Horseradish (Armoracia rusticana L.) Processing By-Products as Potential Functional Ingredients in Food Production: A Detailed Insight into Phytochemical Composition and Antioxidant Properties

Horseradish (Armoracia rusticana L.) root (HRP) and leaf (HLP) pomaces, by-products of juice production by cold-pressing, were analyzed as a novel potential source of natural antioxidants. Chromatography analysis (UHPLC Q-ToF MS) of the bioactive compounds of pomaces was performed along with spectrophotometric determination of total phenolic content (TPC), total flavonoid content (TFC), total phenolic acid (hydroxycinnamic) content (TPAC), and antioxidant capacity (via 1,1-diphenyl-2-picrylhydrazyl (DPPH•) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic-acid) (ABTS•+) radicals’ scavenging activity and ferric reducing antioxidant power (FRAP)). The concentrations of TPC, TFC, and TPAC differed among the pomaces, significantly favoring HLP. However, both horseradish pomaces (HRP and HLP) contained a considerable amount of various phenolics, with kaempferol and its glucosides dominating. In addition, they exhibit pronounced antioxidant activity, which is confirmed by all three methods used (DPPH, ABTS, and FRAP). These results highlight the potential of valorizing horseradish processing waste as a natural, reliable source of health-promoting bioactive compounds and functional ingredients in food products, thereby fortifying food, preventing oxidation, and prolonging shelf-life. In addition, this study supports endeavors to reduce food waste by providing new insights into the valorization of horseradish pomace, thus contributing to sustainable development and environmental protection.