Ultrasound-induced red bean protein–lutein interactions and their effects on physicochemical properties, antioxidant activities and digestion behaviors of complexes

Abstract

The complexation of red bean protein (RBP) and lutein (LU) enhances the functional properties of proteins and increases their applicability as nutraceuticals for LU. The effects of ultrasonic treatment on the interactions between RBP and LU, physicochemical properties, antioxidant activities, and digestion behaviors of RBP–LU complexes were investigated. Ultrasonic treatment promoted the non-covalent binding of RBP with LU through hydrophobic interactions, causing the binding site to be closer to tryptophan than tyrosine. This process resulted in a more flexible secondary structure and less compact tertiary conformation of complexes with higher binding ratios, surface hydrophobicity, surface charge, and smaller particle size. The enhanced RBP–LU interactions and structural modifications of complexes induced by ultrasound possibly enhanced the functional properties. Ultrasonic treatment maximized the emulsifying and antioxidant activities of these complexes, and also enhanced the release of LU in the intestine by altering the digestion behavior of the complex, thereby improving its bioaccessibility. An appropriate ultrasonic treatment could facilitate RBP–LU interactions and modify the structure of complexes to improve their functional properties.