FTIR spectra of pure sugars, S. bicolor juice, and the PLS model calibration set. FTIR spectral fingerprint region collected from: (A) pure sucrose, glucose, fructose, and H2O; and (B) S. bicolor juice containing low, medium, and high concentrations of sugars and a low and high mixture of pure sucrose, glucose, and fructose against a H2O background. (C) Set of 216 samples consisting of varying mixtures of sucrose, glucose, and fructose making up the calibration set. Wavenumbers between 1,190 to 850 cm-1 were plotted. X-axis represents spectral wavenumber (cm-1) and y-axis units are arbitrary. FTIR, Fourier transform infrared; PLS, partial least squares.