Effect of Thermal Treatment on the Physicochemical Properties of Emulsion Stabilized by Gelatin from Black Tilapia (Oreochromis mossambicus) Skin

摘要

This study investigated the influence of thermal treatment (30 degrees C to 110 degrees C, 30 min) on the physicochemical and rheological properties of an emulsion stabilized by black tilapia (Oreochromis mossambicus) skin at pH 4. The protein pattern of tilapia gelatin did not have any significant difference after the gelatin was heated within a temperature range of 30 degrees C to 70 degrees C. However, at 90 degrees C and 110 degrees C, denaturation occurred where alpha-, beta- and gamma-chains of the gelatin were degraded, leading to a concomitant increase in low molecular peptides. The emulsion stability was investigated through a particle size analyzer, zeta potential, microscopic observation and creaming index. The gelatin emulsion was physically stable at 30 degrees C to 70 degrees C with a mean droplet size of less than 13 mu m. When the heating temperature was increased to 90 degrees C and 110 degrees C, the emulsion showed a pronounced increase in droplet size due to coalescence. The gelatin emulsion heated at 90 degrees C and 110 degrees C also displayed instability against creaming after storage at room temperature for 7 days. As the heating temperature increased, the gelatin emulsion exhibited a decrease in apparent viscosity and the flow behavior changed from shear thinning to Newtonian. The rheological data also showed that the storage modulus (G ') of emulsion became more frequency dependent as the heating temperature increased, indicating weak droplet interactions. The tilapia gelatin emulsion was physically unstable when subjected to thermal treatment above 70 degrees C. The data reported in this study provides useful insight into the formulation of acidic food emulsions that require thermal treatment.