Why is Plain Flour Not Self Raising Used in Pastry?

Q.

Why do they use plain flour and not self raising flour for short crust pastry? What difference would it make if I were to use self raising? Also would I be able to use strong/bread flour?

A.

In fact there are good recipes for making shortcrust pastry with a blend of plain and self-raising flour, for example: combine the flours in the ratio 50:50 plain and self-raising, and mix the fats 50:50 lard or white vegetable shortening and butter – this will give a pastry between shortcrust and rough puff. It will rise a little and be more crumbly, so is best used to top a pie, rather than as a base for a filled pie. If you only have wholemeal plain flour and your recipe calls for white (or bleached) plain flour, you can use a blend of 75:25 wholemeal and self-raising which will leaven the heavier wholemeal and give the pastry a lighter texture.

What is Self-Raising Flour?

The point about self-raising flours is that they contain a raising agent, usually a blend of bicarbonate of soda and cream of tartar, and this agent will react with a liquid like water or milk to create a gas that expands and ‘lifts’ the flour mixture to give a light and open texture – the tiny bubbles that you see when you cut into a cake are pockets of this gas that have ‘set’ when heated. That’s why we call it self-raising. If you use self-raising flour in pastry, you get the same effect, so your pastry will be softer and more crumbly than pastry made using all plain flour. This can actually be an advantage if you want to make and use pastry immediately: usually we rest pastry in a cold place for at least 20 minutes before use, but if you use one third self-raising flour, the pastry will be more elastic and can be rolled out more easily.

Recipes for which you cannot use self-raising flour are those containing yeast or another raising agent, because two raising agents together will often disrupt the surface of the food too much, leading to large bubbles that explode, making craters.

Bread Flour

Sadly, you can’t use bread flour to make pastry very successfully because it has a different gluten content that needs to react with more liquid than is used in a pastry recipe and with yeast, to create elastic gluten bonds. Pastry made with bread flour (also called strong flour) will be quite solid and rather difficult to cut.