Quantitative analysis of the network structure that underlines the transitioning in mechanical responses of pea protein gels

Abstract

The objective of this study was to analyze quantitatively the network structure that underlines the transitioning in the mechanical responses of heat-induced pea protein gels. To achieve this, gels were prepared from pea proteins at varying pHs from 3.0 to 4.2 at a fixed 100 mg/mL protein concentration. Gels were also prepared by varying the protein concentration from 100 to 150 mg/mL at a fixed pH 3.0. Mechanical deformation properties of the gels were determined. An increase in protein concentration at a fixed pH resulted in an increase in fracture stress and Young's modulus. Variation of the pH at a fixed protein concentration resulted in transitioning in mechanical responses such as fracture stress, fracture strain, and the recoverable energy. The network structures were visualized by the use of confocal laser scanning and scanning electron microscopy, and the characteristic length scales of these structures were quantitatively analyzed in terms of the pair correlation function. Variation of the protein concentration at a fixed pH did not significantly alter the microstructure of the gels, whereas variation of the pH at a fixed protein concentration resulted in significant changes in the gel structure. Structural transitioning was shown to occur around pH 3.7. The findings from this study show transitioning in rheological responses of pea protein gels occur as a result of structural changes. The results from this study offer opportunities to broaden the application of pea proteins in food products, as products with desirable rheological (textural) and structural properties can be designed from pea proteins.