Figure 1. Absorption coefficients for various sugars and sweeteners extracted from THz transmittance measurement.

Absorption coefficients at THz frequencies for (a) D-glucose (C₆H₁₂O₆), (b) fructose (C₆H₁₂O₆), (c) sucrose (C₁₂H₂₂O₁₁), and (d) cellulose ((C₆H₁₀O₅)_n) pellets. The insets in (a–d) show the structural formulas of each saccharide. Distinguishable absorption features appear at 1.4 THz for D-glucose, 1.7 THz and 2.1 THz for fructose, and 1.4 THz and 1.8 THz for sucrose, as marked by red arrows; however, cellulose has no special spectral features. (e) Colour contour plots of THz fingerprinting for ten different saccharides and two non-saccharide sweeteners. White and black dashed circles denote the specific frequencies of interest.