Determination of nitrates in fresh vegetables and their processed products

The number of nitro compounds of the anthropogenic origin in the general nitrogen cycle is steadily increasing, which leads to an increase in nitrates in products and increases the nitrate-nitrite load on the human body. The aim of the study was to determine the amount of nitrates in raw vegetables and their processed products. Vegetables with high (beetroot, cilantro, radish, green onion), medium (zucchini, carrot, cucumber) and low nitrate content (potato, tomato, onion) have been selected as the objects of the study. For the qualitative determination of nitrates the reactions with diphenylamine have been carried out. For quantitative determination, the ionometric determination of the pH-meterionomer Ecotest 2000 has been carried out using an ion-selective electrode ECOM-NO3. In the course of the study, it has been found out that the vegetables entering the Magnit retail chain do not exceed the MPC in terms of nitrate content, with the exception of the radish and zucchini. When cooking in a microwave oven the amount of nitrates increases dramatically. When cooking vegetables «until ready», the amount of nitrates in vegetables decreases, but their amount in broths increases. With prolonged heat treatment the amount of nitrates increases both in vegetables and in the broth. When freezing and defrosting vegetables in a closed container, a decrease in nitrates is observed, and when defrosting in an open container, the level of nitrates increases sharply. Thus it is recommended not to use a microwave oven during the cooking process. During boiling first drain the water, then pour in new one and boil until ready. Ready-made vegetables should not be left in the broth due to the reverse adsorption of ions. Vegetables should be defrosted in a closed container.