Molecular crowding prevents the aggregation of protein-dextran conjugate by inducing structural changes, improves its functional properties, and stabilizes it in nanoemulsions

Abstract

In most of the recent research on emulsions related to food products containing protein-polysaccharide interactions established via the Maillard reaction have been used as emulsifiers. Key challenges in such studies include long reaction times, uncontrollable extent of reaction, and protein denaturation and aggregation. The living cell is inherently crowded molecularly with biomacromolecules, occupying 20-40% of the total volume. In this study, to mimic cellular crowding conditions, we have used polyethylene glycol as a chemical crowding agent. The degree of glycation and the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that a crowding environment triggers glycosylation and that the glycosylation degree gradually increases (p < 0.05) with increasing PEG concentration, which shortens the reaction time. The surface hydrophobicity of soybean protein isolate (SPI) significant decreased (p < 0.05), and the protein structure gradually unfolded from a helix to a random coil to prevent aggregation of SPI in the crowded environment. The solubility and the emulsifying and antioxidant properties improved upon adding the crowding reagent PEG. The chemical, freeze-thaw, and thermal stabilities of the nanoemulsion-stabilized SPI-dextran conjugate improved with increasing PEG concentration. However, the crowding environment had no effect on the salt stability of nanoemulsions.

Keywords: Macromolecular crowding environment; Maillard reaction; Polyethylene glycol.