Peak Response Identification through Near-Infrared Spectroscopy Analysis on Aqueous Sucrose, Glucose, and Fructose Solution

Abstract

ABSTRACT The measurement of sugars is one of the important methodologies in determining fruits’ intrinsic quality, which can be collectively measured as soluble solids content (SSC) in the unit of oBrix. For fruits, oBrix is the summation of the grams of sucrose, glucose, fructose, vitamins, minerals, amino acids, proteins, hormones, and other soluble solids over 100 g of the particular fruit sample. Although lower range of near infrared (NIR) between 700 to 1100 nm is popularly being used in reliably determining soluble solids content of fruits, profiling of optical response of water-sugar concentration at this range of wavelength is not widely available. Thus, the purpose of this work is to optically profile water-sugar solutions and identify peak wavelengths in quantifying sugar concentration. Spectroscopic measurement in this work was conducted on the range of wavelength between 360 and 1100 nm. Wavelengths within 959–961 nm are identified as producing the highest coefficient of determination, R2, between absorbance and aqueous sugar concentration (oBrix). Combination of NIR wavelengths (, 830, 909–915, 960, and 965 nm) within C-H and O-H bands can reliably quantify individual sugars, namely sucrose (calibration: R2 = 0.992, RMSEC = 0.907; prediction: R2 = 0.985, RMSEP = 1.221), glucose (calibration: R2 = 0.998, RMSEC = 0.426; prediction: R2 = 0.997, RMSEP = 0.540), and fructose (calibration: R2 = 0.996, RMSEC = 0.617; prediction: R2 = 0.995, RMSEP = 0.631).