Applications of ultrasound for the functional modification of proteins and submicron emulsion fabrication

This thesis aims to advance the understanding of ultrasonic processing for the alteration of food microstructures. It considers the impact of ultrasonic processing upon protein structure and for emulsification. It was shown that ultrasound treatment of proteins reduced the hydrodynamic volume of protein aggregates by ultrasonic cavitations. Insufficient acoustic energy was provided to achieve proteolysis. Emulsions prepared with ultrasound treated milk protein isolate, pea protein isolate and bovine gelatin yielded smaller, stable emulsion droplets in comparison to their untreated counterparts. This behaviour is ascribed to more rapid adsorption of protein at the oil-water interface and improved interfacial packing, due to reduction in protein aggregate size. The droplet size of emulsions with sufficient emulsifier (> 0.5 wt. %) emulsion droplet size can be predicted from a mathematical relation between emulsion droplet size (d3,2) and energy density (Ev), an inverse power law. Droplet size predictions were unattainable at low emulsifier concentrations (≤ 0.5 wt. %) due to re-coalescence behaviour attributed to insufficiency of emulsifier and droplet collisions within the acoustic field. Continuous processing yields more efficient utilisation of acoustic energy in comparison to batch configurations due to the intense transmission of acoustic energy within the smaller processing volumes