Plant/dairy protein complexes have emerged as promising natural emulsifiers to mitigate sustainability and health issues. Improving the protein functionality by using the plant/dairy protein complexes enables their uses as emulsifiers and carriers for bioactive compounds in the form of emulsions and powders, showing potential applications to beverages, and delivery systems in the food industry. This PhD project aimed to design plant/dairy protein complexes for encapsulation of lipophilic bioactive compounds in food. Pea and whey proteins were selected as representative commercial plant and dairy proteins. Firstly, sodium alginate addition was found to enhance the stability of pea/whey protein-stabilised emulsions by promoting protein adsorption at oil/water interface and preventing pea proteins from being displaced by whey proteins. As a second step, enzymatic cross-linking between pea and whey proteins was attempted, demonstrating the modified structure of the pea/whey protein complexes upon cross-linking formed more stable emulsions and retarded the chemical degradation of β-carotene compared to non cross-linked protein complexes. Following this work, the structural changes of the pea/whey protein complexes subject to enzymatic cross-linking were analysed using microfluidic modulation spectroscopy (MMS), revealing the increase of β-sheet and random coil contents with cross-linking led to forming more stable emulsions due to amphiphilicity. Lastly, the surface composition of spray dried β-carotene microcapsules using pea/whey protein complexes was investigated using synchrotron infrared microspectroscopy, showing that the protein cross-linking and maltodextrin addition contributed to protecting β-carotene from degradation by reducing its amount on the surface. Overall, polysaccharide addition and enzymatic cross-linking enhanced the emulsifying and encapsulation properties of the pea/whey protein complexes. These processing techniques altered protein structures with the increase of β-sheet content and the exposure of buried hydrophobic sites of the proteins due to the formation of covalent and non-covalent bonds such as disulphide linkage, isopeptide interaction, and hydrogen bonding between heteroproteins. The thesis demonstrates the potential usefulness of pea/whey protein complexes to encapsulate lipophilic bioactive compounds with prospective applications in the emulsion-based food products and powder production.