Determination of organic milk authenticity using carbon and nitrogen natural isotopes

Natural stable isotopes of carbon and nitrogen (12C, 13C, 14N, 15N) have abundances unique to each living creature. Therefore, measurement of the stable isotope ratio of carbon and nitrogen (δ13C = 13C/12C, δ15N = 15N/14N) in milk provides a reliable method to determine organic milk (OM) authenticity. In the present study, the mean δ13C value of OM was higher than that of conventional milk (CM), whereas the mean δ15N value of OM was lower than that of CM; nonetheless both δ13C and δ15N values were statistically different for the OM and CM (P < 0.05). Furthermore, the values of δ13C and δ15N were found to differ statistically with the collection date and the milk brand (P < 0.05). The combination of δ13C and δ15N values was more effective than either value alone in distinguishing between OM and CM. The results of the present study, which is based on preliminary data from a limited sample size and sampling period, could be highly valuable and helpful for consumers, the food industry, and/or government regulatory agencies as it can prevent fraudulent labelling of organic food. Further studies include additional analyses of other milk brands and analyses over longer time periods in order to accurately determine OM authenticity using stable isotopes of carbon and nitrogen.