (1 wt%, 5 wt% and 10 wt%). The clove oil composite films depicted less green and more yellow as compared to thyme oil composite films. Clove oil composite film has shown an 80% increase in the UV blocking efficiency. The tensile strength (TS) of thyme oil and clove oil composite film decreases from 1.35 MPs (control film) to 0.96 MPa and 0.79, respectively. A complete killing of S. aureus that is a reduction from 6.5 log CFU/mL to 0 log CFU/mL was observed on the 10 wt% clove oil incorporated composite film. Clove oil and thyme oil composite film had inhibited E. coli biofilm by 93.43% and 82.30%, respectively. Clove oil composite film had exhibited UV blocking properties, strong antimicrobial activity and has high potential to be used as an active food packaging.

Properties and characterization of thyme essential oil incorporated collagen hydrolysate films extracted from hide fleshing wastes for active packaging

In this investigation, collagen hydrolysate (CH) films extracted from hide fleshing wastes were successfully developed using solvent casting method by incorporating different concentrations of thyme essential oil (TO) (2%, 4%, 6%, and 8%) into the CH. Depending on the concentration of TO, thickness, tensile strength (TS), elongation at break (EAB), film solubility (FS), color, opacity, light transmittance, and thermal properties varied. Addition of TO resulted in the increases in the thickness, EAB (%), and light barrier performance of CH-TO films while there was a significant decrease in TS and FS of the CH films (p ≤ 0.05). According to our findings, the increment of TO content induced higher lightness and yellowness but lower redness values compared to CH film. Fourier-transform infrared spectroscopy was conducted to determine the molecular changes and interactions between CH extracted from hide fleshing wastes and TO. In order to analyze the thermal behavior of the films, differential scanning calorimetry analysis was conducted. Moreover, the structure-property relationships of CH and TO were examined by scanning electron microscopy and a reduction in the compact and homogenous structures of the films containing TO was observed. Promising results have been obtained showing that CH-based films can be used for active packaging purposes, thereby contributing to a significant reduction in the environmental impact of both leather solid waste and plastic packaging materials.

Flavor, antimicrobial activity, and physical properties of composite film prepared with different surfactants

Different surfactants (lecithin, Tween-20, and Tween-80) were added in composite film during the preparation. Flavor, antimicrobial activity, and physical properties of ginger essential oil -gelatin film were investigated, in order to study the effect of surfactants on the properties of film. The flavor of GEO was not detected in the film prepared with Tween-20 and film prepared with Tween-80, and these two films exhibited stronger antimicrobial activity; film prepared with lecithin possessed higher value in thickness, elongation at break, water solubility, ΔE and opacity, lower value in water vapor property, and tensile strength; attenuated total reflectance-Fourier transform infrared spectrum results suggested, Tween-20 and Tween-80 enhanced the strength of covalent bond, and lecithin weakened the strength of hydrogen bond; and the result of scanning electron microscope showed that Tween-20 and Tween-80 improved the dispersion of oil droplets in film. Therefore, this study suggested that surfactants had an influence on the physical properties and molecular structure of a resulting film; in addition, Tween-20 and Tween-80 could reduce the flavor of GEO in film, improving the antimicrobial activity of film.