Spectrometric and liquid chromatographic determination of natamycin in cheese and cheese rind

Methods for determining natamycin content of cheese rind and cheese are presented. Cheese and rind samples are extracted with methanol and the fat precipitated by cooling the sample solution in methanol-water at -15 to -20 degrees C for ca 1 h. Natamycin levels are measured by UV spectrometric detection at absorbance minimum 311 nm, maximum 317 nm, and at exactly 329 nm, or by LC separation over Lichrosorb RP-8 column with detection at 303 nm. For measuring low levels, a concentration step is provided. The method is applicable to natamycin in cheese rind and in the interior of the cheese. Detection limit is 0.5 mg/kg. The method is suitable for controlling a maximum tolerance of natamycin on the cheese rind, at a level of 1 mg/dm2, and for detecting migration of natamycin into the cheese.