Why is solid fat needed to produce flakiness in pie crust (pastry)?

Why is solid fat needed to produce flakiness in pie crust (pastry)?

Incorporation of fat

• When solid fat is incorporated into raw pastry dough the instruction is to incorporate it until the fat lumps are about the size of a pea

• The dough with its fat would appear as follows

Dough ball

Red circles represent pea sized lumps of solid fat

• What happens when the dough is rolled out prior to using it?

• The dough mass now looks as follows

The lumps of fat have been squashed flat by the rolling out process.

When the pastry is baked the lumps of fat melt and are absorbed by the rest of the pastry. This results in voids in the crust which is what producesflakiness.

Eventually producing something yummy like this….

• Note the voids andseparation of layerssuch as hereand here