Effect of protein aggregation on rheological properties of pea protein gels

Abstract

Yoghurt style gels are a promising way to increase the consumption of plant derived proteins. However, reaching texture properties similar to those commonly known from milk yoghurts while incorporating large amounts of plant-derived proteins, is a challenge that needs to be addressed to meet consumers expectations. Therefore, this study aims to investigate the influence of pH conditions (pH 6.0 to pH 8.0) during pre-treatment on the rheological properties of fermentation induced pea protein gels with a protein content of 10%. Results showed a strong correlation between the pH value during pre-treatment and the protein solubility after pH readjustment to pH 8. Solubility was highest if pea protein was pre-treated at pH 8.0 and lowest if it was pre-treated at pH 6.0. Since only soluble aggregates are believed to participate in network formation, networks formed by pea protein pre-treated at pH 6 were coarser, than those formed by pea protein pre-treated at pH 8 owing to a lower degree of crosslinking caused by less available protein. Coarser networks and higher proportions of insoluble particles increased loss of water and lowered the storage modulus G’ as well as the ability of the networks to recover after intense shearing. In particular pre-treatment at pH values below 7.0 led to gels with storage moduli of the same magnitude as those measured in commercial milk derived yoghurts. Adjusting the pH value during pre-treatment of pea protein can therefore be considered a promising approach for the customisation of texture properties while maintaining a constantly high protein content.