The current study aimed to investigate the effects of ultrasound-assisted emulsification on the emulsifying and rheological properties of myofibrillar protein (MP) pork fat emulsions under different protein/fat ratios. Changes in emulsion profile, confocal laser scanning microscope images, cryo-scanning microscope images, particle size, protein solubility, surface hydrophobicity and free sulfhydryl groups were determined. Ultrasound significantly increased the emulsifying activity, the emulsifying stability and the flow index for all emulsions, while it decreased the viscosity coefficient of emulsions except for the treatment of protein/fat ratio of 1:15. The results showed that sonication reduced the particle size of the fat particles and evenly distributed the emulsion droplets. Sonication moved the distribution curve of droplet size to the smaller particle size direction and decreased the D3,2 and D4,3 values of emulsion. Sonication resulted in increased bindings between protein hydrophobic groups and fat particles. After ultrasound treatment, more sulfhydryl groups were exposed to aqueous solution, which might decrease the protein solubility in aqueous solution. Ultrasound-assisted emulsification could directly enhance the emulsifying and rheological properties of MP-stabilized pork fat emulsions at different protein/fat ratios, in particular at the ratio of 1:10.
Keywords: animal fat; emulsified meat products; meat protein; particle size; sonication.