Acid gelation of mixed thermal aggregates of pea globulins and β-lactoglobulin

The acid gelation by glucono-δ-lactone of thermal protein aggregates from mixed pea globulin (Glob) and β-lactoglobulin (βlg), namely “mixed-aggregates” was investigated at 25 °C in comparison to that of mixtures of thermal aggregates of each protein obtained beforehand separately (“mixtures of aggregates”). A phase diagram indicating thermal gelation and acid gelation conditions was obtained from mixed protein systems varying in concentration and composition. The minimum acid gelation concentration was 3% regardless of the protein aggregates system, a value about half the concentration threshold measured for thermal gelation. The rheological properties, the microstructure and the water holding capacity (WHC) of acid gels were then evaluated from 4 wt% protein aggregate solutions at different βlg/Glob weight ratios (0/100, 30/70, 50/50, 70/30 and 100/0). Acid gelation led to weak viscoelastic gels and the gel strength increased with βlg content. The formation of acid gel from “mixed-aggregates” resulted in more elastic gels and improved WHC compared to gels resulting from “mixtures of aggregates”. This behavior seemed to correlate with the regular filamentous and highly entangled gel network structure observed for mixed-aggregates. These properties were believed to originate from the initial structure of the thermal protein aggregates strongly influenced by βlg content.