The effect of the glucono-δ-lactone/caseinate ratio on sodium caseinate gelation

The influence of the acidification rate and the final pH on the properties of sodium caseinate gels (2–6%, w/v) prepared by acidification with glucono-δ-lactone (GDL) at 10°C was investigated. The rheological properties of the systems were analysed under shear at incipient gelation and under uniaxial compression throughout the entire gelation process. The water holding capacity (WHC) of these gels and their amount of soluble protein in different media were also evaluated. Up to ∼50% of the total κ-casein content was soluble in gels with a higher amount of GDL, and this contributed to the high WHC observed under this condition. The acidification rate did not affect the rheological properties measured under shear during gelation, but the GDL/caseinate ratio used had a significant effect on the steady-state properties. Fast acidification resulted in lower Young's modulus and stress at fracture values, but higher residual stress values and relaxation times. In contrast, slow acidification produced a more interconnected network probably because of the extensive reorganization or rearrangement within the segments near the isoelectric point.