Physical stability of emulsion and hydrophilic gels with chitosan and chitosan acetate

Context: Chitosan has received great attention because it is a functional, biodegradable, renewable and non-toxic biopolymer with multiple pharmaceutical applications, including stabilizing agent. Aims: To evaluate the physical stability of emulsified bases and hydrophilic gels containing chitosan or chitosan acetate as stabilizing agents. Methods: Stability of shelf-life formulations at room temperature and in refrigeration was evaluated over a period of 60 days and by thermal stress testing and centrifugal destabilization. The organoleptic characteristics, pH, conductivity and flow behavior were evaluated, the latter through the analysis of the rheograms, the determination of rheological parameters (consistency index, apparent viscosity, creep value and flow index), as well as their comparison statistics. The possible correlations between these parameters and the concentration of the biopolymers were also evaluated. Results: The bases elaborated with chitosan or its soluble derivative showed adequate physical stability during the study time. The effect of the storage temperature, as well as the type and concentration of the stabilizing agent used was evidenced. Emulsifier combinations provided less stability. A linear correlation between the rheological parameters and the biopolymer concentration was evidenced. Conclusions: Chitosan and chitosan acetate can be used as emulsifying agents in semi-solid and gelling bases in hydrophilic gels, due to the electrostatic stabilization and the viscosity they contribute to the system in relation to its concentration.