[The content of nitrates and nitrites in fruits, vegetables and other foodstuffs]

There are presented the results of the investigation of many popular fresh and frozen vegetables as well as in fresh and frozen fruits, such as different kind of apples, strawberries, currants, raspberries and many other tender fruits mainly from market and few from own allotment-cottages performed in the year 1989-1992. The nitrate and nitrite was determined according to the Griess reaction. High levels of nitrate was encountered in lettuce, frozen spinach, fennel, radishes, parsley. Many of this samples contained more than 1000 mg of KNO3/kg of fresh product, but the highest level, over the 3500 mg/kg was found in lettuce. The remaining vegetables like carrots, celery, leeks and frozen French bean contained from several dozen to more than 800 mg KNO3/kg. The level of nitrite in all samples of the investigated vegetables and fruits was very low from zero to decimal part of milligram per kg. Very low level of nitrate was found in 7 species of investigated apples (from 1.3 to 9.7 mg KNO3/kg). A little higher level of this compound was ascertained in currants, gooseberries, raspberries, cherries (from 0.0 to 36.0 mg KNO3/kg product). The highest levels of nitrate occurred in samples of strawberries (maximum to 322.3 mg KNO3/kg) but mean level amounted 58.7 mg KNO3/kg. The encountered levels of nitrate in frozen vegetables and fruits as well as in jams and stewed fruits was only little less than in fresh products. Very high level (from 355.30 to 584.53 mg KNO3/kg) was ascertained in the fruit-vegetable juice named "Rinberen" and "Malberen" to which red beet extract was used for their production. It should be pointed out that when the containers of these juice was opened and stored at the room temperature (+20 degrees C) during 30 days, no changes was observed in the level of nitrate and nitrite. In the juice prepared from blanched carrot, the rate of the reduction of nitrate to nitrite has not been lowered, when this product was storage of this juice at room temperature, the mean level of nitrite increased significantly (from 0.14 to 82.89 mg NaNO2/kg) and the level of nitrate lowered from 261.0 to 46.4 mg KNO3/kg. It should be strongly recommended for consumption the juices from carrot only fresh prepared. There are also presented the results of investigation of nitrate in fermented cheeses.(ABSTRACT TRUNCATED AT 400 WORDS)