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.