--- Join Paul Hollywood as he shows you how to make his favourite bread from around the world, including an entire episode devoted to baking with bicarb soda, in Paul Hollywood’s Bread, double episodes Mondays 8.30pm 6 July to 20 July on SBS Food and SBS on Demand. Catch the bicarb action on July 20 ---
The chemistry of baking powers and baking powder is one of food science’s most basic – and delicious – reactions (although it’s a constant battle with the creation of caramel for number one spot!). They give lift and air to everything from fluffy pancakes to airy honeycomb.
It can be confusing for new cooks, though, given the two leavening agents have such similar names. Here’s our simple guide to baking powder and baking soda, with some tips on how to use and store them.
What are they?
Baking powder and baking soda are both leavening agents. Like yeast, they release carbon dioxide. Whereas yeast produces gas through fermentation, baking powder and baking soda do so through chemical reactions. The combination of mildly acidic and alkaline ingredients creates carbon dioxide gas.
Let’s start with baking soda, also often known as bicarb soda. It is sodium bicarbonate, an alkaline ingredient. When used in a mixture – a cake or pancake batter, for example – that also contains something acidic, such as lemon juice or buttermilk, the reaction creates gas. That gas expands existing tiny bubbles that were created in the mixing process, therefore creating lighter baked goods. Other acidic ingredients that can create the same reaction include yoghurt, honey, molasses, chocolate and vinegar. A classic use of baking soda is soda bread.
Baking soda is also responsible for the delicious crunch of honeycomb (such as that chocolate-coated honeycomb below). The baking soda is added to extremely hot sugar syrup. The heat breaks down the bicarb soda, releasing carbon dioxide.
Baking powder combines baking soda and an acid, such as cream of tartar or sodium acid pyrophosphate. The alkaline and acid components are usually mixed with a starch, such as rice powder or corn starch; that third ingredient has two helpful jobs – to add bulk, so it’s easier to measure the right amount of baking powder for your recipe, and to absorb moisture.
Self-raising flour is made by combining plain flour with baking powder in the right ratio for creating favourites such as scones.
It made baking a lot easier
Before the use of chemical leaveners such as baking soda, creating light, aerated mixtures relied on fermentation (such as sourdough bread) or hard work (such as beating egg whites to add to cakes). In the 18th century, potash, also known as pearlash, was used. As the name suggests, it was usually made from wood ash. It also created gas when used in mixtures, but it created a soapy taste, too. When baking soda appeared in the 1830s, it became much more popular. An early form of baking power was invented in the mid-1800s in England.
When baking soda and cream of tartar are combined, the reaction is swift, starting as soon as they are mixed in a batter or dough. Part of the development of today’s baking powder was the use of slower acting sodium acid pyrophosphate or similar ingredients instead of some or all of the cream of tartar.
What’s that taste?
Sometimes, a bread, pancake or other baked good made with baking soda will have a slightly astringent or metallic-like taste. This can happen if the mixture had too much baking soda, or if it wasn’t mixed properly, leaving small pockets of pure baking soda.
How to DIY
You can make your own baking powder by sifting together 1 teaspoon of baking soda and 2-2½ teaspoons of cream of tartar. And since self-raising flour is created by adding baking powder to plain flour, you can make your own SR flour too: add 2 teaspoons of baking powder to each cup of plain flour and sift at least twice before using.
Twice as nice?
You may see baking powder and baking soda used together in a recipe; or self-raising flour (which contains baking powder) used with baking soda - such as the Armenian nutmeg cake below; or baking soda used with yeast.
There are several reasons why more than one leavening agent is used. One is to spread out the rising effect - for example, if you have baking soda and baking powder in a recipe, this might be taking advantage of the fact that common baking powders (those with some sodium acid pyrophosphate) activate more slowly. The baking soda can react with those mildly acidic ingredients we mentioned - buttermilk and the like - for a quick start, and the baking powder will kick in when the item gets into the oven.
A combination may also be used to add more than just rise to a recipe. Yeast is a slower leavening method, but it can also contribute to flavour and structure (especially with sourdough).
A perfect example of why a combo can be so great: Crumpets. They are often made with a combination of yeast and bicarb soda. The yeast does the heavy lifting to start with, creating a bubbly batter, and then the bicarb soda joins the party, to help create that hole-pocked surface - or as Paul Hollywood poetically says of his recipe, the second raising agent helps create "the crumpets characteristic craters".
Baking powder (most commonly, as part of the self-raising flour in a recipe) can also join forces with whipped egg whites to give a dual-action lift to cakes, such as this Hawaiian layered coconut taro cake (the taro makes an excellent filling, but if you can't get your hands on any, just make extra of the cream cheese frosting!)
Bake your baking soda
If you’d like to go next level with your baking soda, read this fascinating article by Harold McGee, in which he explains why baking your baking soda creates a potent flavour-packed ingredient that can enhance both ramen noodles and pretzels. Just be careful when handling it, as the chemical transformation turns the powder slightly caustic.
Keep it fresh
Store baking powder and baking soda in a pantry or cupboard, not in the fridge. Baking soda lasts pretty much forever. Baking powder does gradually lose its strength but should be fine for up to a year, quite possibly a lot longer. To test if yours is still working, put ½ teaspoon of powder in a cup and pour in ¼ cup of boiling water. If it bubbles vigorously, you’re good to go.
Lead image by kaboompics via pexels.com
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