With a unique culture and a longstanding tradition, sourdough is used in new interpretations for unique creations. Karl de Smedt, sourdough librarian at Puratos, shares insights into the bustling scene of European sourdough creations, how to maintain a strain’s profile and how to work with sourdough in large-scale operations.
Catalina Mihu: What is an overview of the sourdough diversity in Europe, and the products traditionally made with them, in certain countries?
Karl de Smedt: To date, there have been no comprehensive studies of how sourdoughs vary between different countries throughout Europe, but we do know some demographics prefer certain sourdough flavor profiles. Geography also has an impact on the character and bread quality of sourdough, as factors like climate can affect its microbial diversity. What we do see after preserving a sourdough in the sourdough library is that each sourdough is unique. We have currently 153 samples from 31 countries. All of them harbor a different consortium of micro-organisms.
Mihu: What flavor differences can be observed throughout Europe?
Karl de Smedt: Every sourdough culture is unique, with its own history and specific taste, but certain regions across Europe have distinct quirks that make them stand out, such as using different flour combinations. Greece has a long history of making wheat-based sourdough, for example. There’s one variety that originates in Mount Athos, a holy mountain that has been home to 20 monasteries for over 1,000 years. It’s based on the traditional ‘sourdough of the Cross’ – and is made with 40% durum flour, 40% white flour and 20% whole wheat flour, resulting in a tangy sourdough that is very dense.
Further away in Finland, rye-based sourdough is more typical – driven by a long history of cultivating rye on home soil, without the need for imported ingredients. Sourdough is crucial to adding structure to rye bread, while the rye brings a darker color and a stronger, more bitter taste to loaves. Rye-based sourdough continues to be extremely popular among Finnish people thanks to its satiety benefits, as well as its great taste and long shelf life. From our Quest for Sourdough research, we discovered that people in Eastern Europe describe their sourdough as tasting more like cereal compared to those who live in southern or northern Europe, where they say it is more fruity and sour/acidic.
Mihu: And what new developments are noteworthy, in terms of ingredient combinations, processes and end products?
Karl de Smedt: Sourdough brings a variety of different flavor profiles to end products, including roasted, creamy, fruity, sour/toasted and sour/tangy, that appeal to wide-ranging demographics. So, it’s not surprising that we’re seeing consumer demand grow for sourdough options that go beyond bread, such as pizza and pastries, as people want to recreate the same great taste in other products, too. For example, we’ve seen bakeries develop products like sourdough blueberry brioche tarts, which have a velvety cream cheese filling that offsets the tart blueberries.
Caring for sourdough in microorganism detail
Mihu: How should sourdough best be preserved over time/multiplied, to retain its characteristics? Please share examples.
Karl de Smedt: The age of the starter or creation date, the type of flour it is fed with, how often it is fed and where the yeast comes from can all affect the final sourdough result. Maintaining a sourdough starter is crucial to creating end products with consistent taste and quality – it must be fed regularly. However, it can be preserved for longer periods under the right conditions; sourdough starters can be kept for two months in an airtight jar, in the fridge at 4°C, without feeding them – which is how we keep them in the sourdough library. People have been seen drying their starter, freezing it, or keeping it in the fridge unfed for more than two months, but this is not recommended as some of the micro-organisms might not survive the harsh conditions and stress they are subjected to.
Mihu: What are the benefits of comprehensively mapping sourdough’s microbiome? And how can it be accomplished?
Karl de Smedt: Although bread has long been a part of society, we are still learning about its microbial communities and how they affect the taste, texture and appearance of final products. It’s therefore important to map out the microbial ecology of sourdough starters, to build a better picture of the influencing factors. We still don’t know how variations in flour, water, geography and even the microbes on bakers’ hands can have an impact on the sourdough. A study we did into the microbes on bakers’ hands showed that it’s actually the sourdough that influences what lives on some bakers’ hands. Each sourdough starter tells a story of its heritage, but cultures are fragile and can sometimes be lost or damaged – which is where safeguarding them comes in.
Our Puratos Sourdough Library in Sankt Vith, Belgium, was created to collect and preserve the biodiversity of starters. Over 100 bakers from across the globe have sent samples of their sourdough cultures for safekeeping, allowing scientists to analyze the microbes, to see how they differ from starter to starter. Not only does this help roadmap taste heritage in different regions but it means bakers’ livelihoods are futureproofed, too. So far, over 1,500 strains of wild yeast and bacteria have been examined at the Sourdough Library – and it is home to 153 sourdoughs now.
Mihu: How can a sourdough be adjusted in case flavor profile changes over time?
Karl de Smedt: The microbial composition – the wide diversity of lactic acid and bacteria – of sourdough has a significant impact on the flavor profile of end products. The duration and temperature of the feeding process can also influence taste; the warmer it is, the more lactic acid is produced, giving the sourdough a more creamy flavor, while the colder it is, the more acetic acid is produced, hence the more tangy flavor. The type of flour used is significant, too – changing from all-purpose white flour to whole wheat or a different type of grain, like rice, barley, or rye, can contribute to different flavor developments.
Feeding schedules are crucial when adjusting the flavor profiles of a sourdough starter. For instance, keeping the time between feeding with fresh flour short, such as every four to six hours, keeps the sourdough very active, with low acidity development. Leaving a starter for 12, 18, or 24 hours can increase acidification, which can weaken fermentation power, and increase the tanginess of the final product.
Mihu: What types of sourdough best answer to the growing trend for healthier foods, from a nutritional standpoint?
Karl de Smedt: More and more consumers are embracing fermented foods like sourdough for their health-promoting properties, as well as their unique flavor profiles. In fact, 62% of consumers worldwide think sourdough is healthier than other bread options, according to our ‘always-on’ Taste Tomorrow research insights. Scientific studies show that sourdoughs are more digestible than non-sourdough bread types.1 This is down to the pre-digested complex carbohydrates and proteins created during the fermentation process, meaning the body has less work to do, which may help individuals feel lighter. Sourdough also has a lower glycemic index, making people feel fuller for longer and avoid fatigue and cravings after eating.
What’s more, sourdoughs offer enhanced absorption through a special mechanism that helps to release minerals from the grains, so that the body can easily absorb and make use of them.2,3 Consumers are attracted to sourdough products for their gut-
friendly effects, too. Depending on its composition, active sourdough may have prebiotic potential by supporting the gut’s microbiome balance. Bakers are also increasingly adding nutrient-and fiber-rich inclusions, like sprouted grains, to boost the health ‘halo’ of sourdough products even more.
“The age of the starter or creation date, the type of flour it is fed with, how often it is fed and where the yeast comes from can all affect the final sourdough result.”
Karl de Smedt
New areas of sourdough research
Mihu: How can sourdough product consistency be ensured? What are the limitations?
Karl de Smedt: It takes years for a sourdough to change, particularly a mature starter, even by changing its location or feeding it. As long as it’s kept in optimal condition, a sourdough can remain in good health and ultimately, ensure product consistency. However, even kept in its place of origin, starters have been seen to evolve. In an experiment last year, we asked for samples from 17 bakers who had donated their sourdough to the library in the past decade and saw that some samples had lost their diversity. That’s why we believe the sourdough library is an important project as it saves the original biodiversity of the sourdough and stores it for the future. What’s interesting to see is that in the library, biodiversity has also evolved the same way as in the sourdough’s place of origin which raises a lot of questions, paving the way for new areas of research. The sourdough library captures discoveries that overwise would have been lost.
Mihu: What are some best practices for large-volume operations?
Karl de Smedt: Choosing the right partner for quality and consistency is absolutely crucial when it comes to sourdough. We’ve encountered numerous customers with ambitions to produce their own sourdough, but who ultimately found success by allowing us to create a custom solution tailored to their specific needs.
The key ingredient here is consistency. Sourdough is a living entity, influenced by external factors like temperature, time, and flour. Gaining a comprehensive understanding of these elements is a skill that most bakeries struggle to acquire. Even if they do, it’s often concentrated in just one or two individuals and if those people leave, or move into different roles, inconsistency and uncertainty in the sourdough’s environment are introduced – this really should be avoided. At Puratos, we can achieve a level of quality and stability that exceeds what could be managed in-house. When we collaborate with customers on their sourdough production, we are committed to ensuring their success.
