Ultrasound-intensified wet-heating induced Maillard reaction between hemp cake protein and maltodextrin: Structural characterisation, techno-functional and antioxidant properties

Abstract

In this research, hemp protein isolate (HPI) was obtained from hemp cake using isoelectric precipitation and conjugated with maltodextrin through the Maillard reaction using wet-heating alone and combined with ultrasound to enhance its structural, functional properties (including solubility, emulsifying, foaming properties and water/oil holding capcity), and antioxidant properties. Covalent bonds between HPI and maltodextrin were confirmed using methods like SDS-PAGE, FTIR, XRD, fluorescence spectroscopy, secondary structure analysis, amino acid profile, and glycation degree (DG) measurement. Ultrasound significantly accelerated glycation, reaching a DG of 25.06 % in just 60 min, while reducing melanoidin formation, whereas wet-heating required 24 h to achieve a similar level of DG. Structural analysis revealed that wet-heating resulted in greater structural modifications due to its longer reaction time. These changes included a decrease in α-helix and β-sheet structures, higher surface hydrophobicity and zeta potential, and more noticeable microstructural changes. Techno-functional assessments revealed that wet-heating conjugates exhibited superior solubility (up to 95.77 %), emulsifying (emulsion stability index up to 48.67 %), and foaming (foaming capacity up to 107.14 %) properties, and antioxidant properties (71.95 % of ABTS), compared to ultrasound-assisted conjugates. This study highlights how ultrasound can intensify the wet-heating glycation of proteins to modify their structure, consequently improving their techno-functional properties to provide a novel plant-based protein ingredient for various food applications.