Mechanical Characterization of Acidic Casein Gels From Micellar Casein Powder: Influence of Lactose and Sucrose

ABSTRACT This study compared the effects of lactose and sucrose at concentrations of 2%–14% ( w / w ) on acidic casein gels. Lactose significantly compacted casein gel microstructure, whereas sucrose induced minimal changes. All gels exhibited two‐phase linear force–displacement curves, with increasing slopes as the sugar concentration increased, more markedly for lactose. For both sugars, a local force peak was observed at concentrations above 6%. The peak shifted to lower displacements and increased in intensity with concentration, more pronounced for lactose. The sugar‐induced force peaks could be separated by simultaneously fitting our previously developed gel network model to the force curves and their first derivatives. System dynamics analysis revealed that this peak arises from weak sugar–protein bonds. The viscous network delays the build‐up and release of the tension in these bonds by about 4.3 s. Higher lactose concentrations form more bonds, stiffening the gel and accelerating tension development. Consequently, the force peak occurs at lower displacements and the bonds rupture earlier. These results show that sugars can selectively enhance protein interactions in casein gels and that the resulting sugar‐induced force peaks serve as mechanical probes for investigating viscoelastic network dynamics, which has implications for sugar‐modified milk gels and protein‐based functional materials.