A competitive direct enzyme-linked immunosorbent assay (CD-ELISA) for histamine in cheese was compared with a reversed-phase liquid chromatography (RP-HPLC) method. Cheese was homogenized with phosphate-buffered saline (PBS), centrifuged, and filtered, and the supernatant was diluted with PBS for CD-ELISA. For RP-HPLC, biogenic amines (histamine, tyramine, putrescine, and cadaverine) were derivatized with 9-fluorenylmethylchloroformate, followed by reversed-phase chromatography and fluorescence detection. Detection limits and mean recoveries (10-1000 mg/kg) were 2 mg/kg and 93% for CD-ELISA and 1 mg/kg and 99% for RP-HPLC, respectively. Analysis of 50 commercial cheeses according to both methods showed good agreement for histamine (r = 0.979; concentration range = 2-1800 mg/kg). At a threshold level of 10 mg/kg, the ELISA gave no false-negative and three false-positive results. The results show that the ELISA is suitable for the determination of histamine in cheese.
In this study, aflatoxin M(1) (AFM(1)) contamination was investigated in Surk cheese, a traditional Turkish cheese consumed particularly in southern Turkey. For this purpose, 120 Surk cheese samples were collected from different retail markets and analysed by enzyme-linked immunoassay. The level of AFM(1) varied from 16 to 1,043 ng/kg in 72 of the Surk samples (60%), 16 of which (13.3% of 120 samples) contained AFM(1) amounts exceeding the maximum tolerance limit (250 ng/kg) established in Turkey. The results indicated that the occurrence of AFM(1) in Surk cheese samples may be considered as a possible risk for consumer health.
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