Spent coffee grounds (SCGs), an abundant agro-industrial by-product, are rich in phenolics, caffeine, and melanoidins but are limited by inefficient extraction and poor stability. This study optimized microwave-assisted extraction (MAE) of SCG bioactives using response surface methodology and stabilized the extracts via spray-drying microencapsulation. The optimized MAE conditions (4 mg/mL, 77 °C, 10 min) yielded 3.3-, 1.5-, and 2.0-fold higher phenolics, caffeine and melanoidins than conventional extraction, respectively. The optimized extract was microencapsulated using maltodextrin (MD), gum arabic (GA), and their combinations with whey protein isolate (WPI) or inulin (INL). MD-based systems provided higher yields, whereas GA + WPI achieved the highest microencapsulation efficiency (87.5–99.4%). The microcapsules exhibited low moisture content (2.8–6.5%) and water activity (0.16–0.35), high solubility (74.0–88.2%), good dispersibility (71.8–91.8%), and rapid wettability (1.5–10.0 min).Structural analyses confirmed successful encapsulation via non-covalent interactions. This study demonstrates a sustainable valorization pathway transforming SCGs into stable, antioxidant-rich microcapsules for functional food applications. • Microwave-assisted extraction improved SCG phenolic and antioxidant recovery. • Spray drying stabilized SCG extracts with diverse biopolymeric wall materials. • Maltodextrin yielded higher powder recovery than gum arabic-based carriers. • GA + WPI showed >95% microencapsulation efficiency and strong antioxidant retention. • Findings highlight green innovation in functional food and nutraceuticals.
Kanha et al. (Wed,) studied this question.