Abstract
Nutritive value of freeze dried egg white was tremendously decreased by autoclaving at 120°C for 30 min. Male weanling rats rapidly lost their body weight on the diet containing 10% of the heat treated freeze dried egg white as a sole source of protein.
Neither single supplementation of Lys nor the supplementation of Lys together with His, Thr, Phe, Try and Met did not support the growth of rats although the supplementation of 6% of casein supported the growth of animals well. Digestibility of freeze dried egg white autoclaved at 100°C for 30 min. was practically zero and even the digestibility of egg white autoclaved at 100°C for 30 min. was as low as 31%.
When raw egg white was directly autoclaved without freeze drying, at the similar conditions men- tioned above, the digestibility of it was not significantly affected, and the growth of rats was not affected either. Dry heating of freeze dried egg white (120°C or 100°C for 30 min.) did not reduce its nutritive value. Removal of trace of glucose by glucose oxidase eliminated the reduction of nutritive value by autoclaving. When air dried powder of egg white was autoclaved, the nutritive value was significantly reduced but the magnitude was less than that of the similarly treated freeze dried egg white.
The nutritive value of freeze dried egg yolk was not reduced at all by autoclaving at 120°C for 30 min. When the lipids were extracted before autoclaving, however, small but significant reduction of nutritive value was observed.
