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Comparison of gas chromatography and near infrared spectroscopy for determination of butter adulteration

Milk and dairy products are more often the target in order to achieve greater financial gain. Butter is dairy product and the only fat that it contains is milk fat. However, milk fat is one of the most expensive edible fats on the market and is often replaced with cheaper oils and fats of plant or animal origin, the share of which is not stated on the declaration. Preventing the appearance of products on the market that do not comply with the legislation is one of the key challenges in the area of food safety. The aim of this study was to compare the effectiveness of the two techniques, time-consuming gas chromatography and near infrareded (NIR) spectroscopy in detecting the presence of a foreign fat in milk fat in order to provide faster and better system of quality control and correct labeling of butter. Calibration samples with known butter proportions of 0 ; 0.5 ; 1 ; 2 ; 5 ; 10 ; 25 ; 50 ; 75 and 100 % (v/v) of added margarine or pork fat (lard) were prepared, also samples of butter and margarine sampled from retail trade network randomly were analyzed. The application of chemometric techniques enabled the qualitative separation of butter samples as a grouping of butter depending on whether the added butter or pork fat (lard). Also, there was possible quantitative validation and therefore the prediction of the share of added margarine or pork fat, based on the NIR spectrum. In the qualitative analysis of the samples the principal component analysis method (PCA) was used, while the partial least square regression method (PLSR) was applied for the quantitative prediction. The spectra were also associated with the content of PUFA and the following fatty acids: C12:0 ; C18:1n9 and C18:2n6 which showed linear trend changes depending on the added share of margarine or fat. On the basis of analysis detection of butter adulteration obtained by NIR spectroscopy and chemometric methods, it can be concluded that the applied methods in comparison with gas chromatography have great potential in monitoring the quality of butter control and its adulteration with other types of fat. NIR spectroscopy has proved to be a suitable technique for the rapid determination of butter adulteration, and may be applied in rapid "screening" control of correctness labeling which might shorten the time and reduce the cost of butter inspection analysis.

Butter labelling ; Chemometry ; Fatty acids ; Milk fat ; PUFA

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