qNMR as a Tool for Determination of Six Common Sugars in Foods

Nuclear magnetic resonance (NMR) spectroscopy is capable of quantifying molecules. The term so called quantitative NMR (qNMR), has been used for determination of the concentration and purity of small molecules. Carbohydrates are found in various beverages and dietary foods, including crops, milk, fruits, and vegetables. Commercial products frequently use “added sugar” in soft drinks, cookies, candies, and foods. The added sugar in beverages can be sucrose, high-fructose corn syrup (HFCS) and glucose. Here, we report a quantitative method to measure 6 common sugar ingredients in foods from a single one-dimensional 1H-NMR and by using naphthimidazole (NAIM) derived sugars, which are chemically tagging aldoses with 2,3-naphthalenediamine (NADA) at the reducing ends to assist assignment of sugars. The aldoses in native sugars contain α and β anomeric isomers, and may have overlapping signals in 1H-NMR spectra. In contrast, both the anomeric isomers can be converted into a single sugar-NAIM derivative, which resolves the problem of overlapping signals to simplify the NMR quantitative analysis. This NAIM method is especially useful for identification and quantification of multiple kinds of sugars in beverages and foods. This study is to facilitate the quantification of six common sugars in beverages and foods. Our results suggest that a simple treatment of beverage and food with the NAIM labeling method provides a more extensive success rate for the quantification of sugar ingredients.

Keywords: Beverage, Food, Fructose, Galactose, Glucose, Lactose, Maltose, Naphthimidazole (NAIM), q-NMR, Quantitative analysis, Sugar, Sucrose, 1HNMR spectrometry.