RESEARCH IN INTRODUCTORY STABLE ISOTOPES: DETERMINING THE SOURCE OF CARBON DIOXIDE AND ORGANIC CARBON IN SELECT CARBONATED BEVERAGES USING STABLE CARBON ISOTOPES
The sources of CO2 from the δ13C analysis included combustion of methane (δ13C = -44 to -41‰), petroleum hydrocarbon/coal (δ13C = -35 to -33‰), corn fermentation (δ13C = -11 to -7‰) and limestone acidification (δ13C = -3 to -1‰). Different beverage manufacturers and even the same manufacturer used more than one source of CO2 for carbonation. The δ13C of organic carbon showed that high fructose corn syrup, cane sugar, aspartame, sucralose and stevia have similar carbon isotopic values (δ13C = -12 to -10‰) which corresponded to the δ13C of the bulk organic carbon of 72% of the beverages. Beverages with δ13C of the bulk organic carbon that were different from that of the sweeteners can be explained by the addition of “secret” ingredients; ingredients not listed in the labeling. The conclusion of the study was that the stable isotopes of carbon is useful in determining the origin of CO2 used for beverage carbonation and for the bulk composition of carbon in carbonated beverages. Students discussed aspects related to cost of producing/capture of CO2 and how proximity to source affected ingredients use in regional markets. Students experienced firsthand how to use stable isotopes in problem solving. This type of research can lead to new faculty research and can be combined with other student work into a refereed paper.