Microencapsulation of purple tea polyphenols using the vibrating nozzle ionotropic gelation technology: metabolomics, bioactivity, and application in milky tea

No research has been completed on the microencapsulation of purple tea extracts or on the use of such extracts in food models. Considering the worldwide importance of C. sinensis teas, this work aims to optimise the extraction of antioxidant polyphenols from purple tea leaves using a sustainable, green, ultrasonic-assisted extraction, and to design milky teas added with microcapsules produced by the vibrating nozzle ionotropic gelation method. A combination of 28 min, 495 W ultrasound power, and 50% ethanol were the ideal experimental conditions for obtaining the optimal extract (OPM). OPM displayed antioxidant activity and inhibited α-glucosidase (IC50 = 23.0 ± 0.3 μg/mL) and α-amylase (IC50 = 12.4 ± 0.9 mg/mL) in vitro. In human erythrocytes, OPM showed an in vitro antihaemolytic effect and decreased reactive oxygen species generation in a concentration-dependent manner. Also, OPM exhibited a protective effect against H2O2-treated astrocytes at 0.1 and 0.2 mg/mL. The microencapsulation of OPM extract resulting in a high encapsulation efficiency (84%), and milky teas added with OPM and microencapsulated OPM had higher antioxidant activity than the conventional counterpart.