Food traceability is of utmost importance for the safety of the American public and quality of the American food industry. Recently, the Food and Drug Administration recalled hundreds of items containing peanuts due to a potential Salmonella contamination. The number of recalled items is growing due to difficulty in tracing the origin of the contamination and the destination of contaminated food products. The recall’s scope highlights the complexity of food distribution in the USA. Stable isotope analysis may aid in investigations of contamination by providing information on the region-of-origin of food products. Like peanuts, dairy is a nutritive component in many food items. The ability to determine region-of-origin of dairy products and dairy additives is an indispensable tool in today’s complex food industry.
We purchased milk from 30 outlets of a single fast food restaurant located in 17 states of the USA. Water extracted from each milk sample was analyzed for its stable isotope ratios (see figure, below). Included in the figure is the Global Meteoric Water Line, an average representation of the relationship between δ2H and δ18O values in water collected globally. We observed three distinct groups within the data. The lowest δ2H and δ18O values were measured from milk collected in interior Western states (e.g. NV, UT, WY) where the low drinking water values have been previously measured. The highest δ2H and δ18O values were measured from milk collected in TX and the East Coast, where drinking water values are similarly high. These preliminary data demonstrate a link between purchase location and the isotopic composition of milk water, suggesting it may be possible to source milk based on δ2H and δ18O values.
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| The relationship between the hydrogen and oxygen stable isotope ratios of water extracted from milk. The global meteoric water line (GMWL) is also shown |
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| Using the relationships shown at the left, we can produce maps and from this identify the origins for unknown milk samples. |
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