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Exploring the Secrets of Sourdough Science

Sourdough starters harness the power of wild yeast and lactic acid bacteria to create a dynamic and living ecosystem. The process involves capturing and cultivating these microorganisms, allowing them to interact and produce carbon dioxide gas, which leavens the dough. The lactic acid bacteria contribute to the distinctive sour flavour and act as a natural preservative. Let’s dive into some sourdough science.

When we use and cultivate these cultures, we use nature to help us produce food that is easier to digest than bread produced with industrial yeast.


Natural cultures have been used for brewing beer and leavening bread for millennia. Archeologists found evidence of the use of sourdough cultures in ancient Egypt.  
As time passed, sourdough became a staple in various cultures, evolving with regional nuances and techniques. Today, it has become a symbol of traditional, slow fermentation methods in contrast to commercially yeasted bread.


What is behind this sourdough magic? Let’s look at the ingredients:

graphic about sourdough science

Wild yeast

Yeast are fungi that are all around us. These cultures can be found on grain and fruit. They are on most surfaces we touch, and even in the air we breathe. There are many different types of yeast but the ones we use for brewing beer and baking bread are of the “Saccharomyces cerevisiae” family.
Yeast consumes sugar and produces ethanol (alcohol), carbon dioxide and aromatic compounds. Yeast carries out this transition in the absence of oxygen (anaerobic).
By combining flour, water and time, we enable the yeast to work and “eat” the sugars in the grain.

The most common species of wild yeast utilized in baking is Saccharomyces cerevisiae, known for its ability to leaven bread and impart complex flavours. Capturing wild yeast involves creating a starter, a mixture of flour and water left exposed to the environment, allowing ambient yeast and bacteria to take residence.

The symbiotic relationship between wild yeast and lactic acid bacteria in these starters gives rise to a dynamic microbial community, fostering the fermentation process that results in the distinctive taste and texture of sourdough. Wild yeast embodies the essence of traditional bread-making, connecting us to the age-old practice of utilizing the forces of nature to create wholesome and flavorful baked goods.

Lactobacillus Cultures

Lactic acid bacteria (LAB) play a pivotal role in the world of fermentation, contributing not only to the tangy taste and aroma of various fermented foods but also to their preservation. This diverse group of bacteria, including species like Lactobacillus and Streptococcus, is characterized by its ability to convert sugars into lactic acid through the process of fermentation.

LAB are commonly found in nature, and they have been harnessed by humans for centuries in the production of foods such as yogurt, sauerkraut, and sourdough bread. Apart from their culinary significance, lactic acid bacteria also have health benefits, promoting gut health by producing compounds that inhibit harmful bacteria and enhancing the bioavailability of certain nutrients. The intricate dance between lactic acid bacteria and their environment exemplifies the harmonious relationship between microorganisms and the culinary arts, enriching our palates while contributing to the age-old tradition of food preservation.

Health implications

I am not a doctor or a dietician but here are some interesting things I have learned in my research.

1. Improved Digestibility:

The fermentation process in sourdough, driven by wild yeast and lactic acid bacteria, breaks down gluten and phytic acid. This can make the bread more digestible for individuals who are sensitive to gluten or have difficulty with digestion.

2. Lower Phytic Acid Content:

Phytic acid is an anti-nutrient found in grains that can bind minerals, making them less available for absorption. The fermentation process in sourdough reduces phytic acid content, potentially increasing the bioavailability of minerals such as iron, zinc, and calcium.

3. Blood Sugar Regulation:

Sourdough fermentation may lead to lower glycemic index levels compared to bread made with commercial yeast. This can result in a slower and steadier release of glucose into the bloodstream, potentially helping to regulate blood sugar levels.

4. Nutrient Content:

Sourdough fermentation enhances the production of certain nutrients, such as B vitamins and antioxidants. The breakdown of proteins and carbohydrates during fermentation may increase the availability of these nutrients in the bread.

5. Prebiotic and Probiotic Benefits:

The lactic acid bacteria present in sourdough act as a probiotic, promoting a healthy balance of gut bacteria. Additionally, the fibres and resistant starches in sourdough can serve as prebiotics, nourishing beneficial bacteria in the digestive system.

6. Reduction of FODMAPs:

Fermentation can reduce the content of certain fermentable carbohydrates known as FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols). This reduction may make sourdough more tolerable for individuals with irritable bowel syndrome (IBS) or digestive sensitivities.

It’s essential to note that the health benefits of sourdough can vary depending on factors such as the fermentation time, the type of flour used, and individual dietary needs. While sourdough can offer some advantages, moderation and individual tolerance remain key factors in maintaining a balanced and healthy diet.


My Blog – We Almost Lost These Microorganisms
National Library of Medicine – History and Domestication of Saccharomyces cerevisiae in Bread Baking
Can Can Awards – 43 Facts About Wild Yeast
Earth.com – Beginner’s Guide to the Wild World of Wild Yeast
Wikipedia – Sourdough
Serious Eats – The Science of Sourdough Starters
MDPI – Probiotics in the Sourdough Bread Fermentation: Current Status
Eating Well – Is Sourdough Bread Healthy?
Web MD – Sourdough Bread: Is It Good for You?
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