Influence of technical processing units on polyphenols and antioxidant capacity of carrot (Daucus carrot L.) juice

The effect of three processing units (blanching, enzyme liquefaction, and pasteurisation) on polyphenols and antioxidant activity of carrot juices was investigated. Polyphenols and antioxidant activity of carrot juices varied with different processes. Five polyphenolic acids were identified in fresh carrot juice, and the predominant compound was chlorogenic acid. Compared with fresh carrot juice, blanching and enzyme liquefaction could result in the increase of the total polyphenol content (TPC) and the antioxidant activity in scavenging DPPH free radicals (DPPH) and Fe2+-chelating capacity (FC), whereas pasteurisation could result in the decrease of the TPC and the antioxidant activity in DPPH and FC. Meanwhile blanching, enzyme liquefaction, and pasteurisation showed little influence on the antioxidant activity in lipid peroxidation protection. The antioxidant activities in DPPH and FC increased with increasing concentration while no correlation between lipid peroxidation protection and polyphenols concentration. Polyphenols still retained high antioxidant activity after the processes, which have potential health benefits for consumers.