Effect extraction temperature on the emulsifying properties of gelatin from black tilapia (Oreochromis mossambicus) skin

Abstract

The emulsifying properties of tilapia skin gelatin as affected by extraction temperatures (45–75 °C) were investigated. The protein pattern of gelatin showed that the degradation of the major protein components (i.e., α-, β- and γ-chain) of gelatin occurred as the extraction temperature increased and increased the low molecular weight peptides. The surface hydrophobicity and surface activity of gelatin increased as the extraction temperature increased. The isoelectric points of tilapia gelatin decreased with an increase in the extraction temperature. Both gelatin solution and emulsion displayed almost Newtonian behavior except gelatin-stabilized emulsion extracted at 45 °C (G45), which displayed shear thinning behavior. At a given shear rate, the apparent viscosity of tilapia gelatin emulsion decreased as the extraction temperature increased. The G45 emulsion demonstrated the highest stability with no signs of flocculation or phase separation. However, when the extraction temperature increased from 55 to 75 °C, the tilapia gelatin emulsion was unstable due to flocculation and coalescence. The instability of emulsion also was partly due to the decrease of continuous phase viscosity. Besides, G45-stabilized emulsion showed a better creaming and droplet stability compared to bovine gelatin. This study showed that a physically stable oil-in-water emulsion could be formed by tilapia gelatin extracted at 45 °C.