But the simplest way to think of it is that the leavening agent produces the gas, and the gas causes the dough or batter to rise. It is very important as a baker to be acquainted with all the process involved in baking.
My last post on WBT was on importance of 3 key ingredients in baking which are Fat, Egg and Baking Powder.
Today we shall discuss the types of leavening agents: under the following classes - biological, chemical, mechanical, lamination and steam. Sounds like a science class again right? Lol!..Well that is what baking is.
We shall look at each leavening in more detail this time. But first let's understand broadly what's happening when we bake a dough or batter. Aha!
How Leavening Agents Cause Doughs to Rise :-
Dough is made of wheat flour, which contains a pair of proteins called gliadin and glutenin. When you add water and start to mix it, the gliadin and glutenin combine to form a new protein called gluten.
Gluten molecules arrange themselves into chains that can be quite long and elastic. This elasticity is why you can take a piece of bread dough and stretch it between your fingers. The more you knead it, the stretchier it gets.
Next, the gas produced by the leavening agent forms thousands of little bubbles in the dough, which causes it to inflate.
But because of the dough's elasticity, the bubbles expand without bursting, so the gas remains trapped in the bubbles long enough for the third part of the reaction to take place.
And the third part is, the heat of the oven cooks the dough, causing it to set while those little bubbles are in their inflated state. So once the gas finally escapes, those air pockets hold their shape instead of deflating. Guess what? The size of those air pockets determines the texture of your baked good. Small air pockets produce a smooth texture, like with a cake. Larger ones produce a coarser texture, like with a crusty bread. Interesting hun!
Now Let's look at the types of leavening agents:
YEAST: (Biological Leavening Agent)
Yeast are single-celled organisms (a type of fungus, actually) that undergo an existence far removed from anything you and I would recognise as "life." And yet they perform a vital function. Yeast are responsible for the process of fermentation, without which there would be no such things as beer, wine or bread.
How fermentation works is, yeast eat sugar, and they produce carbon dioxide (CO2) gas and alcohol. The alcohol is a boon for winemakers and brewers, and the CO2 comes in handy for bakers too.
There are few types of baker's yeasts:
ACTIVE DRY YEAST :- is what most recipes call for. It's a dry, granular yeast sold in packets or jars. Before working with it, active dry yeast must be activated, or "proofed," by dissolving it in warm water. The ideal temperature is 105F. Cooler than that and the yeast won't fully activate. Hotter than that and you'll kill the little fellows..ouch!
INSTANT DRY YEAST :- is also a granular yeast sold in packets or jars. Unlike active dry yeast, however, instant dry yeast can be mixed directly with your flour. No proofing required. Moreover, you only need to use one-third to one-half as much instant dry yeast as compared with active dry.
FRESH YEAST :- is found mainly in commercial bake shops. It comes in one-pound bricks, and can be added directly to the dough or dissolved with water first. But dissolving it is only to help disperse it more fully. It doesn't need to proof.
In most cases, yeast doughs rise once, then get punched down, and then rise again. Finally, they go into the oven, where the heat rouses the yeast to one last great expulsion of CO2, before they reach 140F and die. Awww!
I should point out that, unlike the other leavening agents, yeast contributes flavour as well. Indeed, adding more yeast to a recipe won't cause the bread to rise more, but it will produce a more intense yeast flavour with fermented taste.
Baking Soda, Ammonium Bicarbonate and Baking Powder: (Chemical Leavening Agents)
BAKING SODA (sometimes called sodium bicarbonate or bicarbonate of soda) is a white powder that comes in a box, and it has a pH level of 8–9, which means it is a base. When combined with an acidic ingredient, it will produce a chemical reaction that causes the release of CO2.
Unlike the reaction of yeast, which occurs slowly over a long period of time, baking soda acts quickly, which is why the breads and muffins it produces are called quick breads.
Some examples of acidic ingredients that will activate baking soda are buttermilk, lemon juice, yogurt, sour cream, molasses or honey. In its dry state, baking soda is inert, but once activated, it reacts immediately. To substitute baking soda for baking powder, use ratio 1:4. That is, 1 tsp baking soda to 4 tsp baking powder.
AMMONIUM BICARBONATE :- Just like the contemporary baking powder and baking soda, ammonium bicarbonate is originally made from the ground antlers of reindeer. It react the same way as baking powder and baking soda. Though not commonly used these days but in Northern Europe it is used mostly in gingerbread cookies and small pastries because it makes it more light and crispy. Unfortunately ammonium bicarb can alter the taste of baked goods, so must be used in little amount and also in small pastries.
BAKING POWDER :- is a product consisting of baking soda plus some other acidic component, also in powdered form. As long as it stays dry, it's inactive. But once moistened, the chemical reaction begins. It's less immediate than a straight baking soda reaction, however. Unlike baking soda, baking powder is double-acting, which means it begins working when mixed, then gives off another burst of gas when heated. That's why some quick bread batters, like pancakes, can be held for a while without them losing their potency.
One thing that can't be said enough, is that substituting baking soda for baking powder will not give exact desired result, or vice-versa. Learn how to make homemade baking powder here
MECHANICAL: (Beating or Whisking)
This type of leavening simply involves beating and whisking by means of air. Mostly done and applicable for eggs and sugar/butter creaming. In other words egg is considered as leavening agent also when properly aerated into batter.
LAMINATION: (Folding and Rolling)
This type of leavening is similar to the mechanical. Sometimes In mixing your dough or cake batter in some recipes, they mostly require you to mix by either folding or rolling method. This helps to trap and incorporate air into the batter. Not much of a technique though! But also effective in baking.
STEAM: ( Vapourous Leavening Agent)
Unlike the leavening agents above, all of which produce CO2 gas, steam is simply water vapour, produced when the water in your dough reaches boiling point and vapourizes.
Steam is a powerful force. When water becomes steam, its volume increases by some 1,500 times. The force or pressure with which this expansion takes place is increased by higher temperatures. There are some notable pastries that use only steam as their leavening agent, yet when prepared properly are superbly airy and flaky. The key is to ensure that the dough captures the steam. Weeeewwww!
Quite a long article, hope you read through to the end? Lol!
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