Oven spring phase during baking

Oven Spring

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Oven spring is the rapid rise of dough during the first few minutes of baking. This post explains what causes it, factors that influence it, and tips on how to manage it

A bread going through the oven spring stage during baking
Oven spring of bread

What Is Oven Spring

Oven spring is the stage of baking when the dough rises and expands in volume (see picture above).

Oven spring begins as soon as the dough is placed in the oven and typically lasts for about 20% of the total baking time, depending on the baking temperature. For example, if bread is baked for 30 minutes, the oven spring occurs within the first 5~ minutes; For pizza baked for 7~ minutes, the oven spring occurs within the first 1-2 minutes.

What Causes Oven Spring During Baking?

So how exactly does oven spring occur, or in other words, what causes the dough to physically expand and gain volume during baking?

The dough contains millions of tiny “air cells” that are filled with CO2 (carbon dioxide) during fermentation, thanks to the activity of the yeast. When the heat of the oven penetrates the dough, it creates pressure inside these air cells, causing them to expand and increase in volume. This expansion is made possible by the elastic gluten network that surrounds the air cells.

During fermentation and prior to baking, some of the CO2 in the dough exists in a liquid state, while some is in a gas state. Generally, as the temperature of the dough rises, the solubility of CO2 decreases. This means that at higher temperatures, more CO2 will be in the gas state and less will be in the liquid state.

Since the solubility of CO2 increases with temperature, most of the CO2 will be in liquid form during cold fermentation. This is why dough that is cold fermented may not always visibly change in volume while in the fridge – Instead of the CO2 being in a gas form and being “pushed” into the air cells to cause expansion, it remains in the dough in a liquid state, becoming a homogeneous part of it.

When the heat of the oven enters the dough, the solubility of CO2 decreases, causing it to change from a liquid to a gas. The CO2 that has been “newly formed” is then pushed into the air cells in the dough, resulting in further expansion.

Colder dough results in a higher concentration of CO2 in its liquid state. When dough is baked cold, this increased concentration of CO2 quickly transforms from liquid to gas during the oven spring stage.

In contrast to a situation where the CO2 is evenly distributed throughout the dough (whether as a liquid or gas) when the dough is at room temperature, baking cold dough inevitably leads to the formation of concentrated “pockets” of CO2 in specific areas. This, in turn, causes the creation of large air bubbles in those particular areas.

These effects can be observed in two ways:
(1) The formation of bubbles in the center of the pizza’s base.
(2) When baking cold dough at high temperatures, such as in a wood-fired oven, large bubbles form on the crust. This is why it is common to see aggressive, big black charred spots on the crust when using cold dough in a wood-fired oven.

In addition to the effect of CO2, two other factors contribute to oven spring (however, opinions about their effects differ, as explained in the next paragraph):

  1. Steam/water vapor created during baking (as water evaporates inside the dough) also contributes to pressure and the expansion of air cells.
  2. When the dough reaches a temperature of 78°C/167°F, alcohol (ethanol) in the dough, which has been in a liquid state until this point, turns into gas, which further expands the air cells.

In conclusion – oven spring is the result of the expansion of the “air cells” in the dough during baking.

The primary factor responsible for oven spring, accounting for at least 50% of it, is carbon dioxide (CO2). CO2 is “pushed” into the air cells, creating pressure and causing them to expand.

Regarding the other factors, there is no consensus on their contribution to the further expansion of the dough beyond the effect of CO2. There are two schools of thought on this matter:

  • The first school of thought argues that the remaining oven spring is caused by alcohol (ethanol) in the dough, while water vapor has no significant effect on oven spring.
  • The second school of thought suggests that the remaining oven spring is due to water vapor, while ethanol has no significant effect on oven spring.

In terms of yeast activity during baking, the consensus is that their contribution to oven spring is negligible or non-existent. The amount of CO2 they produce during baking is not significant enough to impact oven spring.

The Formation of Crust and Its Effect on Oven Spring

In general, the dough continues to increase in volume and expand during baking until it develops a crust (“dries out” or browns). Once a crust forms, the dough can no longer expand, and oven spring stops.

This is particularly important when baking bread because we want to maximize the volume of the loaf, and the premature formation of a crust can hinder this. Therefore, when baking bread, it is common to use techniques that generate steam in the baking chamber (as shown in the examples below); Steam creates a moist environment that inhibits crust formation – that’s why industrial ovens designed for baking bread (not pizzas) include a steam injection function, which aims to maximize the volume of baked goods.

On the other hand, when it comes to baking pizza, adding moisture to the baking chamber is undesirable. In pizza baking, we aim to minimize moisture to achieve a crispy crust.
This example illustrates one of the many reasons why, while pizza and bread share some characteristics, the principles of their preparation and baking often differ significantly.

In general, baking at higher temperatures will cause the crust to form more quickly, potentially limiting oven spring. This is less important for pizza but highly crucial for bread – baking bread at excessively high temperatures without steam will lead to premature crust formation and result in a smaller loaf volume.

Factors That Affect Oven Spring

The main factors that affect oven spring are:

  1. Dough hydration – The higher the hydration, the greater the oven spring will be. This is because the dough is softer and more extensible, allowing it to stretch and expand more.
  2. Degree of extensibility/elasticity of the dough – If the dough is excessively elastic, it will hinder oven spring. Conversely, if the dough is overly extensible, it may collapse during baking.
  3. Baking temperature – The higher the baking temperature, the faster and more intense the oven spring will be (but this does not necessarily mean that it will expand more in general). However, it is important to note that baking at a high temperature can also cause the crust to form more quickly, which may actually limit oven spring.

Among the factors mentioned above, the only one that can be easily identified and consistently shown to have an impact on the oven spring is dough hydration. In other words, the higher the hydration level in the dough, the greater the oven spring will be.

The level of plasticity/elasticity of the dough also plays a significant role in the degree of oven spring; For example, if the dough is over/under-fermented, oven spring is greatly impacted. However, measuring and isolating the exact effect of plasticity/elasticity is more challenging compared to dough hydration.

How to Maximize Oven Spring (When Baking Bread)

To achieve optimal oven spring when baking bread, it is important to create a moist environment in the baking chamber to delay crust formation.

There are three main methods for achieving this when baking at home:

  1. Spraying the inside of the oven and the bread with water using a spritzer.
  2. Baking the bread in a closed vessel, such as a Dutch Oven, which acts as an “oven within an oven” and traps the moisture inside.
  3. Placing a pan filled with boiling water inside the oven, which generates steam during baking.

Methods 2 and 3 are the most effective, while method 1 (spraying with a spritzer) has limited effectiveness. When baking bread, I highly recommend using either a Dutch oven or placing a pan of boiling water in the oven.