DETERMINATION OF AFLATOXIN M1 LEVEL IN MILK AND SOME DAIRY PRODUCTS

The present study was carried out in the laboratory of agricultural microbiology Department, faculty of agriculture, Zagazig University, Egypt, in summer and winter seasons 2013 and 2014. In order to study the aflatoxin M1 (AFM1) contamination in milk, kareish cheese and yoghurt.   AFMI was detected in raw milk in only 10 out of 12 samples (83.3%) in each season. Winter season had higher AFMI concentration than summer season with the mean values of 311.8 and 207.0 ng/l, respectively. AFMI was detected in all samples of kareish cheese (24 samples) in summer as well as in winter season. Winter season had higher AFMI concentration than summer season with average values of 651.36 and 527.40 ng/kg, respectively. The present results observed that 83.33% of cheese sample examined exceeding the limits of EU (50 ng/kg), and (70.83%) of cheese samples examined exceeding the limits of codex (500 ng/kg) in both summer and winter seasons. In yoghurt, the AFMI did not detect in 3 out of 12 samples of yoghurt tested. In summer season the positive samples ranged from 31.46 to 66.05 ng/kg with average of 39.13 ng/kg. AFMI did not detect in only one out of 12 samples tested in winter season. Also, the positive samples ranged from 56.6 to 84.14 ng/kg with an average of 64.68 ng/kg. Cheese had a higher concentration of AFMI than both raw milk and yoghurt. Also, yoghurt had the lowest concentration of AFMI comparing to raw milk and cheese. Heating treatments reduced the concentrations of AFMI in all raw milk samples tested. Boiling caused 26.71% degradion of AFMI, whereas pasteurization caused only 15.45% degredation. In yoghurt, two strains of probiotic bacteria (lactobacillus acidophilus and Bifidobacterium lactis) individually were gradually reduced the concentration of AFMI in contaminated milk with 25 ppt, as a function of time with complete elimination by the end of storage period (3 days) at refrigerator, while the cocktail of the two strains showed more ability for reducing AFMI. Both probiotic bacteria (L. acidophilus and B. lactis) showed more ability for reducing AFMI in contaminated milk with 50.0 ppt or 75 ppt.The most important reductions of AFMI concentration were 41.80 ppt (45.3%), 2.6 ppt (69.90%) and 7.12 ppt (92.8%) which achieved by using the same concentration individually of each strain and in combination, respectively, in contaminated milk with 75ppt after two days. No AFMI was detected using combined strains after three days.