You may not have thought of it this way before, but baking is really a type of chemistry experiment – albeit a tasty and useful one which you perform in your kitchen instead of a lab.
Each of the ingredients you use serves a particular function, reacting with each other to produce new combinations and create the structure, flavor and texture of the finished baked product.
While an element of chemistry is involved in other forms of cooking as well, you can generally be a bit more flexible there in comparison to baking.
If you add or remove an ingredient from a stew, for example, it is likely to only affect the flavor. Remove a critical ingredient from a cake however, and it could be a recipe for disaster!
A Deeper Understanding
It can be helpful therefore to understand the function of the different ingredients in baking.
By knowing the different functions of salt in baking for example, or how different leavening agents produce different effects upon the product, you can get a better understanding of what is going on in the oven.
This can be very useful when troubleshooting bakes which didn’t go quite as you had planned, or when you need to substitute an ingredient for something else.
What’s more, by truly understanding the functions of the various ingredients in baking you can even take the leap from following recipes to developing your own, unique baked creations.
It is worth noting that the ingredients sometimes play different roles, depending on the type of baking they are used in. The chemistry of bread baking differs somewhat to the chemistry of baking a cake, although they do of course share many similarities.
Here follows then an overview of the functions of the most popular ingredients in baking bread, cakes and pastry. We will start with the dry ingredients, before moving onto the fats and liquids, and then finishing with the various leavening agents.
The Function of Flour in Baking
It all starts with the flour. The vast majority of baking uses wheat flour in its various forms, and it is this ingredient which gives form and structure to the baked product. It is the substance of the cake or loaf, providing texture and nutritional content.
Wheat flours contain two proteins called gliadin and glutenin, which when mixed with water join to form the protein gluten.
Gluten can form into long strands and even into a large matrix or web, which can trap the escaping carbon dioxide gas produced by leavening agents during baking. The gluten matrix therefore helps the bread, cake or pastry to rise, and is eventually set in place towards the end of baking.
The amount of protein contained in flour and the extent to which it is allowed to develop are important factors in the final texture of the baked good.
A high level of gluten will produce a tougher, chewy texture that is required for bread, whereas less gluten development will give the tender, crumbly texture desired in cakes and pastry.
Not all wheat is the same, with so-called hard wheats which are grown in cooler climates such as the northern US and Canada, having a higher protein content than soft wheats which are grown in warmer climates such as the southern US and southern Europe.
While these wheats can sometimes be used on their own, millers usually create mixes of several different types of wheat to create flour with a specific protein content and thus specific baking characteristics.
Bread flour contain the highest levels of protein, about 12%, and so creates a strong web of gluten that leads to a soft, fluffy loaf with great volume and a chewy texture.
Specialist bread flours or those produced from single varieties of wheat can have different protein levels however, and produce different types of bread.
A very high protein bread flour, such as Canadian Manitoba Cream, will give the greatest volume to a loaf, whereas a lower protein bread flour will produce bread with a distinctly European character, such as an Italian ciabatta or a French pain de campagne.
Cake and Pastry Flour
Unlike bread, cakes and pastries require only a limited amount of gluten development. Too much gluten will lead to your cakes becoming tough and chewy, more like a sweet bread than a cake.
Cake and pastry flour is therefore mixed to have a much lower protein content, of around 7.5%. This allows the flour to hold together and give structure to the cake or pastry, while still having a tender and crumbly texture that breaks easily apart.
Gluten development is further hindered in cakes and pastries by the addition of fats and sugar (see below).
All-purpose flour sits somewhere in between bread and cake or pastry flour. It is a mix of both hard and soft wheats which creates a flour with about 10.5% protein.
This is enough to form sufficient gluten in bread baking, but not so much that it will have adverse effects upon the texture of a cake or pastry. It is something of a compromise, which will not give quite the same volume as a high-protein bread flour, but which is a good choice for those who do not bake quite as often.
It is advisable to use a little less all-purpose flour in a cake recipe if cake flour is called for.
Self-rising flour is a variety of all-purpose flour which has had baking powder and salt added to it.
This allows it to be used directly in cakes without the addition of salt or a leavening agent. It ensures that the baking powder is distributed evenly throughout the flour, avoiding the need to sift them together before adding the other ingredients.
Baking powder deteriorates over time, so self-rising flour that is past its use-by date may have lost some of its potency.
You can make your own self-rising flour by whisking in 1½ teaspoons of baking powder and ½ teaspoon salt into one cup of all-purpose flour.
Whole Wheat Flour
Unlike bread flour which is made from only the central part of the wheat grain known as the endosperm, whole wheat flour is milled from the whole grain, including in it the bran and germ.
These elements are highly nutritious, containing large quantities of fiber and minerals such as iron and zinc. It is therefore used in place of bread flour wholly or in part to increase the nutritional content of a loaf.
It gives a more complex flavor to bread, less sweet than white bread flour.
The bran in whole wheat flour cuts through the gluten network in a dough during mixing, leading to less volume and a heavier, denser loaf.
The germ contains higher levels of unsaturated fat, and therefore reduces the shelf life of whole wheat flour.
Many alternative flours are also available for baking, some of which, such as rye and corn, have long histories of being used in traditional recipes.
Others have seen increased popularity in recent years with the rise of gluten-free baking, such as soy, buckwheat, oat, rice and potato starch flours.
While these different flours each have their own particular properties and nutritional profiles, what they have in common is a significantly lower level of gluten compared to wheat flours.
This makes their chemistry somewhat different to that of baking with wheat flour, and they often require the addition of additional binding or thickening ingredients to help them rise and give structure to the product.
It is best to follow specific instructions for any recipes that call for these flours, and note that they can rarely be substituted for wheat flour without additional alterations.
The Function of Sugar in Baking
Sugar does much more in baking than just imparting a sweetness of flavor, although this is of course an important function of sugar.
Its various forms, from simple granulated sugar to the more complex caramel, honey and molasses, each offer a different type of sweetness to the baked product.
In yeasted products such as bread or vienoisserie, sugar also acts as a food for the yeast, kick-starting fermentation and helping the product to rise. The yeasts eat the sugar and convert it to carbon dioxide which aerates the dough or batter.
Too much sugar however will slow fermentation, as sugar draws water out of the yeast cells, preventing them from functioning. Very sweet doughs will therefore take longer to rise, and may require a special kind of yeast.
In cakes and pastries, sugar plays an important role in limiting gluten development, increasing the tenderness of the cake. This also allows cookies to spread when baked in the oven.
The water-binding properties of sugar also help baked products to retain their moisture over longer periods, keeping them soft and delaying staling.
Sugar also contributes to crust development, affecting its color and flavor. The crust is the hottest part of the product in the oven, and it is here that complex chemical reactions occur, known as Maillard reactions.
These, along with the process of caramelization, produce many different organic molecules that, when combined, produce the wonderful flavors that are found in bread and pastry crusts, as well as their brown color.
And we should of course not forget sugar’s role in decoration. Icing sugar and pearl sugar can be dusted or sprinkled over baked cakes and pastries to produce a pleasing effect, or icing sugar can be mixed with water to create icing or frosting.
The Function of Salt in Baking
Salt shares some functions with sugar in its role in baking. It not only adds flavor to bread and cakes, but it also brings out the best in the flavors of its fellow ingredients.
A loaf of bread or a cake without salt will taste bland, but too much salt will overpower the other flavors.
Besides flavor, salt helps to strengthen the gluten network in a bread dough, allowing it to trap more carbon dioxide and give volume to the loaf. A bread dough lacking in salt will be very short, sticky, and result in bread that is dense and doughy.
Like sugar, it also binds to water, drawing water from yeast cells and slowing fermentation. This moderating effect is important in bread baking as it prevents the dough from rising too quickly, and allows other fermentation reactions to occur, building more complex flavors.
The Function of Fats in Baking
Fats are used in many forms in baking, and serve a range of functions. Both animal fats such as butter and lard and plant-based oils can be used to differing effect, along with chemically altered fats such as margarine and shortening.
Fats generally serve to shorten a dough, hindering the development of gluten and producing a more tender crumb.
In a pastry dough, butter or some other solid fat is first rubbed into the flour to coat the individual granules with a layer of fat. This stops the proteins in the flour joining together to form gluten.
Butter can also be creamed with sugar to trap air before being added to a cake or pastry mix. This gives a lighter and airier texture to the cake.
In puff pastries and laminated doughs, butter serves to create layers interspersed with dough, which trap escaping steam when baked and cause it to rise.
Fats are also one of the big contributors of flavor and mouthfeel in baking, and like salt add both their own flavor and enhance the flavors of the other ingredients. Butter especially adds a richness of flavor much prized in cakes and pastries, as well as giving pastries a lovely golden-brown color.
When added to a bread dough, a small amount of fat can help the gluten to stretch, which can give the loaf greater volume. It also helps to soften the crumb, however too much will negatively affect the gluten development.
The Function of Milk and Other Liquids in Baking
Liquids are like the ignition keys in baking. The proteins, starches and leavening agents in the other ingredients need to be hydrated for the chemical reactions to occur, otherwise they will simply sit together as dry ingredients in a bowl.
It is the liquid that allows the gluten to form in flour, and that wakes the yeast cells from their hibernation. The hydration of starches and proteins adds moisture to the final product, and kick-start enzymes in the flour that break down the starches into simple sugars for the yeast to eat.
Bread tends to use water for liquid, whereas cakes usually use milk. These are not hard and fast rules however, and they are often interchangeable in recipes.
They will give different results however, with milk adding a softness to the crumb of both cakes and bread. It also provides nutritive value in the form of protein and fat, and assists in the browning of crusts.
White bread will have a particularly white crumb if milk is included as part of the liquid. Cakes will not be as rich if milk is not used, but water can be a good alternative in vegan baking. Generally, milk provides better flavor and mouthfeel.
Liquid also plays an additional role in the rising of baked goods, as the water turns to steam in the oven. This helps to expand the air pockets caused by fermentation, giving greater volume.
In layered puff pastries the steam will be caught between the layers, causing them to puff up.
The Function of Eggs in Baking
Eggs are the real multi-tasker of the group, providing functions similar to each of the other ingredients here, along with some unique to themselves.
They are really two ingredients in one, as the egg whites and yolks have very different properties, each performing different functions. They are therefore often separated in certain recipes in order to take advantage of their individual functions.
Both parts of the egg contribute nutritive value to a cake, the whites providing protein and the yolks fat. Being about 75% water, they also provide liquid to the mix, hydrating the other ingredients.
Used whole, eggs function as a binder of the other ingredients, holding a cake together. They can thicken batters, and be used as a glazing on the surface of baked goods to provide a golden-brown color.
There are many complex proteins in eggs, which undergo transformations when they are beaten, heated, or otherwise manipulated in some way.
Beating an egg incorporates air into it, which can then be added to a cake mix to make it light and airy. They act as a leavening agent, creating structure in cake.
Eggs are also a natural emulsifier of fats and liquid, helping them to be mixed without separating and so creating a uniform structure in the mix.
The fat in egg yolks contribute flavor to a cake, while also improving texture, as with other fats. Egg whites create structure, offering stability, aeration and consequently volume.
Egg whites alone can be manipulated in many ways to create quite complex structures and effects in different baked goods.
The Function of Leavening Agents in Baking
The term “leavening agent” refers to any ingredient that helps a dough or batter to rise. They produce carbon dioxide when they are heated in the oven, which is then trapped in the structure of the dough to form small pockets of air.
These are then baked in place as the cake or loaf sets. These agents can be natural, living organisms, or synthesized chemicals.
Baker’s yeast is a living microorganism that belongs to the kingdom of fungi. The particular strain of yeast used in baking is called saccharomyces cerevisiae, and has been selected and bred for its quick and effective action.
It can be found in dried and fresh forms, with the dried form lasting much longer than the fresh.
Yeast is activated by liquid, and works best at warmer temperatures of around 85-95°f (30-35°c). It feeds upon the sugars in flour, which are themselves broken down from starches by enzymes present in the flour.
The yeast ferments these sugars, producing carbon dioxide, alcohol, and other organic molecules as by-products. The carbon dioxide is caught in the gluten structure of the dough, giving it volume, and contributing to its texture.
The by-products of yeast fermentation also produce much of the flavor and aroma in a yeasted baked product, and the longer that it is allowed to ferment, the more complex the flavor will become.
Once the yeast has exhausted its supply of sugar however it will cease to produce carbon dioxide, and so it must be placed in the oven at just the right time to ensure a good final rise.
The speed of yeast fermentation can be controlled by the addition of salt and sugar. Both ingredients draw out water from the yeast, slowing them down.
Doughs that contain high levels of salt or sugar will therefore need longer proving times or larger quantities or special strains of yeast.
Yeast multiply very quickly in a dough during fermentation, reaching a peak once a critical amount of the sugar has been exhausted. They are all destroyed in the heat of the oven during baking, but their flavorful by-products remain.
Unlike yeast, baking soda is a chemical leavening agent which is more used in cakes than in bread. It is the chemical sodium bicarbonate, which produces carbon dioxide when mixed with an acid ingredient and a liquid.
This carbon dioxide then aerates a dough or batter much like yeast does.
Recipes which use baking soda as a leavening agent will make sure to include an acidic ingredient as well, such as lemon juice or vinegar.
The reaction occurs as soon as the baking soda comes into contact with liquid, and so it is important to bake it as soon as possible after mixing to contain as much of the gas as possible in the batter.
Baking powder is essentially a more convenient form of baking soda and is often used in quick breads. It combines sodium bicarbonate with an acidic ingredient – usually cream of tartar – so that all is needed to start the reaction is the addition of a liquid.
To ensure that the reaction does not occur prematurely in humid environments, a filler material is also added that acts as a moisture absorbent. This is usually a food-derived starch such as potato starch.
Sufficient baking powder or baking soda must be added into a cake or cookie mix to give it an airy texture. Too much however can lead to the final product having a slightly bitter flavor.
Now that you have a solid grasp on the fundamentals, find out which tools you need to take your baking to the next level.
Sarah is the founder of Baking Kneads, LLC, a blog sharing guides, tips, and recipes for those learning how to bake. Growing up as the daughter of a baker, she spent much of her childhood learning the basics in a local bakery.