Bread on trial
Today we put bread dough on trial; or rather, we bring to the stand the various processes that take place while the dough is being made and that are hugely important for how the bread finally turns out.
Bread, as we have stressed at length ever since we first began talking about it, is a single, consistent mixture of four main ingredients in varying proportions: flour, water, yeast and salt, to which other ingredients may be added in small amounts; but it is always these four that give bread its shape. And yet we Italians know all too well that four ingredients give rise to a huge range of products with shapes — but above all tastes, aromas and fragrances — that are completely different from one another.
The processes we are discussing in this post help to generate that surplus of taste, aroma and fragrance. These hugely important processes, which take place during the mixing stage, are of four kinds. Let's look at them together.
PHYSICAL-MECHANICAL PROCESSES: when we make bread, the first stage of preparation is the dough-forming phase, which consists of mixing the ingredients. Whether done by hand or with machines, this operation must in any case yield a smooth, even dough that is soft and elastic. The mixing stage plays a hugely important role in the quality of the finished product, because the very characteristics of the dough — and how it will develop, first during fermentation and then during baking — depend on it.
The physical-mechanical processes call for careful mixing of the ingredients, because kneading them creates a bond, at the molecular level, between the chemical components of the flour and the rest of the ingredients… an aspect that must never be underestimated. During mixing, the main reaction is the formation of the gluten network (recall the union of gliadins and glutenins to form a spongy mass capable of taking in liquids and gases); at this same stage there is always a certain incorporation of air, which allows the density of the dough to decrease and its softness to increase. The oxygenation of the dough — you might not think so — is of fundamental importance, which is why professional machines (plunging-arm or spiral mixers) have been designed to be able to "aerate" the dough. It favours fermentation processes, because oxygenating the dough strongly stimulates the activity of the yeasts. As described in the post on yeasts, remember that in the presence of oxygen (aerobiosis) they multiply and produce ethyl alcohol. What is more, oxygen strengthens the gluten network.
I mentioned that the mechanical action of the dough mixer is of fundamental importance in activating the physical-mechanical processes. The effort the mixer has to exert against the dough is not always constant and changes according to the characteristics of the dough itself. The mixing stage takes place over three periods:
- THE FIRST PERIOD runs from the initial mixing of the ingredients up to the formation of the gluten network, progressively increasing the effort required of the mixer up to a maximum that then remains more or less constant;
- THE SECOND PERIOD: the effort of the mixer brings the dough to take on its optimal characteristics: a smooth, extensible appearance. The gluten network gradually becomes softer and the dough loses resistance thanks to proteolytic reactions. At this stage the dough is ready to be removed from the mixer;
- THE THIRD PERIOD: if mixing is prolonged beyond the second period, the effort of the mixer will begin to decrease, because the dough will become softer and softer owing to excessive overheating, which causes the gluten network to break down.
From all that has been said so far, it is therefore clear that the mixing time plays a fundamental role in the successful outcome of the dough.
For each dough, the time needed to reach the optimal characteristics of the second period depends on three factors:
- THE STRENGTH OF THE FLOUR: the mixing time of a weak flour will logically be shorter than that needed for a strong flour, because the resistance of its gluten network is lower;
- THE TYPE OF DOUGH, whether dry, soft or slack. Dry doughs are generally mixed less than slack doughs, because they need to be fairly "cool" after mixing since they are then run through the cylinder (we will look at cylindering in the next post); slack doughs, on the contrary, need to be mixed longer to reach their maximum consistency;
- THE TYPE OF MIXER: kneading by hand exerts minimal effort and is very slow. A spiral mixer allows faster mixing, because it applies more friction to the dough than kneading by hand does.
COLLOIDAL PROCESSES: when flour is mixed with water, a highly hydrated colloidal mass forms. Gliadins and glutenins absorb an amount of water 2–3 times their own weight. As mentioned earlier, by absorbing water the gluten proteins swell, stretch and bond together to form gluten. Gluten, in turn, continues to absorb water, liquids and gases, which subsequently cause the dough to swell. In food technology, dough is a complex system made up of three phases: a solid phase, a liquid phase and a gas phase.
- THE SOLID PHASE is made up of the gluten proteins, the starch granules and the portion of bran still present in a greater or smaller amount depending on the type of flour used. Starch too is able to absorb liquids, in a smaller amount than gluten, but since its quantity in the flour is considerable, the water it manages to trap is ultimately similar to that of gluten. The bran, finally, is the solid part with the greatest absorbing capacity (800% of its weight), and this explains why wholemeal doughs are very absorbent.
- THE LIQUID PHASE: besides water, this phase is made up of all the soluble substances that the ingredients consist of, namely: soluble proteins, mineral salts and sugars.
- THE GAS PHASE, produced by the air incorporated during mixing and by the carbon dioxide generated by the yeasts during their anaerobic/fermentative phase.
BIOCHEMICAL PROCESSES: these are activated by the enzymes in the flour and the yeast, which act on — and modify — the fats, carbohydrates and proteins of the flour and the other ingredients, thereby also contributing to the formation of that homogeneous mass we call dough. The proteases in the flour, activated by the water, break down its proteins, making the dough softer and more plastic. The amylases hydrolyse the starch as soon as mixing begins, but this peaks during fermentation, providing sugars that nourish the yeasts. The biochemical process of starch hydrolysis also leads to a liquefaction of the dough. The lipases that break down the fats aid the extensibility and malleability of the dough.
MICROBIOLOGICAL PROCESSES: these concern the microflora of the dough, that is, the development and multiplication of yeast cells and lactic acid bacteria, with their respective alcoholic and lactic fermentation. During the mixing stage, as we saw above, the large amount of oxygen assists the multiplication of the saccharomyces, which then begin to ferment during the first stage of working the dough, known as bulk fermentation.
In these few lines we have been able to understand, probably a little better, how many causal factors come into play within that mass of just four ingredients. What does it take to make bread… simply a great deal of knowledge, experience and passion. Hats off to our talented bakers.
Blog by Enrico Gumirato, pastry chef and instructor.
