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Oven humidity is an essential variable in oven operations. However, too much or not enough moisture can lead to quality issues. By effectively controlling the oven environment, your bread will see improvements in texture and appearance.

The dough is in constant contact with its environment in the oven so time, temperature, and airflow controls are important in manipulating oven humidity. Furthermore, the baking chamber humidity cannot be measured as relative humidity. It needs an expression as absolute humidity or mass humidity ratio. Oven humidity is also affected by moisture movement from the product to the surroundings.

Why oven humidity is important

Oven humidity determines the speed of bake out. The lower the humidity, the faster the water escapes from the surface of the bread, and so the faster the bread bakes and browns. It also assists in maintaining desirable sensory properties. A humid environment can keep the surface of a product moist. This improves the stretching of the oven spring and provides an equal break and shred. High humidity ovens provide the glossy crust observed on artisan and bagel-type bread. This is achieved by steam injection.

Effects of oven humidity on bread

• Crust color: excess moisture in the oven obstructs its heat transfer. Therefore, the crust temperature is lower than the target temperature, resulting in a lighter-colored finished product. There is a delicate balance between getting the right crust color and controlling humidity in the oven.
• Dough expansion and product volume: the higher humidity results in an insulation layer around the product. Hence, the yeast kill step is delayed and product expansion continues, resulting in a larger production volume.
• Moisture content: higher humidity ovens result in less bake loss, resulting in lighter colored products that are more moist.
• Crust character: higher humidity will result in a more glossy and thicker crust. Some artisan and hearth bread require steaming to create surface condensation that develops a shiny crust.
• Smooth crust: if the oven is low in moisture, it will dry out the surface of the crust, resulting in a sandpaper feel. To prevent this, make sure that your oven has some humidity at the last two baking zones.

To exhaust or not to exhaust?

The oven humidity sensor measures the oven humidity at the product level and with the oven under full product load. It helps determine product quality based on the relationship between humidity and moisture content in the oven. In addition, you can optimize extraction/purge mechanisms to avoid excessive loss/build-up of moisture and heat from the baking chamber.

Several factors that affect oven humidity

An increase in dough divider speeds will increase oven loads. This increases the overall humidity inside the baking chamber, which would then require a higher heat or more airflow to exhaust the moisture. If care is not taken, an increase in airflow will lead to a drop in the temperature. The key is not to increase the temperature, but to decrease the humidity in the oven. Elevated temperatures reduce the relative humidity in the oven. You can track oven humidity to see if the oven has the right levels.

When steam is injected at the beginning of the baking process for a shiny crust, it also provides an insulated barrier around the dough, resulting in longer baking times. In order to shorten the baking time, or to darken the product at a specific time, it’s important to effectively exhaust the baking zone right after the steam injection zone.

Verifying side-side consistency with traditional tunnel ovens

Heating and other environmental conditions are evenly distributed to a product with a spinning rack, spiral, and twin/oval systems. This results in a more uniform final baked good. However, there can be issues with side-side consistency and uniformity in tunnel ovens.

This effect becomes more influential in the case of small-mass snacks. Bakers desire to have a uniform air and temperature balance for snacks weighing a few grams otherwise, leading to larger differences in coloring or spontaneous fracture. This issue is often noticeable as the product comes in contact with ambient temperature and humidity. To ensure such side-side consistency, it is crucial to control and monitor oven conditions.

Measure the moisture content in your proofer, oven, dryer and cooling tunnel with the SCORPION® 2 Digital Humidity Sensor. It travels through the process with the product, yielding a precise profile of moisture experienced by the product. Learn all about it here.