Potassium sorbate release from poly(vinyl alcohol)-bacterial cellulose films

Active packaging materials are the subject of research because their performance exceeds that of traditional packaging. From this class, antimicrobial materials extend the shelf-life of products and reduce the risk of contamination by pathogens. In this paper, new composite materials with antimicrobial properties are obtained by using polyvinyl alcohol and bacterial cellulose powder. Potassium (2E,4E)-hexa-2,4-dienoate was used as the antimicrobial agent. The films thus obtained were characterised using Fourier-transform infrared spectroscopy and scanning electron microscopy. Mass transfer phenomena concerning the release of potassium (2E,4E)-hexa-2,4-dienoate were investigated. The results indicated that the new biocomposite films could be used as antimicrobial packaging materials.     

Preparation and characterization of hybrid cationic hydroxyethyl cellulose/sodium alginate polyelectrolyte antimicrobial films

This study aimed to develop polyelectrolyte‐structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic hydroxyethyl cellulose was synthesized and characterized by Fourier‐transform infrared, ¹H NMR, and ¹³C NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte‐structured antimicrobial food packaging materials were prepared using hydroxyethyl cellulose, cationic hydroxyethyl cellulose, and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by thermal gravimetric analysis and differential scanning calorimetry. Surface morphology of samples was investigated by SEM. The obtained results prove that produced food packaging materials have good thermal and antimicrobial properties, and they can be used as food packaging material in many industries.     

The Effect of UV-Irradiation on Poly(vinyl alcohol) Composites with Bacterial Cellulose

The development of biodegradable packaging materials, especially from renewable resources is a constant preoccupation of nowadays, because of the environmental problems caused by synthetic polymers. The combination of cellulose with other polymeric materials could be an ecologic alternative and a way to use renewable resources for food packaging. Bacterial cellulose which is produced by microbial fermentation is also a promising material which can be used not only in biomedical application, but also as food packaging material. In this research different composite films between poly(vinyl alcohol)-bacterial cellulose (PVA-BC) were obtained by casting method. The obtained films were UV irradiated for different periods of times from 1 to 10 hours, using a mercury lamp, Philips TUV-30, emitting light mainly at 254 nm. Changes in FT-IR spectra before and after UV irradiation and the modification of transparency and of the swelling characteristics of the films were observed. As it was expected the composites materials are sensitive at UV exposure.     

Mechanically robust,flame-retardant and anti-bacterial nanocomposite films comprised of cellulose nanofibrils and magnesium hydroxide nanoplatelets in a regenerated cellulose matrix

Nanocomposite films consisting of cellulose nanofibrils (CNFs), magnesium hydroxide nanoplatelets (MHNPs) and regenerated cellulose were prepared via simple blending and casting processes. The CNFs were obtained from bamboo pulp by ultrasonic treatment coupled with high shear homogenization. The morphology, structure and properties of the nanocomposite films were comprehensively analyzed using various characterization techniques, including the scanning electron microscope, digital microscope, limiting oxygen index (LOI), micro-scale combustion calorimetry, antibacterial assays, tensile testing, etc. When the MHNP content was optimized to 30 wt%, the nanocomposite film exhibited the best overall properties. The LOI of the composite film increased from 20.0 (0 wt% MHNPs) to 32.7 (30 wt% MHNPs), making it a flame-retardant material in air. In addition, the film containing 30 wt% MHNPs showed excellent antibacterial activity. However, the increase in MHNP content would result in gradual deterioration of the films’ mechanical properties. However, the incorporation of CNFs could significantly suppress this trend. The present work provided a promising pathway for manufacturing multifunctional and high-performance cellulose-based composite films, which were potentially useful for a variety of packaging materials, especially in the biomedical and food packaging fields.     

Antimicrobial active packaging combining essential oils mixture: Migration and odor control study

Thymol is an essential oil (EO), known to have excellent antimicrobial (AM) properties and can potentially be used as an active agent in AM food packages. Mixing Thymol with other EOs may help to reduce the organoleptic impact of its strong odor. In the present study, the effect of thymol, carvacrol, citral, and eugenol binary mixtures on the AM activity, migration over time, and sensory properties of polypropylene (PP)/polyamide (PA)/nanoclays composite blends active package (AP) films was examined. The release of different EOs from the polymer film was found to have a direct correlation with the odor perception of thymol. Varied EOs bearing films have shown different capacity to inhibit bacterial growth over time (Escherichia coli). Lastly, the inhibition of fungal growth on food sample using EO‐loaded films was obtained for over 50 days, indicating the potential use of the developed films as active food packaging.     

Antimicrobial Food Packaging with Biodegradable Polymers and Bacteriocins

Innovations in food and drink packaging result mainly from the needs and requirements of consumers, which are influenced by changing global trends. Antimicrobial and active packaging are at the forefront of current research and development for food packaging. One of the few natural polymers on the market with antimicrobial properties is biodegradable and biocompatible chitosan. It is formed as a result of chitin deacetylation. Due to these properties, the production of chitosan alone or a composite film based on chitosan is of great interest to scientists and industrialists from various fields. Chitosan films have the potential to be used as a packaging material to maintain the quality and microbiological safety of food. In addition, chitosan is widely used in antimicrobial films against a wide range of pathogenic and food spoilage microbes. Polylactic acid (PLA) is considered one of the most promising and environmentally friendly polymers due to its physical and chemical properties, including renewable, biodegradability, biocompatibility, and is considered safe (GRAS). There is great interest among scientists in the study of PLA as an alternative food packaging film with improved properties to increase its usability for food packaging applications. The aim of this review article is to draw attention to the existing possibilities of using various components in combination with chitosan, PLA, or bacteriocins to improve the properties of packaging in new food packaging technologies. Consequently, they can be a promising solution to improve the quality, delay the spoilage of packaged food, as well as increase the safety and shelf life of food.     

Cornstarch/Poly(vinyl alcohol) Biocomposite Blend Films: Mechanical Properties,Thermal Behavior,Fire Retardancy,and Antibacterial Activity

In the present study, biocomposite films of starch/poly(vinyl alcohol) (St/PVA) reinforced with delignified Grewia optiva fiber and methyl methacrylate (MMA) grafted fibers were prepared using citric acid as a plasticizer and glutaraldehyde as the cross-linker. The biocomposite films were subjected to evaluation of mechanical properties, biodegradability, and antibacterial properties. The biocomposite films were characterized by using Fourier transform-infrared (FT-IR) spectrophotometry, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA/DTA/DTG). SEM showed good adhesion between St/PVA blend matrix and fibers. The antimicrobial activity of biocomposite films against pathogenic bacteria such as Staphylococcus aureus and Escherichia coli was also explored. The results confirmed that the biocomposite films may be used for food packaging.     

Antibacterial cellulose acetate films incorporated with N‐halamine‐modified nano‐crystalline cellulose particles

Cellulose acetate (CA) membranes have been widely used as food packaging materials as well as reverse osmosis systems. This study presents the manufacturing of composite CA film with antibacterial properties which is essential for CA film applications in the industry. N‐Halamine precursor of polymethacrylamide‐modified nano‐crystalline cellulose particles (NCC‐PMAMs) were prepared and incorporated into CA film. The composite films with intercalated structure were formed via a solvent‐casting technique. After chlorination, the composite film CA/NCC‐PMAM‐Cl‐1.0 with 1.82 × 10¹⁶ atoms/cm² covalently bonded chlorine showed excellent antibacterial properties by inactivating 6.04 logs of Staphylococcus aureus and 6.27 logs of Escherichia coli within 10 and 5 min, respectively. According to X‐ray diffraction spectra, NCC‐PMAMs behaved as a facilitator for film crystallization. The mechanical strength of the composite film also increased compared with that of pure CA film. However, the composite film became brittle and the maximum decomposition temperature decreased slightly. Preliminary data of in vitro cytocompatibility evaluation indicate that the film is not toxic and has potential use in food packaging. Copyright © 2016 John Wiley & Sons, Ltd.     

New Polylactic Acid Composites for Packaging Applications: Mechanical Properties,Thermal Behavior,and Antimicrobial Activity

The interest in antimicrobial packaging materials based on polylactic acid (PLA) polymers has increased due to the need to improve food safety and environment quality and also to find alternatives to synthetic polymers made from petrochemicals. PLA films by addition of different fillers (grape wastes and celery fibers) were obtained. The mechanical, thermal, surface, and antimicrobial properties of the films were evaluated. The incorporation of inexpensive fillers into the PLA matrix could reduce costs and the studied formulations offer approaches to realize composites with high performances and antimicrobial response, suitable for film food-active packaging materials, especially by use of grape wastes.     

ZnO/PBAT nanocomposite films: Investigation on the mechanical and biological activity for food packaging

Packaging of foods in high barrier materials is essential to attain food safety. Nanocomposite technology is leading in search of the earlier said kind of packaging materials. The role of zinc oxide (ZnO) loadings on poly(butylene adipate‐co‐terephthalate) (PBAT) structure were investigated, in addition to that packaging properties such as barrier, thermal, and mechanical properties were studied. Antimicrobial films are developed based on PBAT and ZnO nanoparticles. The nanocomposites exhibits a significant increase in the mechanical and thermal stability. The resulting PBAT/ZnO nanofilms show superior antimicrobial activity against Escherichia coli and Staphylococcus aureus. Copyright © 2016 John Wiley & Sons, Ltd.     

Water vapour barrier performance of corn-zein coated polypropylene (PP) packaging films

The novel film structure of corn-zein coated on polypropylene (PP) synthetic film for packaging industry was developed to examine the feasibility of resulting coated films as an alternative water barrier performance for food packaging. The effects of coating formulation (solvent, corn-zein, plasticizer concentration and plasticizer type) on final properties of films were observed. Corn-zein is the most important protein of corn and has good film forming property. Composites structures of PP films coated with corn-zein were obtained through a simple solvent casting method. Polyethylene glycol (PEG) and glycerol (GLY) were used as plasticizer to increase film flexibility. Statistical analysis based on full factorial design was performed to observe coating formulation effects. The high water vapour barriers were obtained for films coated with coating formulation consisting of higher amounts of corn-zein plasticized by GLY. The lower glass transition temperatures (T _g) of films were obtained by plasticization of films and T _g decreased by increasing plasticizer content. The statistical analysis defined the key parameters of coating formulation that had major effects on the final properties of coated PP films as corn-zein, plasticizer concentration and plasticizer type. In conclusion, corn-zein coatings could have potential as an alternative to conventional synthetic polymers used in composite multilayer structures for food packaging applications.     

Preparation and properties of cellulose/silver nanoparticle composites with in situ-generated silver nanoparticles using Ocimum sanctum leaf extract

In the present work, silver nanoparticles were in situ-generated in cellulose matrix using Ocimum sanctum leaf extract as a reducing agent. Regenerated wet cellulose films were first immersed in O. sanctum leaf extract and then it was allowed to diffuse into the films. The leaf extract–diffused wet films were dipped in different concentrated aq.AgNO₃ solutions. The leaf extract inside the wet films reduced AgNO₃ into nanosilver. The dry composite films were black in color. Some of the nanoparticles were also formed outside the film in the solution. The nanoparticles were viewed by transmission electron microscopy and scanning electronic microscopy techniques. The composite films showed good antibacterial activity. The cellulose, matrix, and the composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis techniques. The tensile properties of the composite films were higher than those of the matrix. These biodegradable films can be used for packaging and medical purposes.     

Towards a Bioactive Food Packaging: Poly(Lactic Acid) Surface Functionalized by Chitosan Coating Embedding Clove and Argan Oils

Here we introduce a new method aiming the immobilization of bioactive principles onto polymeric substrates, combining a surface activation and emulsion entrapment approach. Natural products with antimicrobial/antioxidant properties (essential oil from Syzygium aromaticum—clove and vegetal oil from Argania spinosa L—argan) were stabilized in emulsions with chitosan, a natural biodegradable polymer that has antimicrobial activity. The emulsions were laid on poly(lactic acid) (PLA), a synthetic biodegradable plastic from renewable resources, which was previously activated by plasma treatment. Bioactive materials were obtained, with low permeability for oxygen, high radical scavenging activity and strong inhibition of growth for Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli bacteria. Clove oil was better dispersed in a more stable emulsion (no separation after six months) compared with argan oil. This leads to a compact and finely structured coating, with better overall properties. While both clove and argan oils are highly hydrophobic, the coatings showed increased hydrophilicity, especially for argan, due to preferential interactions with different functional groups in chitosan. The PLA films coated with oil-loaded chitosan showed promising results in retarding the food spoilage of meat, and especially cheese. Argan, and in particular, clove oil offered good UV protection, suitable for sterilization purposes. Therefore, using the emulsion stabilization of bioactive principles and immobilization onto plasma activated polymeric surfaces we obtained a bioactive material that combines the physical properties and the biodegradability of PLA with the antibacterial activity of chitosan and the antioxidant function of vegetal oils. This prevents microbial growth and food oxidation and could open new perspectives in the field of food packaging materials.     

Antibacterial and antifungal LDPE films for active packaging

Active antimicrobial packaging is a promising form of active packaging that can kill or inhibit microorganism growth in order to maintain product quality and safety. One of the most common approaches is based on the release of volatile antimicrobial agents from the packaging material such as essential oils. Due to their highly volatile nature, the challenge is to preserve the essential oils during the high‐temperature melt processing of the polymer, while maintaining high antimicrobial activity for a desired shelf life. This study suggests a new approach in order to achieve this goal. Antimicrobial active films are developed based on low‐density polyethylene (LDPE), organo‐modified montmorillonite clays (MMT) and carvacrol (used as an essential oil model). In order to minimize carvacrol loss throughout the polymer compounding, a pre‐compounding step is developed in which clay/carvacrol hybrids are produced. The hybrids exhibit a significant increase in the d‐spacing of clay and enhanced thermal stability. The resulting LDPE/(clay/carvacrol) films exhibit superior and prolonged antibacterial activity against Escherichia coli and Listeria innocua, while polymer compounded with pure carvacrol loses the antibacterial properties within days. The films also present an excellent antifungal activity against Alternaria alternata, used as a model plant pathogenic fungus. Furthermore, infrared spectroscopy analysis of the LDPE/(clay/carvacrol) system displayed significantly higher carvacrol content in the film as well as a slower out‐diffusion of the carvacrol molecules in comparison to LDPE/carvacrol films. Thus, these new films have a high potential for antimicrobial food packaging applications due to their long‐lasting and broad‐spectrum antimicrobial efficacy. Copyright © 2014 John Wiley & Sons, Ltd.     

Layer-by-layer assembly of cationic guar gum,cellulose nanocrystals and hydroxypropyl methylcellulose based multilayered composite films

Eco-friendly sustainable materials provide an appealing template to replace contemporary synthetic-nonrenewable resource-based materials while maintaining the acceptable material properties to meet the performance requirements. Here, a layer-by-layer (LBL) self-assembly technique was used for fabricating multilayer composite films using all bio-based polymers/polysaccharides, i.e. cationic guar gum (CGg), carboxylated cellulose nanocrystals (cCNCs) and hydroxypropyl methylcellulose (HPMC). A five layered composite film was fabricated by depositing polymeric layers as follows: CGg→cCNCs→HPMC→cCNCs→CGg. The structural analysis of (CGg/cCNCs/HPMC)_5 L multilayered composite films indicated the existence of electrostatic interaction as well as H-bonding between polymeric layers that resulted in homogenous, dense and compact film surface with improved smoothness and strength properties. As compared to pure CGg film, the (CGg/cCNCs/HPMC)_5 L multilayered composite films showed improved tensile strength (84.8?% increment) and modulus (29.19?% improvement). Importantly, the deposition of HPMC layer contributed in achieving multilayer composite films with more flexible behavior (46.55?% improvement in elongation at break). Furthermore, owing to the high transparency (89.5?% transmittance), appreciable gas and oil barrier performance and resistance to various solvents (e.g. acetone, THF and DMAc), these multilayer films are promising candidates for various applications including renewable/sustainable packaging materials.

     

Effect of sunlight on the preparation and properties of cellulose/silver nanoparticle composite films by in situ method using Ocimum sanctum leaf extract as a reducing agent

Cellulose/silver nanoparticle composite films with in situ-generated silver nanoparticles (AgNPs) were prepared using Ocimum sanctum leaf extract as a reducing agent in the absence and presence of sunlight and were characterized by SEM, FTIR, XRD, and antibacterial tests. Sunlight hastened up the preparation of these composite films. The average size of the in situ-generated AgNPs was reduced by the sunlight. The antibacterial activity and other properties of the composites were enhanced by the sunlight. The cellulose/AgNP composite films with improved properties by sunlight can be considered for medical purpose as antibacterial dressing materials.     

Antibacterial membranes based on chitosan and quaternary ammonium salts modified nanocrystalline cellulose

Etherification of nanocrystalline cellulose (NCC) with three kinds of quaternary ammonium salts epoxypropyltrimethylammonium chloride, N,N‐dimethyl‐N‐dodecyl‐N‐(1,2‐epoxypropyl) ammonium chloride (DMDEPAC), and N,N‐dimethyl‐N‐octadecyl‐N‐(1,2‐epoxypropyl) ammonium chloride (DMOEPAC) was successfully performed via a nucleophilic addition reaction. The synthesized DMDEPAC and DMOEPAC were characterized by nuclear magnetic resonance. The modified NCC particles, NCC epoxypropyltrimethylammonium chloride, NCC‐DMDEPAC, and NCC‐DMOEPAC, were characterized by energy dispersive spectrometer. Nanocomposite films based on chitosan (CS) containing quaternary ammonium salts modified NCC were prepared with nanoparticle loadings of 5.0, 7.5, and 10.0%, respectively. The effect of nanoparticle content on the tensile strength of composite films was studied. The results indicated that the films with 5.0% nanoparticle loading exhibited the biggest increase in tensile strength. Surface morphology, smoothness, and antibacterial properties of composite films containing 5% modified NCC were also studied. CS/NCC‐DMDEPAC‐5.0 and CS/NCC‐DMOEPAC‐5.0 displayed excellent biocidal abilities against both Gram‐positive Staphylococcus aureus (ATCC 6538) and Gram‐negative Escherichia coli O157:H7 (ATCC 43895). The bio‐based nanocomposite films with increased mechanical strength and excellent antibacterial properties show great potential as food packaging materials. Copyright © 2017 John Wiley & Sons, Ltd.     

Sustainable nanocomposite films based on bacterial cellulose and pullulan

Bionanocomposites with improved properties based on two microbial polysaccharides, pullulan and bacterial cellulose, were prepared and characterized. The novel materials were obtained through a simple green approach by casting water-based suspensions of pullulan and bacterial cellulose and characterized by TGA, RDX, tensile assays, SEM and AFM. The effect of the addition of glycerol, as a plasticizer, on the properties of the materials was also evaluated. All bionanocomposites showed considerable improvement in thermal stability and mechanical properties, compared to the unfilled pullulan films, evidenced by the significant increase in the degradation temperature (up to 40 °C) and on both Young’s modulus and tensile strength (increments of up to 100 and 50%, for films without glycerol and up to 8,000 and 7,000% for those plasticized with glycerol). Moreover, these bionanocomposite films are highly translucent and could be labelled as sustainable materials since they were prepared entirely from renewable resources and could find applications in areas as organic electronics, dry food packaging and in the biomedical field.     

Zein films with ZnO and ZnO:Mg quantum dots as functional nanofillers: New nanocomposites for food package with UV-blocker and antimicrobial properties

The preparation of a new nanocomposite by combining zein and quantum dots (QDs) was the main interest of the present work. By the sol-gel method, colloidal ethanolic dispersions of zinc oxide (ZnO) particles and ZnO particles doped with magnesium (II) (ZnO:Mg) were obtained, sized 4.26 and 3.65 nm, respectively, as determined by UV–Vis spectroscopy. The prepared QDs were used as nanofillers in order to obtain zein-based nanocomposite films, which displayed good visual appearance, homogeneity, and transparency. The presence of QDs increased the hydrophobicity and reduced, up to three times, the amount of water uptake of the composite films when compared to pure zein. Those effects were more pronounced for ZnO:Mg QDs. TEM, FTIR, and fluorescence microscopy analysis indicated that zein interacts more effectively with ZnO:Mg than with ZnO. In addition, and most importantly, the presence of QDs in the films showed an important advantage when compared to those of pure zein: the extended UV-blocking in the absorbance spectra. The antimicrobial assays demonstrated that the ZnO NPs, loaded into zein films, are promising antibacterial materials since the inhibition of growth of S. aureus reached (96.5 ± 4.9)% at 44.8 wt% of ZnO NPs. Therefore, the nanocomposites show promising features for the development of food packaging, UV protective films, and for the development of new and sustainable materials.     

Comparison of hydroxypropyl and carboxymethyl guar for the preparation of nanocellulose composite films

The gas barrier and mechanical properties are crucial parameters for packaging materials, and they are highly correlated to the molecular interactions in the polymer matrix. To improve these properties of TEMPO-oxidized cellulose nanofibers (TOCNs) composite films, we studied the effect using hydroxypropyl guar (HPG) or carboxymethyl guar (CMG) in the preparation of TOCN composite films, which were made by following the solution-casting method. The subsequent film characterizations were carried out by UV–Vis spectra, scanning electron microscopy, oxygen and water vapor permeability measurements, tensile and thermogravimetric analyses. SEM results showed that CMG-based films had denser structures than their HPG counterparts. Moreover, the improved hydrogen bonding of the CMG-based films was partially responsible for the improved gas barrier performance, tensile strength and thermal stability. These results support the conclusion that CMG had advantages over HPG when used in the preparation of TOCNs packaging composite films.