A dough fermenting in the fridge

How to Cold Ferment Pizza Dough: Guide to Cold Fermentation (2 Methods)

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Cold fermentation is the most popular method for fermenting pizza dough, but what is the best approach? In this article, we will learn how to master the process of cold fermentation and explore two effective methods to consistently produce high-quality dough

This article is part of a series on fermentation. It is recommended that you read the previous article before proceeding with this one: Cold vs. Room Temperature Pizza Dough Fermentation: Which Method is Best?.

There are two primary ‘methods’ or dough management procedures for cold fermentation:

  1. Placing the dough in the fridge immediately after kneading and balling it (what I refer to as the Lehmann method).
  2. Hybrid fermentation, which involves allowing the dough to ferment at room temperature before and/or after the time it spends in the fridge.

In the following sections, we will explore each method, discussing their benefits and/or drawbacks, as well as how to perform them properly.

The Lehmann Method: Immediately Placing the Dough in the Fridge After Kneading

This is the fermentation method to be used with PizzaBlab’s dough calculator and also the method I recommend for cold fermentation. Whether you are using the dough calculator to make dough for pizza or for other purposes, the principle remains the same: once you have finished kneading and portioning the dough, place it in the fridge as soon as possible.

This fermentation method was established by the late Tom Lehmann, also known as “The Dough Doctor”. Tom was a food scientist, a renowned baking and dough consultant, and the former chairman of the American Institute of Baking. He was one of the most influential mentors and experts in the field of pizza in the USA (and possibly worldwide). I personally learned a great deal from his extensive knowledge. His contribution to the world of pizza is immense and deserves recognition above all else. This is my humble contribution to carrying on his legacy.

This fermentation method is my personal favorite and is also the preferred method used by the majority of pizzerias for cold fermentation. It is also the fermentation method to be used with PizzaBlab’s dough calculator for cold fermentation (and we will soon understand why).

The primary purpose of this fermentation method is to provide predictable and consistent fermentation results, which are crucial in dough preparation, especially in a pizzeria or business setting. Hence, this method is preferred for cold fermentation in pizzerias. This is achieved by cooling the dough as quickly as possible after kneading and portioning/balling it.

The main advantage of this fermentation method is that it minimizes the factors that can influence the rate of fermentation (which we will discuss later). This creates an optimal and predictable fermentation process, allowing us to consistently achieve dough with excellent performance and a wide usability window.

The Advantages of the Lehmann Cold Fermentation Method

In order to understand how cold fermentation using the Lehmann method helps achieve more consistent and predictable fermentation results, it is important to first understand what happens to the dough when it is refrigerated, especially when dealing with a large amount of dough. A detailed article about this subject will be published in the future.

In short:

  1. The larger the mass of dough, the longer it takes for its interior to cool. When a large mass of dough is placed in the fridge, it can take up to 12 hours or more for the interior to reach the fridge’s actual temperature. This means that the dough will ferment at a much higher temperature than that inside the fridge.
  2. When the dough is left to ferment at room temperature before being refrigerated, the yeast produces CO2, which forms an “insulating layer” within the dough. This layer slows down the cooling process of the dough’s interior. The longer the dough ferments prior to refrigeration, the more CO2 is produced, resulting in a larger insulating layer and a longer cooling time in the fridge. 
  3. The yeast generates heat as it works in the dough, further impeding the cooling of the dough’s interior.

As can be seen, the combination of these factors means that dough that is cold fermented in bulk or allowed to ferment before being placed in the fridge will actually ferment at a higher temperature than the temperature inside the fridge. Consequently, the dough will ferment much faster, potentially resulting in unexpected fermentation outcomes, such as over-fermentation.

Using the Lehmann method allows us to effectively ‘solve’ the two issues mentioned above:

  1. Instead of having one large mass of dough, we divide the dough into smaller balls. This allows for quicker cooling compared to a larger mass of dough. Think about what freezes faster in the fridge: a whole bottle of water or small ice cubes.
  2. We “prevent” the yeast from starting to work and producing CO2 before placing the dough in the fridge. This prevents the formation of an insulating CO2 layer and allows for faster cooling.

By combining these two approaches, we achieve a dough that cools much faster once it is in the fridge. Consequently, the dough spends more time at the intended fermentation temperature and avoids being at a significantly higher temperature than planned, as is the case with hybrid fermentation (which we will discuss later).

In essence, using the Lehmann method allows us to ferment the dough in the fridge at a temperature that closely aligns with the intended fermentation temperature. This yields fermentation results that are more predictable and consistent.

As we will explore later, hybrid fermentation often leads to the dough fermenting at a temperature significantly higher than intended, making it challenging to attain consistent and predictable fermentation results.

Another key advantage of the Lehmann method is its simplicity: you can refrigerate the dough immediately after kneading and use it almost straight from the fridge, eliminating the need for precise timing or additional fermentation steps:

  1. Immediate refrigeration: The dough goes straight into the fridge after kneading, eliminating any waiting period. This prevents accidental over-fermentation at room temperature, ensuring consistent results.
  2. Ready-to-use after refrigeration: The dough is fully fermented when removed from the fridge, requiring no additional fermentation time. Simply allow it to reach working temperature before use.

Using the Lehmann Method: Step-by-Step Guide

  1. Knead the dough as usual and aim for a final dough temperature of 21-24°C / 70-75°F. This lower final dough temperature allows the dough to cool faster after being placed in the fridge.
  2. After finishing kneading, immediately divide the dough into balls. If you only made dough for a single pizza, there is no need to divide it (obviously).
  3. Place the dough balls in the fridge right away, preferably within 20 minutes of finishing kneading. Let them ferment in the fridge for the intended fermentation duration. If you need to make folds, it’s fine to take the dough out of the fridge, fold it, and put it back in.
  4. If your process involves reballing the dough after a certain period of time, take the dough balls out of the fridge and reball them as usual.
  5. At the end of the fermentation period, take the dough balls out of the fridge and allow them to rest AT room temperature. There is no need to let them come TO room temperature; just rest them at room temperature until the internal temperature of the dough balls reaches at least 10°C/50°F (this should take between 30 minutes to 3 hours, depending on the room temperature). This minimum temperature ensures that the dough is workable and can be stretched into a pizza base without being too elastic and resistant.

Please note: with this fermentation method, we do not remove the dough from the fridge at the end of fermentation to allow it to “finish” fermentation at room temperature. Using the Lehmann method, the dough fully ferments in the fridge. When you take it out, it is ready for baking. This means that it has doubled in volume inside the fridge and there is no need to let it further ferment outside the fridge.

At refrigerator temperatures (1-7°C/34-44°F), yeast and enzyme activity slows down but does not stop completely. As a result, the dough continues to ferment and mature in the fridge, albeit at a much slower rate. If you are using the Lehmann method for cold fermentation and do not observe any visible signs of fermentation (such as an increase in volume or bubbles in the bottom/sides of the container), it indicates that something went wrong during the fermentation process (e.g., incorrect yeast quantity, final dough temperature, actual fridge temperature, etc.). When following the Lehmann method, the dough should double in volume while in the fridge.

The reason for removing the dough from the fridge before baking is to allow it to reach a working temperature so that it can be easily stretched into a pizza base. It is recommended to let the dough reach a minimum temperature of 10°C/50F, but you can experiment to find the temperature that is most comfortable for you to work with – it could be 10°C/50F, 15°C/60F, or 20°C/68F.

When baking different types of pizzas, there are some considerations to keep in mind. For baking a Neapolitan pizza in a wood-fired oven, it is advisable to let the dough reach a higher internal temperature, around 20°C/68F. Baking cold dough at a very high temperature in a wood-fired oven can result in aggressive “leoparding” with many large, burnt bubbles.

For hand-stretched pizzas that are baked in an electric/gas oven, such as New York style or al taglio, the dough can be baked at an internal temperature of 10°C/50F, as long as you feel comfortable working with and shaping it.

For pizzas that are baked in a pan, like Sicilian or Detroit style, you can bake the dough directly from the fridge without any problems.

Why Does Pizzablab’s Dough Calculator Recommend Such a High Amount of Yeast for Cold Fermentation?

If you are accustomed to other cold fermentation methods, specifically hybrid fermentation (which we will discuss in the next section), you may find the yeast amount provided by the calculator to be very high compared to what you are used to. The reason for this is simple: as we learned in the article discussing fermentation, the lower the fermentation temperature, the more yeast is needed.

PizzaBlab’s calculator was designed to be used with the Lehmann method for cold fermentation in order to achieve consistent and predictable results as much as possible. Therefore, the yeast amount provided for cold fermentation is based on the assumption that the dough is divided into balls and immediately placed in the fridge after kneading, so that it reaches the desired temperature as quickly as possible. On the contrary, in hybrid fermentation, the internal temperature of the dough will be higher for a significant portion of the time in the fridge, so the yeast amount should be smaller accordingly.

Let’s consider an example to illustrate this (the numbers used are arbitrary for demonstration purposes, but not necessarily far from reality):

We have two doughs: one fermented using the Lehmann method, and another fermented using hybrid fermentation (bulk fermented in the fridge). The total fermentation duration is assumed to be 24 hours in both cases, with a fridge temperature of 4C/40F degrees.

  • The dough fermented using the Lehmann method is immediately placed in the fridge after kneading and dividing into balls. Out of the 24 hours in the fridge, each ball will have an internal temperature of 4C/40F for 20 hours.
  • The dough fermented using the hybrid method goes into the fridge as a single mass (bulk) after one hour of fermentation at room temperature. Out of the 24 hours in the fridge, the internal temperature of the dough will be 4C/40F for only 5 hours. During the remaining 14 hours, it will actually ferment at a higher temperature (a temperature that cannot be accurately predicted).

The above example perfectly illustrates why it is necessary to use more yeast when using the Lehmann method. Fermentation at a lower temperature requires more yeast, while fermentation at a higher temperature (hybrid fermentation) requires less yeast.

This is why many calculators, which only calculate hybrid fermentation, provide a very small amount of yeast, and why PizzaBlab’s dough calculator provides a relatively high amount of yeast.

It is important to note that using a higher amount of yeast is not inherently worse, and the “goal” of fermenting dough is not to use as little yeast as possible, but rather to adjust the amount of yeast according to the fermentation duration and temperature in order to achieve optimal fermentation. The amount of yeast is a means to an end, not the ultimate goal.

Theoretically, in both cases in the above example, it is possible to achieve the same level of flavor in the dough by adjusting the amount of yeast to different fermentation conditions (lower/higher fermentation temperature). As long as the amount of yeast is adjusted to the duration and temperature of fermentation, a dough containing 0.5 grams of yeast is not ‘better’ or more flavorful than a dough containing 2 grams of yeast. This distinction is completely meaningless and should not be a consideration.

This is precisely why PizzaBlab’s calculator provides a relatively high amount of yeast for cold fermentation. The amount is tailored to the Lehmann method and takes into account the actual fermentation at a low temperature, compared to other calculators, which are specifically designed for hybrid fermentation. Based on my experience and the experience of many others, using PizzaBlab’s calculator’s recommended amount of yeast in combination with the Lehmann method yields optimal fermentation results for cold fermentation.

Hybrid Fermentation

Hybrid Fermentation: Definition and Process

Hybrid fermentation is a method that combines cold fermentation with room temperature fermentation. The principle behind this method is simple: the dough is fermented at room temperature for a certain period of time before (and after) being refrigerated for the remaining fermentation time.

The key aspects of this fermentation method include:

  1. After kneading, the dough is allowed to ferment at room temperature for an hour or more to “activate” the yeast.
  2. The dough is then transferred to the fridge for the desired fermentation duration (24-48-72 hours).
  3. A few hours before baking, the dough is taken out of the fridge to complete the fermentation process at room temperature. If the dough was fermented as a bulk, it is divided into balls after removing it from the fridge and allowed to ferment further before baking.

In the hybrid fermentation method, a very small amount of yeast is usually used. There are two reasons for this:

  1. The dough should undergo additional fermentation at room temperature. The fridge is used to slow down the fermentation process – the dough is not very active during its time in the fridge, primarily because of the relatively low amount of yeast.
  2. This fermentation method causes the dough to ferment in the fridge at a temperature higher than the actual fridge temperature, which means less yeast is needed.

These two reasons result in the need for a relatively small amount of yeast (usually between 0.1-0.3% instant dry yeast), which is suitable for the fermentation conditions of this method.

Due to the small amount of yeast, dough undergoing hybrid fermentation does not show significant signs of fermentation while in the fridge. This is why it is important to allow the dough to “complete” its fermentation after removing it from the fridge. The amount of yeast in the dough is too low to cause significant rising and maturation activity in the fridge, but enough to cause these activities when the dough is fermented at room temperature.

At low temperatures, the CO2 produced by the yeast (which is what causes the dough to gain volume) becomes much more soluble in water, transitioning from a gas to a liquid state.

This is one of the reasons why dough that undergoes cold fermentation, with a small amount of yeast, and specifically hybrid fermentation, often shows no significant physical change in volume during its time in the fridge. The concentration of CO2 in the dough is low (due to the small amount of yeast), and most of the CO2 is in a liquid state rather than a gas, preventing the dough from physically rising.

When the dough is removed from the fridge, the liquid CO2 becomes less soluble and reverts back to a gaseous state. This contrasts with the Lehmann method, in which a larger amount of yeast produces more CO2, leading to visible signs of fermentation in the dough even during the refrigeration period.

In other words, in hybrid fermentation, the fermentation time outside the fridge can sometimes be more important than the time spent in the fridge in terms of maturation and flavor development. That’s why in hybrid fermentation it’s crucial to allow the dough to “finish” fermenting outside the fridge before baking, unlike the Lehmann method where the dough is ready to be baked after the fermentation time in the fridge. In fact, it can even be said that the flavors in dough undergoing hybrid fermentation primarily come from the time outside the fridge, as the contribution of the time in the fridge to flavor development is smaller than commonly believed, although it still exists.

It’s important to note that not every dough undergoing hybrid fermentation will necessarily follow the same pattern. The results depend on specific temperatures and other variables, which is why this fermentation method can yield inconsistent and less predictable results compared to the Lehmann method, as we’ll see in the next section.

Like any fermentation method, the hybrid fermentation method works well when done correctly. The challenge, however, is that consistently executing it correctly is not a simple task. Personally, I believe in simplifying the process as much as possible, because why work harder when you can work smarter?

Challenges and Potential Drawbacks of Hybrid Fermentation

So, what is the main drawback of the hybrid fermentation method? In short, dough that undergoes hybrid fermentation will ferment much less consistently and predictably, and is much more susceptible to external influences such as the room temperature before and after being in the fridge, the time spent outside the fridge, and the final dough temperature. The longer the fermentation time in the fridge, the more significant these effects will be.

Why does this happen? I have already discussed this in previous sections, but to summarize:

  1. The yeast activity in the dough produces carbon dioxide (CO2) or “gas bubbles” that make the dough less dense and more airy. These gas bubbles act as a physical “insulation layer” inside the dough, slowing down the transfer of heat or cold between the environment and the dough. Less compressed dough (more airy) means it is better insulated from the environment.
  2. The metabolic activity of the yeast itself generates heat (about 0.5°C per hour). Depending on the degree of insulation from the environment, this heat may remain inside the dough and further affect its internal temperature.
  3. The larger the mass of dough, the longer it will take for the external temperature to have an effect on it, and the effect will occur more slowly. For example, compare the melting time of a small ice cube to that of a shoebox-sized block of ice.

The above process is a kind of “cycle” – as the dough ferments (becoming more airy and creating a larger insulation layer), it is less affected by the ambient temperature. At the same time, the yeast’s activity generates more heat in the dough (which is retained due to the insulation layer). This heat, in turn, increases yeast activity and accelerates fermentation (more heat equals higher yeast activity). As a result, the insulation layer continues to grow, thus perpetuating the cycle.

What does this mean in practice? The longer we let the dough ferment at room temperature before refrigerating it, and the higher the temperature and/or the larger the dough (in terms of weight and volume), and/or the higher the final dough temperature, the “thicker” the “insulation layer” will become. As a result, the dough will be better able to maintain its internal temperature.

In other words, when we place such dough in the fridge, it already has an insulating layer that prevents its core from reaching the temperature of the fridge. As a result, the dough ferments at a higher temperature than intended, which leads to unpredictable and inconsistent fermentation results.

In practice, this means that controlling the fermentation of dough fermented using the hybrid method is much more challenging. It depends on several factors that are not easy (or even possible) to account for, even when using various calculators. This is why PizzaBlab’s calculator does not offer an option for hybrid fermentation. Even if a certain amount of yeast is obtained for hybrid fermentation, it cannot be relied upon (the same applies to other calculators that calculate yeast amounts).

I had the opportunity to see (and taste) many pizzas that people made using the hybrid fermentation method, and they were highly satisfied with the results. However, upon observing and tasting pizzas made by the same person at different times using a supposedly identical process (hybrid fermentation), there is a noticeable lack of consistency in the final product. At times, the dough ferments perfectly, while at other times it is over-fermented or under-fermented. This inconsistency is often a result of hybrid fermentation.

On top of that, the fact that the individual dough balls need to undergo additional fermentation after being taken out of the fridge can lead to potential problems. The time it takes for the balls to be ready for baking varies greatly depending on factors such as temperatures and the amount of yeast used.

This requires us to allow the dough balls to undergo another fermentation “step”, which also involves (physical) rising and, most importantly, ensuring that the dough “relaxes” and becomes extensible enough to be easily stretched into a pizza base without being too elastic and resistant (a relatively common case with hybrid fermentation). This is in contrast to the Lehmann method, where the dough balls are ready for baking in terms of fermentation and maturation once they are taken out of the fridge. Using the Lehmann method, we simply need to wait for the dough balls to reach working temperature, without the need for another fermentation stage.

When using hybrid fermentation, the speed at which the above processes occur (the dough balls rise enough and become extensible enough) greatly depends on room temperature, the amount of yeast used, and the extent of fermentation before and during the time spent in the fridge. In other words, this method can be highly inconsistent and unpredictable, making it challenging to determine when the dough will be ready for baking after being taken out of the fridge.

In conclusion, while the hybrid fermentation method is relatively common for fermenting pizza dough, it is much less consistent than the Lehmann method, especially for those who are just starting out or have less experience in controlling and assessing the fermentation process.

Let it be clear – this method can work excellently with the right process and the proper amount of yeast. However, the problem lies in the fact that making these adjustments is not necessarily easy, and achieving consistent results becomes much more difficult as a result. If you’ve ever heard statements like “In the winter, you need to allow the dough to rest for X hours outside the fridge, and in the summer for Y hours”, it illustrates why the hybrid fermentation method is inconsistent compared to the Lehmann method. It complicates matters and is highly influenced by external factors that are not necessarily within our control, which inevitably affects the final product.

Additional Tips for Cold Fermentation

Dough Placement in the Fridge

Usually, the temperature inside the fridge varies at different points, and the location of the dough in the fridge can greatly impact the rate of fermentation.

In general:

  • The temperature at the back of the fridge is lower.
  • The shelves at the same level as the cooling unit (usually the upper shelves) have a lower temperature due to the cold air coming out.

It’s important to note that there can be significant temperature differences, ranging from 1°C/34°F to 7°C/44°F, that can noticeably affect yeast activity and the rate of fermentation. To accurately measure the temperature in a specific location inside the fridge, use a temperature sensor, and make sure you place the dough in the same spot to achieve consistent fermentation results.

Condensation in the Fermentation Container

Condensation on the lid of a container containing cold fermented dough
Condensation on the lid of a container containing cold fermented dough

Condensation is the process through which water vapor in the air transforms into water droplets when it encounters a colder surface. When we place dough in a closed container in the fridge (which is always at a lower temperature than the container), the hot air inside the container comes into contact with the sides of the container (which cools down faster than the dough itself). As a result, the air cools and loses its ability to hold moisture. Consequently, the excess moisture in the air condenses, forming water droplets on the lid and sides of the container (as shown in the picture above).

In summary, the temperature difference between the dough and the fridge causes condensation and the formation of water droplets in the container (particularly on the lid), which then drip back onto the dough.

Condensation always occurs when room temperature dough is placed in a closed container inside the fridge.

When the dough is bulk fermented in the fridge, condensation is not necessarily a significant issue, as the dough will later be shaped into balls and the water will be “incorporated” back into the dough. However, when the dough ferments in the fridge as balls, the water dripping onto the dough can lead to several negative consequences:

  1. The drops of water can make the dough sticky. The water may remain on the surface or be absorbed into the dough over time (although only partially and unevenly), resulting in the formation of “wet spots”.
  2. During baking, the water in these wet spots evaporates and may cause the formation of large bubbles, either at the base of the pizza or around the crust.
  3. When stretching the dough into a pizza base, bench flour may stick to these wet spots, resulting in an accumulation of bench flour in certain areas. During baking, this excess flour may burn and create a bitter taste.
  4. The dough may become stickier and harder to work with, sticking to the work surface or pizza peel.

How to Prevent Condensation in the Container

To prevent condensation in the container, it is necessary to allow the dough to cool down in the fridge until it reaches an internal temperature of at least 10°C/50°F before closing or sealing the container.

To accomplish this, simply place the container with the dough in the fridge uncovered (without a lid), and let it sit like this for approximately one to two hours. Once the dough has sufficiently cooled (you can check its internal temperature with a thermometer), you can then close or seal the container and continue with the fermentation process as usual.

To prevent the upper part of the dough from drying out while it is in the fridge uncovered, it is advisable to lightly spread oil on top of the dough balls (any type of oil will work). Following the same principle, you can also place a damp towel over the container, which will prevent hot air from entering and help absorb any water droplets caused by condensation.

Alternatively, you can place the dough in one of the closed drawers in the refrigerator, such as the vegetable or “fresh” drawer.

Accelerating Dough Cooling for Cold Fermentation

As we have discussed in the previous sections, it is important to cool the dough in the fridge as quickly as possible for effective cold fermentation. This is key to achieving a controlled, consistent, and predictable fermentation process, with a wider usability window.

In addition to the methods we have already covered (specifically using the Lehmann method), here are some additional tips for speeding up the cooling process, especially if you choose to bulk ferment dough in the fridge rather than as individual balls. These tips can help you achieve a more uniform fermentation, with a greater usability window:

  1. Divide a large mass of dough into several smaller portions and use different containers for each portion. Similar to dividing the dough into balls, dividing it into separate portions will result in faster cooling compared to having one large dough mass.
  2. Flatten the dough inside the containers as much as possible. A flat(ter) dough will cool faster than a spherical one, thanks to its larger surface area-to-volume ratio.
  3. Aim for a lower final dough temperature of 18-21°C/64-70°F. This lower temperature will help facilitate faster cooling of the dough.
  4. Use a fermentation container with high heat conductivity, such as aluminum. This will enable the cold from the refrigerator to transfer to the dough more quickly.
  5. Place the dough in the coldest spot of the fridge, ideally close to the vents from where the cold air comes out. Usually, this spot is at the back of the top shelf. To be certain, you may need to explore different areas of your refrigerator.

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