Abstract
In recent years, the demand for nutritive, functional and healthy foods has increased. This trend directed the food industry to investigate novel technologies that enable to produce ingredients with enhanced functional and physicochemical properties. Encapsulation is a strategy to entrap active ingredients within a carrier material. In food formulation, it is common to entrap sensitive bioactives like antioxidants, vitamins or unsaturated oils into a shell made of food grade polymers. The result is an ingredient, usually with enhanced storage stability, increased bioavailability, superior protection against environmental factors, such as light, temperature and humidity or chemical impacts by oxygen and pH-changes. Depending on the bioactive and the final application, every encapsulation technology has its advantages and disadvantages. Among those, encapsulation techniques based on supercritical fluids are one of the most promising, due to their mild processing conditions and the possible absence of organic solvent and oxygen. This PhD project aimed to investigate novel encapsulation techniques for food-grade bioactive formulations. Accordingly, a supercritical carbon dioxide (SC-CO2) based encapsulation technique, called Particle from Gas-Saturated Solution (PGSS) was used to encapsulate bioactive compounds into different food-grade wall materials. Besides the process optimization, also a comparison with spray chilling, another solvent free technology, was performed to identify major differences in physical-chemical properties, oxidative stability, and bioactive release of the generated microcapsules. Also, a detailed characterization of the extracted and encapsulated bioactives and their decay products was carried out. Furthermore, the influence of the pure PGSS encapsulation process on the degradation of the bioactive was assessed. The results showed the efficiency and strengths of the PGGS process, by highlighting the high encapsulation efficiency and the mild process conditions of the technique. The comparison of the two encapsulation techniques revealed the importance of process conditions and resulted in a deeper understanding of possible practical applications. Regarding the evaluation of the final ingredients, it was demonstrated that the isothermal calorimetry is an appropriate technique to monitor directly and continuously the oxidation of PGSS microparticles. Finally, a clear understanding of the oxidative stability of the bioactives and their degradation products was achieved.