High pressure processing of carrot juice: Effect of static and multi-pulsed pressure on the polyphenolic profile, oxidoreductases activity and colour.

The aim of this study was to determine the influence of static and multi-pulsed hydrostatic pressure processing (HPP) treatments on the polyphenolic profile, oxidoreductase activity, colour, and browning index of carrot juice. Phenolic acids, flavonoids, lignans and other polyphenols were the predominant polyphenols detected with Triple-TOF-LC-MS/MS. The highest concentration of ferulic acid, didymin, dihydro-p-coumaric acid, sesaminol and matairesinol isomers were found among all the compounds detected. After HPP treatment, irrespective of the pressures applied, new simple polyphenols like oleuropein, 4-vinylsyringol, isocoumarin, and 4-hydroxybenzaldehyde were detected. Both phenomena could be attributed to the release of bounded phenolic compounds after applying HPP, as well as enzymatic degradation and/or condensation. The highest inactivation of polyphenoloxidase (PPO) enzymes (57%) was obtained at 300 MPa × 3 pulses, and peroxidase (POD) enzymes (31%) at 600 MPa working in static mode. Significant changes in the colour parameters and browning index were observed in all HPP-treated juices.