The effect of heat-denaturation on the base-binding capacity of beef-muscle press-juice

Publisher Website
Google Scholar
Abstract
Press-juice from freshly killed beef muscle was dialyzed to remove non-protein buffers and centrifuged to remove globulin X. The clear fluid consists mainly of myogen with some myoalbumin and myo-globulin, isoelectric point being pH 6.3. Heat denaturation (4 min. at 100[degree]C) produces no coagulum at pH 2.5-5.5 and 9.5-11, slight coagulum at pH 5.5-6, and thick fibrous coagulum at pH 6.5-8.5. Below pH 7 hydrogen ions were absorbed with peak at pH 4, and above pH 7 H-ions were released during the heat denaturation. The buffering capacity is reduced at pH 3-5, corresponding to either the suppression of 3.3 of a total of 8.5 milliequivalents of carboxyl groups per g. coagulable N, or a shift in their pK to the acid side. The buffering capacity is increased at pH 6-7, corresponding to the release of 1.1 milliequivalents of imidazole groups per g. coagulable N. The release of H-ions on denaturation above pH 7 may be explainable on the basis of liberation of sulf-hydryl and phenolic groups. Similar results were obtained with acid denaturation at pH 3.6. It is suggested that heat or acid denaturation results in a fission of the protein chain at labile linkages involving imidazole, sulfhydryl and hydroxyl groups, followed by hydrogen bond formation between carboxyl and amino groups.