Why Do Loaf Cakes Sink?

The deeper sides of a loaf tin cause the outside of the cake to cook more quickly than the inside, so the cake rises in the oven but the centre of the cake has not cooked quite enough to permanently set the proteins in the cake batter (from the flour and egg) and hold the cake up - so it will sink as it cools.

How do I stop my loaf cake from sinking?

Moderate Sinking:

If your cake is noticeably sunken in the center but is still cooked through, use a cake leveler to even it out. A cake leveler makes quick and easy work of creating a perfectly even cake layer. If you don't have one, you can also use a serrated knife.

What causes a loaf cake to sink in the middle?

The most common reason why cakes sink in the middle is that they're underbaked. If a cake isn't fully baked through, the center doesn't have a chance to set and it will sink. This creates a doughy, dense texture in the center of your cake layer.