The mineral and trace element composition of vegetables, pulses and cereals of southern India
T. S. Srikumar*
Department of Applied Nutrition and Food Chemistry, Chemical Center, University of Lund, Lund, Sweden (Received 4 March 1992; revised version received and accepted 28 April 1992)
Some cereals, pulses and vegetables commonly used in vegetarian dietsin southern India were analysed for their content of minerals and trace elements. The contents of zinc, iron, manganese and potassium were higher in wheat than in rice and different pulses. Wheat, rice and pulses contained higher concentrations of zinc, copper, magnesium, selenium, calcium and iron than did vegetables. The concentrations of lead, cadmium and mercury were higher in wheat and ricethan in pulses; among the vegetables amaranth leaves had much higher concentrations of these elements. Compared to other vegetables (raw plantain, brinjal, amaranth leaves), lady's finger contained higher concentrations of zinc, copper, magnesium, calcium and selenium. The estimates of daily intake of zinc and calcium seemed to be inadequate while those of copper, magnesium, selenium, manganeseand iron were apparently sufficient; estimates of lead and mercury were below the tolerable daily intake level but that of cadmium was above. INTRODUCTION The high content of fibre and phytate in vegetarian diets may inhibit the intestinal absorption of certain minerals and trace elements (Freeland-Graves et al., 1980); moreover, animal foods are better sources of selenium in several countries (Varo& Koivistoinen, 1980). In view of this a number of studies investigating the effects of vegetarian diets on mineral and trace element status have been reported (Gibson et al., 1983; Freeland-Graves, 1980). In a recent study (Srikumar et al., 1992b) it was found that the vegetarian diet of southern Indians maintained adequate magnesium, copper, selenium and maybe also zinc status, and that haircontents of lead, cadmium and mercury were higher than values reported from several European countries. The aim of the present study was to determine the contents of elements in the major food items used in the same vegetarian diet regime of southern Indians and to estimate the daily intake. M A T E R I A L S AND M E T H O D S purchased from six different local markets in southern India during thespring of 1988 and were identified by a botanist (Table 1). Visible contaminants were handpicked from the food samples. Wheat, rice and pulse samples were then washed 3 times with distilled water and finally rinsed twice with deionised water in an acidwashed glass beaker and dried at room temperature for at least 3 days. The samples were powdered in a high speed mill which was coated inside withTiO2. After each milling, the inside of the mill was washed with distilled water followed by de-ionised water. The leaves from amaranth plants were hand-picked, and the non-edible parts of lady's finger, raw plantain and brinjal were removed using a plastic knife. The edible portions of vegetables were washed and dried as described above. Homogenisation of vegetable samples was done using alaboratory homogenizer (Ultra Turrax, Janke & Kunkel, Staufen, Germany). A representative portion (approx. 5 g) of the powdered or homogenised food sample was used for moisture and ash determinations. The vegetable samples (approx. 1 kg) were then lyophilized and stored in a desiccator for further analysis. Moisture and ash were assayed according to the AOAC methods 14004 and 14006, respectively (AOAC,1984).
Sample collection and handling
Some 15 kg each of three cereals, three pulses and four vegetables, all commonly used in vegetarian diets, were * To whom correspondence should be addressed, at: Department of Applied Nutrition and Food Chemistry, Chemical Center, PO Box 124, S-221 00 Lund, Sweden Food Chemistry 0308-8146/93/$05.00 © 1992 Elsevier Science Publishers Ltd, England. Printed...