Head down and ferment - Part 1
Friends of Erre4m good morning and welcome to this new post. Today we're going to pedal the bread dough; we're going to start dealing with one of the most important processes in dough and that is bread fermentation.
In the last post we talked about all the very important processes that happen mainly during bread kneading and their fundamental role in the success of the finished product. Before talking about today's topic, I would like to point out that this information is meant not only for salty leavened products but obviously also for sweet ones (brioche, croissants, panettone, doves, etc...).
The fermentation, which is the subject of today's discussion, is another indispensable element necessary to understand what happens in a mass of flour, water, yeast and salt that is transformed into bread.
The fermentation is fundamental to obtain a dough with ad hoc characteristics for its formation, leavening and baking. During the fermentation phase, some of the processes discussed in the last post continue: colloidal processes due to gluten and starch granules, absorb liquids and gases introduced into the dough (solid phase); while the production of carbon dioxide generated by the yeasts increases, increasing the volume and softness of the dough (gaseous phase).
During fermentation, the gluten proteins (gliadins and glutenins) continue to swell because they absorb the CO2 generated by the saccharomycetes, they stretch and bind together making the dough more spongy, while the proteolytic enzymes help to make the dough more malleable.
Another important action of fermentation is the increase in the temperature of the dough. This increase is due to the breakdown of sugars by the yeast. This reaction is, in technical jargon, called exothermic reaction which means that it generates heat. The exothermic reaction, towards the end of fermentation, causes the dough to lose 2-3% of its weight. This weight loss is, in detail, caused:
- by the transformation of sugars (which are dry/solid substances) into volatile substances (carbon dioxide and ethyl alcohol);
- by the evaporation of water.
The main processes that occur during dough fermentation are: alcoholic fermentationand lactic fermentation
THE ALCOHOLIC FERMENTATION
As previously mentioned, the absolute protagonists of alcoholic fermentation are yeasts. In the post dedicated to them I specified that they are unicellular fungi classified as Saccaromyces Cerevisiae that belong to the family of Saccharomyces and that we commonly call beer yeasts. Like all unicellular beings, yeasts also have reproductive and fermentative capacities.
For didactic purposes, I would like to remind you that Saccharomyces reproduce and multiply in the presence of oxygen (aerobiosis), while in the absence of oxygen (anaerobiosis) they ferment, producing volatile substances.
You can use yeast either in tablet form or in dry form. It is interesting to know that 1g of yeast contains 10 billion saccharomyces cells which, once inserted in the dough and in a suitable environment, begin to reproduce rapidly.
It may seem strange but the multiplication of yeast cells is more active if their initial quantity is small. Laboratory tests have shown that if the flour in the dough contains 0.5% yeast, the increase in cell mass will be as high as 88%, while with 2% the growth is reduced to 29%. So you can start a dough if you already have flour with yeast in it.
In addition, the cellular multiplication of yeasts is also stimulated by the presence of some important substances that are necessary for their metabolism. I am talking about vitamins and mineral salts that are naturally present in stone-ground flours and in sufficient quantities; while in very refined flours they are found in scarce proportions and therefore it may be necessary to add them in order to favour the multiplication of the yeast and its subsequent fermentation.
Another very important factor that largely affects the optimal fermentation of yeasts is the temperature. The optimum temperature that facilitates yeast multiplication is 25-30°C, while their maximum fermentation activity is reached at 35°C. Therefore, both the temperature of the dough and the temperature of the environment play a fundamental role. The temperature of the water (as seen in the previous posts) and the temperature of the fermentation and leavening environment are to be taken into account.
To complete the discussion, humidity is also necessary for fermentation. In fact, bakeries are equipped with leavening cells that not only heat the environment but also regulate the humidity. The humidity necessary for the yeasts is about 80%. A home-made system is to create a leavening cell in the oven (at minimum) by inserting a bowl of warm water at the bottom; or to use the oven at minimum covering the bread with transparent film so that the humidity is generated by the bread itself as it rises (in this case the bread must be placed in a container high enough to avoid contact with the film).
During the kneading process, a considerable amount of oxygen is inserted by the movement of the kneading organ of the machine, which allows the yeasts to become aerobic. In this state they begin to reproduce and multiply. Once they have exhausted the oxygen present in the dough, the yeasts begin to ferment.
The alcoholic fermentation carried out by saccharomyces is fundamental for leavened dough because it allows the production of gas in the form of carbon dioxide, which increases the volume of the dough and makes it soft, both for dough and for baked bread.
In this phase, the yeasts, thanks to their enzymes called zymes, transform simple sugars (glucose above all) into ethyl alcohol and carbon dioxide. As we know, yeast can only feed on simple sugars, while all the other sugars in the dough such as maltose and sucrose are reduced to simple sugars by the amylase in the flour.
To conclude, the speed of fermentation of a dough depends on a few factors. Let's look at them:
- quantity and quality of yeast =with a suitable amount of yeast (2-4%) having an optimal vital activity the fermentation will be fast; however, having an excessive amount of yeast exceeding 6% of the amount of flour (because it is on this that the proportions of the rest of ingredients are measured), the opposite effect will occur;
- recipe =the higher the rate of hydration of the dough (i.e. the amount of water), the greater the fermentation activity of the yeasts;
- method of preparation =doughs prepared using the indirect method (biga-poolish) ferment faster than those prepared using the direct method;
- environmental conditions =the higher the temperature and humidity, the faster the yeasts ferment. Be careful though! The temperature should not exceed 38 ° C because above 40 ° C the Saccharomyces begin to inactivate and reached 50 ° C completely stop their metabolism
I don't know about you but I personally am always amazed at how many variables are involved in a bread dough...in those only four ingredients. It's not really true that it doesn't take anything to make bread.
See you at the next one to talk about lactic fermentation...HAPPY BREADMAKING TO ALL!
Blog by Enrico Gumirato pastry chef and trainer.