Chemical and Related Osmotic Changes in Egg Albumen During Storage

Experimentation was conducted to study the relationship of albumen pH, bicarbonate buffering system and migration of components across the vitelline membrane to the osmotic properties of egg albumen. The effects of storage time, storage temperature and shell oiling were also evaluated. Sealing the egg with oil resulted in a reduction of albumen pH. When the eggs were refrigerated (7°C.) a greater decrease in albumen pH was found when compared to those at 22°C. (room temperature). Titrations of albumen from eggs stored at 22°C. for 14 days indicated that the buffering capacity was reduced as the pH increased. pH increase leveled off after 7 days and the volume of acid required to titrate the albumen was reduced 58 percent. The largest reduction in buffering capacity came between pH 9.0 and 9.3 (3 and 7 days storage). The largest change in pH occurred between 0 and 3 days. Thick albumen lost buffering capacity more quickly than did thin in unoiled eggs. No differences were found when the eggs were oiled. Storing eggs sealed with oil to prevent CO2 loss resulted in no change in osmotic concentration of the albumen. When the eggs were not sealed a decrease in osmotic concentration was observed. This decrease was more pronounced at 22°C., 255 to 230 milliosmols, than at 7°C., 255 to 239 milliosmols. It was apparent that the osmometer could detect CO2 loss from the albumen. A new osmotic equilibrium was established at a lower level of osmotic concentration. From the data it appeared that the eggs were not in osmotic equilibrium when laid. Carbon dioxide loss from the egg over a 7 day storage period was determined and compared to the osmotic concentration. Most of the CO2 was removed from the eggs during the first 2 days. The first day accounted for a majority of the loss. Free amino acids were demonstrated to move from the yolk across the vitelline membrane to the albumen. Most of this movement was found to occur after 14 days of storage. Sulfhydryl groups increased in the albumen over a 28 day storage period but did not diffuse from the yolk. The source of SH groups was apparently from reduction of S-S bonds.