Science behind baking is as interesting as the art of baking itself. What causes breads and cakes to rise has been a topic of research for many. In the baking jargon, rising is often called leavening and the agents that help this are called leavening agents or leaveners. It is important to have a good understanding of these rising agents as it affects the rise and eventually the texture of the cake. Through this write up, I have tried to give some insight into the natural and chemical leavening agents used in baking. The objective is to understand :
- the role of the leveaning agents in baking
- the leaveners that are available
- how to choose the correct rising agent depending upon what is to be baked
- the amount to be used and
- what other ingredients do they need to be paired with
One needs to understand the magic that transforms flour into a cake or bread. Upon mixing with water or liquids, the starch in the flour releases enzymes resulting in gluten formation. When we mix batter or dough a criss cross structure of gluten strands develops. The rising agents release gases which fill up the cells of this matrix of strands giving it that characteristic volume. The gluten then coagulates and firms up and the baked product retains its final structure. Urgh! Sounds too technical doesn’t it? Let me try and simplify by giving an analogy.
Think of an air mattress or an air bed. It has a matrix of inflatable chambers which are filled with air using a pump. Inflated air mattress increases in volume. The structure of the chambers in the mattress is comparable to the matrix of gluten strands. But that is not the topic of this blog and I will talk about it in one of the later blogs. In an air mattress, an electric pump fills up the air in the chambers. Whereas in case of breads and cakes, the leavening agents generate the gases that fill up the strands network. The analogy ends here, because the baked goods do not deflate due to firming up of gluten during baking unlike the the air mattress which can be totally deflated.
There are both natural as well as chemical leavening agents that cause the batter or the dough to rise while baking. Natural agents are the ones that occur naturally or biologically such as air, steam, eggs, yeast. Let us look at the role played by each one of them.
This is the unsung hero amongst the rising agents. There are so many ways of incorporating air in the batter. Firstly, when the flour is sifted we are aerating it. Hence so many recipes call for sifting the flour three time. When I started baking as a teenager I always wondered about this magical number three for sifting the flour. One obvious reason of sifting was removing impurities. But other than that the only objective of sifting the remaining two times would be to fluff up the flour.
Other way of incorporating air in the batter is by creaming the butter and sugar together till light and fluffy. This gives the cake a great texture.
Beating of eggs also incorporates air, but eggs require a separate mention as leavening agents.
Steam is another one of the unsung heroes. Liquids like water or milk or buttermilk used in the batter/dough evaporate at the time of baking and produce steam. Its common knowledge that water expands upon heating converting to steam and this is what contributes to the the volume of the baked goods.
Eggs are one of the most versatile ingredients of baking. They contribute to leavening in two ways. Firstly, remember eggs are liquid right? So they produce steam which is a primary raising agent as discussed above. Secondly, whole eggs when beaten turn to pale yellow and almost triple the volume, thus incorporating another primary agent that is air into the batter. Thirdly, whipped egg whites create air pockets that will be filled with steam and thus increase the volume of the baked product. The room temperature egg whites will whip most easily. Addition of salt or cream of tartar stabilises the protein structure and in retain the volume achieved by whipping. Egg whites once beaten must be used immediately and should be folded into batters gently to avoid loss of volume.
The amount of eggs to be used totally varies from recipe to recipe as it also depends on the other ingredients used.
Yeast can be classified as wild yeast and baker’s yeast. Wild yeast is the one available in the nature and causes fermentation or leavening in sourdough breads. It was first discovered in 1857 by the French scientist Louis Pasteur and then on baker’s yeast was isolated as a single strain from the wild yeast. Baker’s yeast became a very quick and reliable fermenting agent in bread baking. Yeast feeds on sugars from the flour and added sugars and generates carbon dioxide which causes the leavening action.
These four are the natural rising agents.
Then there are chemical agents which are equally important.
- Baking Soda
The chemical name of baking soda is Sodium Bicarbonate. Its an alkali which reacts with acids in the batter like cream of tartar, butter milk, fruit purees and juices, honey, molasses etc to produce carbon dioxide and hence the rising of the baked product. The action of soda starts as soon as it comes in contact with moisture and acid i.e as soon as it is added to the batter. It does not require heat to start the reaction. Hence, the cakes using soda need to be put to baking immediately. The amount of soda used in a particular recipe depends on the amount of acid it needs to balance. So if we want more rise in the cake, we need to add baking powder and not increase the soda.
- Baking Powder
Baking powder is a combination of baking soda which is an alkali and cream of tartar which is an acid and is a complete leavening agent in itself, unlike baking soda which requires acidic ingredients to be added to the batter. It additionally has a tiny amount of starch which absorbs moisture and prevents lumps getting formed. Its a complete rising agent in itself and hence more popular in recipes as it doesn’t require the additional know how of adding an appropriate balancing acidic ingredient. Unlike baking soda, baking powder requires heat to complete production of gases. Too much of baking powder can cause undesirable flavour. Also the cake becomes every crumbly if too much is used and it may rise a lot and then flop down. These undesirable effects are true with baking soda as well.
Generally speaking the amount of baking powder used is 2% to 6% of the weight of flour.
- Baker’s Ammonia
Baker’s ammonia was used as a leavening agent earlier before baking soda and powder. It is a combination of ammonium carbonate, ammonium bicarbonate and ammonium carbamate. It is quick acting when it comes in contact with moisture and heat and produces carbon dioxide, ammonia gas. It is typically used in cookies and biscuits where the resulting product is dry so that ammonia gas gets completely expelled. Other wise the baked good can smell badly. Remember another name for baker’s ammonia is smelling salt and also used to revive a person who has fainted :).
- Club Soda/beer/Coke
Carbonated drinks like club soda and colas have been used in cake baking. The advantage is that they act as raising agents and are mostly always available at home. Colas also add to the flavour. The sugar needs to be adjusted as colas are super sweet. Beer is mostly used in batters, a very popular example of which is beer batter onion rings. Some times beer is used in baking of breads.
Whether they are chemical or natural, these leaveners play a major role in the lightness of the resulting baked product and are in literal sense the Rising stars of the baking world. It still fascinates me and fills me up with joy every single time to watch a cake or bread fluff up. Joys in life can be so simple !