Nitrate and nitrite in leek and spinach from Urmia district and their changes as affected by boiling

Aims: This study was carried out to determine nitrite and nitrate levels in fresh leek and spinach from different greengrocers' shops of Urmia (Iran) and then the effect of boiling and the effect of aqueous boiling pH were studied. Materials and Methods: Nitrite and nitrate content of 15 market samples of leek and spinach from Urmia region were determined by spectrophotometric method. Effect of boiling and their pH levels at home processing condition were studied. Results: Results showed that the fresh vegetables had only traces of nitrite and the level of nitrate was 36-328 ppm KNO ₃ . In the most of samples, nitrite and nitrate contents in spinach were greater than in leek, but lower than standard International Organization for Standardization levels in Iran. Boiling process was carried out, according to home conditions and it caused a decrease in nitrate levels between 23% and 61% in leak and spinach samples, respectively. T-test analysis of the boiled vegetables showed a significant reduction about 75% in nitrate content (in dry weight vegetable content), in the samples, but an increase in nitrate content in the boiled water of the sample was observed. The effect pH of boiling (4-8) shows that with an increase in pH, there was a decrease in nitrate contents of boiled water. Conclusion: The experiment showed that the leek and spinach marketed in Urmia region were safe for consumption and boiling of vegetables caused the release of nitrates from vegetables to water after the cooking process. It is of particular importance not to use the vegetable cooking water for use in pureeing homemade baby foods.