What Causes Cheesecakes to Sink in the Middle After Baking & Cooling?
The Science of Cheesecake
Cheesecake is essentially a custard, or a thickened mixture of milk, sugar and eggs. The eggs are responsible for thickening the cheesecake, but they also add protein that coagulates at high heat, leading to cracks.
A cheesecake that cracks too deeply will sink in the middle because there will not be enough structure to support its weight.
Cheesecakes that completely cave in after baking and cooling are generally not cooked long enough to set the middle firmly. The outer edges may be fully cooked, but if the eggs in the center have not been fully cooked, their proteins will not coagulate enough to hold the center together, and it will fall as the cheesecake cools.
Temperature and coagulation are the key elements to control to produce a reliably creamy, firm cheesecake.