Vegetables, including spinach (Spinacia oleracea, L.), constitute the major source of nitrate providing 72-94% of the average daily human dietary intake. The presence of nitrate in vegetables is a serious threat to manzs health, not so much due to its toxicity, which is low, but for the dangerous compounds it originates in the organism (methaemoglobin and nitrosamines). Nitrate concentration, during spinach cultivation, is influenced by the mineral N fertilization, weather conditions, season and regional differences. Remarkable differences have been observed between the leaf petiole and blade in nitrate (4062 vs 925 mg/kg of fresh mass). The content of nitrite in spinach is low, but high contents have been found, probably due to improper storage conditions during transportation (the activity of nitrate reductase in spinach leaves). The aim of this study was to determine the nitrates and nitrites content (using spectrophotometric method) in samples of frozen and fresh spinach of different producers purchased from market and changes in their content after cooking and preparing the meal, after keeping it for 4 hours at room temperature (24degreesC) and after 24 hours storage in the refrigerator (4degreesC) with additional heating to consuming temperature. Results showed that nitrite content in fresh spinach was in the range from 0.26 to 25.90 mg/kg and in frozen spinach from 0.26 to 3.46 mg/kg. Nitrate content in fresh spinach was in the range from 95.79 to 415.08 mg/kg and in frozen spinach from 93.53 to 2208.39 mg/kg. In both species of the investigated samples, after cooking (preparing a meal), 4 and 24 hours storage with additional heating to consuming temperature, nitrite content was increased while nitrate content was decreased.
