Effect of industrial juice concentrate processing on phenolic profile and antioxidant capacity of black carrots

Summary: Black carrot concentrate has gained increasing interest in recent years as a natural colourant due to its substantial content of bioactive compounds, especially anthocyanins. Black carrot concentrate production includes several steps, some of which are milling, mashing, pressing, pasteurisation and concentration. In this study, every step of black carrot concentrate processing was investigated to elucidate both the quantitative and qualitative changes in antioxidative compounds using spectrophotometric, HPLC-based and LC-QTOF-MS-based analyses. The results obtained indicated that processing the raw black carrot material into its concentrate led to an overall reduction of 70%, 73% and 44% in total phenolic, total flavonoid and total monomeric anthocyanin contents on a dry weight basis, respectively. Moreover, concentrate processing resulted in 67% and 71% decreases in total antioxidant capacity, determined using DPPH and CUPRAC methods, respectively, on dry weight basis. Untargeted LC-MS-based metabolomics analysis enabled the identification of ten phenolic components including seven anthocyanins and three phenolic acids. HPLC-based quantification of individual anthocyanins revealed cyanidin-3-xylosyl (feruloylglucosyl)galactoside as the major anthocyanin component.