No abstract

In the literature several contradictionary results have been published on the aflatoxin formation at temperatures below 10 degrees C. Therefore experiments with pastes made from milk and cheese powder artificially contaminated with Aspergillus parasiticus, were performed at temperatures of 1 degree C, 5 degrees C, and 10 degrees C for 28 days at a relative humidity of 90--95%. Even at 1 degree C, the aflatoxins B1, B2, G1, G2, and M1 could be determined quantitatively. The lactose content did not have a significant influence on the aflatoxin values. Even storage of cheese (camembert and cottage cheese) in a 10% salt solution did not inhibit aflatoxin formation at 20 degrees C.

Due to the greatly differing incidence of molds on cheese and thus the extremely differing amounts of aflatoxin reliable sampling in cheeses is difficult, particularly if only one semi-hard of hard cheese is available. Experiments were undertaken now to sample--hopefully without losses and suitable for commercial application--in order to be able to ascertain the possible aflatoxin content of a cheese. Based on storage results with artificially contaminated Provolone and Tilsit cheeses as a pretest determination of aflatoxins in scrapings from a 100 cm2 surface are is recommended. At high levels (20-30 microgram/kg) the sampling of several borings at different locations on the cheese is necessary. The aflatoxin content on the surface is not constant, a fact which can be explained by biochemical reactions and by migration of aflatoxins into deeper layers. Washing of cheeses seems not to be of any significant influence on the aflatoxin-content.

No abstract

Between May 10 and August 9 1976, a total of 197 commercial cheese samples were tested on their aflatoxin M1 content; 136 samples (69%) were positive. The highest value was at 0.23 mug/kg, the average value of all positive samples was at 0.09 mug/kg. In more than half of the positive samples (54%), only traces of aflatoxin M1 could be detected, 21% contained up to 0.1 mug/kg and 14% more than 0.1 mug/kg. In soft cheese definitely less aflatoxin was found (57% positive samples) than in other cheese varieties (83--85% positive samples). Supplemental feeding of concentrates during spring season and pasture grazing of dairy cows resulted in more respectively less aflatoxin-positive cheese samples. This was especially true in soft cheese. The other cheeses with longer ripening periods showed the same effect, however, less pronounced with a clear lag phase. Inspite of many positive identity reactions on aflatoxin M1, a routine control of cheeses so far cannot be recommended because of the negative results on mass spectrometry.