Geographical Region-of-Origin Assignment of American Milk Using Stable Isotope Analysis

CHESSON, LESLEY A; VALENZUELA, LUCIANO O; O'GRADY, SHANNON P; CERLING, THURE E; EHLERINGER, JAMES R

Washington

Conferencia; Forensics Isotope Ratio Mass Spectrometry Conference; 2010

There is increasing demand for reliable information on the region-of-origin of foodstuffs as recent outbreaks of food borne illness have generated concern regarding the traceability of food. Stable isotope analysis may be a useful food-sourcing tool because the stable isotope ratios of hydrogen and oxygen in water vary across landscapes in predictable patterns. Animals and plants incorporate the isotopic signal of local water and the stable isotope analysis of an animal- or plant-derived food product could therefore be used to investigate the product s geographical origin. In this survey, we purchased milk from USA supermarkets and fast food restaurants and analyzed the δ2H and δ18O values of water extracted from milk. We also collected paired samples of milk and cow drinking water from dairies across the USA. We hypothesized that milk water stable isotope ratios record information on the geographic location of dairy cows. We further hypothesized that it would be possible to predict the original region-of-origin for a milk sample if we understood the relationship between cow drinking water and milk water.Measured δ2H and δ18O values for supermarket and restaurant samples spanned large isotope ranges. Restaurant samples clustered into three distinct groups, indicative of the regional distribution pattern for restaurant milk. We found the hydrogen and oxygen stable isotope ratios of paired cow drinking water and milk samples were significantly related. Using the equation that described the relationship between cow drinking water and milk water, we calculated predicted cow drinking water δ2H and δ18O values for samples in the three restaurant sample groups. From this survey, we have demonstrated the feasibility of geographical origin assignment using the stable isotope analysis of milk.