I have been using Nigella's Shortcrust Pastry recipe and the ASK comments on pastry to try and prevent my pastry from shrinking. I still get some shrinkage and was wondering what the best equivalent of UK “plain flour” is in the US. Everyone usually says “all-purpose flour”, but is that really true? I didn’t think you could make bread out of UK plain flour but I make delicious bread all the time with US AP flour, so they can’t really be equivalent. Any thoughts?
Nigella's Shortcrust Pastry recipe (from HOW TO EAT and the pastry for the Star-Topped Mince Pies both use UK plain flour, or Nigella also suggests in HOW TO EAT using 00 pasta flour. All pastry will shrink slightly as the water used to bind the pastry evaporates during baking and also the glutens in the flour will shrink back during baking. Mixing an acid into the water used for binding (as Nigella does in her pastry recipes with citrus juice) can also help to keep the pastry tender and reduce shrinking a little. But the best way to reduce shrinking is by using as little liquid as possible to bind the pastry, gently rolling the pastry and chilling the pastry before baking.
Gluten is a protein and in the UK the protein (gluten) content for plain flour is usually 10-11% (or 10-11g protein per 100g flour). In the US the protein content of all-purpose flour varies more, usually between 10% and 13% (or between 3g and 4g protein per 1/4 cup). So depending on the brand you use, some all-purpose flours will have protein contents closer to bread flour (usually 13-14%) and will make good bread but may cause pastry to shrink more. We suggest that when you are shopping you look for an all-purpose flour with a lower gluten content (such as Gold Medal flour). You can check the nutritional information on the side of the packaging and look for a flour that has around 3g protein per 1/4 cup. In the US you can also buy pastry flour, which usually has a protein content of 8-10% (2.5-3g per 1/4 cup) and you may find gives slightly better results. However in our experience some pastry flours are slightly darker than AP flour, so if you are looking for pastry flour try to look for one that is labelled as "white" if you prefer a paler pastry crust. Finally we do not suggest using cake flour for pastry, as although it has a low protein content it can be difficult to roll out a pastry made with this type of flour.