Investigating the Encapsulation Efficiency and Stability of Purple Onion Peel Anthocyanin: Effects of Storage...

Anthocyanins are bioactive compounds widely recognized for their antioxidant and health-promoting properties; however, their application in food systems is often limited due to instability under environmental conditions. Purple onion peel, a rich and underutilized source of anthocyanins, was selected as a sustainable raw material for valorization. Encapsulation of anthocyanins derived from purple onion peel using different wall materials: sucrose (CC), HI-CAP, a modified starch known for its excellent emulsifying properties, and sodium alginate (ALG) were designed. This study was conducted to encapsulate anthocyanins from purple onion peel using different wall materials. Oven drying (HI-CAP), ionic gelation (ALG) and co-crystallization (CC) were selected as the encapsulation method. Encapsulation efficiency was highest with HI-CAP (82.56%) and lowest with CC (9.80%). ALG capsules showed the strongest bioactivity, with the highest total phenolics (26.94 mg GAE g^-1), flavonoids (5.33 mg CE g^-1), and antioxidant capacity. HI-CAP capsules had the lowest bulk (0.42 g/cm³) and tapped (0.48 g/cm³) densities but poorer flowability as indicated by higher Carr index (12.52) and Hausner ratio (1.14). CC and ALG provided better flow properties. CC had the highest water solubility and dry matter, while ALG had lower water activity and a darker color. Stability tests under various temperatures (4, 25, and 65°C), light, and oxygen showed that ALG and HI-CAP offered better protection of anthocyanins, especially at 4°C. However, significant degradation occurred at 65°C and under sunlight. Overall, ALG and HI-CAP capsules were most effective in preserving anthocyanin stability and bioactivity, making them suitable for food and pharmaceutical use.