Effect of heat processing of dried egg white on in vitro iron bioavailability

Egg white (EW) was desugared, adjusted to either pH 7 or pH 9, and freeze-dried. Portions were held at 25 degrees, 50 degrees, 60 degrees, 70 degrees or 80 degrees C for 1 wk. In vitro iron bioavailability (IVIB) was estimated by the method of Kane and Miller (1984) and no differences in IVIB were observed due to EW pH. IVIB of EW held at 50 degrees, 60 degrees, or 70 degrees C was not different (P greater than 0.05) than that of EW held at 25 degrees C [9.87% dialyzable iron (DI)]; only the 80 degrees C treatment led to IVIB lower (6.76% DI, P less than 0.05) than the 25 degrees C control. Differential scanning calorimetry and nondissociating electrophoresis showed that native protein structure, including that of the iron-binding protein ovotransferrin, was maintained after the 70 degrees C treatment but not after the 80 degrees C treatment