RAPID SEMIQUANTITATIVE FLUOROMETRIC-DETERMINATION OF CITRININ IN FUNGAL CULTURES ISOLATED FROM CHEESE AND CHEESE FACTORIES

A new rapid semi-quantitative fluorimetric assay for citrinin producti on testing in mould cultures has been developed. The chemical structur e of the citrinin makes it a weak native fluorophore. This fluorescenc e can be strongly enhanced in an acidic environment. A standard curve where the concentration of HCl needed to show the yellow fluorescence signal of different concentrations of citrinin was established, thus p roviding a semi-quantitative method to prove the capacity of toxin pro duction of fungal cultures. Two Penicillium strains from the Spanish N ational Collection of Type Cultures, were studied for the toxin produc tion on YES broth at 25 degrees C for 21 d. The culture was assayed da ily for the presence/absence and quantification of citrinin by adding the HCl concentration set, and also quantified by RP-HPLC as a confirm ation procedure. Experiments demonstrate that 5 d are necessary to sho w the presence of citrinin. As an illustration, a total of 48 strains of Penicillium isolated from cheese and cheese factories were analysed with the proposed method.