Rheology and Microstructure of Lecithin-Stabilized Tuna Oil Emulsions Containing Chitosan of Varying Concentration and Molecular Size

Abstract

The purpose of these experiments was to determine the influence of chitosan concentration (0–0.25 wt.%) and molecular weight (120, 250 and 342.5 kDa) on the rheological properties and microstructure of lecithin-stabilized tuna oil emulsions. The apparent viscosity of the emulsions significantly increased with increasing chitosan concentration and molecular weight (P ≤ 0.05). However, the studied chitosan chain lengths did not play a major role in determining the flow characteristics of the emulsions. The emulsions containing 0.1–0.25 wt.% chitosan were stable to droplet aggregation. All of these emulsions showed Newtonian flow with a flow behavior index of approximately 1. In the contrary, the 0.05 wt.% chitosan emulsions showed highly unstable droplet aggregation and a shear thinning behavior. The emulsion microstructure visualized using a confocal laser scanning microscope was consistent with the rheological data. These results have important implications for the utilization of tuna oil emulsions stabilized by lecithin-chitosan membranes in emulsion based food products.