Effects of Blueberry and Black Carrot Extracts Addition on Antioxidant Properties and Protein-Precipitating Capacity of Ultrasound-Treated Cider

The results presented in this study highlight the level of total phenolic content (TPC), total flavonoid content (TFC) and protein-precipitating capacity (PPC) correlated with the antioxidant capacity of new cider varieties enriched with valuable bio compounds by the addition of blueberry and black carrot extracts. The cider variants were treated with ultrasound (constant frequency of 20 kHz) at 20%, 30% and 40% amplitude (A) for two, five or seven minutes. TPC determination was performed by Folin–Ciocâlteu method and TFC was determined by an aluminum chloride colorimetric method. The antioxidant capacity was determined by ferric-reducing antioxidant power assay (FRAP), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The results showed that the antioxidant performance indicators (FRAP, ABTS and DPPH) were positively correlated with the TPC and TFC of the ultrasound-treated cider variants, suggesting that the content of these bio compounds may be improved by the treatments applied. The highest mean values for TPC and TFC were found in the cider variant enriched with black carrot extract (0.3%, v/v), subsequently ultrasound-treated (A20%, five minutes) Conclusively, the extracts used in this study could improve the antioxidant capacity of the cider, especially in case of variants ultrasound-treated.