Sodium Caseinate- stabilized Emulsion: A Carrier Matrix to Improve the Delivery of Epigallocatechin-gallate
Oral bioavailability of tea polyphenols may improve using food matrices as their carrier. Tea polyphenols have a high affinity to bind to proline rich proteins such as caseins. This thesis focuses on the interactions between epigallocatechin-gallate (EGCG) and sodium caseinate at an oil-water interface, the stability and colloidal behavior of the designed emulsion at neutral and low pH, as well as the emulsion digestibility, and efficiency as EGCG carrier. After addition of EGCG to a model emulsion the stability, size, and charge of the emulsion particles were not affected, and the sodium caseinate oil-water interface showed a high loading capacity for EGCG up to 1 mg/m2. Moreover an increased interfacial tension in the presence of EGGC was demonstrated which confirmed the EGCG-sodium caseinate interactions at the interface. Under acidification, the presence of EGCG at the interface lowered the pH at which emulsion destabilized, and resulted in less droplet coalescence at pH 4.5. While under acidification, sodium caseinate emulsion was stabilized by the addition of 0.3 and 0.45% high methoxyl pectin (HMP), presence of EGCG reduced the electroadsorption of HMP to the interface, affecting emulsion’s colloidal behavior and microstructure. Designed emulsions were subjected to a static in vitro digestion, simulating the three stages of human upper gastrointestinal. Results indicated that sodium caseinate was fully hydrolyzed in the the presence of EGCG, while less fatty acids were released. Futhuremore higher amount of intact EGGC in the digested emulsions containing EGCG was detected compared to equivalent EGGC solutions which suggested a preserved bioactivity for the carried EGCG in the emulsion system. This was also confirmed by digested emulsions containing EGCG showing higher anti proliferative activity than digested EGCG solutions. Intestinal absorption of EGCG after digestion was also studied using an in vitro transport experiment. Although it was quite challenging to measure the EGCG recovery after an in vitro absorption analysis, the transported fractions showed anti-proliferative activity which was an indicative of presence of EGCG or its bioactive metabolites. The findings from this thesis propose the application of an emulsion/dairy-based designed structure as a novel vehicle for improving the bioaccessibility of EGCG.