Abstract:

Milk and dairy products are frequently included as important components of a healthy diet and are widely consumed by the majority of the human population. Addition of vegetable oils in milk and dairy products is an old and illegal practice that has become increasingly common and complex. The motivation for milk adulteration is economic, as well as the fluctuation in seasonal availability of sheep and goats’ milk. Adulteration of milk and dairy products reduces their quality and might be dangerous for human health. Fatty acid composition of milk fat has been used for a long time as a criterion to detect adulteration with vegetable oils, mainly because milk fat is characterized by short-chain fatty acids, whereas vegetable oils have medium to long-chain fatty acids. Based on this knowledge, the aim of this study was development and validation of GC-FID method for detection of vegetable oils in dairy products according to fatty acid composition. FAMEmix standard solution (C4:0-C24:0) was used for identification of individual fatty acids. For detection and quantification of vegetable oils in dairy products the following reference materials were used: butter fat, palm and coconut oil. The linearity of the calibration curves of fatty acid standards showed high correlation coefficients (R2=0.9845-0.9999). The LOD was from 0.02-0.04 mg/ml and LOQ was from 0.1-0.3 mg/ml. Precision was assessed by determining the coefficient of variation (CV, %) of the areas obtained from the injection of six replicates of the standard solutions and reference materials. The CV was in the range from 0.35-1.91% for standard solution, 0.73-6.50% for butter fat, 0.51-8.19% for palm oil and 0.76-2.16% for coconut oil. The recovery of the method was from 78.93-113.52%. From 60 analysed dairy products samples, purchased from the local market, vegetable oils were detected in 23 samples. Palm oil was detected in 21 samples, and coconut oil was detected in 2 samples. High concentration of C16:0, C18:1n9c and C18:2n6c were found in samples which contain palm oil. Moreover, in the samples which contain coconut oil the content of C12:0 and C14:0 was increased. The results from this study provide valuable information for the consumers and for future studies in this area.