Terahertz spectral characterization and quantitative analysis of sugar substitutes in a chocolate matrix

Sugar substitutes are increasingly used in food products to reduce caloric content and mitigate glycemic impact. However, reliable analytical methods for their identification and characterization remain limited, especially in complex food matrices. In this study, terahertz time-domain spectroscopy (THz-TDS) was used to characterize ten representative sweeteners-acesulfame-K, aspartame, D-maltitol, D-sorbitol, D-xylose, mannitol, saccharin, sucralose, stevioside, and xylitol-over 0.5-2.5 THz. Most compounds exhibited distinct absorption features, providing compound-specific spectral fingerprints. Based on independently reported glycemic index (GI) values, the sweeteners were further organized into GI = 0 and GI > 0 groups for an exploratory comparison of their THz spectral characteristics. To evaluate applicability in a complex food matrix, sucralose, stevioside, and mannitol were incorporated into sugar-free dark chocolate at concentrations of 5-25 wt%. The concentration-dependent changes in absorption coefficient were closely associated with the refractive index differences between each sweetener and the chocolate matrix, with coefficients of determination ranging from approximately 0.94 to 0.99 at selected frequencies. These results demonstrate the potential of THz-TDS as a non-destructive, label-free technique for the characterization and quantification of sugar substitutes in processed foods. This approach offers a promising analytical tool for food quality control and compositional assessment.