Changing Carbon Isotope Ratio of Atmospheric Carbon Dioxide: Implications for Food Authentication

Document Type


Publication Date



Carbon isotopes are often used to detect the addition of foreign sugars to foods. This technique takes advantage of the natural difference in carbon isotope ratio between C3 and C4 plants. Many foods are derived from C3 plants, but the low-cost sweeteners com and sugar cane are C4 plants. Most adulteration studies do not take into account the secular shift of the carbon isotope ratio of atmospheric carbon dioxide caused by fossil fuel burning, a shift also seen in plant tissues. As a result statistical tests and threshold values that evaluate authenticity of foods based on carbon isotope ratios may need to be corrected for changing atmospheric isotope values. Literature and new data show that the atmospheric trend in carbon isotopes is seen in a 36-year data set of maple syrup analyses (n = 246), demonstrating that published thresholds for cane or corn sugar adulteration in maple syrup (and other foods) have become progressively more lenient over time. ©2010 American Chemical Society.

Publication Title

Journal of Agricultural and Food Chemistry