Determination of total phenolic content and antioxidant capacity of blueberries using Fourier transformed infrared (FT-IR) spectroscopy and Raman spectroscopy

This study investigated the feasibility of using Fourier-transform infrared (FT-IR) and Raman spectroscopies to quantify total phenolic content and antioxidant capacity of blueberries. Blueberry extracts were applied to determine total phenolic content (Folin–Ciocalteu assay) and antioxidant capacity [oxygen radical absorbance capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH)], while pressed juices were used for spectroscopic analysis. Six partial least squares regression models with cross-validation were developed using FT-IR and Raman spectra of blueberries from 11 locations and their corresponding chemical testing values, followed by prediction tests using samples from another five locations. FT-IR prediction models show relatively good prediction power for ORAC, DPPH, and Folin–Ciocalteu values (R2-prediction = 0.6359, 0.6580, and 0.8092; RMSE-prediction = 6.19 and 0.71 µmol trolox equivalents/g fresh weight, and 0.14 µg GAE/g fresh weight), but Raman prediction models did not yield a satisfactory result. FT-IR spectroscopy may be used to rapidly determine blueberry antioxidants.