Green extraction of bioactive compounds from Coffea arabica sidestreams with aqueous deep eutectic solvent and their application in mayonnaise as antioxidant agents

Coffee processing generates large quantities of sidestreams that are often underutilized despite their high levels of bioactive compounds. This study investigated the application of antioxidant compounds from four Coffea arabica sidestreams: (i) skin & pulp , (ii) husk , (iii) silverskin , and (iv) parchment in mayonnaise using microwave-assisted extraction combined with glycerol–water aqueous deep eutectic solvent. Among the three tested solvent systems, 61.3% (v/v) glycerol–water yielded the highest total phenolic content, as evidenced by the skin & pulp (16.5 mg GAE/g) and husk (15.2 mg GAE/g). Chlorogenic acids, particularly 5-CQA, were the dominant phenolics extracted (0.07–2.3 mg/g), while the caffeine content ranged from 5.3 to 13.6 mg/g across sidestreams. Antioxidant activity followed the order: skin & pulp > husk > silverskin > parchment , and was strongly correlated with phenolic content (R 2 of 0.8–0.9). Additionally, incorporation of the aqueous deep eutectic solvent extracts into mayonnaise significantly improved its oxidative stability. Peroxide and p-anisidine values were markedly reduced ( p < 0.001), with phenolics extracted from 1.5% skin & pulp using an aqueous deep eutectic solvent showing the lowest oxidation levels. Color parameters were affected by extract pigmentation, while pH remained within safe limits (4.3–4.4). Textural properties, including hardness, adhesiveness, cohesiveness, and elasticity, were largely unaffected by the addition of the extract. Overall, this study demonstrates that coffee sidestream extracts obtained via green deep eutectic solvent extraction can serve as effective natural antioxidants in emulsion systems.