Horseradish ( Armoracia rusticana L.) Leaf Pomace: From By‐Product to Novel Natural Antioxidant in Mayonnaise Production

ABSTRACT The global issue of organic waste accumulation and disposal could be addressed by using it as functional ingredients, enhancing the food nutritional profile or storage stability, and replacing the technological functions of food additives. Horseradish leaf pomace (HLP), a residual product of cold‐pressing horseradish leaves for juice production, was evaluated as a potential novel natural antioxidant for mayonnaise preservation. Before being added to mayonnaise, HLP was dried using a mild, nutrient‐preserving, high‐quality‐producing freeze‐drying technique and characterized by physicochemical, spectrophotometric, and chromatographic analysis. The use of lyophilized HLP in mayonnaise formulation as a potential antioxidant was investigated by analyzing mayonnaise quality and oxidative stability during storage. Low moisture content (6.36%), water activity (0.30), and hygroscopicity (12.02%) of HLP were achieved by lyophilization. Untargeted UHPLC Q‐ToF‐MS analysis revealed various phenolic compounds in lyophilized HLP, especially kaempferol glycosides, as well as sinigrin as the only detected glucosinolate, confirmed by comparison with a reference standard. Quantitative and semi‐quantitative analyses showed a predominance of tentatively identified hydroxybenzoic acid, phenolic acid glycosides, kaempferol 3‐ O ‐(2″‐ O ‐pentosyl)hexoside, and sinigrin in lyophilized HLP. Other investigated glucosinolates were not detected, which may indicate degradation during processing. Spectrophotometric assays showed a considerable amount of total phenolics and flavonoids in lyophilized HLP, along with promising radical scavenging capacity and reducing ability. The favorable physicochemical properties of lyophilized HLP and its diverse phenolics contributed to the mayonnaise quality retention during long‐term storage, as shown by the peroxide value, p ‐anisidine value, total oxidation value, pH, and acidity. Accelerated oxidative stability analysis showed that lyophilized HLP demonstrated comparable efficacy to the synthetic antioxidant in delaying mayonnaise oxidation under the tested conditions. Valorizing horseradish processing residue in the formulation of innovative food products can provide significant benefits, protecting the environment and supporting sustainable development by maintaining the oxidative stability of mayonnaise, substituting synthetic antioxidants, and preventing agricultural and food‐deterioration waste generation.