Validation of the Methods for the Non-milk Fat Detection in Artificially Adulterated Milk With Palm Oil

Abstract

Background Dairy products are among the most adulterated food products. Especially the milk fat can be replaced with foreign fats or oils. Because of the current high price of milk fat, it has been replaced by low-cost oils, especially those oils that have the same fatty acid profile as milk fat. This study aims to validate some classic methods (saponification number and iodine number) and the use of modern devices (gas chromatography, reverse phase high performance liquid chromatography and Fourier Transform Infrared) to detect palm oil in milk and to confirm the minimum levels of palm oil added to milk. Five treatments of fresh milk cream and an emulsion of palm oil were used to prepare different levels of palm oil in the final liquid milk. Results The results of this study showed that the values of the saponification number decreased with the increase in the percentages of added palm oil, but there was no decrease from the limits of the Egyptian standards until the addition of 25% palm oil. The iodine number is less sensitive than the saponification number in the detection of palm oil. Butyro refractometer reading is unable to detect the palm oil in milk. The fatty acid profile in milk determined by gas chromatography correlated well with the addition of palm oil. Also, there is a good relationship between the cholesterol and β-sitosterol content measured by reverse phase high performance liquid chromatography and the level of added palm oil. There was no relationship between the behavior of the spectra resulting from Fourier transform infrared spectroscopy and the presence of palm oil. Conclusions Gas Chromatography has potential to be used for the detection of palm oil in milk, the levels of some fatty acids in the milk could be used as an indicator. Also, Reverse Phase High Performance Liquid Chromatography analysis could be used for the same purpose, as the addition of palm oil caused a gradual decrease in the cholesterol percentage and increase in the β-sitosterol content of milk.