Stability of Chokeberry Bioactive Polyphenols during Juice Processing and Stabilization of a Polyphenol-Rich Material from the By-Product

Chokeberries (Aronia melanocarpa) are nowadays believed to exhibit potential cardioprotective and antidiabetic effects principally due to their high content in bioactive phenolic compounds. The stability of the phenolic compounds was studied during different stages of a juice production line and a method for the valorization of pomace was evaluated. Samples were taken from a commercial juice production plant, extracted and analyzed for phenolic constituents and antioxidant potential. Prototypes of functional food ingredients were produced from the pomace by wet milling and micro-milling. Alongside juice processing, the contents of phenolic berry constituents did not vary to a great extent and the overall antioxidant activity increased by about 34%. A high quality juice and a by-product still rich in polyphenols resulted from the process. The phenolic compounds content and the overall antioxidant activity remained stable when milling and micro-milling the pomace. During coarse milling, extractability of total phenolic compounds increased significantly (40% to 50%). Nanosized materials with averaged particle sizes (x_50,0) of about 90 nm were obtained by micro-milling. These materials showed significantly enhanced extractability of total phenolic compounds (25%) and total phenolic acid (30%), as well as antioxidant activity (35%), with unchanged contents of total procyanidins and anthocyanins contents.