Rheological properties of rennet-induced skim milk gels made from milk protein concentrate solutions with different ratios of α_s-: β-casein

The rheological properties of rennet-induced skim milk gels made from milk protein concentrate (MPC) solutions with α_s- (i.e., α1_s- + α_s2-):p-casein ratios of 1.00:0.70 (LBCN), 1.00:0.80 (MBCN) and 1.00:0.87 (HBCN), each having identical pH, concentrations of total calcium and casein (2.4%), were studied using dynamic low amplitude oscillatory rheometry. The ratio of α_s-:β- casein had no significant (P ≥ 0.05) effect on rennet coagulation time. LBCN samples had significantly (P ≤ 0.05) higher plateau values of storage modulus (G'; index of firmness), higher yield stress and lower plateau values for loss tangent compared with MBCN or HBCN samples. Thus, the ratio of α_s-: β-casein was an important parameter in determining both the small and large deformation rheological properties of rennet-induced skim milk gels.