title: Composition and antioxidant activity of kale (Brassica oleracea L. var. acephala) raw and cooked.
abstract: BACKGROUND
  Cabbage vegetables, like Brassica group, are perceived as very valuable food products. They have a very good nutritive value, high antioxidant activity and pro-healthy potential. Especially, kale (Brassica oleracea L. var. acephala) is characterized by good nutritional and pro-healthy properties, but this vegetable is not popular in Poland. The aim of this work was to assess the chemical composition and antioxidant activity of kale variety Winterbor F(1) and investigation of cooking process on selected characteristics.
  
  
  METHODS
  The chemical composition and antioxidant activity were determined in leaves of kale Winterbor F(1) variety after three subsequent years of growing. In one season, analyses were performed on raw and cooked leaves.
  
  
  RESULTS
  The investigated kale was characterized by high average contents of: β-carotene (6.40 mg/100 g f.m.), vitamin C (62.27 mg/100 g f.m.), alimentary fiber (8.39 g/100 g f.m.) and ash (2.11 g/100 g f.m.). The average amounts of nitrites (III) and (V) were 3.36 mg NaNO(2)/kg f.m. and 1206.4 mg NaNO(3)/kg f.m., respectively. The investigated kale contained polyphenolic compounds at average level of 574.9 mg of chlorogenic acid/100 g f.m., and its antioxidant activity measured as ABTS radical scavenging ability was 33.22 μM Trolox/g of fresh vegetable. It was observed a significant lowering of antioxidant compounds as a result of cooking. The losses of vitamin C were at about 89%, polyphenols at the level of 56%, in calculation on dry mass of the product. The highest stability was shown in the case of beta-carotene, for which the losses were at about 5%. Antioxidant activity of cooked vegetable lowered and reached the level of 38%. There were also some losses observed in macro-components from 13% for zinc to 47% for sodium. The contents of harmful nitrites and nitrates in calculation on dry mass were significantly lower as a result of cooking, by 67% and 78%, respectively.
  
  
  CONCLUSIONS
  Winterbor F(1) variety of kale has a great nutritive value and high antioxidant activity. The cooking process of kale resulted in lowering of the antioxidant activity of its antioxidants especially of vitamin C, polyphenols and to the lesser extent of β-carotene what confirms that vegetable should be eaten in raw form or just undergo little processing before consumption, for example blanching.
authors: Department of Human Nutrition, University of Agriculture in Krakow, Balicka 122, 30-149 Cracow, Poland. rresikor@cyf-kr.edu.pl
authors: Elżbieta
authors: E
authors: Sikora
authors: Izabela
authors: I
authors: Bodziarczyk
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000032:analysis; D001205:Ascorbic Acid / Q000032:analysis; D001937:Brassica / Q000737:chemistry*; D003296:Cooking; D004043:Dietary Fiber / Q000032:analysis; D006358:Hot Temperature / Q000009:adverse effects*; D018977:Micronutrients / Q000032:analysis; D009566:Nitrates / Q000032:analysis; D009753:Nutritive Value; D018515:Plant Leaves / Q000737:chemistry*; D059808:Polyphenols / Q000032:analysis; D019207:beta Carotene / Q000032:analysis
chemical_list: D000975:Antioxidants; D004043:Dietary Fiber; D018977:Micronutrients; D009566:Nitrates; D059808:Polyphenols; D019207:beta Carotene; D001205:Ascorbic Acid