Investigation of stabilizing property of chitosan-G-caffeic acid complex in oil in water emulsion

Emulsion is a mixture of two immiscible liquids, one liquid acts as disperse phase and another continuous phase, and oil in water (o/w) or water in oil (w/o) emulsions are most known emulsion types. Recently consumers have increasing demands for clean label, eco-friendly and plant derived (for vegetarians) products lead to seeking natural alternative solutions. In this thesis, the aim was that enhancement physiochemical properties of chitosan with caffeic acid modification to obtain eco-friendly emulsifier with antioxidant property and this study might give a perspective to literature about antioxidant and emulsion studies of modified chitosan; because, there is a gap about these studies in literature. For this purpose emulsification ability of chitosan, chitosan-g-caffeic acid and applicability and effectiveness of emulsification methods were evaluated. After the optimization studies, the dropwise method at 60 ℃ and normal Blk method that following 15, 000 rpm at 15 min was evaluated for 1, 1.5 and 2 percent (v/v) chitosan and 1 percent(v/v) chitosan-g-caffeic acid including emulsions. Also, 1 percent (v/v) chitosan and chitosan-g-caffeic acid based emulsions were evaluated against ionic strength and pH conditions. The emulsion characterization results showed that obtained emulsions mean droplet size were < 100 µm so emulsion type was conventional. Caffeic acid modification produced (IC50) value as 2.5, 1.3, 0.6 mg/ml and (EC50) value as 1.8, 0.3, 0.4 mg/ml for 5, 10, 20 mM caffeic acid containing chitosan-g-caffeic acid complexes respectively. The radical scavenging activity of caffeic acid modified samples (48.6 percent) reduced their activity in emulsion (4.9) but reducing power of samples (0.5 abs at 700 nm) increased in emulsions (1.9 abs at 700 nm). Caffeic acid modification caused to decrease in surface charge of emulsions from ~60 to ~20 mV. Also lowest viscosity values of chitosan modified samples were the reasons of higher creaming fraction values. These results were implied that both Ch and Ch-g-Ca had emulsifier and stabilizing activity and also Ch-g-Ca might be candidate for specific emulsion mixtures with its antioxidant property.