food cake. Minimal folding of the flour allows cell walls to form when it comes in contact with the egg protein foam and sugar mixture. If the batter is over-mixed, the egg white proteins may coagulate causing the bubbles to break during baking, or the cell walls may become too rigid, lacking elasticity. This would reduce the volume and result in a coarse texture. However, if the batter is under-mixed, a weak foam will form. A gluten matrix is formed when the proteins glutenin and gliadin, found in wheat flour, are mixed in the presence of water. When the batter is agitated, these two proteins form cross-links, disulfide bonds, ionic bonds, and hydrogen bonds. The matrix that forms is strong and very flexible. Although no water is added to the batter, the gluten reacts with the water found in egg whites. Since air has already been entrapped in the foam, the flour proteins can only coat the already entrapped air. This helps to strengthen the cell walls and batter during baking or any other handling. This is beneficial because the meringue on its own is weak, cannot expand in heat, and does not have any elasticity normally expected in cakes. Starch gelatinization occurs around the same time as when expansion stops and the cake sets or collapses. When starch granules are exposed to heat and water, they swell, leaching out some starch and forming hydrogen bonds with other starch granules. About 96% of the starch granules are gelatinized. Starch granules create very strong and rigid gel networks. The starch gel network is interspersed throughout the structure along with the aggregated protein network. The formation of the starch gel may interfere with expanding bubbles, causing them to burst and air to leave the cake. This would result in a collapsed cake. Sugar Sugar functions as a sweetener, stabilizer, and tenderizer. The amount of sugar has a large impact on the overrun and stability of the foam. When sugar and egg whites are whipped together, a meringue is formed. If the amount of sugar is less than or equal to the amount of egg whites, a soft meringue is formed. A stiffer meringue is formed when there is more sugar than egg white. Angel food cakes usually have equal parts sugar and egg white. Sugar will disturb protein foam formation in a positive or negative manner. It is also important that the