Baking Temperature & Its Importance

Baking temperature causes physical transitions and chemical reactions to take place in the dough/batter. The following stages are temperature-dependent and participate in the sequential transformation of bread dough.

1. Development (also known as oven spring)

As temperature increases, the free water/alcohol mixture in the product vaporizes, fermentation gases (CO2) dissolved in the liquid dough phase become less soluble, and are released into the cells, causing them to expand in response to the rise in pressure.

As a result, cells increase in volume by retaining gases due to their deformable nature as these are surrounded by the continuous gluten/starch soft matrix. This results in a large reduction in the density of the dough as the product gradually develops an aerated structure. Note that the size to which the gas bubbles can grow is limited by the ability of the gluten/starch film surrounding them to stretch without rupturing.

In this stage, the product undergoes a series of irreversible chemical and physical transformations. Oven spring is accompanied by the following changes and conditions:

• The killing of yeast cells at 50–60°C (122–140°F)
• Maximum enzymatic activity at 60°C (140°F). The enzyme-driven reactions that convert starch into sugars and break proteins into amino acids increase with heat, so they increase most near the dough surface.
• Starch gelatinization. It starts at 55–65°C (130–150°F) as granules become fully swollen with local free water.
• Denaturation of gluten proteins at 50°C (122°F) and coagulation at 70–80°C (160–180°F). As a consequence, gluten becomes increasingly tough and stiff as it irreversibly forms a gel.
• Above 85°C (185°F), starch looks glassy, and gluten looks rubbery. This is the start of the dough-crumb transition process (setting).
• Inactivation of naturally-occurring and added enzymes inside the dough (70–85°C) (160–185°F).

2. Drying (reduction of dough/batter moisture)

• Under the action of the heat transfer mechanisms, high temperatures develop inside the baking chamber (200–300°C) (390–570°F), and water molecules at the dough surface absorb latent heat and start to evaporate.
• Due to the low humidity of the air inside the baking chamber, a water vapor pressure (air moisture concentration) gradient is created. Liquid-state water starts to diffuse and migrates from the product core to the surface, where it evaporates and is lost to the oven atmosphere.
• The loss of moisture from the dough piece is dependent on the baking chamber temperature, colligative properties of the free water in the product, heat transfer methods used, and the humidity of the oven.

3. Color formation

The external surface of the product is exposed directly to the high temperatures of the oven and readily absorbs the heat from the energy sources. These high temperatures trigger non-enzymatic reactions that give rise to the desirable brown crust:

• Maillard browning takes place above approximately 105°C (220°F) and requires the presence of reducing sugar (glucose, maltose, or lactose) together with an amino acid, the type of which determines color and flavor.
• Sugars caramelize at 160°C (320°F). This reaction will happen only in the presence of water.