Make your own self raising flour

Make your own self raising flour - (metric grams and U.S. cup versions):

• Sift together 1.5 teaspoons of baking powder and a quarter of a teaspoon of salt per cup of flour in your recipe
• which if you prefer is 5-7 grams of baking powder (about a teaspoon), and 1 gram (a small pinch) of salt for every 100g of flour.

Source for the baking powder ratio: Harold McGee in On Food and Cooking: The Science and Lore of the Kitchen.

Self raising flour, or self-rising flour as it's sometimes less gracefully called is plain, all purpose white flour with the raising agents already included, along with salt. The raising agents used in self raising flour vary depending on the brand but all include a dry acid component along with an alkaline base, that react to produce carbon dioxide bubbles that leaven the batter - Odlums self raising flour uses sodium bicarbonate, monocalcium phosphate and sodium acid pyrophospate for example, and Tesco's self-raising flour uses calcium phosphate and sodium bicarbonate.

If you look at the label of the baking powder you'll use to create your self raising flour you'll see a similar mix of ingredients - an acid such as calcium acid phosphate, an alkaline base usually sodium bicarbonate (baking soda), and you'll also see a filler such as corn starch to keep the mixture from getting moist and to make it easier to measure out. Which, incidentally, is the difference between baking powder and baking soda - baking powder often contains baking soda as the alkaline base to react with the dry acidic component, where baking soda is just the dry alkali. Many American recipes for things like muffins use baking soda only because the other ingredients such as yoghurt or buttermilk provide the acid for the reaction.

All commercially available baking powders are double-acting, meaning that you get some of the carbon dioxide gas produced when the baking powder gets wet during mixing, and the remainder is released when a specific temperature is reached during baking. The amount of gas released at each stage varies depending on the leavening chemicals used, with aluminium-based leaveners seeming to reserve most of the gas production for the temperature-induced phase.

Some people prefer to avoid the use of aluminium-based baking powders such as Clabber Girl, Calumet and the Japanese brand 'Home Made Cake' due to the stronger taste or health concerns, and opt for an aluminium-free baking powder such as Rumford or Aikoku. Although Rumford is a double-acting powder, the only acid used is monocalcium phosphate (calcium acid phosphate) which releases 2/3 of the carbon dioxide within 2 minutes of coming into contact with water - so best not to let your batters hand around too long!

While we're at it, here is some fun chemistry Japanese to help you figure out what your baking powder is made of (I should note here that though this information is correct in my understanding, I'm not a chemist):

• 炭酸水素ナトリウム / たんさんすいそナトリウム: sodium hydrogen carbonate (baking soda)
• 重炭酸ナトリウム / じゅうたんさんナトリウム: sodium bicarbonate (also baking soda)
• 重曹 / じゅうそう: also baking soda (abbreviated for of above)
• 第一リン酸カルシウム / だいいちりんさんカルシウム: monocalcium phosphate
• 酒石酸水素カリウム / しゅせきさんすいそカリウム: potassium bitartrate, also called potassium hydrogen tartrate (cream of tartar)
• (焼き)ミョウバン / やきミョウバン: potassium aluminium sulfate (burnt alum, potash)
• 硫酸カリウムアルミニウム / りゅうさんカリウムアルミニウム: also potassium aluminium sulfate
• 硫酸ナトリウムアルミニウム / りゅうさんナトリウムアルミニウム: sodium aluminium sulfate
• ピロリン酸カルシウム / ピロリンさんカルシウム: calcium pyrophosphate
• 酸性ピロりん酸ナトリウム /さんせいピロリンさんナトリウム: sodium acid pyrophosphate or disodium pyrophosphate
• クエン酸 / クエンさん: citric acid
• フマル酸 / フマルさん: fumaric acid
• グルコノデルタラクトン: glucono delta-lactone

If you read Japanese, there is also an excellent investigation into a whole set of aluminium-free baking powders commonly available in Japan and their chemical components here.

Thanks to Nick-chan for sparking the idea for this post!