Sourdough has had a huge renaissance in recent years, spurred on by the increase of artisanal bakers and the search for healthier products.
The sourdough leavening process is one of the oldest known food biotechnologies.
In simplistic terms, the process consists of mixing flour and water and allowing the mixture to undergo fermentation, either spontaneously or after the addition of a starter culture.
Fermentation is triggered by lactic acid bacteria – or lactobacilli – and yeasts, which use the carbohydrate fuels from the cereal grains to produce ethanol (alcohol), carbon dioxide, lactic acid and acetic acid.
Bubbles of carbon dioxide become trapped in the dough, making it rise.
Evidence is growing that the slow-fermentation process creates products that are easier to digest and have a higher nutritional benefit than those containing brewer’s yeast.
The use of sourdough fermentation in baked goods is particularly favoured in the US – currently the largest market valued at $3.2bn – but according to Market Research Reports Search Engine (MRRSE), it could soon be rivalled by the Western Europe sourdough market, which was valued at more than $1.2bn last year.
In volume terms, over 552k tons of sourdough was sold in 2016, estimated to reach over 975k tons in 2026.
MRRSE reported Germany is expected to be the biggest consumer of these products in the region, with a market forecast to value more than $400m by the end of 2026, recording a 7.3% CAGR between 2016 and 2026.
The market researcher noted the APAC market, too, is expected to grow swiftly owing to changing lifestyles and the inclination of Asian consumers towards Western foods.
The popularity of sourdough stems from its ability to break down gluten into amino acids, which makes it easier to digest – a fact that is being picked up by all consumers, not just those with gluten sensitivity.
A study by Italian researchers published in The Journal of Nutrition in February 2018 again suggested the process promotes gastrointestinal function in healthy adults.
The study - supported by Italian pastry producer Fresystem – also noted it removes the oft-felt “postprandial symptoms” of fullness and bloating often associated with standard wheat breads prepared with brewer’s yeast.
Proving the benefits
Studies suggest sourdough-based products are highly nutritious in nutrients such as vitamin B and C, which are retained afterfermentation.
Don't knock it
The Real Bread Campaign has strict definitions when it comes to sourdough dough and notes it must be made only using a live sourdough culture (not inactive dried dourdough powder), without the use of processing aids or any artificial additives (which includes most flour 'improvers', dough conditioners and preservatives), chemical leavening agents (eg, baking powder) or other souring agents (eg, vinegar or yogurt).
The only exceptions the consumer watchdog makes is the four ‘fortificants’ added to most flour by law in the UK, being iron, thiamine (vitamin B1), nicotinic acid or nicotinamide (vitamin B3) and calcium carbonate.
According to The Bread and Flour Regulations 1998, the process of milling wheat causes a loss of iron and vitamin Bs and thus these mineral and vitamins need to be restored.
Calcium is added for fortification purposes.
The fermentation process reduces sugar levels as well, making it easier for blood sugar level. Sourdough also neutralizes the anti-nutrients allowing better absorption of minerals.
Researchers also found the acidity created by the lactobacilli acts as a preservative even after being subjected to high heats during the baking process, resisting microbial deterioration and increasing the shelf life of products.
Conversely, commercial baking yeast – although fast acting and easy to produce – is intolerant of acidic environments.
The case for sourdough
During their research, scientists from the Universidad Auto´noma de Coahuila in Mexico noted the fermentation process of sourdoughs also enhance the functional properties of baked goods without sacrificing any of the organoleptics.
They found the fermentation process gives the dough a richer and more aromatic flavor to baked goods and can improve the mouthfeel and palatability of products without removing any nutritionally important components.
The enzymatic action of sourdough also modifies some dough components, leading to the formation of smaller molecules.
No similar changes occur in bakery products prepared with brewer's yeast.
While the origin of sourdough fermentation is thought to stem from around 4700 BCE, the use of baker’s yeast as a leaving agent dates back less than 150 years.
However, it could be a case that ago-old technology trumps ‘modern’ processes in this instance, enabling bakery goods producers to capitalize on the growing health and wellness trend.
Postprandial Gastrointestinal Function Differs after Acute Administration of Sourdough Compared with Brewer's Yeast Bakery Products in Healthy Adults
Barbara Polese Emanuele Nicolai Daniela Genovese Viviana Verlezza Carmine N La Sala Marco Aiello Marianna Inglese Mariarosaria Incoronato Giovanni Sarnelli Tiziana De Rosa Alfio Schiatti Francesco Mondelli Danilo Ercolini Rosario Cuomo
The Journal of Nutrition, Volume 148, Issue 2, 1 February 2018, Pages 202–208, https://doi.org/10.1093/jn/nxx049