Effect of microwave heating on the near infrared spectra and on the prediction accuracy of chemical parameters in red grape homogenates

This study reports the effect of microwaving on the chemical composition [pH, total soluble solids (TSS), dry matter (DM) and total anthocyanins extraction], and the visible (VIS) and (NIR) spectra of red grape homogenates. It was observed that microwaving red grape homogenates prior to analysis improved the NIR calibrations for total anthocyanins (SECV: 0.21-0.13 mg g ^-1) and TSS (SECV: 0.89-0.54 °Brix), however no improvements in the NIR calibrations for DM were observed. Microwaving red grape samples prior to NIR scanning also caused an increased in absorbance for samples heated for up to 3 min, particularly in those wavelengths associated with water (1400 nm and 1930 nm). The practical implication of this study is that microwaving of red grape samples prior to scanning did not improve the NIR calibration statistics for the most common chemical parameters measured in red grapes.