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Inside Our Food

Sourdough | History Rises Again

Today sourdough is considered an artisanal bread, but 160 years ago nearly all bread was sourdough. What changed?

Sourdough – History rises again

No one knows who made the world’s first raised bread. But it’s likely to have happened after humans invented agriculture. Settling in one place, experimenting with mixtures of grain, someone probably noticed a mixture of crushed grains and water forming bubbles after a few days – the tell-tale sign of fermentation.

From Fermentation to Sourdough

Fermentation occurs when microbes (like bacteria and yeast) digest substances, producing gas and other products. Milled flour naturally contains strains of Lactobacillus bacteria and wild yeast from the environment, and these microbes can digest starches and sugars in the flour. Ancient civilisations would have found out that this frothy mixture, when baked, produces a softer and fluffier alternative to early flatbreads. This began the trend of ‘leavening’ bread, making bread rise by incorporating substances (like microbes) to put gas bubbles in the mixture.

Sharing the Dough

Does this process sound familiar? It’s actually how sourdough is traditionally made! So ancient leavened bread was just sourdough. Sourdough was eaten by the ancient Egyptians, taken to America by French bakers during the Gold Rush, and nurtured in bakeries across Europe.1

So what changed? Eventually, bakers figured out that yeast did the bulk of the leavening – adding yeast to a dough mixture gave fast and reliable results. In 1857, French microbiologist Louis Pasteur identified yeast under the microscope, which led to commercial baker’s yeast creation. Bread production was transformed, and sourdough was no longer the only option.2  

Fun fact: For a while, bakers used brewer’s yeast, which gave the bread a bitter flavour.

What’s in a sourdough?

But Lactobacillus and yeast don’t just change the texture of bread; they change its chemistry. Raw sourdough is a living thing, a changing blend of microbes, and it’s the natural balance between the yeast and bacteria which makes sourdough so special.

As the microbes grow and live and ferment, the Lactobacillus produce lactic acid, and the yeast produces alcohol, giving the bread a tangy and acidic flavour. The acid in the dough also keeps out other types of fungus and bacteria, so the eventual bread has a longer shelf life. The microbes also digest gluten, meaning that real sourdough should either be low in gluten or gluten-free—so people with gluten intolerance and celiac disease might be able to eat sourdough.3

Fun fact: The lower amount of sugar means sourdough also has a lower glycaemic index than many types of other bread.

You might be eating 100-year-old sourdough

In the past, bakers found they could save some leavened sourdough to add to new mixtures, converting them into more sourdough. With careful feeding of flour and water, these so-called ‘starter doughs’ can be kept alive indefinitely. In fact, there are starter doughs in modern bakeries that may be hundreds of years old.

Across the world, jars of starter doughs have been treated like family heirlooms, passed down through generations. Starter doughs were carried by frontier settlers and Gold Rush prospectors, snuggled at night to keep them warm and alive.

Fun fact: Each starter dough is unique, a potted history of local flour and microbes from the environment - including the Lactobacillus found naturally on the baker’s hands.4

Traditional sourdough continues to be made and sold today in bakeries and artisanal markets. A sourdough library in Belgium aims to collect and catalogue starter doughs from around the world.5 In Sweden, a sourdough hotel will maintain your starter while you vacation.6 You could make your own starter using just flour, salt and water, or purchase a regional starter dough over the web. And you might decide the starter’s history doesn’t really matter - scientists have found the same distinct strains of Lactobacillus in San Francisco starter doughs as in bakeries across Europe.7

But is it real sourdough?

But while some bakers are fiercely proud of their traditional sourdough and treasured starter doughs, sourdough has no legal definition. It’s really the Lactobacillus which is key to creating sourdough, yet no official legislation states a sourdough loaf must contain any Lactobacillus.8

Though 30–50 % of European breads are produced using sourdough, industrially-produced sourdough uses dried starters rather than a spoon of sticky dough from a treasured pot.  Other ‘sourdough mimics’ are likely leavened using yeast and artificially soured with additives. And sourdough mimics may not have the time or microbes needed to break down the gluten in grains. This means if you are gluten-intolerant or avoiding high GI foods, there is even more reason to care whether your sourdough is authentic or not.


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