Mineral profile of raw and cooked leafy vegetables consumed in Southern Brazil

Butterhead lettuce, rucola, watercress, kale, chicory, cabbage, Chinese cabbage, and a spinach substitute (Tetragonia expansa) are widely consumed in Southern Brazil. Samples were collected five times during a year in food markets and analyzed for total potassium, sodium, calcium, magnesium, iron, manganese, copper, and zinc by flame atomic absorption spectrometry and for moisture content. All vegetables can contribute to diet in terms of potassium, calcium and magnesium. Kale offers the highest amounts of calcium (283±43 mg Ca/100 g) and Chinese cabbage, cabbage, and butterhead lettuce the lowest, with values from 33 to 58 mg Ca/100 g. The highest concentrations of magnesium were found in kale and in the spinach substitute and they were 52±4 and 55±16 mg Ca/100 g, respectively. Moisture content varied less among samples of the same vegetable than minerals did. Four of the vegetables (kale, chicory, Chinese cabbage, and cabbage) were cooked briefly during 3 min and analyzed for the same elements. The brief cooking did not cause appreciable losses for any of the minerals.