Heat aggregation of dry heated egg white and its inhibiting effect on heat coagulation of fresh egg white

The characteristics of dialyzed and freeze-dried egg white that was dry-heated under various conditions (70-125 degrees C, 0 min-6 h) were studied. The dry-heated egg whites (DHEWs, 120 degrees C) showed the formation of insoluble aggregates (coagula) within 50 min, turbid soluble ones (50 min-a h), and transparent soluble ones (2-6 h) according to the dry-heating times when solubilized at 10% concentration (pH 7.4) and reheated at 60 degrees C for 3.5 min. A transparent DHEW solution without any coagula when reheated was obtained by using a shorter dry-heating time and elevating the dry-heating temperature. It was also found that NaCl suppressed the turbidity development of DHEW solution promoted by CaCl2. When 10% DHEW solutions (120 degrees C, >2 h) were mixed with fresh egg white at the ratio of 1:1 in volume and heated at 60 degrees C for 3.5 min, coagulum formations in their mixtures were inhibited. The patterns of native- and SDS-PAGEs and gel filtration suggest that soluble aggregates of ovalbumin formed in the dry-heating process inhibit the formation of ovotransferrin coagula.