Factors affecting milk clotting activity of sweet leavening extract involved in coagulation of a yoghurt-like product

The effects of salts (NaCl, KCl, CaCl2, MgCl2, CuCl2 and FeCl2), milk pH (pH 6.0–6.6) and milk constituents (casein, lactose, α-lactalbumin and β-lactoglobulin) on the milk clotting activity (MCA) of sweet leavening extract, a well-known by-product from cereal wine-making, were evaluated. The MCA was improved predominantly by salts and CaCl2. On the other hand, the enhancement of the MCA was also increased by casein in combination with α-lactalbumin or β-lactoglobulin, but suppressed by the increasing milk pH. Furthermore, degradation of casein (α-, β- and κ-casein) was observed during incubation with sweet leavening extract by means of sodium dodecyl sulphate-polyacrylamide gel electrophoresis.