Red cabbage anthocyanin-rich natural colorant: Optimization of ultrasound-assisted extraction, microencapsulation, bioaccessibility, and functional yogurt development

Anthocyanins from red cabbage (Brassica oleracea var. capitata f. rubra) are promising natural pigments with notable health benefits, but their thermal and gastrointestinal instability limits functional food applications. This study employed ultrasound-assisted extraction (UAE) and spray-drying microencapsulation to enhance their stability, bioaccessibility, and functionality. Optimization using a Box-Behnken design (pH 3.0-5.0, 30-60 °C, 20-90 min, 0.025-0.05 g/mL solid-liquid ratio) identified optimal UAE conditions (pH 3.5, 45 °C, 55 min, 0.0375 g/mL), yielding 125.72 ± 0.83 mg/L anthocyanins. Freeze drying retained the highest anthocyanin content (129.02 ± 3.36 mg/L), while spray-drying with 10 % maltodextrin achieved excellent encapsulation efficiency (96.36 ± 0.80 %) and yield (99.40 %). FTIR confirmed the presence of phenolic groups, and SEM revealed spherical microcapsules (∼10.27 µm) with smooth surfaces. Encapsulation significantly improved thermal stability at 70 °C, reducing the degradation rate constant (0.00043 min^-1) and increasing half-life (1919.02 min), compared to non-encapsulated samples. During simulated digestion, bioaccessibility of encapsulated anthocyanins was lower in the oral (53.28 %) and intestinal (25.37 %) phases than free forms, but stability was enhanced. Antioxidant activity (DPPH: 66.90 %, ABTS: 71.76 %) and enzyme inhibition (α-amylase IC₅₀: 46.00 µg/mL, α-glucosidase IC₅₀: 51.51 µg/mL) indicated potent bioactivity. Cytotoxicity testing on HEK-293 cells showed > 90 % viability, confirming safety. Yogurt fortified with 3 % encapsulated powder received high sensory scores (8.30 ± 0.86), especially for color and taste. These findings validate the integrated UAE and encapsulation approach as a scalable method to stabilize red cabbage anthocyanins for functional food applications.