GC-IRMS analysis to detect the use of genetically modified feed in milk production.

Verifying the description of food in terms of its composition, processing or origin is challenging, but the consumers need clear and accurate information to make informed choices about their diet and the foods they buy. The problem of genetically modified organism (GMO) safety is an open question and for which the public opinion has a particular sensitivity and concern. Even if the current European standards allow the use of authorized GMOs only, it should be stressed that is mandatory to label their presence just above 0.9%, while there is no obligation to inform the consumer about their use in the production process. It follows that the consumer may be informed of the presence of GMOs in food only when it exceeds the threshold value of 0.9%, while being completely unaware if animal products were obtained by feeding the animals with even 100% GMOs. Analytical techniques based on the measurement of stable isotope ratio mass spectrometry (IRMS) were demonstrated to be a powerful tools for determining the both the geographic origin and the production system of food, milk and dairy products included. In particular, the ratio 13C/12C of animal products is able to discriminate between a diet based on C3 or C4 plants , and 13δ of glycerol has been shown to increase with maize amount. 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, largely used in conventional zootechny. Conventional and organic (GMO free) milk samples 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. When compared to conventional milk, organic milk resulted in an enrichment in 13C (P < 0.02), showing a different diet regimen, rich in C4 plants, and therefore suggesting a GMO-free diet. These encouraging results can be combined with data deriving from the investigation of different isotope ratios, to assess also the geographical origin of the milk (e.g. no EU countries, with different GM regulations) and screening of milk for transgenic DNA presence.