The rise of sourdough: is it the heathiest bread?

In recent years, a sourdough renaissance has occurred in Australia, partly driven by the pandemic and lockdown baking, with Google searches for sourdough increasing by 400% from March to April 2020.

Due to a long fermentation process and a small number of additive ingredients, sourdough is perceived to be healthier, which is a driving factor in its popularity.

Researchers Jaimee Hughes and Associate Professor Sara Grafenauer from UNSW Medicine & Health investigated the health of sourdough when compared with hundreds of Australian bread products, looking into the ingredients and nutritional profile of each bread type.

They found that many sourdough products contained non-traditional added ingredients and that sourdough products were not necessarily more nutritious than others, with the healthiest choices being wholegrain breads.

What is sourdough?

Sourdough is the oldest way of leavening bread, using sourdough starter — a live fermented culture of flour and water — rather than baker’s yeast. Typically, the fermentation period for the dough is longer, ranging from four hours up to 72 hours. The resulting bread has a characteristically sour taste.

Sourdough bread should only contain flour, water and salt, something which is reflected in the bread requirements of certain countries such as France. Other jurisdictions, such as the United Kingdom and Australia, do not have any guidance on the definition of sourdough, allowing supermarket chains and industrial bakeries to create bread with non-traditional ingredients and sell it as sourdough.

Supermarket research

The researchers visited four supermarket chains (Coles, Woolworths, Aldi and IGA) and the Baker’s Delight franchise in Sydney in October 2019 and October 2021 and surveyed all available bread products across the stores, which grew from 669 in 2019 to 800 in 2021. They collected information such as ingredient lists, nutritional information and claims on the product packaging.

From October 2019 to 2021, the number of products labelled as sourdough grew from 72 to 108, a 50% increase. This outstripped the growth of the bread category overall, which was 20%.

The researchers found that 83% of sourdough products contained non-traditional ingredients such as yeast, emulsifiers, preservatives and stabilisers.

“You may think that you’ve got a beautiful sourdough bread, but it’s actually got a whole range of other ingredients added to it,” Grafenauer said.

In 2021, 26% of the sourdough products had claims on the packaging about the fermentation process. This was an 86% increase from 2019. The researchers did not test the validity of these claims, but Grafenauer said the length of the fermentation period for sourdough products is not the most important nutritional quality.

“A big number of claims were related to fermentation, particularly fermentation time ranging from eight hours to 72 hours. Other research has found that you can actually see changes in the bread with as little as four or five hours of fermentation,” Grafenauer said.

Sourdough fermentation has previously been shown to reduce the levels of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) in the bread, which may assist people with irritable bowel syndrome (IBS). However, these changes were shown to be relatively small and don’t require long periods of fermentation.

“People might be taken in by claims about long fermentation time thinking: this is real sourdough,” Grafenauer said. “But what they actually need to do is look at the list of ingredients.”

The researchers also assessed the nutritional profiles of the different bread products and found the most nutritional were the ones that contained higher levels of protein and dietary fibre, as well as lower levels of sodium.

Whether or not a product was sourdough did not significantly influence its nutritional profile. The more important factor was the type of flour used, with wholegrain breads being more nutritious than white breads. This is consistent with recent research showing that there isn’t a particular health advantage to sourdough unless it is wholegrain sourdough.

“If someone is confused about what bread to choose, wholegrain is the best choice,” Grafenauer said.

Image caption: Associate Professor Sara Grafenauer studied the ingredient lists, nutritional information and on-pack claims of bread products sold in Sydney supermarkets. Image credit: UNSW.