Baking is the final step in making products such as breads, cakes, buns, rolls, crackers and biscuits.

Baking


What is Baking?

Baking is the final step in making products such as breads, cakes, buns, rolls, crackers and biscuits. It’s a thermal process that uses an oven, which transfers heat to the dough pieces via conduction through heated surfaces, convection through hot air, and radiation from heat sources such as flames. The heat in turn activates a series of physicochemical changes, responsible for transforming the raw dough into a baked good with a firm, dry crust and a soft interior crumb.

Origin

Baking is probably as ancient as human kind. The first civilizations in recorded history, the Egyptians and Mesopotamian people, cultivated wheat. They learned the art and craft of baking bread after discovering that wheat kernels could be eaten in a palatable form by grinding and turning them into flour, adding water to create paste, which was ready to be cooked and consumed. Back then, fire and manual work were key for the development of the primitive baking processes.1

How does baking work?

Baking sets the final structure to baked goods. It involves simultaneous heat and mass transfer phenomena. The heat travels from the surrounding air into the interior of the dough while moisture travels/escapes from the core towards the exterior or surrounding air due to evaporation.2

Coming out of the final proofer, the bread dough is well aerated with a typical internal temperature close to that of the proof box, around 35°C (95°F). As the dough pieces enter the oven, their surface temperature begins to increase and heat transfers slowly towards the core of the product. The oven temperature can be set, according to the type of product being processed, at any point between 200–300°C (390–570°F).

In general, there are three major stages in the baking process: expansion of the dough, drying of the surface, and crust browning. These can be subdivided into the following steps (in order of temperature increase):2,3,4

1. Formation and expansion of gases (oven spring). A rapid rise in volume takes place at the beginning of baking at a core temperature of 35–70°C (95–158°F). This rise creates the oven spring. Five things work together to produce the oven spring in the first 5–8 minutes of baking:

  • Yeast reaches its maximum fermentation rate and generates more carbon dioxide gas before yeast cells die.
  • Release of carbon dioxide gas from the saturated liquid dough phase into the surrounding gas cells.
  • Expansion of the existing gasses trapped in cells (air and CO2) generated during mixing, makeup, and proofing. This buildup of pressure causes air cells to become larger.
  • Vaporization of water/ethanol mixture.
  • Carbon dioxide production from chemical leaveners.

The surface of the dough being slightly moist allows the dough to move, flow, and expand due to the air cells increasing in size.

2. Killing of yeast and other microorganisms. This usually occurs at an internal temperature of 60–70°C (140–160°F). The yeast cells are killed and no longer contribute to the gas production or increase in volume.

3. Gelatinization of starch. Beginning at 76°C (170°F), starch begins the gelatinization process  as granules become fully swollen with local free water. Thanks to starch gelatinization and protein denaturation, the dough is converted into bread and a structure is set.

4. Coagulation/denaturation of egg and gluten proteins. From 60 to 70°C (140 to 160°F), the proteins begin denaturing. As a consequence, gluten becomes increasingly tough and stiff as it irreversibly forms a gel. The moisture loss also imparts rigidity in the product being baked.

5. Inactivation of enzymes. Inactivation of naturally-occurring and added enzymes inside the dough at 80–95°C (176–203°F).

6. Crust formation and browning (non-enzymatic reaction and caramelization). Maillard browning takes place above approximately 105°C (220°F) and requires the presence of a reducing sugar together with an amino acid. Sugars caramelize at 160°C (320°F).

Baking is responsible for major weight loss in the dough, with a 8–12% loss in moisture and volatile organic compounds in the case of pan bread, buns, rolls and other yeast-leavened products.2 This loss in weight is taken into account during dividing.

The main parameters of the baking process are time, oven temperature, chamber humidity, air flow (convection heating), and heat flux. These process variables are function of the size, unit weight, formulation and type of product, and target characteristics of the finished products. Baking times may range from 2–60 minutes, depending on the type of oven and heating pattern.

References

  1. Walker, C.E., and Eustace, W.D. “Wheat Processing” Encyclopedia of Food Grains, vol. 3, Elsevier Ltd., 2016, pp. 299–304.
  2. Fellows, P.J. “Baking and Roasting.” Food Processing Technology; Principles and Practice, 4th edition, Woodhead Publishing, Elsevier Ltd., 2017, pp. 733–752.
  3. Gisslen, W. “Basic Baking Principles” Professional Baking, 7th edition, John Wiley & Sons, Inc., Hoboken, New Jersey, 2017, pp. 93–101.
  4. Figoni, P. “Overview of the Baking Process” How Baking Works, 3rd edition, John Wiley & Sons, Inc., 2011, pp. 34–44.