Perspectives for chitosan based antimicrobial films in food applications

Chitosan, a versatile hydrophilic polysaccharide derived from chitin, has a broad antimicrobial spectrum to which gram-negative, gram-positive bacteria and fungi are highly susceptible. In the current review, three possible and accepted antimicrobial mechanisms for chitosan are presented and briefly discussed. The activity dependence on polymeric molecular weight (MW) and degree of acetylation (DA) are described. The chitosan minimum inhibitory concentrations (MIC) are summarized according to recent data found in the literature. The potential to improve inhibitory growth of bacteria by using water soluble chitosan derivatives is also discussed. The data indicate that the effectiveness of chitosan varies and is dependent on species of target microorganisms.

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A Review of the Antimicrobial Activity of Chitosan

Listeria: A foodborne pathogen that knows how to survive

Chitosan based edible films and coatings: A review

Over the last years, considerable research has been conducted to develop and apply edible films and coatings made from a variety of agricultural commodities and/or wastes of food product industrialization. Such biopolymers include polysaccharides, proteins, and their blends. These materials present the possibility of being carriers of different additives, such as antimicrobial, antioxidant, nutraceuticals, and flavorings agents. In particular, the use of edibles films and coatings containing antimicrobials has demonstrated to be a useful tool as a stress factor to protect foodstuff against spoilage flora and to decrease the risk of pathogen growth. The more commonly antimicrobials used are organic acids, chitosan, nisin, the lactoperoxidase system, and some plant extracts and their essential oils. For the selection of an antimicrobial, it must be considered the effectiveness against the target microorganism and also the possible interactions among the antimicrobial, the film-forming biopolymer, and other food components present. These interactions can modify the antimicrobial activity and the characteristics of the film being these key factors for the development of antimicrobial films and coatings. The main objective of this article is to review the bibliography of the last years concerning the main hydrocolloids and antimicrobials used for developing edible films and coatings, the methods used to evaluate the antimicrobial activity, the applications and the legislation concerning edible films and coatings. Also, the different strategies related to the modification of structural characteristics and the future trends in the development are discussed. The information update will help to improve the design, development, and application of edible films and coatings tending to increase the safety and quality of food products and to prepare for food legislation changes that might be necessary while identifying future trends concerning a better functionality of edible films thought as a stress factor for lengthening shelf life of food products.

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Development of Edible Films and Coatings with Antimicrobial Activity

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.

Chitosan Polymer as Bioactive Coating and Film against Aspergillus niger Contamination

To develop biodegradable packaging that both acts as a moisture barrier and as antimicrobial activity, nisin and stearic acid were incorporated into a hydroxy propyl methyl cellulose (HPMC) based film Fifteen percent (w/w HPMC) of stearic acid improved film moisture barrier However, film mechanical resistance and film antimicrobial activity on Listeria monocytogenes and Staphylococcus aureus pathogenic strains were both reduced This lower film inhibitory activity was due to interactions between nisin and stearic acid The molecular interaction was modeled, and an equation was developed to calculate the nisin concentration needed to be incorporated into the film matrix to obtain a desired residual antimicrobial activity Because the molecular interactions were pH dependent, the impact of the pH of the film-forming solution on film inhibitory activity was investigated Adjusting the pH to 3 totally avoided stearic acid and nisin interaction, inducing a high film inhibitory activity

Edible Bioactive Fatty Acid−Cellulosic Derivative Composites Used in Food-Packaging Applications

Cross-linked hydroxypropylmethylcellulose (HPMC) cast films with citric acid as polycarboxylic cross-linker were elaborated to study the effect of cross-linking level on various properties. Increased amounts of cross-linking agent were not connected to statistically different tensile strength and Young's modulus. Whatever the cross-linking level of the film was, the ultimate elongation parameter decreased by ∼60% compared to the HMPC control film. Moisture sorption isotherms and water contact angle meter showed that the effect of cross-linking degree tends to reduce the hygroscopic and hydrophilic characteristics of films. In addition, to control bacteria growth on food surfaces, the antimicrobial activity of both 98% cross-linked HPMC−nisin and control HPMC−nisin films was tested on Micrococcus luteus. Despite the incorporation of a significant content of nisin, cross-linked HPMC−nisin films were completely inactive on the microbial strain compared to the HPMC−nisin control films. Cross-linking condition...

Issam Sebti

Papers

Chitosan Polymer as Bioactive Coating and Film against Aspergillus niger Contamination

Edible Bioactive Fatty Acid−Cellulosic Derivative Composites Used in Food-Packaging Applications

Physicochemical properties and bioactivity of nisin-containing cross-linked hydroxypropylmethylcellulose films.