title: Thermal-induced changes of kale's antioxidant activity analyzed by HPLC-UV/Vis-online-TEAC detection.
abstract: Generally, boiling of vegetables is assumed leading to lower nutritional values because of leaching effects and activity loss of bioactive compounds. Kale (Brassica oleracea var. sabellica) reveals a great diversity of flavonoids, which have been shown to be good antioxidants. As Brassica vegetables are mainly consumed cooked, the influence of boiling on kale's flavonoids and their antioxidant activity was investigated. Therefore, three kale cultivars were cooked at 100°C for 2 and 4h prior to analysis. The total phenolic content (TPC) and the total antioxidant activity (TEAC assay and EPR spectrometry) of each cultivar were determined and revealed no change, independent of cooking time, although kale samples visually altered. Using the HPLC-UV/Vis-online-TEAC approach, distinct changes in composition and antioxidant activity of the flavonoids were detectable. Thus, it was observable, that the antioxidant activities of the reaction products compensated the "loss" of the antioxidant activity of the original compounds of the uncooked material.
authors: Institute of Food Technology and Food Chemistry, Technische Universität Berlin, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany.
authors: Michaela
authors: M
authors: Fiol
authors: Annika
authors: A
authors: Weckmüller
authors: Susanne
authors: S
authors: Neugart
authors: Monika
authors: M
authors: Schreiner
authors: Sascha
authors: S
authors: Rohn
authors: Angelika
authors: A
authors: Krumbein
authors: Lothar W
authors: LW
authors: Kroh
mesh_terms: D000975:Antioxidants / Q000032:analysis*; D001331:Automation; D001937:Brassica / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods; D003296:Cooking; D005419:Flavonoids / Q000032:analysis*; D006358:Hot Temperature; D010636:Phenols
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols