Encapsulation of rutin in underutilized plant protein-carbohydrate conjugates: A novel approach for enhancing polyphenols bio-accessibility and stability

• Rutin was encapsulated in Maillard conjugates from rice and pumpkin proteins. • Maillard conjugates showed better rutin encapsulation than native proteins. • FTIR and SEM confirm hydrogen bonding between rutin and encapsulation materials. • Encapsulated rutin shows enhanced thermal stability and digestion resistance. • Antioxidant properties of rutin enhanced, with rice conjugates showing highest activity. Despite its significant therapeutic potential, rutin, a polyphenol, faces challenges in food applications due to low bioavailability, poor palatability, and instability. This study investigated using Maillard conjugates of rice and pumpkin proteins with inulin (a prebiotic dietary fiber) to encapsulate rutin for enhanced stability. We assessed encapsulation efficiency (EE), loading ability (LA), color changes, physicochemical stability during digestion and processing, and antioxidant properties. Results showed that protein-inulin conjugation improved EE and LA of rutin compared to native proteins, with rice conjugates achieving the highest EE (97.58 %) and LA (14.64 µg/mg). Encapsulated rutin exhibited color changes due to the Maillard reaction and bathochromic shift. FTIR and SEM analyses revealed hydrogen bonding interactions between rutin and wall materials. Encapsulated rutin showed higher thermal stability and resistance to simulated gastrointestinal digestion (SGID) than free rutin, with pumpkin proteins conjugates retaining 90.41 % of rutin after digestion. The antioxidant properties of rutin were also enhanced, with rice protein conjugates showing the highest DPPH (6775.26 µM TEAC) and ABTS (9815.00 µM TEAC) values. Overall, these results suggest that protein-carbohydrate conjugates can be used as effective and novel carriers to deliver rutin or other bioactive components in food products.