Development and evaluation of a novel biodegradable film made from chitosan and cinnamon essential oil with low affinity toward water

Combining antimicrobial agents such as plant essential oils directly into a food packaging is a form of active packaging. In this work chitosan-based films containing cinnamon essential oil (CEO) at level of 0.4%, .0.8%, and 1.5% and 2% (v/v) were prepared to examine their antibacterial, physical and mechanical properties. Scanning electron microscopy was carried out to explain structure–property relationships. Incorporating CEO into chitosan-based films increased antimicrobial activity. CEO decreased moisture content, solubility in water, water vapour permeability and elongation at break of chitosan films. It is postulated that the unique properties of the CEO added films could suggest the cross-linking effect of CEO components within the chitosan matrix. Electron microscopy images confirmed the results obtained in this study.     

Coating-Activation and Antimicrobial Efficacy of Different Polyethylene Films with a Nisin-Based Solution

Antimicrobial packaging can be considered an extremely challenging technology that could have a significant impact on shelf-life extension and food safety of fresh meat and meat products. In this study, different commercial polyethylene films differing in vinyl acetate ethylene, erucamide contents, and oxygen permeability were used for the coating treatment with a nisin-based antimicrobial solution (NS). Detection and measurement of the activity of the NS was determined against different food spoilage bacteria. NS was then spread manually on food contact layer of different plastic films using coating rods providing thickness of 6, 40, 60, and 100 μm. The polyethylene films before and after treatment were analysed by atomic force microscopy (AFM). NS was active against Gram-positive bacteria and the best activity was obtained against Brochothrix thermosphacta. Viable staining and epifluorescence microscopy analysis of indicator strains in contact with activated plastic films showed that the effect of the film on the various indicator strains changed very much on the basis of both type of film and indicator strain. The highest numbers of lysed cells were shown by two polyethylene films that, according to the AFM and roughness parameters analyses, were characterized by significant increase or decrease of roughness after the coating treatment. AFM analysis showed that the homogeneity of the coating was much influenced by the type of plastic films used. In order to test the efficacy in food, portions of beef chuck tender slices were prepared and covered with the antimicrobial plastic films on both sides. After 1 h and 1, 7, and 12 days of storage at 4 °C the meat samples were analyzed by standard plate counting targeting spoilage associated microbial populations. The antimicrobial plastic films after 1 h of contact with the meat caused a significant reduction of lactic acid bacteria and B. thermosphacta. The most effective antimicrobial activity of films was shown against the same populations after 24 h of storage.     

Polypropylene/Montmorillonite Nanocomposites Containing Nisin as Antimicrobial Food Packaging

Antimicrobial nanocomposites prepared with polypropylene, montmorillonite, and nisin were developed as food packaging material. Nisin was incorporated at 1, 2.5, and 5 % (w/w) and the characterization included antimicrobial, mechanical, thermal, barrier, and structural properties. Composite films inhibited the Gram-positive bacteria Listeria monocytogenes, Staphylococcus aureus, and Clostridium perfringens when tested on skimmed milk agar plates. Antimicrobial activity was released in food simulants after contact with the nanocomposites, increasing until 48 h in solutions containing the surfactant Tween 20 or acetic acid. The addition of nisin caused no significant modification in deformation at break values as compared with control films. However, results of tensile strength and Young modulus differed significantly among samples. The higher value for Young modulus was observed for films with 5 % nisin. Water vapor barrier properties were not significantly different among control and antimicrobial films, whereas oxygen permeability was higher for nanocomposites containing nisin. The nanocomposites tested had no significant differences in the melting temperature (165 to 167 °C), and the crystallization temperature ranged from 121 to 129 °C, with lower values for films containing 5 % nisin. Scanning electron microscopy showed that nanocomposites containing 1 and 2.5 % nisin present similar homogeneity to that of control films. Some film properties were affected after nisin incorporation in polypropylene/montmorillonite matrix but active antimicrobial films were obtained, showing suitable behavior as a food packaging material.     

Postharvest Quality of Fresh-Cut Carrots Packaged in Plastic Films Containing Silver Nanoparticles

Active food packaging containing antimicrobial additive goes beyond traditional functions of packaging, once it can extend food shelf life maintaining its quality, safety and reducing postharvest losses by controlling food spoilage. Among several antimicrobial additives employed in polymeric films for packaging, metallic nanoparticles outstand due to its facility for synthesis, low-cost of production, and intense antimicrobial properties. In this work, extruded plain films of low-density polyethylene (LDPE) containing silver nanoparticles (AgNPs) embedded in SiO₂ and TiO₂ carriers (namely MS and MT, respectively) were produced and used as active packaging for maintaining the physicochemical and microbiological quality of carrots (Daucus Carota L. cv. Brasília). The neat (LDPE) and composite films containing MS and MT were characterized by scanning electron microscopy and permeability to oxygen and used for packaging fresh-cut sliced carrots stored at 10 °C for 10 days. After the storage time, the physicochemical properties of carrots were characterized, while the antimicrobial properties of films and AgNP migration were investigated. Our results revealed that both MT and MS packages showed antimicrobial activity even for films containing low concentration of AgNP. In addition, AgNP antimicrobial activity demonstrated to be carrier-dependent, once MT-LDPE showed improved performance compared to MS-LDPE. Regarding the physicochemical properties of packaged carrot, lower soluble solids and weight loss and higher levels of ascorbic acid were observed for carrots packaged with MT-LDPE films (compared to MS-LDPE), leading to a better postharvest quality conservation. Such differences observed in physicochemical properties of carrots are related to the distinct antimicrobial and film permeability properties for each composite film. In addition, under the conditions employed in this study, AgNP migration from the packages to fresh-cut carrot was not observed, which is highly desirable for food packaging safety, indicating the potential of such active packages for food preservation application.     

Layer-by-Layer Technique to Developing Functional Nanolaminate Films with Antifungal Activity

The layer-by-layer (LbL) deposition method was used to build up alternating layers (five) of different polyelectrolyte solutions (alginate, zein-carvacrol nanocapsules, chitosan and chitosan-carvacrol emulsions) on an aminolysed/charged polyethylene terephthalate (A/C PET) film. These nanolaminated films were characterised by contact angle measurements and through the determination of water vapour (WVTR) and oxygen (O₂TR) transmission rates. The effect of active nanolaminated films against the Alternaria sp. and Rhizopus stolonifer was also evaluated. This procedure allowed developing optically transparent nanolaminated films with tuneable water vapour and gas properties and antifungal activity. The water and oxygen transmission rate values for the multilayer films were lower than those previously reported for the neat alginate or chitosan films. The presence of carvacrol and zein nanocapsules significantly decreased the water transmission rate (up to 40 %) of the nanolaminated films. However, the O₂TR behaved differently and was only improved (up to 45 %) when carvacrol was encapsulated, i.e. nanolaminated films prepared by alternating alginate with nanocapsules of zein-carvacrol layers showed better oxygen barrier properties than those prepared as an emulsion of chitosan and carvacrol. These films containing zein-carvacrol nanocapsules also showed the highest antifungal activity (～30 %), which did not significantly differ from those obtained with the highest amount of carvacrol, probably due to the controlled release of the active agent (carvacrol) from the zein-carvacrol nanocapsules. Thus, this work shows that nanolaminated films prepared with alternating layers of alginate and zein-carvacrol nanocapsules can be considered to improve the shelf-life of foodstuffs.     

Modelling natamycin release from alginate/chitosan active films

In antimicrobial active films, the active agent is incorporated in the polymeric matrix and is released from the film to the product surface where most deterioration processes take place. In this study, films structured solely by alginate and by blends of alginate:chitosan (82.5:17.5 and 65:35) were obtained by casting. The film formulations received natamycin (4 and 8 g/100 g biopolymer) as antimicrobial agent. Films were characterised according to their thickness and morphology. Diffusion experiments in water indicated very slow release kinetics of the antimicrobial, being markedly hindered in the alginate and chitosan composite films, probably due to electrostatic interactions between chitosan and natamycin. Fickian diffusion prevailed and the diffusion coefficients found for the films varied from 2.6 × 10^?11 to 2.5 × 10^?12 cm² s^?1.     

Controlled Release System by Active Gelatin Film Incorporated with β-Cyclodextrin-Thymol Inclusion Complexes

Essential oils such as thymol are added to food packaging film to obtain active films with antimicrobial and antioxidant properties. However, thymol is insoluble in water, and release rate of thymol is usually too fast. Therefore, a need exists to increase thymol solubility and to deliver thymol in a controlled manner from film matrix to food surface. In this study, spray dried inclusion complexes of β-cyclodextrin/thymol (1:1 molar ratio) was incorporated into gelatin solution to obtain active gelatin films. Both inclusion complexes and active films showed sustained release of thymol. Physical properties and thymol release kinetics were evaluated for active films. For gelatin films with 8.25% (mass ratio) inclusion complexes, complete thymol release took 235 h, compared with 38 h for thymol release from inclusion complexes. The diffusion coefficient reached 2.04?×?10^?15 m² s^?1.     

The Evaluation of Mechanical,Thermal, Optical and Microstructural Properties of Edible Films with Solid Lipid Nanoparticles-Xanthan Gum Stored at Different Temperatures and Relative Humidities

Solid lipid nanoparticles (SLN) were obtained using the hot homogenization method and incorporated into a xanthan gum matrix (XG) to prepare edible films. The effects of SLN content (60, 65, 70, and 75 g/L) on the mechanical, color, thermal and microstructural properties, and water vapor permeability (WVP) were studied. The SLN film-forming systems remained stable for 7 weeks. Particle size was in the range of 222–257 nm. The mechanical properties of the films improved significantly when the SLN were introduced into the polymeric network to provide greater strength and flexibility with elongation at breaking of 2–9 %, affected by temperature (4–25 °C), SLN concentration (60–75 g/L), and relative humidity (60–90 %). WVP was lower when edible films based on XG were incorporated with SLN at values of 0.50–0.70 g m-2 h-1 kPa^?1. The distribution of the SLN in the XG matrix was observed under scanning electron microscopy and showed changes in the arrangement as a function of SLN concentration. This explains the positive effect on the properties of the film of SLN-XG at 60 and 65 g/L. Total color difference (ΔE) increased with SLN content at values of 3.5–14. Thermal analysis showed that higher SLN content increased the melting temperature, while the plasticizer reduced it.     

Physical and Antimicrobial Properties of Compression-Molded Cassava Starch-Chitosan Films for Meat Preservation

Cassava starch-chitosan films were obtained by melt bending and compression molding, using glycerol and polyethylene glycol as plasticizers. Both the starch/chitosan and the polymer/plasticizer ratios were varied in order to analyze their effect on the physical properties of the films. Additionally, the antimicrobial activity of 70:30 polymer:plasticizer films was tested in cold-stored pork meat slices as affected by chitosan content. All film components were thermally stable up to 200 °C, which guaranteed their thermostability during film processing. Starch and chitosan had limited miscibility by melt blending, which resulted in heterogeneous film microstructure. Polyethylene glycol partially crystallized in the films, to a greater extent as the chitosan ratio increased, which limited its plasticizing effect. The films with the highest plasticizer ratio were more permeable to water vapor, less rigid, and less resistant to break. The variation in the chitosan content did not have a significant effect on water vapor permeability. As the chitosan proportion increased, the films became less stretchable, more rigid, and more resistant to break, with a more saturated yellowish color. The incorporation of the highest amount of chitosan in the films led to the reduction in coliforms and total aerobic counts of cold-stored pork meat slices, thus extending their shelf-life.     

Characterization of salmon gelatin based film on antimicrobial properties of chitosan against E. coli

Salmon gelatin and chitosan are high potential biopolymer to obtain edible films with antimicrobial effect for fresh meat. Therefore, it is important to characterize the structural (glassy or rubbery) state of the gelatin film on antimicrobial properties of chitosan. Extracted salmon (Salmo Salar) gelatin (acid-basic extraction) and low molecular weight chitosan solutions (0; 0.25; 0.5 and 1% w/w) at pH 5.5 were prepared to obtain a final concentration to 7% w/w (gelatin + chitosan). Films were obtained by casting at 5 °C and equilibrated at 33% and 85% of relative humidity (RH) in order to obtain a glassy and rubbery state, respectively. Water content, specific volume and glass transition temperature (Tg) were measured and antimicrobial properties against Escherichia coli (E.c.) (105 ufc/ml) were obtained by agar plate diffusion and kinetic measurements at 37 °C. Chitosan diffusion in agar plate was determined using liquid solutions and films over agar plate. The results showed diminution of Tg (maintaining structural state) as increase chitosan concentration, increasing also specific volume and water content due their high capacity to adsorb water. Although inhibition by chitosan of bacteria growth kinetic was 100%, solutions and films samples could not diffuse in the agar. In conclusion, the chitosan could not diffuse on the films matrix and also in agar plate and therefore in food when is combined with salmon gelatin. The implication of this work have been investigate the use of edible films from marine sources with antimicrobial effects in an effort to growing demand from consumers for safer and better quality foods.     

Physical Characterization and Pork Packaging Application of Chitosan Films Incorporated with Combined Essential Oils of Cinnamon and Ginger

Combinations of essential oils (EOs) can be an effective approach to reinforce their antimicrobial effects. In this sense, incorporation of two EOs into edible films may have supplementary utilizations in food packaging. Chitosan films containing combined EOs of cinnamon and ginger (1:1) at levels of 0.00, 0.05, 0.20, and 1.00% were developed and preliminarily characterized in the current study. The effect of the resulting materials on the antimicrobial and antioxidant properties of pork was then investigated during refrigerated storage (4 °C) over 9 days. Results showed that the presence of EOs markedly increased the thickness and opacity of the chitosan films, but did not modify the film solubility and water vapor permeability. When applied to the preservation of pork slices, these films were effective in retarding total microbial growth, increases in pH as well as lipid oxidation. The highest antioxidant and antimicrobial activities were observed in chitosan films incorporated with 1.00% EOs. These results suggest that chitosan-EO films have potential for application in pork packaging.     

Improvement of active chitosan film properties with rosemary essential oil for food packaging

Rosemary essential oil (REO) was used to develop an active film from chitosan. The effects of REO concentration (0.5, 1.0 and 1.5% v/v) on film properties were studied by measuring the physical, mechanical and optical properties of the REO‐loaded films. Scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopy were used to study microstructure and the interaction of the chitosan‐based films. The solubility and water gain of the chitosan film decreased about 25% and 85%, respectively, by REO incorporation, up to 1.5% v/v, because of the interaction between hydrophilic groups of chitosan and REO as confirmed by FTIR. It was determined that REO improved the transparency of the films from 4.97 in neat chitosan up to 7.61; moreover, it reduced the films’ light transmission in UV light more than 25%. Films containing REO showed more antibacterial activity and total phenol content. The films containing REO showed potential to be used as active film in food preservation.     

One-Step Synthesis of Zirconia and Magnetite Nanocomposite Immobilized Chitosan for Micro-Solid-Phase Extraction of Organophosphorous Pesticides from Juice and Water Samples Prior to Gas Chromatography/Mass Spectroscopy

In this research, a magnetic sorbent was prepared by immobilizing zirconia and magnetite (Fe₃O₄) nanoparticles in chitosan, which is characterized and used as an effective nanosorbent in magnetic dispersive micro-solid-phase extraction (MDMSPE) of organophosphorous pesticides (OPPs) from juice and water samples prior to gas chromatography-mass detection (GC-MS). The properties and morphology of synthesized sorbent were characterized by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and differential scanning calorimetric (DSC) analysis. The main experimental parameters including pH level, extraction time, sorbent mass, salt concentration, and desorption conditions were investigated and optimized to maximize extraction efficiency. Under optimized conditions, the calibration curves were obtained in the concentration range of 0.1–500 ng mL^?1 with correlation coefficients between 0.9993 and 0.9999. The limits of detection (signal-to-noise ratio (S/N) = 3) and limits of quantification (S/N = 10) of the method ranged from 0.031 to 0.034 ng mL^?1 and 0.105–0.112 ng mL^?1, respectively. The intra-day and inter-day RSDs were 2.2–5.7 and 2.5–7.5%, respectively. The method was successfully applied to the analysis of OPPs in fruit juices (apple, peach, and cherry) and water (mineral, tap, and river) real samples, with recoveries in the range of 86.0–106.0% for the spiked juice and water samples. The results showed that with combination of high selectivity of zirconia and magnetic property of magnetite as well as immobilizing ability of chitosan, the fabricated sorbent exhibited exceptional extraction ability toward the OPPs.     

Assessment of the migration potential of nanosilver from nanoparticle-coated low-density polyethylene food packaging into food simulants

An experimental nanosilver-coated low-density polyethylene (LDPE) food packaging was incubated with food simulants using a conventional oven and tested for migration according to European Commission Regulation No. 10/2011. The commercial LDPE films were coated using a layer-by-layer (LbL) technique and three levels of silver (Ag) precursor concentration (0.5%, 2% and 5% silver nitrate (AgNO₃), respectively) were used to attach antimicrobial Ag. The experimental migration study conditions (time, temperature and food simulant) under conventional oven heating (10 days at 60°C, 2 h at 70°C, 2 h at 60°C or 10 days at 70°C) were chosen to simulate the worst-case storage period of over 6 months. In addition, migration was quantified under microwave heating. The total Ag migrant levels in the food simulants were quantified by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Mean migration levels obtained by ICP-AES for oven heating were in the range 0.01–1.75 mg l^?1. Migration observed for microwave heating was found to be significantly higher when compared with oven heating for similar temperatures (100°C) and identical exposure times (2 min). In each of the packaging materials and food simulants tested, the presence of nanoparticles (NPs) was confirmed by scanning electron microscopy (SEM). On inspection of the migration observed under conventional oven heating, an important finding was the significant reduction in migration resulting from the increased Ag precursor concentration used to attach Ag on the LDPE LbL-coated films. This observation merits further investigation into the LbL coating process used, as it suggests potential for process modifications to reduce migration. In turn, any reduction in NP migration below regulatory limits could greatly support the antimicrobial silver nanoparticle (AgNP)-LDPE LbL-coated films being used as a food packaging material.     

Development of an Active Packaging Film Based on a Methylcellulose Coating Containing Murta (<Emphasis Type="Italic">Ugni molinae</Emphasis> Turcz) Leaf Extract

A new active packaging film based on murta leaf extract was elaborated. The extract was incorporated into a methylcellulose layer which was coated on a low-density polyethylene (LDPE) film. Its antioxidant effectivity, antimicrobial activity, and physicochemical properties were evaluated. The active film was able to keep its antimicrobial and antioxidant properties for at least 60 days. During this time, the growth of Listeria (L.) innocua was reduced by 2 log cycles and free radical formation could be inhibited by about 90 % for films stored under light and dark conditions. The active coating on the LDPE film did not affect the thermal and water vapor transmission properties; however, slight changes in the mechanical, color, and optical properties were observed. Finally, a sensory analysis showed that active coating did not change the flavor and odor properties of a fatty food packed inside the active material. This suggests that this active packaging film could be used to extend the shelf-life of packaged food.     

Functional Properties of Antimicrobial Lysozyme-Chitosan Composite Films

ABSTRACT: Lysozyme-chitosan composite films were developed for enhancing the antimicrobial properties of chitosan films. A 10% lysozyme solution was incorporated into 2% chitosan film-forming solution (FFS) at a ratio of 0%, 20%, 60%, and 100% (w lysozyme/w chitosan). Films were prepared by solvent evaporation. Lysozyme release from the film matrix, the antimicrobial activity of films against Escherichia coli and Streptococcus faecalis , and basic film properties were investigated. The lysozyme release proportionally increased with increasing initial concentration of lysozyme in the film matrix, and the amount of released lysozyme was in natural log relationship with time. The films with 60% lysozyme incorporation enhanced the inhibition efficacy of chitosan films against both S. faecalis and E. coli , where 3.8 log cycles reduction in S. faecalis and 2.7 log cycles reduction in E. coli were achieved. Water vapor permeability of the chitosan films was not affected by lysozyme incorporation, whereas the tensile strength and percent elongation values decreased with increased lysozyme concentration. Scanning electron microscopy images revealed that lysozyme was homogeneously distributed throughout the film matrix. This study demonstrated that enhanced antimicrobial activity of lysozyme-chitosan composite films can be achieved by incorporating lysozyme into chitosan, thus broadening their applications in ensuring food quality and safety.     

Antimicrobial properties of polypropylene films containing AgSiO<Subscript>2</Subscript>, AgZn and AgZ for returnable packaging in seafood distribution

Active antimicrobial films were prepared by incorporating AgSiO₂, AgZn and AgZ at 1, 3, 5 and 10 % (w/w) into a polypropylene (PP) matrix. Complete thermal, structural, mechanical and functional characterization as well as antimicrobial efficiency and returnable antimicrobial efficiency were determined according to the Japanese Industrial Standard method. The morphology of the films showed agglomerates of particles in the composites. The active formulation had decreased elongation compared to the pure PP sample. Thermal analyses indicated that the active formulation compositions had increased thermal stability. The films showed 50 % antimicrobial properties after the fifth wash against the tested microorganisms, presenting better activity against Gram negative organisms than Gram positive ones. These findings suggest that PP films with AgSiO₂, AgZn and AgZ particles can provide a significant contribution to the quality and safety of seafood in the distribution chain.     

Antimicrobial Activity of Chitosan Films Enriched with Essential Oils

ABSTRACT: Antimicrobial and physicochemical properties of chitosan films and chitosan films enriched with essential oils (EO) were determined in vitro and on processed meat. Antimicrobial effects of pure EO of anise, basil, coriander, and oregano, and of chitosan-essential oil films against Listeria monocytogenes and Escheri-chia coli O157:H7 were determined by an agar diffusion test. The antibacterial effects of the EO were similar when applied alone or incorporated in the films. The intensity of antimicrobial efficacy was in the following order: oregano > > coriander > basil > anise. The chitosan films and chitosan-oregano EO films were applied on inoculated bologna samples and stored 5 d at 10 °C. Pure chitosan films reduced L. monocytogenes by 2 logs, whereas the films with 1% and 2% oregano EO decreased the numbers of L. monocytogenes by 3.6 to 4 logs and E. coli by 3 logs. Pure chitosan films were 89 μm thick, whereas addition of 1% and 2% oregano EO increased thickness to 220 and 318 μm, respectively. During application on bologna discs, the films absorbed moisture, resulting in the final thickness of 143, 242, and 333 μm, respectively. Addition of oregano essential oil into the chitosan films decreased water vapor permeability, puncture and tensile strength, but increased elasticity of the films. The films have the potential to be used as active biodegradable films with strong antimicrobial effects.     

Physicochemical,Water Vapor Barrier and Mechanical Properties of Corn Starch and Chitosan Composite Films

Biodegradable flexible films were developed from corn starch (CS) and chitosan (CH); their microstructure, mechanical and barrier properties were evaluated. Chitosan and starch blend filmogenic suspensions showed a pseudoplastic behavior, similar to that of chitosan solutions. Smooth surfaces, homogeneous and compact film structures were observed from microstructure studies using scanning electron microscopy (SEM). The addition of glycerol reduced film opacity and increased film solubility of both CS and composite CS‐CH films. Water vapor permeability values of composite CS‐CH films plasticized with glycerol ranged between 3.76 and 4.54× 10⁻¹¹ g s⁻¹ m⁻¹ Pa⁻¹, lower than those of the single component films. CS‐CH films were resistant and their flexibility increased with glycerol addition. Tensile strength values of CS‐CH films were comparable to those of low‐density and high‐density polyethylenes but lower than that obtained for cellophane, however, composite biodegradable films showed lower elongation at break values than the synthetic commercial ones. In conclusion, CS‐CH films can be described as biofilms with a homogeneous matrix, stable structure and interesting water barrier and mechanical properties, with great possibilities of utilization, and with the advantage of biodegradability.