A study of proteins, minerals and heavy metals present in green vegetables growth in Dar es Salaam.

This Dissertation reports on crude proteins, moisture, dry matter, mineral elements and heavy metals present in ten varieties of green vegetables grown in Dar es Salaam, Tanzania. The crude proteins were determined by Macro-Kjeldahl method. The crude protein content- of the green vegetables examined in this study ranged from 1.03 to 5.38% fresh weight and from 14.90 to 31.76% dry weight. Dar es Salaam vegetables contained high levels of crude protein when compared to the levels reported by FAO. The crude protein contents on a dry weight basis were comparatively similar to those found in most seeds of legumes of Tanzania, but higher than those reported for cereal grains grown in Tanzania. The results suggest that the green vegetables may be used as important sources of dietary protein. The moisture contents of the vegetables were in the range from 77.5 to 95.0% fresh weight. The dry matter ranged from 5.0 to 22.5% fresh weight. The high moisture contents of these vegetables indicate low energy values. As suggested by various authors such vegetables may be useful for the treatment of obesity. In all vegetables examined from Kariakoo market and those from cultivated sites along Sinza and Msimbazi rivers, potassium was predominant. The levels of potassium, sodium, magnesium and calcium compared well with the Recommended Dietary Daily Allowance (RDDA) and FAO values. There would be no deficiency of these mineral elements in the diet if people would use these vegetables daily in their meals. The levels of heavy metals present in the vegetables varied widely among the vegetables and from site to site. Vegetables from Msimbazi showed high levels of nearly all heavy metals studied except for cadmium and lead. Iron was in high concentration in all vegetables with the exception of pumpkin leaves which had an average values of 9.72 mg/ 100 g dry weight. In general, the vegetables coming from Mikindu showed relatively very low concentrations of most of the heavy metals as compared to those from Buguruni, Sinza and Msimbazi. All metals reported in this study were determined using a dry washing method followed by atomic absorption spectrophotometry technique.