Impact of Some Domestic Processing on Nitrate, Nitrite and Oxalates Contents of Selected Leafy Vegetables

The objective of this study was to identify the changes of certain hazard compounds in some leafy vegetables grown in Upper Egypt. The vegetables under investigation, which commonly consumed in Upper Egypt, were used in this study. Spinach contained the highest concentration (3837.5ppm.) of nitrate while coriander leaves had the lowest concentration (575.28ppm.). Nitrite content was higher in cabbage leaves (95.85ppm.) compared with other leafy vegetables. Spinach and chard leaves contained the highest levels of oxalate (40.11 and 42.38mg/g (DW) than other fresh vegetables. Ordinary cooking process of leafy vegetables led to a significant loss of nitrate and nitrite contents of leafy vegetables under study. The losses of nitrite content were 74.12, 35.13 and 74.12% in spinach, cabbage and green Jew’s mallow, respectively as a result of cooking process. The loss of oxalate in cooked leafy vegetables ranged between 33 and 100% of its initial values. In the cooked spinach, the loss was lowest (33%), while cabbage recorded higher loss in oxalate content reached 100% of its content in raw material. The effects of Blanching and freezing on nitrate, nitrite and oxalate contents of some selected leafy vegetables were investigated. The losses of nitrate as a result of blanching and freezing processes in leafy vegetables were: 42.3, 49.1 and 54.6% in spinach, cabbage and Jew’s mallow, respectively. From the obtained results, it can be observed that the highest loss of oxalate was in blanched frozen cabbage leaves which reaching 100%, followed Jew’s mallow by 58% and spinach by 30%.