Effect of Heat Treatment on the Stability of the Tuna Protein Emulsion

Heat treatment is an important factor affecting the stability of the protein emulsion. This paper investigated the effects of different heat treatment temperature (30, 50, 70, 80 and 90 ℃, 30 min) on the physicochemical properties of tuna protein emulsion. The results showed that the emulsifying property of the heat-treated protein emulsion changed significantly compared with those without heat treatment (P<0.05). Surface hydrophobicity, viscosity, Zeta-potential, emulsifying activity and emulsion stability of tuna protein emulsion increased first and then decreased with the rise of heat treatment temperature. Within 30~70 ℃ of heating, protein secondary structure unfolded, hydrophobic groups exposed, the viscosity of emulsion increased, the particle size of the droplet decreased and the stability of the emulsion increased. After the heating temperature exceeded 70 ℃, the protein molecules reassembled, the amino acid residues bound to the oil droplets reentered the protein interior, the droplets appeared flocculation and the emulsion became unstable. The results of SDS-PAGE illustrated that the amount of protein adsorption at the oil-water interface increased, the droplet distribution was uniform, the particle size reached the minimum value of 102.6 nm, the viscosity reached the maximum of 43.87 Pa·s at 70 ℃ for 30 min. There was no stratification in the emulsion after 28-days of storage and the emulsion had the best stability at this temperature. To sum up, appropriate heat treatment could improve the stability of the tuna protein emulsion.