Understanding the importance of dough fermentation in bread-making: factors, effects and considerations

Because we have seen intense discussions on various forums regarding the purpose, duration, and necessary conditions for dough fermentation, we thought of providing our own explanations regarding this stage of the bread-making process.

Many people believe that the purpose of fermentation is to accumulate carbon dioxide in the dough mass. However, this is merely the means by which the purpose is achieved. The goal is to increase the volume of the dough while maintaining the shape imposed during the previous mechanical processing of the dough. You should know that yeast produces carbon dioxide at a rate dependent on temperature. It is capable of doing so even at 0 degrees Celsius, which is why certain bread-making techniques involve long fermentations under refrigeration or longer-term preservation techniques for specific types of starters.

As a byproduct of yeast metabolism, and considering that yeast metabolism intensifies with temperature, the amount of carbon dioxide will be greater as the temperature of the environment in which the yeast evolves increases. The maximum amount of carbon dioxide is reached around 43 degrees Celsius, and its production ceases at 55 degrees Celsius due to cell death (irreversible denaturation of cellular proteins occurs).

Although the highest rate of carbon dioxide production is observed at a temperature of 43 degrees, you have not encountered bakers working at these temperatures for fermentation or working with dough temperatures in this range. There is a reason for this as well: the dough temperature affects the rate of enzymatic reactions in the dough, and this rate must remain correlated with the metabolic activity of the yeast. The dough must be able to maintain its rheological properties (extensibility, strength, gas retention capacity) at least during the early stages of baking, which is impossible if certain enzymes in the dough are overexpressed (e.g., proteases or oxidases). Additionally, due to the extremely low thermal conductivity of the dough, introducing a piece of dough into an environment at 43 degrees will only result in superficial heating. It is evident that in these superficial layers, yeast will have more intense activity than in the middle of the product, and as a result, these superficial layers of the dough will lose their gas retention capacity by the end of fermentation.

The likely result will be a product with reduced volume, coarse and uneven porosity. The ideal fermentation temperature is somewhere in the range of 35-40 degrees Celsius, with proper control of the room’s humidity. Insufficient humidity leads to the evaporation of water from the dough’s surface, forming a crust. This crust prevents the dough from expanding in volume during the initial stages of baking, resulting in insufficiently risen products, uneven coloration (due to inadequate water for proper Maillard reactions), and cracked crust. Excessive air humidity in the proofing chamber will increase the stickiness of the dough, causing issues with rising or transport on the conveyor belt. In this case as well, the resulting products may have uneven coloration (this time due to excess water in certain areas), with the presence of spots on the crust, blisters, and even the appearance of voids beneath it. Ideally, practical experiments suggest that the humidity in the proofing room should be around 75-80%.

During the fermentation process, our goal is for the dough to reach approximately 80-90% of the final product’s volume. Therefore, a bread that does not increase in volume in the oven or whose volume decreases during baking is likely the result of improperly conditioned dough. There are certain situations where excessive volume increase during baking, caused by excessive extensibility of gluten networks, can be accompanied by a decrease in volume after baking. This occurs particularly in breads made from recipes with a high gluten content capable of forming large protein networks in the dough, which are not stabilized by an adequate amount of starch gel or due to altered starch gelatinization properties. In this case as well, an increase in protein quantity at the expense of starch, without the intervention of recipe elements that limit water mobility, is a symptom of improperly conditioned dough.

Immediately after the dough enters the oven, its temperature increases from the outside towards the geometric center. Consequently, successive concentric layers of dough around the geometric center will briefly pass through the temperature range around 43 degrees Celsius, where the carbon dioxide production rate is at its maximum. This phenomenon, combined with the varying degree of gas bubble expansion due to the temperature gradient, creates a series of uneven deformation stresses in the dough. These stresses can result in a loss of the intended shape of the product, uneven porosity, or insufficient volume. A well-prepared dough (characterized by optimal rheological parameters) is capable of withstanding these local deformations and uniformly transferring them throughout the entire mass of the product.