Microencapsulation protects oxidation-sensitive oils by embedding them in a solid matrix, creating a barrier against environmental oxygen. Despite this separation, oxidation can still occur due to two sources of oxygen: internal and external. Internal oxygen is present in the spray-dried powder, while external oxygen comes from the surrounding environment. To explore the causes of oxidation in these systems, the thesis is divided into three parts. Part I examines the contributions of internal and external oxygen by preparing feed emulsions and final powders under various conditions, including atmospheric and inert environments, and storing them under vacuum. Part II investigates the role of non-encapsulated oil, which remains in contact with the powder surface and is exposed to external oxygen, potentially increasing oxidation. Part III analyzes how powder properties—such as particle size, oil droplet size, and oil load—affect the reaction between external oxygen and encapsulated oil. Additionally, a theoretical simulation based on Fickian diffusion models oxygen diffusion into the particle, while the reaction kinetics of the oil are studied to connect hydroperoxide formation rates to oxygen levels. Comparing experimental and calculated data enhances the understanding of the physical protection mechanisms at play.
