Alimentos e Nutrição Araraquara, Vol. 14, No 1 (2003)

Tamanho da fonte:  Menor  Médio  Maior

A fractionation study of mineral elements in raw and cooked leaf vegetables consumed in Southern Brazil

L. M. KAWASHIMA, L. M. V. SOARES

Resumo


Five samplings of leaf vegetables widely consumed in Southern Brazil (lettuce, rucola, watercress, kale, chicory, Chinese cabbage, and cabbage) were taken during the period of a year in food markets of the city of Campinas, Brazil. A selective extraction of potassium, sodium, calcium, magnesium, iron, manganese, copper, and zinc was conducted on the raw vegetables and four of the vegetables (kale, chicory, Chinese cabbage, and cabbage) were also cooked briefly under dry heat for three minutes and submitted to the selective extraction. The extraction separated the minerals into fractions containing mineral elements bound to soluble complexes, bound to ligands solubilized by mild acidic oxidizing conditions, and bound to insoluble ligands under mild acidic oxidizing conditions. The minerals concentrations in each fraction were determined by flame atomic absorption spectrometry. The amount of K, Na, Ca, and Mg extractable at pH 7.0 (soluble fraction) from raw vegetables varied between 22 to 75 % of the total content of the mineral present. The soluble fractions of minor elements such as Mn, Zn, and Fe varied from 0 to 100% in the raw vegetables. The brief cooking used besides causing negligible losses of the minerals also increased the solubility of the minerals by 44% to 200%.

KEYWORDS: Leaf vegetables; soluble mineral elements in vegetables.


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