Formation mechanism of ovalbumin gel induced by alkali

Abstract

In this paper, the alkali-induced gelling behavior of ovalbumin, including its microstructure characteristics, intermolecular forces, and molecular structure changes, was investigated. The results showed that ovalbumin formed a three-dimensional gel with an ordered fibrous mesh structure under alkali conditions. The active force between gel molecules was maintained by a large number of ionic bonds (∼85%), a small number of disulfide bonds (∼5%), and very few hydrophobic interactions and hydrogen bonds. SDS-PAGE analysis showed that ovalbumin formed aggregates via ionic and disulfide bonds. ANS fluorescence spectroscopy analysis showed that strong alkali caused rapid denaturation of ovalbumin molecules to expose the hydrophobic core, thus greatly increasing the surface hydrophobicity. However, the hydrophobicity decreased during the gelation stage. FTIR analysis showed that strong alkali induced the secondary-level structure of ovalbumin molecules to interconvert, and most of them existed in a relatively stable α-folding structure. Endogenous fluorescence and UV spectroscopic analyses showed that the amino acid residues of ovalbumin in the gelation stage moved towards the polar environment. It was concluded that the secondary and tertiary structures of ovalbumin changed after treatment with strong alkali and that a crystal gel formed through the action of ionic and disulfide bonds. In addition, the long-term action of strong alkali gradually decreased the gelatinous property.