Natural and Chemical Leavening Agents: Differences, Applications, Benefits

04 July 2025

The leavening process is one of the key elements in transforming food from a raw phase to a stable, digestible structure with complex organoleptic properties. In this context, it is essential to distinguish between natural and chemical leavening agents, two technically very different categories in terms of composition, activation dynamics, and applications. Natural leavening agents are biological agents, made up of living microorganisms – mainly yeasts and lactic acid bacteria – capable of triggering alcoholic and/or lactic fermentation. Through this process, the sugars in the dough are transformed into carbon dioxide and secondary compounds, directly influencing the leavening, structure, and sensory characteristics of the final product. This category includes brewer’s yeast, sourdough, and kefir.

In the context of Italian baking, fresh brewer’s yeast remains the most widely used leavening agent, with a market share nearing 90% and an annual consumption exceeding 35,000 tons. However, recent years have seen growing interest in alternative products, particularly sourdough, due to its nutritional benefits and the greater digestibility of the resulting baked goods. This trend aligns with the increasing consumer demand for artisanal, health-conscious, and sustainable products that emphasize local ingredients and traditional production methods.

Brewer’s yeast, sourdough, and kefir

Brewer’s yeast, composed primarily of Saccharomyces cerevisiae, is a single-cell agent used in either active dry or fresh compressed form. Its effectiveness relies on rapid and controllable alcoholic fermentation, making it ideal for industrial and semi-industrial baking applications where short processing times and standardized results are required.

Sourdough, or natural starter, is instead a complex and spontaneous culture of yeasts and lactic acid bacteria, activated through a mixture of water and flour. Compared to brewer’s yeast, it undergoes a longer, more acidic, and variable fermentation, but it imparts greater microbiological stability, longer shelf life, and a more complex open crumb structure to the final products.

Kefir, although not commonly used in baking, is an interesting example of mixed natural fermentation. It contains a symbiotic community of yeasts and bacteria, and its application is gaining traction in experimental projects, particularly in alternative fermented products or probiotic-enriched doughs with high hydration.

Chemical leavening agents, by contrast, are not living organisms but mixtures of compounds that release gas -mainly CO₂ – through chemical reactions. The most common are sodium bicarbonate (NaHCO₃) and cream of tartar (potassium bitartrate), often used in combination. The reaction can be triggered by heat or moisture, without the need for biological fermentation. This type of leavening agent is especially suited for baked goods that require short baking times and are meant for immediate consumption, such as cakes, cookies, and soft pastries, where extended development time is not necessary.

Natural leavening or chemical leavening? The differences

The differences between natural and chemical leavening agents go beyond their nature and mechanism of action—they also significantly impact the final product. Natural leavening agents, especially sourdough, allow the development of complex aromas thanks to secondary metabolites released during fermentation and contribute to improved digestibility. The presence of lactic and acetic acids, produced by lactic acid bacteria, also acts as a natural preservative. Moreover, some studies suggest that natural fermentation can help reduce the glycemic index and increase the bioavailability of minerals by breaking down antinutrients such as phytic acid.

On the other hand, chemical leavening agents ensure precise control over the leavening power and are ideal for production environments where biological variability is undesirable or where processing times are extremely short. However, they do not offer nutritional benefits or significant improvements in product structure.

The choice between natural and chemical leavening should therefore be guided by technical considerations related to the type of product, processing times, desired shelf life, and market requirements. In artisanal and semi-industrial settings where flavor, sensory quality, and naturalness are prioritized, the use of natural leavening agents is increasingly seen as a strategic choice.