STERIGMATOCYSTIN - INCIDENCE, FATE AND PRODUCTION BY ASPERGILLUS VERSICOLOR IN RAS CHEESE

The occurrence, distribution, and stability of sterigmatocystin (STG) in Ras cheese were investigated. An incidence value for STG in marker samples of Ras cheese was 35% with a mean value of 22.2 mu g/kg. In ex perimental Ras cheese from milk contaminated with STG, 80% of the toxi n was retained in the curd while 20% was found in the whey. The temper ature for cheese ripening affected the toxin content. At 6 degrees C t he toxin concentration was hardly affected, but at 20 degrees C the co ncentration was reduced by 16% after 90 days. In Ras cheese contaminat ed with spores of Aspergillus versi-color, toxin production started af ter 45 days of the ripening, reached a maximum after 90 days, and decl ined thereafter. Cow's milk favoured toxin formation in comparison wit h buffaloe's milk. Aged cheese (more than 6 months) inhibited toxin pr oduction.