Chitosan food packaging

The basic types of antinucrobial food packaging films are outlined and additives used in antimicrobial materials are discussed, with particular reference to potassium soibate, nisin, imazalil, allyl isothiocyanate and triclosan. The production of antimicrobial films by modification of the polymer chain itself is also mentioned and the natural antimicrobial activity of chitosan is considered. 17 refs. 

Keywords Biopolymer, chitosan, active food packaging, membrane, permselective, antimicrobial, bioactive... 

The following sections of this chapter will look at recent developments of both cellulose and chitosan for specific application in water purification, energy and food storage as (1) permselective membranes for chemical sensing and polymer electrolyte membranes for fuel cells and (2) antimicrobial/lipid barrier films for active food packaging. 

In the case of natural polymers, polysaccharides like cellulose and chitosan are widely studied as antimicrobial films and barrier/coating materials. The following section reviews the recent studies on cellulose and chitosan having current and potential use as antimicrobial material for active food packaging systems. 

The ongoing efforts have been promising, especially in the antimicrobial food packaging area. For this part, we would like to summarize the recent developments on antimicrobial systems utilizing chitosan, cellulose, their derivatives and blends (Table 3.3). 

A novel organic (chitosan) and inorganic (tetraethyl orthosilicate) composite membrane has been prepared, which is pH sensitive and drug permeable [258]. The latter possibly involved in ionic interactions. By plasma source ion implantation technique, the adhesion between linear low-density polyethylene and chitosan could be improved [259]. Such bilayer films showed 10 times lower oxygen permeability, a property of use in food packaging applications. These multilayer films were easily recyclable. 

Chitosan, the deacetylated product of chitin, is obtained by treating chitin with 40% caustic soda at elevated temperatures. In contrast to chitin, chitosan is soluble in dilute mineral acids. It is used for making biodegradable food packaging film, as an additive to improve the wet strength of paper, as an ion exchanger in water treatment, and to cover wounds. 

Various methods are employed to prepare antimicrobial chitosan films and coatings for food packaging applications. Solution casting method is one of the popular methods. As a general practice, chitosan films are prepared by using various kinds of cross-linkers. Some typical preparative techniques are euumerated below. 

Tripathi, S., Mehrotra, G. K., and Dutta, P. K. 2008b. Chitosan based antimicrobial films for food packaging applications, e-Polymers, no. 093,1-7. 

Tripathi, S Mehrotra, G. K Dutta, P. K. Preparation and physieochemical evaluation of chitosan/poly(vinyl alcohol)/pectin ternary film for food-packaging applications. Carbohydrate Polymers, v. 79, p. 711-716, 2010. 

There are other biomaterials with great potential in food packaging applications which are directly extracted from biomass, such as proteins (gluten, zein, etc.) and polysaccharide (i.e., chitosan). Some proteins and polysaccharides have excellent barriers under dry conditions, comparable to EVOH. However, under humid conditions these deteriorate to a much larger extent than EVOH. On the other hand, thermoplastic biopolymers such as PLA or PCL are not as strongly affected by moisture but have lower barriers than the benchmark PET. Research should therefore aim to diminish the water sensitivity of proteins and polysaccharides and to enhance the gas barrier of thermoplastic biopolyesters to make them suitable for monolayer and multilayer food packaging applications. 

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