Residual Nitrate in potato tuber samples collected from fields (important production areas) and the main frout and vegetables supply center of Tehran

Nitrate is an ion which is part of the nitrogen cycle, and is considered as an approved food additive. It plays an important role in the nutrition and other plant functions. Exceeded amounts of absorbed nitrogen can accumulate in plant organisms as nitrate (NO3). It is one of important harmful compounds that can accumulate in plants edible portion. It normally comes from assimilated nitrate that have not been changed to amino acids. Misusing of fertilizers, especially over using of nitrogen fertilizers can lead to nitrate accumulation in plant tissues. Human exposure to nitrate is mainly exogenous through the consumption of vegetables, and to a lesser extent water and other foods. Nitrate changes to nitrite and then to nitrosamine which is a carcinogen compound, in digestion system of human and animal bodies. Potato is an important agricultural product in Iran and it is important to undrestand the nitrate pollution risk in this crop. Potato tuber samples were collected from the main Fruit and Vegetables Supply Center of Tehran once a week, from May 2008 to May 2009. On the other hands Potato samples were collected directly from different farms in 9 most potato producing regions, Esfahan, Charmahal, Hamadan, East-Azarbaijan, Ardabil, Tehran, Khozestan, Fars and Kerman (Jiroft and Kahnoj). Nitrate content in edible part and water content of fresh potato tubers were determined in all 341 samples in the central laboratory of Soil and Water Research Institute of Iran in Karaj. Results showed that nitrate content in potato tubers ranges from 10.2 mg Kg FW-1, to 524 mg Kg FW-1 with a mean of 163.5 mg Kg FW-1, which was in accordance with world normal range. Assuming 200 mg Kg FW-1 as the acceptable nitrate limit in potato tubers, it exceeded from this level in about 30% of tuber samples. Results showed that harvest season could affect Nitrate content in potato tuber. Mean Nitrate content in potato tubers which have been taken from Fruit and Vegetables Supply Center of Tehran during spring-summer was 216.55 mg Kg FW-1 and for samples have been taken during autumn-winter was 131.53mg Kg FW-1. Keywords: Nitrate residue – Potato - Fruit and Vegetables Supply Center of Tehran - Potato producing regions