2022 Volume 21 Issue 4 Pages 491-499
Attenuated total reflection (ATR)-Micro electro mechanical systems (MEMS)-infrared (IR) spectroscopy was applied to determine total free sugar content in fresh juice of fruit, with only one independent variable without direct water subtraction. The reference values of the total free sugar content were determined using high-performance liquid chromatography (HPLC). After the spectra of tomato and strawberry juice samples (n = 21 and 11, respectively) were measured, smoothing of ATR-MEMS-IR spectra was processed, and each calibration was generated using absorbance at 1032 cm–1 and 1000 cm–1 with a correlation coefficient of 0.98 and 0.98, respectively. The sugars of tomatoes were mainly glucose and fructose, and those of strawberries were sucrose, glucose, and fructose, and these results corresponded to the absorption of sucrose occurring at a lower wavenumber than those of glucose and fructose. These calibrations predicted other sample lots. Nevertheless, they were predicted well with a root mean square error (RMSE) of 0.22 (n = 13) and 0.46 g/100 mL (n = 13), respectively. Moreover, Bland-Altman plots were within limits of agreement (LOA). Water solutions of sucrose, glucose, and fructose also showed high correlation coefficients (1.0) between the concentration and absorbance at these wavenumbers with high sensitivity.
