Fatter is better, or is it?
For most amateur bakers, what we wish for our cakes is exactly opposite of what we wish for our bodies… with cakes, the fatter they puff up, the better we feel! I wish – like myself – I could leave my cakes lying around with some soft drinks and junk food watching TV in a room and they would fatten up to twice their size in no time! Obviously, what works for me doesn’t work for my cakes…. or so I realised, the hard way. My first couple of cakes, of which fortunately there were no witnesses/survivors, were flat and hard as bricks. No matter what I tried, how accurately I got the ingredients together, how short or long I baked them for, how hot or cold the oven – they would stay flat. Although I never kept them long enough to test them, I bet they would have comfortably stopped a bullet or two if put to the test. Anyway, since I wasn’t planning on making a hobby out of inventing a Kevlar replacement, I tried to learn more about what was really happening in my batter without raising the body count – and then I finally discovered the fascinating science of Leavening!
So what is Leavening?
In baking, leavening refers to the process of making your product puff up or rise, as a result of various processes, and this is how the amateur science buff in me got hooked. Strange as it may seem, the art (and science) of leavening involves physics, chemistry as well as biology – and as such is a wonderful way to get children interested in the sciences, that is if you are fine with cleaning up after the lessons. Before we get down to how all this works, the other thing that I intend to address in this post, is what exactly do those pesky ingredients like baking soda, baking powder, yeast, egg, cream of tartar and GMS do to your cake or bread when you’re not watching. I found these ingredients highly intimidating early on, but once you understand how they work – your cakes will get a lot more predictable and a lot less deadly.
Before we jump into the details, we must remember that not all baked goods need leavening; brownies, cookies, pies, some types of flatbread are all unleavened and are no less delicious for it. But this topic is specifically about cakes and breads which do require to “rise” to the occasion.
Types of Leavening
In theory, there are four broad types of leavening used in baking –
- Chemical Leavening – Use of a chemical reaction to produce gas bubbles in the batter which expand before and during the baking process.
- Biological Leavening – Use of a biological leavening agent – usually some form of yeast – to produce gas bubbles in the dough.
- Mechanical Leavening – Use of a mechanical process to introduce gas bubbles in the dough – usually to supplement one of the previous two leavening techniques.
- Steam Leavening – Not used a lot in baking, this is used when the dish is heated at a high enough temperature to quickly convert moisture into steam and trap the steam bubbles in the firming batter as it cooks or bakes – used for example in Popovers. Indians would be familiar with this process while making Dhokla, Vada and Idli. Since this post is targeted at baking, I will not be covering this technique.
Chemical Leavening
Sorry if I sound like your fifth grade science teacher, but I hope you will find this a tad more interesting – what do you think happens when you mix an acid and a base (or alkali) together? Let me give you a hint, they don’t exactly fall in love at first mix. In fact, it’s the exact opposite – they react fairly violently! Before you start wondering what I’m on about and why we’re talking about violent reactions in a conversation about food, don’t worry! The magic of chemical leavening is in harnessing this violence to help our cakes rise relatively instantly. See, the thing about the other leavening techniques is – they take time, and with cakes we generally do not have the patience to wait an entire day to see the effects on our batter. Also, cake batter is more runny and is not very good at trapping gas before the baking process begins. So we rely mostly on Chemical Leavening while baking cakes, and this involves using a base or alkali, which is usually sodium bicarbonate – commonly known as baking soda, and a weak acid like lemon juice, buttermilk, yogurt, vinegar or cream of tartar. The trick is in the timing of introducing our two main characters to each other. Too early and the reaction would fizzle out before you are ready to bake – too late and the reaction does not get time to get properly started before the cake sets. Either way, the “rise” is defeated. Time it right, and they produce millions of bubbles of carbon dioxide (CO2) which if trapped in the batter will expand when heated and make your cake fluffy!
What could go wrong?
One of the other issues that may occur is that the acid and base are overwhelmed by the other ingredients, and don’t meet in the batter enough to cause a good rise. Enter our good friend baking powder. Baking powder usually has baking soda and at least one weak acidic salt mixed together in dry form. Now, acidic salts can live happily with bases as long as they are dry. No reaction, but introduce moisture and the reaction begins. You will also find something called double-acting baking powder which produces gas twice, once during the mixing process and once more during baking. Some recipes call for the use of both baking powder and baking soda. They are not interchangeable, so please try to avoid experimenting with the prescribed proportions. Remember, any un-reacted acid or base will stay in your cake and neither of them taste very nice. If you sense an unnatural tang to the taste of the cake, you have too much leftover acid. If the cake has a bitter aftertaste, it means you have too much leftover soda. If your cake rose too high too fast and then collapsed in the centre, it means you had way too much acid/base reaction. Last of all, if you happen to encounter a recipe that does not list an acid ingredient, be very suspicious!
Famous last words…
Typically, keep three things in mind to get this right –
- Keep the acid and base separate for as long as possible. This is usually achieved by keeping the base in the dry ingredients during mixing, and keeping the acid in the wet ingredients. For example – cream of tartar is usually added to the egg while beating. This is because the acid helps the eggs stay firm and the foam stable during the beating process. The other purpose that the acid has is to react with the baking soda/baking powder when they meet, which is usually the last step before popping the batter in the oven. You may be required to use other acids – such as buttermilk, yogurt or lemon juice. Remember, keep it with the wet ingredients until the last step.
- If you are working with batter that may be too clumpy, thick or thin, you reduce the chances of the acid and base coming together. One of the ways this can be helped is to use an emulsifier and anti-caking agent such as Glycerol Monostearate or GMS (ironically, caking here refers to unmixed clumps forming when you mix solids and liquids/fats). GMS helps create a smoother batter and this promotes the reaction purely by allowing the baking soda to mix with the acids in the wet ingredients. GMS also has other benefits in baking like giving the cake a richer crumb and also happens to be a preservative, but more on that in another post.
- Once the reaction begins, you need to get the batter into the oven as quickly as possible. Don’t let mixed batter stand waiting outside the oven for too long if you really want a fluffy cake. So what do you do if you need to bake two tins but your oven isn’t big enough for both of them. Simple, mix only half of the wet and dry ingredients at first, and when the first cake is about to get done, mix the rest. Trust me, timing is super important here.
Do these things and your cake should turn out nice and pillowy!
So now that we’ve fixed our cakes, what if you’re making bread, and you need a more patient, long-drawn leavening process?
More on that, and the other kinds of leavening, in the next part…