TRACING THE ORIGIN OF MILK AND MILK PRODUCTS: A SIMPLIFIED PROCEDURE FOR EXTRACTION/ISOLATION OF GLYCEROL FROM WHOLE MILK AND GC-IRMS ANALYSIS

Recently the consumer demand of transparency and attention on foodstuff quality and safety is increasing, and, related to that, the need of qualified origin products on the market (1). Livestock feeding regimen, breeding conditions and growing environment are parameters that need to be traced to reveal origin, not only geographic, in order to certify quality, authenticity, and typicality of diary products. Isotope ratio analysis was demonstrated to be a suitable tool for determining the origin of food, milk and dairy products included (2). It is known that the ratio 13C/12C of animal products is correlated to animal diet since it discriminates between C3 and C4 plants (3), and in particular 13δ of glycerol has been shown to increase with maize amount (4). The possibility to trace OGM presence in the fodder can be speculated on the same hypothesis, since transgenic fodder is mainly made up of soybean, a typical C3 plant. Milk samples from pasture-fed and silagefed cows were collected from the Italian market and analyzed for 13C/12C ratio of glycerol. A sample preparation from whole milk was set up, specifically targeted for GC-IRMS analysis. First, proteins were precipitated, then fat was separated, and through saponification glycerol was released from triglycerides and then isolated from fat components such as fat acids. After derivatization the acetylated mixture was purified in HPLCUV. The purified fraction collected underwent GC-IRMS analysis. When compared to milk from silage-fed cows, milk from pasture-fed cows resulted enriched in 13C, showing a different diet regimen, rich in C4 plants, and therefore suggesting a GMO-free diet. Future developments of the present work will include the investigation of different isotope ratios and other parmeters such as fatty acids compositional profile and screening of milk for exogenous DNA presence. Finally the whole data collected will be processed with chemometric methods