Abstract
The stabilization of bioactive compounds remains a central challenge in the development of functional foods. Many naturally derived bioactives, such as unsaturated oils, polyphenols, and carotenoids, are highly susceptible to oxidation, photodegradation, and often exhibit poor stability during processing and storage. Conventional encapsulation methods, while widely used, typically require high processing temperatures, extended drying times, or chemical cross-linkers, which limit their suitability for thermolabile compounds and clean-label formulations. Among the emerging alternatives, supercritical carbon dioxide (SC-CO₂)-based techniques, particularly the Particles from Gas-Saturated Solutions (PGSS) process, offer a solvent-free, mild, and scalable route for encapsulating sensitive bioactives. This thesis investigates the use of PGSS to produce stable functional ingredients from plant-based bioactives, including underutilized by-products. The first study examined the encapsulation of oils recovered from olive stones under varying pressures, nozzle diameters, and oil-to-wall ratios. The resulting microparticles were characterized in terms of morphology, encapsulation efficiency, and oxidative stability, demonstrating the feasibility of converting agri-food by-products into functional microparticles suitable for food and cosmetic applications. Building on this, the second study focused on the development of a co-encapsulation strategy to enhance the stability of highly unsaturated oils. Sequential extraction of Citrus aurantium flowers yielded apolar and polar antioxidant fractions, which were incorporated with linseed oil into PGSS microparticles. Isothermal calorimetry showed that the addition of natural antioxidants significantly prolonged oil oxidative stability, highlighting the complementary protective roles of antioxidant incorporation and encapsulation. The final study addressed the encapsulation of a curcumin-rich turmeric extract to improve photostability. The effect of processing pressure was examined on microparticle properties and curcumin retention, yielding powders with enhanced resistance to photo-degradation. Incorporation of these microparticles into mayonnaise as a model food system enhanced oxidative stability without compromising product quality, confirming both the technological feasibility and functional relevance of this approach. Overall, this research highlights the potential of PGSS as an effective encapsulation technology for stabilizing diverse bioactives and valorizing underutilized plant by-products. By integrating green extraction techniques with SC-CO₂ encapsulation, the thesis outlines sustainable approaches toward clean-label, and functionally enhanced food products.