GELATION OF BETA-LACTOGLOBULIN TREATED WITH LIMITED PROTEOLYSIS BY IMMOBILIZED TRYPSIN

The gelation of P-lactoglobulin treated by limited proteolysis with im mobilized trypsin was studied by dynamic rheometry. Gelation condition s were (1) 80 degrees C for 3 h with 7% protein (w/v) in 20 mM CaCl2 a t pH 7 and (2) 60 degrees C for 12 h with 7% (dr 15%) protein (w/v) in 20 mM CaCl2 (or 100 mM NaCl) at pH 7. Thermal transition temperatures of the different components in the limited proteolysis mixture were d etermined by differential scanning calorimetry to be 54.0, 58.8, 64.0, and 81.8 degrees C, which are believed to correspond to fragments of the beta-barrel domain and native beta-lactoglobulin. The partially hy drolyzed beta-lactoglobulin had a lower gel point and gelled more rapi dly than native beta-lactoglobulin at 80 degrees C. Hydrolyzed beta-la ctoglobulin, heated at 60 degrees C in 20 mM CaCl2, formed a weak gel at 7% (w/v) protein and a strong gel at 15%;(w/v). By comparison, very weak gels were formed with native beta-lactoglobulin at both 7% and 1 5% (w/v) protein at 60 degrees C.