Liquid chromatographic determination of natamycin in cheese at residue levels

A high performance liquid chromatographic method, with special reference to the cleanup procedure, is described for the measurement of natamycin in cheese. Co-extracted fats and proteins are removed by cooling the methanol extract of the cheese. Amounts as low as 1 ng natamycin can be detected; the limit of determination is better than 0.05 mg/kg. Recovery at the 1 mg/kg level is better than 90%. Reproducibility at the 0.4 mg/kg level shows a coefficient of variation of 10%. Some results obtained with Dutch cheese samples from the local market are reported.