Detection of added beet or cane sugar in maple syrup by the site-specific deuterium nuclear magnetic resonance (SNIF-NMR (R)) method: Collaborative study

Results of a collaborative study are reported for the detection of added be et or cane sugar in maple syrup by the site-specific natural isotope fracti onation-nuclear magnetic resonance (SNIF-NMR (R)) method. The method is bas ed on the fact that the deuterium content at specific positions of the suga r molecules is different in maple syrup from that in beet or cane sugar. Th e syrup is diluted with pure water and fermented; the alcohol is distilled with a quantitative yield and analyzed with a high-field NMR spectrometer f itted with a deuterium probe and fluorine lock. The proportion of ethanol m olecules monodeuterated at the methyl site is recorded. This parameter (D/H )(1) is decreased when beet sugar is added and increased when cane sugar is added to the maple syrup. The precision of the method for measuring (D/H), was found to be in good agreement with the values already published for th e application of this method to fruit juice concentrates (AOAC Official Met hod 995.17). An excellent correlation was found between the percentage of a dded beet sugar and the (D/H), isotopic ratio measured in this collaborativ e study. Consequently, all samples in which exogenous sugars were added wer e found to have a (D/H), isotopic ratio significantly different from the no rmal value for an authentic maple syrup. By extension of what is known abou t plants having the C-4 cycle, the method can be applied to corn sweeteners as well as to cane sugar. One limitation of the method is its reduced sens itivity when applied to specific blends of beet and cane sugars or corn swe eteners. In such case, the C13 ratio measurement (see AOAC Official Method 984.23, Corn Syrup and Cane Sugar in Maple Syrup) may be used in conjunctio n.