Quantification of phenolics and antioxidant properties in dried grape pomace by near infrared spectroscopy

This study evaluated the potential of near-infrared (NIR) spectroscopy, combined with partial least squares regression (PLSR) to quantify bioactive properties in dried grape pomace powders. Twenty-four samples of red-pink and purple-black grapes were examined for total monomeric anthocyanins, phenolics, flavonoids, proanthocyanidins, and antioxidant capacity utilizing CUPRAC (cupric reducing antioxidant capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl) assays. Chemical analyses verified higher phenolic and antioxidant contents in purple-black pomace than red-pink. PLSR models from NIR spectra produced promising results, showing strong calibration and cross-validation for all analytes. These outcomes indicate that NIR spectroscopy provides a simple, nondestructive, and eco-friendly alternative to conventional wet chemistry methods. Moreover, the approach offers potential for monitoring bioactive compounds in grape pomace, thereby supporting the valorization of agro-industrial residues as sustainable sources of phenolics and antioxidants for food, nutraceutical, and cosmetic applications.