Ernest Blog: Karl De Smedt (Interview)


“We do what is done in every library, study!”

Could you tell me a little bit about yourself and what brought you to this project, I understand that you are a trained confectioner and baker?

I graduated from bakery and patisserie school in 1988. I worked for six years in a confectionary in Brussels before joining Puratos in 1994 as a test baker. That’s where I worked with sourdough for the first time. The sourdough was brought back in 1989 by a colleague from San Francisco, as part of some research to produce sourdough solutions for the company’s customers. You could say this sample was the very first sourdough in our collection.

Since 2008, I’ve been responsible for the Centre for Bread Flavour, a specialist branch at the forefront of the company’s sourdough production efforts, which handles clients from all over the world. It’s here that we opened the sourdough library in 2013. As a result, I’ve travelled to almost 50 countries over the last 24 years and discovered a variety of different food cultures. I love food, especially when it’s fermented: cheese, beer, wine, sausages and, especially, bread.

Why has it been so important to collect and conserve these different sourdough starters?

150 years ago, when ‘bakers yeast’ was just starting to be produced commercially, the sourdough process was inconsistent and time-consuming (bakers had to wake up every 3-4 hours to refresh their starters). So, bakers and households alike largely abandoned the lengthier sourdough process and switched completely to bakers yeast. As a result, a lot of the previous knowledge around sourdough was lost. Therefore, it is important for us to preserve this tradition and the biodiversity of the resulting starters. Having a library where sourdough can be studied is an important contribution to the world of baking and fermentation.  

Where has your quest for the finest and most diverse starters taken you?

I just had an amazing journey to the Klondike Gold Rush. I went from Seattle to Skagway, Whitehorse down to Dawson City in Yukon. That was an amazing adventure, and we even made a movie about our travels. On our quest to discover the heritage of sourdoughs, we’ve also been to Altamura in Italy, San Francisco, Greece, Japan, China, Mexico and the UK.  

How varied and unique can the final product be with the infinite possibilities of extracts and microbes?

Very. We like to compare the sourdoughs to cheese: the main ingredient is just milk, but there are still so many different types of cheese – due to the origin of the milk, the fermentation temperatures, the ageing, the place, the producer…

With sourdough, it’s the same: different flours, different bakers, other processes. In our library, we have identified over 900 different microorganisms from 108 starters. The same goes for wine, beer and other fermented goods. Fermentation is an incredible thing!

I understand that the original baker of each starter also needs to donate yearly supplies of flour to the library for maintenance. So, will this change the outcome of the mix later on?

Indeed, we do ask for a supply of flour from the owners for their sourdough contributions. However, we do that to minimise the impact of change, a protocol recommended to us by Professor Marco Gobbetti from the University of Bolzano and Bari in Italy. We are well aware that the starters might be subject to change. But with Gobbetti’s protocol, the sourdough cultures are kept in optimum conditions to preserve them for longer; we have the micro-organisms stored in a freezer at -80°C and the sourdoughs themselves are stored at 4°C.

When a sourdough enters our library, it’s like taking a picture. We capture that moment! But at least we have the composition of the sourdough at that point in time. That allows us to go back to the bakery after 5,10 or 20 years to compare the two starters with each other and the original sample. There is no other place in the world that is doing this for sourdough. That’s why this library is so important to us.

We do what is done in every library, study!

Does the library undertake research into the microbes in the starters?

Yes of course. Through DNA sequencing, we can define each and every microbe that we find in a starter. So far, we have identified more than 900 different ones. We do this in close collaboration with the universities we work with; Professor Gobbetti and his team have already been able to produce a couple of scientific publications as a result of our work together.

What is the strangest thing you have found in a starter?

I do not know quite what you mean by strangest, but there have been some very interesting and quite unbelievable findings. In a starter from Switzerland, made from rye flour, and one from Guadalajara in Mexico, we found the same strain of yeast: Torulaspora delbreucki. It’s a strain often found in premium wines. The only relation we could see between the two is that the bakeries were located at about 1500 metres altitude.

What kind of foods have you made with the starters from your collection?

I have already baked some bread, soft and sweet ones. But also waffles and pancakes.

Did you find any particularly good starters here in the UK?

Right now, we only have two starters from the UK. One is from Vanessa Kimbell at the ‘sourdoughschool’. The other one is from Village Bakery.

Last year, I went on a tour in London with a Belgian journalist for a newspaper article about sourdough. I visited Sharmin and Fergus Jackson at Brick House and I tasted their incredible morning buns and discovered their sourdough. That could be the next one from the UK.

I also had the honour to be introduced to a sourdough from St. John’s by Mr. Trevor Gulliver himself. He was also interested in participating in our library project.

Where can I get a taste of these wonderful sourdoughs, I see that your website is also a resource for bakers too?

Our website ‘the Quest for Sourdough’ was created to get a better view of the world of sourdough. We ask everybody from professionals, schools and home bakers to register their sourdough online. That way, we get a better view of what’s going on out there and it helps us to identify starters that we would never have been able to find through our network alone.

As a result of people visiting the site, I discovered a sourdough from Seattle that dates back to the Klondike Gold Rush. After being intrigued by her story, I interviewed Ione Christensen from Whitehorse in Canada. She was talking about her sourdough that dated back to 1896 when her great-grandfather made his way to Dawson city to find gold. I shared her recipe on our website so that people were able to reproduce her fantastic waffles.

I could give you a list of bakeries, but I think it might be nicer if your readers start having looking on our website for who is baking what and where. They can also follow us on our Facebook page to find out more, or follow me on my adventures on Instagram @the_sourdough_librarian. I have already made a couple of movies about my adventures in different countries and I’m happy to share some tips and tricks for those who want to give it a try. Maybe one day their starter will end up in our library, or I’ll come over and see for myself.

Short of visiting the library in Belgium (we hear although it’s not officially open to the public, Karl and his team are happy to give tours when they can), here’s a link to their fantastic virtual tour:

And a link to the Quest for Sourdough website:

Or a link to the Quest for Sourdough Facebook:

And even a link to the Puratos sourdough hub:

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