Even though sourdough has been around for at least 5000 years, we are still learning and uncovering new sourdough secrets about it. Two recent experiments looked at understanding the precise influence the bakers have on their sourdough, and how influential flour is on the profile and resulting taste of different sourdoughs.

Summer 2017, Puratos wanted to understand the way bakers (and their hands) influenced the sourdough bread they make. So, with the assistance of Rob Dunn and Ann Madden from the North Carolina State University, we asked 15 professional bakers from around the world to make a new sourdough starter from the same flour and then come to The Puratos Center for Bread Flavour to bake and see the results.

When tested, it turned out the starters were both similar and different at the same time, with the main differences being linked to who and where they were made. There was, in effect, a part of the baker in each of the starters, as the bacteria in the starters and hands appeared to match. It confirmed that bakers impart certain microbes to their bread. But of greater interest was the fact that some bakers, with really unique microbes on their hands, impart more.

One other interesting finding was obtained following a swab test on the bakers’ hands. It seems that the bread dough itself had actually influenced the baker’s hands, and that compared to non-baker’s hands, those of bakers were much more likely to be covered with Lactobacillus bacteria. The bakers had, in some very real way, become their bread.

How important is the flour?
In 2018, we asked seven professional and eight hobby bakers to help us find out what happens to various sourdough profiles when they are refreshed with the same flour. In essence, would using the same flour standardize the sourdoughs and make them all alike, or would they keep their initial character?

Each participating baker received the same bag of new flour. This was of course a different flour to the ‘usual’ starter-refreshment flour they used ordinarily. Over a period of 10 days, each baker was asked to refresh his or her own sourdough every day with the flour provided. Once refreshed 10 times, the bakers were invited to the Puratos Center in Sankt Vith (Belgium) to bake loaves using the same ingredients, materials and recipe as each other. In effect the only possible difference between the breads would be the source sourdough starter.

The breads were then ‘sensorially analysed’ by the participants themselves. This isn’t always an easy task, but you didn’t have to be a taste expert to spot the differences in the breads. A clear first indication that, despite being refreshed with the same flour over a period of 10 days, all the sourdoughs remained very much unique.

However, to really uncover the sourdough secrets, we wanted a more systematic approach and therefore enlisted our expert researchers for help. During the refreshment phase, four samples of the sourdough were taken: one before the first refreshment, and one just after, one after the sixth refreshment and then one last sample after the tenth and final refreshment. Puratos researchers then analysed the microbial culture of each of the samples. The experts’ conclusion? While spontaneous sourdoughs may have an unstable pH and acidity level, they all have a robust microbial culture.

Our quest for sourdough
If you want more sourdough secrets, check out the Quest for Sourdough website questforsourdough.com. This website lets every sourdough owner on the planet profile his or her starter; to date we’ve already registered 1610 sourdoughs, from 1421 cities and 87 different countries.

The introduction of bakers yeast approximately 150 years ago essentially lost much of the world’s sourdough heritage. But fortunately today, sourdough is rightfully back on the map.