No abstract

A polyelectrolyte complex (PEC) matrix formed between chitosan and pectin was developed to entrap a bioactive compound (anthocyanin), obtaining an useful pH indicator device. Polysaccharides of opposite charges such as chitosan and pectin can have a very strong intermolecular interaction. The innovation lies in obtaining a new system based on natural and biodegradable compounds, which is simple to manufacture, to indicate variation in pH by visual changes in colour. This device has potential applications in food packaging. The PEC was studied using chitosan and pectin solutions at different pHs values (3.0, 4.0, 5.0 and 5.5) and pectin/chitosan molar ratios (1.0 to 10/1.0 to 5.0). PEC films were homogeneous and showed the highest yield (60.0%) at pH 5.5. Diffusion tests indicated efficient bioactive compound entrapment in the PEC matrix. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy indicate the compatibility between the polymers and bioactive compound.

Kraft paper was coated with chitosan emulsion film. The novelty of this paper is the formation of a packaging bilayer system in only one drying step, which combines a biodegradable polymer emulsion (chitosan and palmitic acid) with Kraft paper. This system is described in detail and characterized for barrier properties (water vapor permeability rate (WVPR), air permeability and water absorption capacity (Cobb test)), mechanical properties (tensile properties, Taber stiffness and tear strength) and structural properties. The application of chitosan coating (3.5 g m−2, wet basis) on Kraft paper sheets provides a significantly lower WVPR (by ca 43%) and water absorption capacity (by ca 35%) as compared to uncoated Kraft paper. The incorporation of palmitic acid into the chitosan film solutions at 1.8 g m−2 improves the properties of Kraft paper even more by further reducing the WVPR and water absorption capacity by 51 and 41%, respectively. The air resistance of the coated Kraft systems is lower by 8‐ and 11‐fold compared to uncoated Kraft paper, which could be associated with the chitosan film acting as a gas barrier and as a coating agent that fills the pores between cellulose fibers. Copyright © 2011 Society of Chemical Industry

With the aim of achieving 'tailor-made' chitosan fi lms, the effects of several variables on the properties of chitosan fi lms were studied. These variables were chitosan concentration and molecular weight of thermally depolymerized chitosan, addition of lipids (palmitic acid, beeswax or carnauba wax) and plasticizer (glycerol). The water vapour transmission rate (WVTR) and mechanical properties of these fi lms were measured. The innovative feature of this study is that it provides specifi c information to support the design of tailor-made fi lms. These can only be formulated when the effects of the important variables are well understood. It was found that WVTR was reduced by 57% in fi lm made from chitosan that had been thermally treated for 7 h at 100°C (molecular mass 13.7 kDa), while in the emulsion fi lms, the WVTR was increased by incorporation of palmitic acid, beeswax or carnauba wax incorporation. The mechanical properties (tensile strength and elongation at break) were improved when glycerol was used as plasticizer, resulting in more elastic fi lms (increasing the elongation at break by 62%).