A Straightforward Method for Disaccharide Characterization from Transverse Relaxometry Using Low-Field Time-Domain Nuclear Magnetic Resonance

Abstract

The necessity of identifying and quantifying sugars in food processing is endless for maintaining food quality attributes such as color, taste, texture, monitoring regulatory compliance, labeling packages, and maintaining authenticity. Despite available analytical methods for characterizing sugar molecules, the limitations of conventional methods drive researchers to seek more convenient alternatives. This study aimed to characterize common disaccharides such as sucrose, lactose, maltose, and trehalose using a time domain nuclear magnetic resonance (TD-NMR), facilitating a quick, cost-effective, and user-friendly approach. In this experiment, transverse relaxation distribution curve was analyzed for characterizing disaccharides. Two peaks, referred to as the main and secondary peak(s), were observed for all the disaccharides, while a single peak (the main peak) was observed for pure water. Although they have similar molecular formulas and weights, lactose exhibited the longest relaxation time for the secondary peak, followed by trehalose, sucrose, and maltose. This behavior was assumed due to the interaction of sugar molecules with water. The increasing concentration of disaccharide in the solution displayed the leftward shifting of peaks. Maltose showed two secondary peaks, which were not observed in other sugar samples. The NMR showed potential to distinguish disaccharides from unknown powders and solutions by analyzing either the relaxation time of the secondary peak or the ratio of the secondary to the total peak. Moreover, quantification is possible from the standard curves of relaxation time and the combined peak area of the main and secondary peaks with the corresponding sugar concentration. However, it shows challenges in discrimination between α- and β-isomers.