The leaves of lettuce are very reach source of vitamins, macro and microelements and biologically active compounds. However, these plants contain also anti-nutritional compounds as nitrates and nitrites which levels depend on growth and storage conditions. The aim of this study was to determine the effect of foliar application of CaCl₂ treatment before harvest on nitrate and nitrite accumulation, in whole leaves and leaf blades in fresh and stored lettuce. The experimental material was lettuce cv. Omega which was grown in greenhouse. The solution of CaCl₂ was used in the concentration of 0.1M and 0.2M on plants, 20 and 10 days before harvest. After harvest, some plants were directly analysed, while the remaining plants were cold-stored at 4ºC for 7 and 14 days in dark polyethylene bags. The higher concentrations of nitrate and nitrite was noticed in fresh whole leaves than in leaf blades. The foliar CaCl₂ treatment of plants before harvest contributed to a statistically decrease in the nitrate levels and nitrite increase in whole leaves in fresh plants. The greatest changes were noticed after using of 0.1M CaCl₂ solution on plants. During the storage time of lettuce in the non-treatment plants were observed the higher concentration of nitrates and nitrites in leaf blades compared to fresh plants. The CaCl₂ treatment on lettuce caused a significant decrease in the nitrite concentration of whole leaves of plants stored for 7 days, while in the leaf blades higher nitrite amounts were accumulated in lettuce which was stored in cold conditions during all experimental time.

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