Nitrate-nitrite, Vitamin C and in-vitro methemoglobin formation from some vegetables
The content of nitrate, nitrite and Vitamin C in eleven samples of fresh vegetables were determined. The levels of nitrate were beyond 300 ppm recommended in six of the vegetables, namely, Celisia sp, Lactuca saliva, Amaranthus hybrids, Brassica oleracea variety acephala, Talinum sp, Spinacia oleracea. Minute quantities of nitrite were detected in Celosia so and Daucus carrots. With a accompanying high concentration of Vitamin C (a reducing agebt) present in Celodia so, this vegetable may be a potential source of nitrite in foods. Effects of cooking caused less than 25% reduction in nutrate-nitrite content of the vegetables. When in vitro testing methemoglobin formation was carried out with extract from the samples, modified haemoglobin formed paralleled content of nitrate in the vegetables. It is suggested that caution must be exercised in the use of some of these vegetables in infant foods as they may contribute to the induction of methemoglobin.