CHEMICAL POLLUTION OF MILK AND CHEESE WITH NITRATES AND NITRITES AND ITS HYGIENIC SIGNIFICANCE

Two hunderd random samples of milk and cheese were collected from different supermarkets at Alex. Province for spectrophotometric determination of the levels of nitrates and nitrites. The data indicated that the mean values of nitrates in raw and pasteurized milk samples were found to be 3.9 + 1.3 and 4.8 + 2.7 mg/kg, respectively while the average values in milk powder and condensed milk samples were 87.3 + 7.3 & 94.6 + 6.4 mg/kg respectively. Meanwhile the nitrates concentrations in soft cheese, full cream, processed and hard cheese were 62.5 + 4.8, 71.20 + 9.6, 29.20 + 9.6, 29.20 † 5.9 & 17.81 + 3.8 mg/kg respectively. The mean values of nitrites in milk powder and condensed milk samples were found to be 1.30 + 0.2 & 1.02 + 0.1 mg/kg respectively. While they were not detected in raw and pasteurized milk samples. However the nitrites concentrations in soft cheese, full cream, processed and hard cheese samples were 0.90 + 0.4, 1.1 + 0.6, 0.51 + 0.3 & 2.92 + 0.7 mg/kg respectively. The results were evaluated according to STEPHNY et al. (1978) and BERTELSEN (1979). The obtained data indicated that high concentration of nitrates and nitrites in some types of milk and cheese samples may favour nitrosamines formation which constitutes a hazard for human health. Thus the use of such preservative in milk and cheese must be strictly controlled to prevent the possible formation of the carcinogenic nitrosamines.