When Rose Levy Beranbaum wrote her UK version of The Cake Bible, self-raising flour in the UK was still bleached even although plain flour was untreated. The trusty Food Industries Manual suggests that this was purely because people wanted the colour of self-raising flour to be bright rather than because it was necessary for the success of the recipes they were using … which was fortuitous for Rose but perhaps helps explain why there was no apparent demand by home-bakers in the UK for a replacement to bleached flour when chlorination was prohibited in 2000.

The Food Industries Manual also states however:

Since chemically aerated goods are baked shortly after the dough has been made, there is no opportunity for the gluten to ‘ripen’ hence self-raising flours need to be weaker and to contain less proteinous material than bread flours.

Since starting out on my flour quest, it has been a source of great frustration to me that self-raising flour has a lower protein content than plain and 00 grade flours. McDougall’s Supreme Sponge flour with its finely-milled soft wheats and 8% protein content has been sitting, laughing mockingly at me on the shelf of every supermarket. Why couldn’t they just leave out the baking powder and let me have some of it ‘plain’ and unadulterated?

I wasn’t sure what would happen to the baking powder components if I microwaved this self-raising flour … would they be deactivated by the heat, or would they remain unaffected until there was sufficient moisture for a reaction? Was it single-acting or double-acting baking powder? Would it explode?! My head was already spinning and that was even before I delved into the chemical formulations!

Well, today I finally took the drastic step of nuking it regardless.

I would never have believed that the two cakes I made this afternoon used exactly the same starting flour and exactly the same recipe, and were baked under as near to exactly the same conditions as is possible in my kitchen … only the flour in one cake was given the kate-flour treatment whilst in the other it was used straight from the packet.

Here’s the first – Rose’s Yellow Butter Cake recipe made with McDougall’s Supreme Self-Raising Sponge flour, untreated.

Here’s the same cake made with kate flour. I didn’t expect it to work. I almost forgot to take it out of the oven, I was so sure it would be a total flop … literally, as I’d gone for the US recipe and assumed that the flour was no longer self-raising after it had been microwaved. Instead, this cake has almost exactly the same vital statistics as a 9 x 1 1/2 inch cake made with authentic cake flour! (Info for Woody: height of batter in pan = 1.9 cms; 27 mins baking time; height at sides = 3.2 cms; height in middle = 4.2 cms).

The only thing … it seems you can either have cake-flour colour … or cake-flour crumb … but not both at once!