Bioaccessibility and antioxidant activity of PCL-microencapsulated olive leaves polyphenols and its application in yoghurt

Polycaprolactone (PCL)was used via double emulsion/solvent evaporation technique for the encapsulation of polyphenols olive leaves (OLs) extracts. In this study, the PCL-microcapsules loaded with OLs polyphenols extract powder were characterized by scanning electron microscopy and fourier transform infrared spectrometry analysis. Their total phenolic (TPC), total flavonoid (TFC) contents, and antioxidant activities (DPPH, FRAP, and ABTS), and polyphenols stability were measured after oral, gastric, and intestinal steps of in vitro digestion. PCL-microcapsules were utilized in formulating novel functional yogurt containing 0, 25, 50, and 75 mg of TPC estimated as mg GAE (added as PCL-microcapsules) per 100g yogurt. All yogurt samples were evaluated for their pH, acidity, syneresis, viscosity, and color during storage. In vitro digestion significantly affected the phenolic composition in non-encapsulated extract whereas it had a lower impact on encapsulated phenolics. Higher protection was provided for encapsulated OLs extract and their higher release was observed at the intestinal phase. Unlike the undigested OLs extract, which had a TPC of 490 mg GAE/100 g, lower values of TPC (136 and 289 mg GAE/100 g) were obtained for non-encapsulated and encapsulated OLs extract, respectively, in the intestinal fluids. Yogurt with PCL-microcapsules had lower viscosity, syneresis, and color parameters, compared to control yogurt. Thus, OLs represent a valuable and cheap source of polyphenols that can be successfully applied in microencapsulated form, in formulating functional yogurt.