Causes of Dough Rising in Bakery

The rising of dough is a fundamental process in bakery science, determining the texture, volume, and flavour of bread and other baked products. The phenomenon results primarily from the production and entrapment of gas within the dough matrix, causing it to expand and become light and porous. Several physical, chemical, and biological factors contribute to this process, with yeast fermentation being the most significant. Understanding these causes helps bakers control the quality and consistency of baked goods.

Role of Yeast Fermentation

The principal cause of dough rising is yeast fermentation. Yeast, most commonly Saccharomyces cerevisiae, is a single-celled fungus that feeds on sugars present in flour and other ingredients. Through enzymatic activity, yeast converts these sugars into carbon dioxide (CO₂) and ethanol under anaerobic conditions:
C₆H₁₂O₆→enzymesyeast2C₂H₅OH+2CO₂\text{C₆H₁₂O₆} \xrightarrow[\text{enzymes}]{\text{yeast}} 2\text{C₂H₅OH} + 2\text{CO₂}C₆H₁₂O₆yeastenzymes​2C₂H₅OH+2CO₂
The carbon dioxide gas produced becomes trapped in the elastic gluten network of the dough, causing it to expand. The ethanol evaporates during baking, leaving behind characteristic bread flavour compounds.
Factors influencing yeast fermentation include:

• Temperature: Optimal yeast activity occurs between 27°C and 35°C. Excessive heat kills yeast, while low temperatures slow fermentation.
• Sugar Concentration: A moderate amount of sugar promotes fermentation, but excessive sugar exerts osmotic pressure that inhibits yeast activity.
• pH: Yeast thrives best in slightly acidic conditions (pH 4.5–5.5).
• Oxygen: Initially required for yeast growth, but fermentation proceeds anaerobically once oxygen is depleted.

Gluten Development and Gas Retention

The flour proteins glutenin and gliadin combine with water to form gluten, an elastic and extensible protein network. This gluten structure is crucial for retaining the carbon dioxide produced during fermentation. As gas accumulates, the gluten strands stretch, causing the dough to rise.
Without proper gluten development, gas would escape, and the dough would remain dense. Strong wheat flour with high protein content is therefore preferred for bread-making because it produces a robust gluten network capable of retaining gas effectively.

Role of Enzymes

Enzymes naturally present in flour or added during processing also contribute to dough rising by breaking down complex carbohydrates and proteins into simpler compounds. Key enzymes include:

• Amylase: Converts starch into maltose and glucose, providing fermentable sugars for yeast.
• Protease: Modifies gluten proteins, making the dough more extensible and easier to handle.
• Maltase and Zymase: Found within yeast cells; they catalyse the conversion of maltose to glucose and glucose to carbon dioxide and ethanol.

These enzymatic reactions ensure a continuous supply of fermentable sugars during fermentation, sustaining gas production and dough expansion.

Chemical Leavening Agents

In addition to yeast, chemical leavening agents such as baking powder and baking soda can cause dough to rise. These agents release carbon dioxide through acid–base reactions without requiring fermentation.

• Baking soda (sodium bicarbonate, NaHCO₃) releases CO₂ when it reacts with acidic ingredients (e.g., buttermilk, lemon juice, or vinegar):

NaHCO₃+H⁺→Na⁺+CO₂+H₂O\text{NaHCO₃} + \text{H⁺} \rightarrow \text{Na⁺} + \text{CO₂} + \text{H₂O}NaHCO₃+H⁺→Na⁺+CO₂+H₂O

• Baking powder contains both an acid (cream of tartar or calcium acid phosphate) and a base (sodium bicarbonate). When moistened and heated, it produces carbon dioxide, causing expansion similar to yeast activity.

Although these chemical agents are commonly used in cakes, biscuits, and quick breads rather than yeast-leavened bread, they operate on the same principle of gas generation and entrapment within the dough.

Mechanical Incorporation of Air

During mixing and kneading, air is physically incorporated into the dough. These air bubbles act as initial gas nuclei that expand as carbon dioxide is produced during fermentation. Proper kneading ensures uniform distribution of air cells and yeast, promoting consistent rising. Over-mixing, however, may damage the gluten network, reducing gas retention capacity.

Effect of Temperature and Humidity

Temperature and humidity play critical roles in dough rising:

• Temperature: Warmth accelerates yeast metabolism and fermentation rate, leading to faster gas production. Excessive heat, however, can denature enzymes and kill yeast. Cold conditions slow or halt fermentation.
• Humidity: Adequate moisture is necessary to activate yeast and facilitate enzymatic reactions. Too little moisture produces a dry dough, while excessive moisture weakens gluten, reducing gas retention.

Proofing chambers in bakeries are carefully controlled to maintain optimal temperature (30–35°C) and relative humidity (75–85%) to ensure uniform dough rising.

Influence of Salt, Fat, and Sugar

The addition of salt, fat, and sugar also affects the dough-rising process:

• Salt: Strengthens gluten and regulates yeast activity. Too much salt inhibits fermentation, while too little can cause overexpansion and weak structure.
• Fat: Lubricates gluten strands, improving elasticity and gas retention. It also slows fermentation slightly, leading to finer crumb texture.
• Sugar: Acts as a substrate for yeast fermentation but must be balanced to prevent osmotic stress on yeast cells.

Proofing and Dough Expansion

Proofing (also called proving) refers to the resting period during which the dough is allowed to rise after kneading. During proofing, yeast continues to ferment sugars, generating more carbon dioxide. The trapped gas expands existing air cells, increasing dough volume and improving texture.
Proper proofing ensures the dough reaches its optimal expansion before baking. Under-proofed dough will yield dense bread, while over-proofed dough may collapse due to weakened gluten structure and excessive gas pressure.

The Baking Stage

During baking, several changes consolidate the dough’s structure:

• As the oven heats, yeast activity accelerates until it ceases at about 60°C when yeast cells die.
• The residual CO₂ and steam further expand the dough, producing the “oven spring” effect.
• Starch gelatinisation and protein coagulation occur, solidifying the structure and fixing the porous texture.
• Ethanol and volatile compounds evaporate, contributing to aroma and flavour development.

This transition transforms soft, pliable dough into firm, aerated bread with a characteristic crumb and crust.

Other Biological Agents

Apart from yeast, bacteria and moulds can also produce gas under certain conditions. In sourdough bread, for instance, lactic acid bacteria (Lactobacillus species) coexist with wild yeasts. The bacteria produce lactic acid, contributing to flavour, while the yeast generates CO₂ for leavening.
This symbiotic fermentation results in a slightly tangy bread with a chewy texture and longer shelf life.

Summary of Key Factors Causing Dough Rising

Industrial Control of Dough Rising

In modern bakeries, dough rising is carefully monitored using temperature-controlled proofing chambers, yeast improvers, and enzyme-based dough conditioners to ensure uniform quality. Some industrial processes use compressed or instant yeast for consistent gas production, while others employ time–temperature control systems to manage proofing stages precisely.