Baking Powder and Baking Soda

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For culinary purposes, Baking Powder and Baking Soda are classed as leavening agents, and can therefore be grouped in with ingredients such as yeast. However, it should be noted that these are chemicals or chemical compounds and as such, should be considered as chemical additives. It is also important to remember that in most recipes, you cannot use baking soda if the recipe calls for baking powder due to the different way in which they chemically react in order to produce the rise required and it's safer by far not to try to substitute either one for the other.

For this reason, we are going to start this section, not with the history as in most of the Ingredient of the Month sections, but with an explanation of exactly what they are and how they work.

What is Baking Powder and Baking Soda?

Baking Soda is pure Sodium Bicarbonate, also called Bicarbonate of Soda (NaHCO3). It is a white crystalline alkali which reacts by effervescing (fizzing) when it comes into contact with acids, thus producing gasses, namely carbon dioxide. Because of this chemical reaction, it is often used in fizzy drinks and antacid remedies and it's precisely this reaction which facilitates the rising action in baked goods.

Baking Powder is more complex. It is composite of Sodium Bicarbonate (baking soda), one or more acid salts such as Cream of Tartar (Tartaric Acid), Sodium Aluminium Sulphate, Calcium Acid Phosphate plus a drying agent such as cornflour and the exact mix determines whether it is "Single" or "Double" acting. The difference between baking soda, single and double acting baking powders, is when the chemical reactions actually take place, and is explained below. However, the rising principal is the same in that a chemical reaction produces carbon dioxide bubbles which expand through the cooking mixture.

What's the difference between baking powder and baking soda ?

When using baking soda, the mixture to which it is being added must contain some sort of acid, often in the form of honey, molasses, brown sugar, sour cream, yoghurt, cocoa, citrus juice or fruits. The chemical reaction takes place as soon as it is added to the acid ingredient in the mixing bowl. This means you have to work swiftly and get the mixture into the oven as soon as possible before the carbon dioxide starts to dissipate, which they will quite quickly. (Think back to those fizzy drinks once they've been poured into a glass - that initial burst of fizz soon dies down to a little murmur).

When using "Single Acting" baking powder, the chemical reaction, once again, takes place in the bowl at the mixing stage, with the catalyst being any liquid as opposed to an acid, so the same applies as to the speed at which you get the mixture into the oven. Remember, the acid is already present in the baking powder usually in the form of Cream of Tartar: it just needs to be triggered off by the addition of moisture (water, milk etc).

"Double Acting" baking powder adds another dimension. Not only does it start reacting in the bowl as with baking soda and "single acting" baking powder, but it also reacts a second time when it is cooked. This is achieved by the addition of slower reacting acids to the single acting baking powder, which hardly react at room temperature. These only become active once they achieve higher temperatures. So it has a double action - once when subjected to moisture in the bowl and once when subjected to heat in the oven. This quality means that the rush to mix and get it into the oven is avoided, which is especially useful if there are many ingredients which need thorough blending.

History of baking powder

Food historians believe the use of baking soda dates back to ancient civilization and it is perhaps this age-old use of it which has prevented its demise as a chemical additive.

Until the late 1700's, yeast was the main leavening ingredient used. However once it became widely accepted that bicarbonate of soda would create carbon dioxide gas in the presence of certain acids, housewives began making their own chemical leavening. Although the rising process was faster, it was a little hit and miss due to the majority of the leavening gases being released in the bowl (at the bench stage).