Preparation and Characterization of Antimicrobial Films Based on Chitosan for Active Food Packaging Applications

The aim of this paper was to characterize chitosan samples from the shrimp shells for the later development of antimicrobial active systems. These systems include 100 % chitosan-based films obtained by casting, polyamide films with 5 and 10 % of chitosan obtained by extrusion and polyethylene/polyethylene terephthalate films with a coating of 0.6 % of chitosan. For that purpose, several analytical techniques including IR, ¹H NMR, GPC, and microscopic techniques (scanning electron microscopy and transmission electron microscopy) were used. Within the studied samples, C1 showed the lowest DA and MW and consequently presented the most suitable properties for the development of an active packaging. Additionally, mechanical properties were performed. The effectiveness of the developed systems was evaluated by means of microbiological assays. The tested films showed antimicrobial capacity against coliform enterobacteria, mesophilic aerobic microorganism, and yeast and moulds.     

Chitosan Polymer as Bioactive Coating and Film against Aspergillus niger Contamination

ABSTRACT: The inhibitory activity of chitosan-based edible coatings and films was assessed against the Aspergillus niger food pathogen and deterioration microorganism. Spore-counting assays showed an almost total inhibition of A. niger growth when either film-forming solution or film were used at a low concentration of chitosan (0.1% w/v). Epifluorescence microscopic results showed the action of chitosan on the relative proportion of RNA compared with DNA. The water vapor permeability (WVP) of chitosan film was relatively low compared with the poor moisture barrier of some polysaccharide films. Moreover, a coating with chitosan film on an agar gel, used as a food model, induced a 30% reduction in water loss. These results showed potential applications of chitosan-based films as bioactive packaging with properties to limit the food dehydration phenomenon.     

Characterization and antimicrobial analysis of chitosan-based films

Chitosan-based films for food packaging applications were prepared by casting and dried at room temperature or heat-treated in order to study functional properties and antimicrobial activity. In all cases, films were flexible and transparent, regardless of chitosan molecular weight, glycerol content, and temperature. Regarding antimicrobial activity, chitosan film forming solutions showed antimicrobial behaviour against Escherichia coli and Lactobacillus plantarum. It was also observed that the bacteriostatic property of chitosan-based films against bacteria employed in this study was notably affected by temperature. Moreover, temperature produced significant variation in the functional properties of chitosan-based films, such as colour, wettability, resistance against UV light and mechanical properties. In good agreement with this behaviour, total soluble matter (TSM), fourier transform infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) results suggested a change in the chemical structure of chitosan films, possibly due to Maillard reaction when heat treatment was used.     

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.     

A novel active bionanocomposite film incorporating rosemary essential oil and nanoclay into chitosan

Montmorillonite (MMT) nanoclay and rosemary essential oil (REO) were incorporated into chitosan film to improve its physical and mechanical properties as well as antimicrobial and antioxidant behavior. The MMT weight percent relative to chitosan was varied from 1 to 5 and was activated by three REO levels (0.5%, 1%, and 1.5% v/v), and their impact on physical, mechanical, and barrier properties of the chitosan films was investigated. Total phenolic and antimicrobial activity were also evaluated. Microstructure of chitosan/MMT–REO nanocomposites was characterized through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed that incorporating MMT and REO into chitosan improves water gain, water vapor permeability, and solubility of the chitosan film by more than 50%. It was also shown that the combined effect of clay and REO improves significantly the tensile strength and elongation of chitosan (p < 0.05). The XRD and FTIR results confirmed that the improvements are related to the MMT exfoliation and good interaction between chitosan and MMT in the presence of REO. Antimicrobial properties of the films also improved by REO incorporation in 1.5% v/v.     

Chitosan application for active bio-based films production and potential in the food industry: Review

During the past decade, there was an increasing interest to develop and use bio-based active films which are characterized by antimicrobial and antifungal activities in order to improve food preservation and to reduce the use of chemical preservatives. Biologically active bio-molecules such as chitosan and its derivatives have a significant potential in the food industry in view of contaminations associated with food products and the increasing concerns in relation with the negative environmental impact of conventional packaging materials such as plastics. Chitosan offers real potential for applications in the food industry due to its particular physico-chemical properties, short time biodegradability, biocompatibility with human tissues, antimicrobial an antifungal activities, and non-toxicity. Thus, chitosan-based films have attracted serious attention in food preservation and packaging technology. This is mainly due to a fact that chitosan exhibits high antimicrobial activity against pathogenic and spoilage micro-organisms, including fungi, and both Gram-positive and Gram-negative bacteria. The aim of the present review was to summarize the most important information on chitosan from its bioactivity point of view and to highlight various preparative methods used for chitosan-based active bio-films and their potential for applications in the food preservation and packaging technology.     

Characterization of antimicrobial properties on the growth of S. aureus of novel renewable blends of gliadins and chitosan of interest in food packaging and coating applications

The biocide properties of chitosan-based materials have been known for many years. However, typical antimicrobial formulations of chitosan, mostly chitosonium salts, are known to be very water sensitive materials which may impair their use in many application fields such as food packaging or food coating applications. This first work reports on the development and characterization of the antimicrobial properties of novel fully renewable blends of chitosan with more water-resistant gliadin proteins isolated from wheat gluten. Chitosan release to the nutrient broth from a wide range of blends was studied making use of the ninhydrin method. The results indicated that both pure chitosan and its blends with gliadins presented significant antimicrobial activity, which increased with increasing the amount of chitosan in the composite formulation as expected. The gliadins-chitosan blends showed good transparency and film-forming properties and better water resistance than pure chitosan. The release tests revealed that dissolution of the biocide glucosamine groups, i.e. the chitosan water soluble fractions, also increased with the amount of chitosan present in the formulation. The release of these groups was for the first time directly correlated with the antimicrobial properties exhibited by the blends. Thus, incorporation of chitosan into an insoluble biopolymer matrix was revealed as a very feasible strategy to generate novel chitosan-based antimicrobial materials with potential advantages, for instance active food packaging applications.     

Encapsulation of coriander essential oil in cyclodextrin nanosponges: A new strategy to promote its use in controlled-release active packaging

In this work, we exploit the antimicrobial properties of coriander essential oil (CEO) incorporated in dextrin-derived nanosponges to create a stable controlled release system. Nanosponges (CD-NS) were loaded with CEO, characterized by means of scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction (XRD), and tested for their antimicrobial activity against foodborne pathogens. A head-space-solid phase microextraction coupled to gas chromatography (HS-SPME-GC–MS) method to assess CEO five major compounds was successfully validated. CEO loading was dependent on solvent and CD-NS choice. Additionally, CEO incorporation in CD-NS increased its crystallinity. While β-CD-NS and HP-β-CD:β-CD-NS incorporated higher CEO amounts than α-NS, the later proved more effective regarding their antimicrobial activity. CEO-α-CD-NS and CEO-HP-β-CD:β-CD-NS revealed a predominant bactericidal activity, CEO-β-CD-NS only exhibited a bacteriostatic action. We describe, for the first time, the incorporation of whole EOs in CD-NS and their ability to provide a controlled oil release, especially in the cases of β-derived-CD-NS, while inhibiting bacterial growth, creating a potential new strategy to overcome the poor efficacy of current antimicrobial food packaging.Industrial relevanceThe manufacturing of antimicrobial food packages is still hindered by the problems posed by its lack of efficiency and poor compound stability. The fact that the cyclodextrin nanosponges synthetized in this work can provide a controlled release of antimicrobial active agent, in this case, coriander essential oil while preserving this compound's antimicrobial activity against foodborne pathogens can open the doors for its use in antimicrobial food packaging films. Furthermore, given that cyclodextrin nanosponges are stable at temperatures over 200 °C, gives the packaging industry the opportunity of incorporating this technology during the extrusion process of film making, making the process of active packaging materials cheaper, faster and more readily scalable.     

壳聚糖复合膜在果蔬保鲜中的应用

壳聚糖具有良好的生物相容性、可生物降解性、安全性、成膜性、抗菌性等,常用于果蔬保鲜。但由于机械性能和生物活性不足,为了增强其理化性能和生物活性,常添加生物聚合物、抗菌剂、抗氧化剂等功能成分以提高膜综合性能。综述了壳聚糖膜和壳聚糖/多糖、壳聚糖/蛋白质、壳聚糖/脂质、壳聚糖/抗菌剂、壳聚糖/抗氧化剂等壳聚糖基复合膜在果蔬保鲜中的应用进展,从壳聚糖的诱导活性、成膜特性和抗菌活性三个方面总结了壳聚糖膜的保鲜机理,分析了壳聚糖基复合膜目前在果蔬保鲜实际应用中存在的问题,并对未来发展方向进行了展望,以期为开发安全、高效、绿色、经济的壳聚糖基果蔬保鲜膜提供一定的理论指导。     

可食性肉桂精油复合膜的制备及其缓释性能

为了拓展肉桂精油（cinnamon essential oil, CEO）的应用途径,将CEO作为活性物质加入到氧化羟丙基木薯淀粉中,制备出复合膜。以力学性能、阻隔性能作为测试指标,通过单因素和正交试验优化CEO膜制备工艺,并测定其在不同食品模拟物中的释放速率。结果表明,淀粉质量分数为5.0%（m/v,以蒸馏水体积为基准）,CEO、甘油、吐温-80质量分数分别为1.5%、1.0%、1.0%（m/v,以淀粉溶液体积为基准）时,制得薄膜性能最好,断裂伸长率和抗拉强度较大,分别为27.87%和1.42 MPa,水蒸气透过系数与透油数较小,为1.27×10?12 g·cm/cm2·s·Pa和0.2131 g·mm/mm2·d,透光率30.56%;在同种食品模拟物中,CEO的释放量达到最大值的时间随着CEO含量增多而延长;在不同食品模拟物中,CEO在水包油乳状液和含酒精食品模拟物中释放速率最快,在脂肪食品模拟物中最慢。结果表明CEO可改善淀粉基膜的阻隔性能和机械性能,制备出的CEO膜有利于油脂类食品的包装,CEO可以缓慢释放,较长时间发挥活性作用。     

Chitosan-based biodegradable functional films for food packaging applications

Chitin is the structural material of crustaceans, insects, and fungi, and is the second most abundant biopolymer after cellulose on earth. Chitosan, a deacetylated derivative of chitin, can be obtained by deacetylation of chitin. It is a functionally versatile biopolymer due to the presence of amino groups responsible for the various properties of the polymer. Although it has been used for various industrial applications, the recent one is its use as a biodegradable antimicrobial food packaging material. Much research has been focused on chitosan-based flexible food packaging and edible food coatings to compete with conventional non-biodegradable plastic-based food packaging materials. Various strategies have been used to improve the properties of chitosan - using plasticizers and cross-linkers, embedding the polymer with fillers such as nanoparticles, fibers, and whiskers, and blending the polymer with natural extracts and essential oils and also with other natural and synthetic polymers. However, much research is still needed to bring this biopolymer to industrial levels for the food packaging applications.Industrial relevanceAs a major by-product of the seafood industry, a massive amount of crustacean shell waste is generated each year, which can be used to produce value-added chitin, which can be converted to chitosan using a relatively simple deacetylation process. Being extracted from a bio-waste product using many energy-efficient methods, chitosan is much cheaper as compared to other biopolymers. Nevertheless, the exceptional properties of chitosan make it a relatively stronger candidate for food packaging applications. Chitosan has already been used in various industries, such as biomedical, agriculture, water treatment, cosmetics, textile, photography, chromatography, electronics, paper industry, and food industry. This review article compiles all the essential literature up to the latest developments of chitosan as a potential food packaging material and the outcomes of its practical utilization for this purpose.     

添加丁香精油对玉米醇溶蛋白膜性能及结构的影响

以玉米醇溶蛋白为原料制备可食性膜,将丁香精油添加到玉米醇溶蛋白膜中,研究其对玉米醇溶蛋白膜物理性能及微观结构的影响。结果表明,丁香精油体积分数在0.5%～2.0%范围内时,随着体积分数的增加,玉米醇溶蛋白膜的厚度、断裂伸长率和水蒸气透过系数逐渐增加。丁香精油体积分数为0.5%～1.0%时,玉米醇溶蛋白膜的拉伸强度显著增加（P＜0.05）。添加丁香精油改善了膜的机械性能,增加了阻光性和透湿性。通过红外光谱和扫描电镜分析表明,添加丁香精油并未显著改变玉米醇溶蛋白的结构,且添加丁香精油的成膜液在干燥过程中会产生微孔,使得玉米醇溶蛋白膜的表面粗糙不均匀。     

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.     

壳聚糖/植物精油可食性抗菌膜研究进展

壳聚糖包埋植物精油制备的可食性抗菌膜具有原料来源广泛、可食、可降解,抗菌效果强等优势,在食品保鲜领域显示了重要的应用价值。本文综述了壳聚糖和精油各自的结构、性质、壳聚糖/精油复合膜及添加了其它天然高分子如蛋白质、淀粉等的复合可食性抗菌膜的研究进展,同时指出了目前该研究领域中存在的问题,并对未来的研究方向进行了展望,为壳聚糖/植物精油复合可食性抗菌膜研究的进一步开发利用提供参考。     

Antibacterial Activity and Physical Properties of Edible Chitosan Films Exposed to Low-pressure Plasma

The challenge for food industry is developing gentle processes concept, which will prevent food spoilage and leave a food natural, minimally processed, fresh-like and safe. A new technique of food preservation could be usage of combined methods of green process, such as cold gas plasma with bioactive substances, and protective coatings. The aim of this study was to determine the antibacterial activity of chitosan films incorporated with lysozyme exposed to helium plasma treatment as well as evaluate their physical properties. The edible films have been prepared basing on low molecular weight chitosan by casting from lactic acid solution with water solution of lysozyme in three various concentrations (0, 0.5 and 1 %). Dried films were then modified by exposition on cold helium plasma treatment for 0, 5 and 10 min. Obtained films were tested against growth of Listeria monocytogenes, Yersinia enterocolitica and Pseudomonas fluorescens. In order to characterize chitosan-based films, their mechanical properties, theromogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), contact angle measurement, water vapour permeability (WVP) and scanning electron microscopy (SEM) were evaluated. The films with 1 % lysozyme incorporation enhanced the inhibition efficiency of chitosan-based films against gram-positive (L. monocytogenes) and gram-negative (P. fluorescens) bacteria, where reduction zones were 42.5 and 69.8 mm, respectively. Besides that, hydrolytic changes of chitosan chain caused by lysozyme activity were confirmed by TGA and DMTA. Contact angles and WVP of tested films were not significantly affected by helium plasma exposition, nor lysozyme dosage. Hydrophilic natures of chitosan-based films were confirmed by both tests. Microscopy image of cross-section structure was smooth and continuous due to lysozyme addition in film composition. Application of chitosan films incorporated with lysozyme and low-pressure plasma treatment could be used as innovative preservation method in a wide range of food products.     

Effect of storage time and temperature on structure,mechanical and barrier properties of chitosan-based films

The mechanical (tensile strength, elongation at break, mechanical work of deformation) and barrier (water vapor permeability and water vapor uptake) properties of chitosan films produced with acetic and lactic acids have been studied as a function of storage time, molecular weight of chitosans, concentration of plasticiser and the storage temperature. It was demonstrated that mechanical properties of chitosan-based films can be improved to a great extent during storage at low temperatures in freezer and refrigerator. Transition of chitosan molecules during storage in the solid state to more extended conformations and free volume changes are considered as mechanisms for the improvement of mechanical and barrier properties of chitosan films. The best mechanical properties are achieved for chitosan films produced with acetic acid and plasticized by the addition of 20% of glycerol. Sharp decrease in water vapor permeability has been demonstrated for thinner chitosan films and related to more dense packing and orientation of linear chitosan macromolecules.     

Physical properties of chitosan-basil essential oil edible films as affected by oil content and homogenization conditions

This work studies the influence of basil essential oil, its content and the homogenization treatment on the physical properties of chitosan-based edible films. Two homogenization treatments were applied, without (H1) and with (H2) microfluidization (MF). Composite films were softer, less rigid and more stretchable than pure CH films. MF intensified these changes. H2 films showed microcracks due to the weak interactions between chitosan and oil, which affected their mechanical behaviour. In pure chitosan films, MF significantly increased water vapour permeability. Homogenization treatment greatly affected this property. Gloss was reduced by the essential oil addition, whereas MF tended to yield glossier films.     

Physical properties and antioxidant activity of an active film from chitosan incorporated with green tea extract

An active film from chitosan incorporated with aqueous green tea extract (GTE) was developed. The effects of GTE concentrations including 2, 5, 10 and 20% (w/v) of green tea in the film-forming solution on the film properties were determined by measuring physical properties, total polyphenolic content and antioxidant activity of the active films. Fourier Transform Infrared (FTIR) spectrometry was carried out to observe the potential modifications of the chitosan films when incorporated with GTE. The results suggested that incorporation of GTE into chitosan films improved mechanical and water vapor barrier properties and enhanced polyphenolic content and antioxidant activity of the films. Changes in the FTIR spectra of the chitosan films were observed when GTE was incorporated, suggesting some interactions occurred between chitosan and the polyphenols from GTE. This study showed the benefits of incorporation of GTE into chitosan films and the potential for using the developed film as an active packaging.     

Optimization of the biocide properties of chitosan for its application in the design of active films of interest in the food area

The influence on biocide performance of some unprecedented physicochemical features of chitosan cast films such as film thickness, pH of the nutrient broth, film neutralization, film autoclave sterilization and temperature exposure were analyzed against Staphylococcus aureus and in some experiments also against Salmonella spp. The work demonstrates for the first time the influence of the release or positive migration of protonated glucosamine fractions from the biopolymer into the microbial culture as the responsible event for the antimicrobial performance of the biopolymer under the studied conditions. From the results, a reliable and reproducible method for the determination of the bactericidal activity of chitosan-based films was developed in an attempt to standardize the testing conditions for the optimum design of active antimicrobial food packaging films and coating applications.