The Science and Art of Cake Baking

by Les Saidel - March, 2012

Queen Marie Antoinette is accredited with the statement "If they don't have bread, let them eat cake!" Marie, born in Austria, was no foreigner to baked delicacies, at a time when Vienna was the epicenter of the baking arts, centuries before that mantle passed to the French. Her infamous statement that sparked a revolution, typified the detachment of the aristocracy from reality. If the impoverished masses could not afford to buy bread (made from flour, water, salt and yeast), they could hardly afford cake (made from more expensive ingredients such as eggs, milk, sugar, fats etc.)

To be historically accurate, Marie, who spoke French, used the word "brioche", which has commonly been translated to English as "cake". However the resemblance between cake, as we know it today and the brioche to which Marie was referring, is distant. Brioche is in fact "rich" bread, yeasted bread to which other ingredients have been added such as egg, sugar and fats (oil/margarine). In fact brioche closely resembles what we know today as egg bread or challah.

The dividing line between what some people regard as bread and cake is not totally clear. Even in Jewish tradition, custom differs between Ashkenazi and Sephardic communities. When eating a sweet challah for example, a Jew of Ashkenazi origin will recite the benediction for bread, while a Sephardic Jew will recite the benediction for cake.

For the purposes of this article, we refer to the modern, non-yeasted version of a cake (such as chocolate cake or chiffon cake) and not the yeasted brioche version referred to above.

Baking a cake is both a science and an art. In industrial production, science far outweighs the art due to the use of controlled environments and specialized equipment such as pressurized mixers. For the home baker who does not have access to this high powered technology, baking a cake is more of an art, as obtaining the required textures and results rely predominantly upon observation and instinct.

Many who have baked a cake, simply follow the recipe, without understanding the how's and the why's. To be a truly prolific and expert cake baker however, it is necessary to have at least a basic understanding of some of the science of cake baking.

Before discussing the various types of cakes, let us first examine the primary ingredients of a cake and their functions.

Flour - cake flour, as opposed to bread flour, is lower in protein content and therefore has a diminished gluten structure. Highly developed gluten structure in bread is essential to trap the expanding air of the yeast. In a cake however, too much gluten can lead to a tough, chewy crumb, something which is undesirable. A certain, smaller amount of gluten is required to maintain basic form, and this is usually the case in cake flour.

Fat has many functions in a cake. It provides lightness by aerating with sugar (creaming). Its tenderizing action makes for a soft, light texture by coating the protein particles in the flour and it acts as an emulsifier for combining the liquid and fat components in the mix. Certain fats also add flavour, such as butter.

Sugar is more than just a sweetener. Its osmotic properties help to tenderize the crumb and retain moisture.

Eggs also have multiple functions, they act as a hydrating agent, they tenderize the crumb and they contain natural lecithin which acts as an emulsifier. In addition, the egg whites have a primary function in foam based cakes providing the aeration component of the mix.

Leavening agents such as baking soda and baking powder provide additional aeration in the cake batter via a chemical reaction that begins when the agent is combined with liquid and heated. Baking soda (sodium bicarbonate) and baking powder (a combination of a leavening acid, sodium bicarbonate and a buffer ingredient like cornstarch) undergo a chemical reaction that releases CO2 into the mixture.

Like most baked products, cake is essentially a combination of air - that gives it lightness, form - which is provided by the flour/liquid ingredients, texture - provided by the eggs/sugar/fat and flavour - provided by sugar, salt, cocao, etc.

One of the most important features of a cake is its lightness. In order to create a light, fluffy cake, lots of air needs to be incorporated in the mixture. In bread, this air is created by yeast (in the form of CO2). In cakes, where yeast is generally not used, other methods are employed to inject large quantities of air. The methods by which air is incorporated into a cake differ between the two main categories of cakes - fat-based cakes and foam based cakes.

Fat Based Cakes

These are so called because they contain a substantial amount of fat which comes in either solid form, such as butter/margarine or in liquid form, such as oil. Fat based cakes are rich, moist and dense. American-style cakes are the generally of this type.

Incorporation of air in solid fat-based cakes is provided by creaming the fat with sugar. The process of creaming is a vigorous mix that combines the sugar, fat and air at a high speed, thus creating a fluffy, light, aerated emulsion. Following the creaming process, eggs are gradually added to the mix and then whipped. Finally the dry ingredients (flour, baking powder, cocao, etc.) and the wet ingredients (milk, fruit juice etc.) are gradually added alternately (starting and ending with the dry ingredients) and mixed until incorporated.

Creaming of the fat is usually not sufficient to provide the total air requirement in the cake and further aeration is provided by leavening agents. These leaving agents react with the liquid components in the batter and with heat to produce additional air in the form of carbon dioxide.

To incorporate air into liquid fat-based cakes (using oil instead of margarine), we rely more on the order of adding ingredients, and timing and speed of mixing to produce the required aeration To mix liquid fat-based cakes, one would fill a bowl first with the liquid ingredients followed by the dry ingredients. These are then slowly blended for about 90 seconds, followed by high speed whipping for 4 minutes. The bowl is then scraped and the mixture whipped again for a further 3 minutes on medium speed.

Another type of fat-based cake is called a high ratio cake due to the higher ratio of sugar and liquid ingredients compared to flour. These cakes use specialized fats containing added emulsifiers that help combine the larger liquid content with the fat. Mixing a high ratio cake is a more complex process and starts by coating the dry ingredients with the fat, followed by mixing in the liquid ingredients. Precise mixing times and bowl scrapings in between are essential for the success of this advanced method.

Foam Based Cakes

These rely on whipped eggs to create the leavening infrastructure for the cake. Usually the white of the eggs is whipped to create a foam.

To understand how this process works, consider blowing into water with a straw. If you blow too fast and too hard, large bubbles form that quickly float to the surface and dissipate. If you blow slowly and with less force, the bubbles formed are smaller and take longer to rise. In a cake batter, which is more viscous than water, these smaller bubbles become trapped in the emulsion. Slower mixing creates smaller bubbles, faster mixing creates larger bubbles.

Therefore when whipping egg whites one should start off at a slower speed that creates smaller bubbles and forms an initial uniform foam structure. Once this structure has been developed, you may switch to a higher speed to incorporate the air faster. The small bubble structure will help trap the additional air coming in on the high speed. Following the high speed whip, you then reduce the speed again to medium to reinforce the foam structure. One should be careful not to over whip the egg whites, especially if sugar is added to the whip. If the eggs are whipped until they are too dry, they will break up when mixing in with the remaining ingredients.

There are a number of methods of mixing foam based cakes and each gives a special character to the cake.

The Sponge Method uses the whole egg and leavening agents for the leavening structure. The warmed whole egg is mixed with sugar and then whipped on medium-high to the ribbon stage (the batter falls in ribbon like strands from the attachment into the bowl). You then gently fold in the dry ingredients, pour the mixture into an un-greased, papered pan and bake immediately without delay. Cool upside down as these cakes have a tendency to deflate. Sponge cakes tend to be dryer than high-fat cakes and slightly "eggy" tasting. This type of cake is more European-style and the dryness is offset by soaking the cake in syrup during assembly.

The Chiffon Method uses a combination of whipped egg whites and leavening agents. Chiffon cakes always contain liquid oil which softens the texture. In this method the wet and dry ingredients are combined, followed by the egg foam, which is folded in. Because Chiffon is so delicate in structure, the method of pan preparation and cooling is important. The pan should NOT be greased. This will cause the cake to stick to it and avoid collapse while cooling, which is done with the pan upside down.

The Angel Food Method uses only egg whites as the leavening structure. The egg whites are whipped to soft peaks, at which stage tartaric acid (cream of tartar) is added to reinforce the emulsion. The flour and sugar are then gently folded into the foam. Angel food cakes are baked in un-greased pans and cooled upside down to prevent deflating.

After discussing the two main types of cakes - fat-based cakes that use the creaming method and foam-based cakes that use the sponge/chiffon/angel-food methods, it is worth mentioning that there exists a third category which is basically a combination of the two, called the Modified Creaming Method that combines creaming with an egg foam.

Up till now we have discussed the basics of the science of cake baking - the ingredients and their functions, the different categories of cakes and their respective mixing and baking methods. These guidelines are only general. For example when it says in a recipe "cream sugar and margarine until light and fluffy", what does that mean? The recipe book does not know that you - Mrs. Cupcake - have a 'xxx' electric mixer, you live in Colorado at an altitude of 'n' meters and that today there is 65% humidity in the air. For you to get a light/fluffy texture would require something different than for Mrs. Fortunecookie baking the same recipe using a 'yyy' mixer in Hong Kong at sea level.

This is where the "art" of baking comes in. In an industrial setting, everything is standardized and controlled - the mixer, the atmospheric pressure, the temperature, the humidity, the ingredients etc. In your home however, you have to rely on instinct.

In addition, the above discussion delves only into the first stage of cake baking. In most cases, the above cakes only serve as the basis for the final product. Add to that layering, frosting, filling and more advanced assembly methods using creams, syrups and glazes. When last did you make a birthday cake without frosting? Have you ever eaten in a hotel where they give you plain cake with no adornments?

That aspect of cake production is a world in itself and beyond the scope of this article. If you think the initial stage of baking the cake base is an art, wait until you start decorating and assembling the cake. That really is art.

They say that a great structure starts with a firm foundation. Unless your foundation cake is stupendous, your final assembly can never be. First learn to bake basic cake types, experiment over and over again. Feed the successes to your family and the failures to the dog. Soon you will become a baking expert if you develop the correct instincts by careful observation and learning what works and what doesn't. Most importantly, don't be intimidated, this is not rocket science. The worst thing that can happen is that you will have a fat dog!

So get out those recipes, learn to distinguish the different types and try to bake them and experience their different textures and properties. Practise, practise, practise! Experiment - try mixing for an extra few minutes, or fewer minutes and see the results.

Soon you will develop those instincts and be well on your way to becoming a pastry chef extraordinaire!

Les Saidel


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