Complex coacervate formation between hemp protein isolate and gum Arabic: Formulation and characterization

In this study, intermolecular interactions and structure formation between hemp protein isolate (HPI) and gum Arabic (GA) were investigated to unravel their complexation mechanisms. For this purpose, structural transition as a function of pH (2.0-7.0) and protein to polysaccharide ratio (HPI:GA, R = 0.5:1-13:1 w/w) was evaluated via turbidimetric analysis, zeta-potentiometry, state diagram construction and coacervate yield. It was proved that critical phase transition pH shifted to higher values with R increase, until reaching a plateau at ratio 10:1, with complexes to be formed even at pH region where both biopolymers were negatively charged. The shift of pH value, where maximum turbidity was noticed (pHopt), was well in accordance with net charge neutrality of HPI-GA mixtures found by electrophoretic mobility measurements. Maximum coacervation, occurred at ratio R = 2:1 and pHopt = 3.5, was depicted by the highest yield (92%), while morphological characteristics of liquid as well as freeze-dried HPI-GA coacervates, obtained through optical and scanning electron microscope measurements, gave a further perception of the associative processes during complex coacervation. Additionally, the molecular interactions between HPI and GA were confirmed by Fourier transform infrared spectroscopy (FTIR) revealing primarily electrostatic interactions with secondary stabilization of hydrogen bonds. Therefore, these findings could provide useful information for the development of HPI - GA coacervates as a potential bioactive encapsulation means. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the intermolecular interactions and structure formation between hemp protein isolate (HPI) and gum Arabic (GA), revealing their complexation mechanisms under different pH and protein to polysaccharide ratios. The results showed that critical phase transition pH shifted to higher values with the increase in ratio (R), until reaching a plateau at ratio 10:1, where complexes were formed even in regions where both biopolymers were negatively charged. Maximum coacervation occurred at ratio R = 2:1 and pHopt = 3.5, with a yield of 92%, confirming the molecular interactions between HPI and GA primarily through electrostatic interactions with secondary stabilization of hydrogen bonds. These findings could be valuable for the development of HPI-GA coacervates as a potential bioactive encapsulation means.