Covalent conjugation of whey protein isolate hydrolysates and galactose through Maillard reaction to improve the functional properties and antioxidant activity

Galactose was grafted onto whey protein isolate (WPI) and whey protein hydrolysates (WPHs) via the Maillard reaction (95 degrees C, 0-4 h). The pH, browning intensity, structure, functional properties and antioxidant activity of conjugates were evaluated. The pH, browning and degree of conjugation were at maximum after heating for 4 h. The Maillard reaction changed the WPI and WPHs to a looser secondary structure. Conjugates of WPI and WPHs with galactose had higher water holding capacity, foaming capacity and stability, and antioxidant activity. Compared with the WPI-Galactose conjugates, WPHGalactose conjugates showed better functional properties and higher antioxidant activity, and its highest reducing power was 0.923; ABTS(+) radical scavenging ability was 69.81%; hydroxyl radical scavenging ability was 89.05%. These findings indicate that the covalent conjugation of WPH-Galactose conjugates can be used as a potential ingredient and a novel wall material to encapsulate bioactive compounds. (C) 2019 Elsevier Ltd. All rights reserved.