Detection of Foreign Fat Adulteration of Milk Fat by Near Infrared Spectroscopic Method

A near infrared spectroscopic method for the detection of foreign fat adulteration in dairy products was examined using the extracted fats from samples of butter and margarine mixtures and from milk and soymilk mixtures. Butter and margarine mixtures were also analyzed. The near infrared absorptions at 1164, 1660, 2144, and 2176nm are due to cis unsaturation of fatty acid moieties, the ratio of which is intrinsic to each oil. We suggest that the near infrared spectra around these wavelengths could be used as a simple index for fatty acid profiles in oil. As for the original near infrared spectra, the difference of spectral data at log 1164, 1660, 2144, or 2176nm from 2124nm correlated very well with the mixing ratios. As for their second derivative spectra, spectral data at log 1164, 1660, 2144, or 2176nm correlated with the mixing ratios very well, and further, the correlation proved to be better by employing the difference between these values and those at 2124nm. The application of near infrared method to dairy products indicated that the adulteration of the fat with as little as 3% foreign fat could be detected simply, rapidly, and “nondestructively” for butter and margarine mixtures.