Saturday, September 21, 2013

Few weeks ago, someone asked me what is the difference between baking soda and baking powder? Why does people need it to bake a cake and cookies? Why do some recipes need baking powder only, but the others need both of them? How does actually this thing work? Hmm... good question. Yeast, baking powder and baking soda, all of them are leavening agent which are needed to make the cake, bread, and the cookies rise up in volume during baking process.

Leavening agent is a substance which is causing expansion of dough and batters by the release of gasses within such mixtures, producing baked products with porous structures (Encyclopedia Britanica, 2013). Yeast is the most popular leavening agent, especially for making breads products. Based on fermentation process, yeast will use fructose, glucose, and other simple sugar that are present in the dough ingredients as its food. Yeast's enzymes will break down the sugar and produce alcohol and carbon dioxide as by-product. The alcohol will evaporate during the baking process. Meanwhile, the carbon dioxide will trapped inside the dough and cause the bread to rise. Yeast fermentation need time to leaven the bread. Meanwhile, cake and cookies need something fast. That's why, we have chemical leavening agents which are baking powder and baking soda.

Baking Soda

Baking soda is one of chemical leavening agent which is actually chemically named bicarbonate (HCO3). 
This bicarbonate is usually bound with another molecule such as sodium or pottasium and ammonium. In the market, it usually present as Sodium bicarbonate (Mostly Natrium bicarbonate or NaHCO3). With the presence of water, Sodium bicarbonate will react with any acidic material and release Carbon dioxide gas (CO2). The heat from the baking process will be the catalyst to speed up the reaction process.

NaHCO3 + HCl ----> NaCl + H2CO3
( H2COis called Carbonic acid and this acid is unstable so it will automatically separate into water and carbon dioxide)

  H2CO3 ----> H2O + CO2

Because it is an acid-base reaction, in order to be able to produce gases, baking soda definitely needs acid. With the presence of acid, baking soda can react  and produce gas during the baking process. That's why, most of the cake recipes that use acidic ingredients will need baking soda as the leavening agent. Acidic ingredients that can induce the reaction of baking soda include : Cream of Tartar (COT), lemon juice (or other fruit juice), yogurt, buttermilk, vinegar, molasses, etc. The more acidic the ingredients, the more baking soda that are needed. and This is a diagram of the acidic level of some common ingredients of baking product. But be careful. Too much baking soda can cause the product has a soapy and bitter taste.
Source : Potter, J. 2010

Baking Powder

Nowadays, in modern baking process, baking powder is more famous than baking soda. Baking powder is actually a chemical leavening agent which is contained baking soda, dry acid, and starch. By adding some water, baking powder become wet  and will produce carbon dioxide gas. Baking powder doesn't need additional acidic ingredients on the batter because it has dry acid on baking powder itself.
Baking powder contain starch as well to increase the shelf life by absorbing moisture and preventing sodium bicarbonate and dry acid inside baking powder react prematurely. That's why, baking powder can always be substitute by mixing 1/2 tsp Cream of Tartar + 1/4 tsp baking soda + 1/4 tsp corn starch for each tsp baking powder that are needed on the recipe.

In the market, there are 2 different type of baking powder which are single acting and double acting baking powder. Single acting baking powder contain only 1 acid and 1 base and will cause only 1 reaction. This single acting baking powder will react and cause a bubble soon after all the dry and wet ingredients are mixed. So, if the food is not baked as soon as possible after all the ingredients are mixed, we will lose all the bubbles and the food becomes flat. Single acting baking powder is not common on the market. Commercial baking powder mostly are double acting baking powder. Double acting baking powder contain 2 acid and will cause 2 step of acid-base reaction during the whole process. Fist acid is fast-acting acid which will react with presence of liquid. That's why, the first step will happen during the mixing process. The example for this kind of acid are : cream of tartar and calcium acid phosphate. Meanwhile, the second step will happen during the baking process because the second acid is slow-react acid or heated-activated acid. The example of this kind of acid are : sodium aluminium phosphate, sodium aluminium sulfate, and sodium acid pyrophosphate. This double acting baking powder are commonly available on the market and more reliable than single acting baking powder.

I found this interesting video on youtube about baking soda and baking powder.

Why do some recipes need both baking soda and baking powder?
Hmm.... It's a good question. For example : buttermilk muffin would need both baking soda and baking powder. Why? There are many explanation that i found on the internet. Most of them said that is because of the acid. If the recipe is a bit acid or contain a lot of acid ingredients but you don't want your muffin has sour taste because it contains too much acid, than baking soda is needed to neutralize the acid ingredients. Meanwhile, baking powder will be functioned as leavening agent. That's the theory. Now, let's play with them. :)

My small experiment
Yesterday, I tried to make buttermilk muffin. This is the original recipe from Allrecipes. From one recipe, I divided the batter into 12 portion. Each portion is enough for 1 normal muffin or 2-3 mini muffins. I took 4 portion out of it, and gave a different treatment for each of them. First treatment : no leavening agent at all. Second treatment : only baking soda. Third treatment : only baking powder. Fourth treatment : baking soda and baking powder. I just want to see the difference between all of them. (I made bacon muffin from the rest of the batter) Of course I divide the amount of leavening agent into 12 as well. It was not easy tough. After mixing well all those different the batter, I poured them into small muffin tin and bake them. Same temperature, same time. And this is the result.

1 : No baking soda and baking powder
2 : Baking  powder only
3 : Baking soda only
4 : Both baking soda and baking powder.

Like I was expected, buttermilk muffin without baking soda and baking powder will come out flat and sour. Same thing with buttermilk muffin with baking powder only. It will rise and leaven but still sour because the acid from buttermilk was not neutralized with baking powder. The buttermilk muffin number 4 rise well and doesn't have sour taste like buttermilk muffin number 1 and 2. But, buttermilk number 3 was not like I was expected. I was expecting that muffin with baking soda will a little bit flat and not sour because I was hoping the acid from buttermilk will react fast with baking soda and the the muffin will lose the gas during baking process because of the fast reaction of baking soda. But my muffin leavened pretty well. The taste of the muffin turned out not like i was expected as well. It is bitter and soapy. I think I gave too much baking soda for my batter.

One more thing that make me curious. The color of the muffin. Why does muffin with baking soda has darker color than muffin without baking soda? As we can see on the pictures above, the muffins number 3 and 4 are are darker and more brown than muffins number 1 and 2. What did baking soda do during the baking process? After hours looking for the answer, It turned out that baking soda increase alkalinity on the batter and enhance the maillard reaction during the baking process.

Maillard reaction is one of non-enzymatic browning reaction that happened  when amino acid from protein and simple sugar break down and recombine into another components which will give brown color and unique intense flavor and aroma. This reaction is usually triggered by heat. Simple example for this reaction is browning process on cookies, cake, bread, roasted chicken, etc. There are a lot of factors that can affect maillard process, including pH or the acidity of the ingredient. Maillard reaction will accelerate in alkaline environment (pH >7) and acidic environment (pH <7) can inhibit the reaction. Baking soda is alkaline and I know my muffin is alkaline as well. (I was adding too much baking soda as well. It was proved with the soapy and nasty taste). That's why the color of the muffin number 3 (only using baking soda) is very brown. Meanwhile, muffins number 1 and 2 (without baking soda) are very pale because the acid from buttermilk inhibit the browning reaction. 

Well, there are many fun facts about baking soda and baking powder. I personally would like to have both of them on my kitchen. They're quite handy for a lot of thing, not only for baking cake. Even baking soda can be used for a small science adventure with the children. For making volcano eruption for example. But make sure to store and keep them in a dry place to prevent premature reaction in the storage. There is an easy way to test the effectiveness of baking powder. Just mix 1 tsp baking powder with 120 ml warm water. If there're any bubbles  then the baking powder is still good. For baking soda, just mix 1/4 tsp baking soda with 2 tsp vinegar and see if there's any bubbles appear immediately.  Have fun in the kitchen. :-)

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