A rapid validation of the antioxidant capacity of food commodities based on their fluorescence excitation emission spectra as applicable to coffee and peppermint extracts

• Simultaneously antioxidant and fluorescence properties of foods were evaluated.
• PLS and N-PLS methods were used to model antioxidant properties.
• A novel calibration methodology is developed and validated.

A novel and rapid approach to screening antioxidant content is proposed. Its usefulness is illustrated for coffee and peppermint extracts. The antioxidant properties of extracts were predicted from their excitation–emission fluorescence matrices using the partial least squares and the N-way partial least squares regression. The total antioxidant capacity and the total phenolic content were estimated using oxygen radical absorbance capacity (ORAC) and Folin–Ciocalteau assays, respectively. Prediction errors of calibration models describing the total antioxidant content evaluated using the ORAC assay were equal to 448.33 (6.29%) and 647.74 (9.04%) of the Trolox equivalents for coffee and peppermint extracts, respectively. The prediction error of the total phenolic content for coffee extracts was about 0.270 (7.02%) expressed as gallic acid equivalents. The limits of detection were below 85.43 of the Trolox equivalents and 0.038 of the gallic acid equivalents, and the relative standard deviation was in a range of between 1.61% and 7.13%.