This study investigated the impact of egg storage on the properties of pound cake batter and cake.
During storage, ovalbumin was (partly) converted into different forms of which S-ovalbumin was the more thermostable. After storage for 28 days at 6 °C, an important part of the ovalbumin in the egg white samples had been converted to the intermediate forms while after storage for 28 days at 23 °C egg white samples contained mainly S-ovalbumin. The differences in denaturation temperature of these samples impacted the thermal exposure of SH groups. Egg white containing ovalbumin, intermediate forms or S-ovalbumin had a similar total amount of SH groups, but egg white with S-ovalbumin required the highest temperatures to expose its SH groups.
The presence of S-ovalbumin instead of ovalbumin in cake batter had no impact on the level of extractable protein in cake. The exposure of SH groups was influenced by the denaturation temperature of egg white, and this in turn caused differences in network formation during batter heating. The presence of S-ovalbumin delayed the incorporation of other proteins into the protein network. We conclude that the key role of ovalbumin in protein network formation during cake baking results from exposure of its SH groups. Cake crumb structure formation is due to starch gelatinization and swelling and protein network formation. Differences in protein network formation during baking resulted in differences in batter viscosity and thus in structure formation during baking. When heating to up to 95 °C, batter viscosity increased more for batters containing mainly ovalbumin than for batters containing mainly S-ovalbumin.
Although cake crumb structure formation during baking was modified, there was no difference in cake volume between cakes baked with egg white from fresh or egg white from stored eggs. Stored egg white samples did however impact cake crumb cohesiveness and springiness.
From all of the above, we conclude that ovalbumin plays a key role in the protein network and thus in the texture of pound cake. Increased thermostability of ovalbumin by conversion into S-ovalbumin increases the temperature at which all its SH groups become exposed. This delays the incorporation of both ovalbumin and an important fraction of other proteins into the protein network during baking and results in a changed structure formation and a less cohesive and springy texture of cake crumb.