When you sift the flour to make the dough, you introduce air. Then, with mixing and later during folding, more air is incorporated into the dough.
However, is oxygen essential for the dough to ferment, or can it rise in an airtight space?
In the first stage of dough preparation, incorporated air helps the gluten structure to develop and yeast cells to multiply. However, air is no longer necessary for the fermentation process. The yeast is capable of anaerobic respiration, which means that it produces energy from the sugar in the dough without using oxygen, and produces alcohol and carbon dioxide as byproducts. The lactic acid bacteria present in the dough can also function anaerobically. Therefore, the formation of lactic acid and acetic acid, which play an important role in the development of the flavors of the dough, also does not require air.
Effect of air on the dough
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Oxygen helps the gluten to form. However, mixing too much air into the dough will eventually cause its structure to break down, making the dough soft and sticky. Therefore, you have to be careful not to mix too strongly and for too long, especially when using a mixer.
Overworking the dough leads to oxidation. Too much oxygen incorporated as a result of excessive mixing breaks down the carotenoid pigments in the flour, which give the bread its color and aroma.
When you make a sourdough starter, air plays an important role, because wild yeasts are airborne.
The presence of air speeds up fermentation. Yeast cells multiply rapidly because of the oxygen and consume the available sugars faster. The energy produced in this way is used by the yeast for various cellular functions. However, without oxygen, the yeast does not multiply but produces carbon dioxide and alcohol. While we’re on the subject of yeast, you might be interested in my article on if adding more yeast to homemade bread can make it softer.
If the dough rises in the presence of air, the moisture content evaporates and the surface dries out. However, the ideal environment for fermentation is moist. You can cover the bowl in which the dough rises with a wet kitchen towel or a lid. Using plastic wrap to cover the dough is also a common solution, but it is not environmentally friendly.
I use a Tupperware mixing bowl, similar to the one available on Amazon, to rise the dough. I have been using my Tupperware bowl regularly for 27 years. A truly high-quality product that is still in perfect condition apart from some discoloration.
The closed container helps to keep the dough in a moist environment while it ferments, without the influence of outside air. Airless fermentation favors the development of rich flavors in the dough.
However, we must also note that the ambient temperature has the greatest effect on the fermentation of the dough. At room temperature, the dough rises quickly, but in the refrigerator at 6-7°C/42-44°F, the activity of the yeast slows down significantly but doesn’t stop.
How does air get into the dough?
Most of the air enters the dough during mixing, starting with sifting the flour. The dough can be kneaded in the traditional way by hand, but you can achieve fast and good results by using a standing mixer, like the top-quality Kenwood Chef I regularly use and highly recommend. When using a mixer, it is important to take care not to overwork the dough.
Air is also incorporated into the dough by folding during the first rising period, also known as bulk fermentation. By folding the dough, the yeast cells reorganize and continue the fermentation, having access to fresh nutrients.
What is actually in the air pockets of the dough?
The air holes in the dough contain carbon dioxide, which is produced by the yeast during the fermentation of sugar. Part of this carbon dioxide is gaseous, while the other part is in a liquid state in the dough. During baking, however, it also becomes gaseous under the influence of heat and further increases the volume of the bread, eventually evaporating.
Final thoughts
Yeast can ferment with or without oxygen, but it needs it for reproduction. However, lactic acid bacteria, which play an important role in the development of dough flavors, also don’t require oxygen for their activity.
In summary, a certain amount of oxygen is required at the beginning of the dough preparation, during mixing, but the fermentation process can also take place in an airtight place. It is very important to protect the dough from drying out during fermentation, so it is a good idea to rise it in a covered container.