No other shop in the world attracts passers–by with its aromas quite like a bakery. An irresistible, almost “magical” smell, which owes its tantalising appeal to science. It is no exaggeration to say that our universal love of bread is a matter of ... chemistry. Today, we will learn why.
What are bread ingredients?
Bread is one of the simplest foods. It is made from just four ingredients: water, flour, yeast and salt. Even its preparation is a procedure of unarming simplicity: the ingredients are mixed together with the gradual addition of water to the flour in order to obtain a smooth and elastic dough.
Behind these simple gestures, such as the hands at work kneading the dough and a jug pouring out clear water, lies the first secret of bread-making. Flour, in fact, contains great quantities of proteins, called glutenin and gliadin, which together form the gluten we are all so familiar with.
A good flour for bread–making must contain at least 7% gluten but, the more gluten there is, the better the dough and the resulting bread will be. The addition of water causes the glutenin and gliadin to form a strong network resulting from two types of chemical chains: those of hydrogen and disulphide. Usually, the two proteins have a somewhat rolled up shape and almost keep their bonds to themselves, but kneading unrolls them and exposes the chains so that they bind to each other.
Finally, the more the dough is kneaded the stronger these bonds, and consequently the network, will become. Hence, a perfect loaf of bread requires the gradual addition of water and flour with a high percentage of gluten, and plenty of time dedicated to kneading the dough.
At this point, the bread is left to rest, but don’t be fooled into thinking it has gone to sleep: the most important chemical reaction takes place during this phase. Firstly, the water activates the enzymes in the flour, which convert the starch into maltose, a form of sugar. The yeast, on the other hand, a harmless fungi, makes good use of the maltose and any other existing sugars to start the fermentation process.
So, this is the second golden rule: add a little sugar to the dough to facilitate the action of the yeast. Fermentation is a process, one which we have previously addressed in our column, which transforms sugars into other compounds, comprising carbon dioxide. The latter, in the form of bubbles, causes the bread to rise and makes it soft. The third rule is to knead the bread again halfway through its rest-phase, in order to make these bubbles the same size and distribute them evenly throughout the mixture. Finally, when the dough is ready, it must go into the oven to be baked.
Is that all? Not likely! Do you remember all the sugars mentioned in the previous phases? Thanks to the high oven temperature, these combine with the proteins to trigger the Maillard reaction. This gives rise to those substances responsible for the typical aroma and flavour we find so captivating when passing by a bakery.
The ultimate bread secret? Temperature
This brings us to the final rule for perfect bread: when baking, pre–heat the oven to a temperature between 140 and 165°C, which is the temperature range in which the Maillard reaction performs best.
Higher temperatures may be used, but there is always a risk of finding yourself with a nicely coloured, deliciously smelling loaf that is completely uncooked inside.
Some final tips? Use salt to regulate how much the bread rises: the more salt is added, the more the compact the bread will be.
Finally, bear in mind the flour to water ratio: with high gluten flour, it should be around 5:3. For example, 500g of flour and 300g of water. Nothing to it, is there? But then, Italians have a saying that goes: “As good and simple as bread”.