Starch stabilized Pickering emulsions : Colloidal starch particles and their effects on emulsion properties

Particles can be used to stabilize multi-phase systems known as Pickering emulsions. The aim of this thesis was to investigate how starch particles affect emulsion properties. Starch granules were used individually as well as in binary mixtures. To obtain a wide variety of starch properties granules were selected based on botanic variation (quinoa, oat, waxy barley, waxy maize and potato). The properties of the starch particles were furthermore changed by size fractionation by sedimentation, acid hydrolysis, cold gelatinization, or dissolution-precipitation, which resulted in different particle sizes and shapes. Almost all samples were modified with octenyl succinic anhydride (OSA) to 1.7%-3%. The particle size was found to be important, since decreased particle sizes lead to decreasing emulsion drop size and increased stabilization against creaming. Decreased particle size up to 89% (potato), 64% (waxy maize) and 62% (waxy barley) by acid hydrolysis, and from 15µm to 120nm (waxy maize) by dissolution-precipitation, had a strong impact on decreasing emulsion drop size. The shape also influenced the affinity for the oil/water interface. Smooth rounded particles (waxy barley <10µm) seemed to provide smaller emulsion drops than smaller/similar sizes of polyhedral particles (quinoa and oat). Starch particles from ~120nm (nanoparticles) to