Hydrolytic Imbalance
"The center is gummy, rubbery, or appears raw despite long baking."
1The Technical Cause
Too much liquid or fruit puree prevents the starches from setting. The steam gets trapped inside, creating a rubbery texture.
2The Professional Fix
Ensure you measure liquid ingredients by weight. If using fruit purees, reduce them on the stove first to concentrate the flavor and remove excess water.