Rapid spectrophotometric method for analyzing natamycin in cheese and cheese rind.

A rapid spectrophotometric method for determining natamycin in cheese and cheese rind has been developed. Samples are homogenized with acidified aqueous acetonitrile and homogenates are filtered. Natamycin is directly quantitated in filtered extracts on the basis of the characteristic third-derivative trough at 322.6 nm. Additional cleanup of extracts is not required because derivative transformation of the conventional analytical band at around 319 nm eliminates spectral interferences from other compounds. The analysis is simple and can be completed in 6 min. The equipment is easily accessible because most modern spectrophotometers allow instant generation of derivative spectra. The method needs small amounts of solvents and has good analytical characteristics. Overall recovery was 98.4 +/- 0.7%, and linearity was excellent (r = 0.9998) in the range examined (0.5-20 mg/kg). Quantitation and detection-limits were estimated at 0.5 and 0.25 mg/kg, respectively. Precision statistics based on within-day and between-days variations suggest an overall relative standard deviation of 1.4%.