Antioxidant activity and phenolics content in “manteiga-kale” (brassica oleracea l. var. acephala) submitted to different cultivation systems and methods of preparation

Abstract

The study evaluated of cropping systems and methods of preparation on the antioxidant activity and phenolics content in leaf and kale stalks (Brassica Oleracea L. var. acephala). Kale samples were analyzed crops by organic and conventional system. The vegetable was weighed, cleaned and stems were separated from leaves. After separation were submitted to the modes of preparation: raw (fresh kale); dry heat (braised kale) and moist heat (kale immersed in boiling water). Each treatment consisted of 3 repetitions. The samples were subjected to analysis antioxidant activity and phenolics compounds by the spectrophotometric method. Identification of phenolics compounds with antioxidant activity was performed by Thin-Layer Chromatography (TLC). Organic system and the preparation in dry heat were the treatments that had the highest percentage of antioxidants and levels of phenolics compounds in leaf and kale stalks. Antioxidant activity varied from 38 and 87% in leaves and 13 and 56% in stalks. As for the phenolics compounds average levels were between 173 and 244 mg GAE / 100g in leaves and between 86 and 180 mg GAE / 100g in stalks. Analysis by TLC revealed that all extracts of leaf and kale stalks presented phenolics compounds as well as components with antioxidant activity, but not all with correlation. It follows that the combination of organic system and dry heat cooking can be effective in preserving and or increase the content of phenolics and antioxidant activity in leaf and kale stalks.