Sourdough Library | American Society of Baking
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Sourdough Library

What is the sourdough library?

The sourdough library is a non-profit global initiative by Puratos. It’s designed to gather sourdough starters for their protection and preservation.

Available to all bakers worldwide, it’s for anyone interested in learning about sourdough. 

The ultimate purpose of the library is preserving the biodiversity of natural leavening microflora. However, it’s also for sharing knowledge about sourdough fermentation and its use in baked goods.

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The sourdough library is the result of a long-term research program between Puratos and professor Marco Gobbetti from the Department of Applied Microbiology at the University of Bari, Italy. Professor Gobbetti’s work focuses on the isolation and identification of different strains of yeast and lactic acid bacteria present in sourdough. He also studies the chemical composition of sourdoughs.

In 2013 the library started with 43 sourdoughs. Now, it has over 100 starters from bakeries from all over the world. The sourdough library is located at the Center for Bread Flavour of Puratos in Saint-Vith, Belgium. The collection is from over 20 countries, including:

  • France
  • USA
  • Hungary
  • China
  • Spain
  • Portugal
  • Australia
  • Mexico
  • Russia
  • And others

The sourdough library has more than 700 strains of wild yeast and 1,500 lactic bacteria.

How it works

Getting involved in the sourdough library is simple. Any baker can participate and contribute to this collection. First, a portion of sourdough is donated.

  • The library collects the sourdough sample
  • The person who gives the sourdough provides:
    • Enough original flour to feed the sourdough for about a year
    • The recipe/formula to feed or refresh the starter
    • A feeding procedure and schedule
    • Optimum conditions for storage
  • All related documentation is securely handled by Puratos under strict confidentiality policies for traceability purposes and inventory control.
  • Then, the sourdough is stored with strict control of temperature, relative humidity and hygiene. The conditions are provided by donors.
  • The starter is fed periodically.
  • The starters are kept and grown in perfectly regulated conditions.

These steps help ensure the original sourdough does not change with time.

By sending a portion of their sourdough starters, donors get a secure backup. So in case the original sourdough gets lost or changed, there is a record preserved. The library has the capacity to keep thousands of sourdoughs samples.

Why it matters to bakers

There is no other place like the sourdough library in the baking industry. It is the perfect place to preserve the unique microflora in sourdoughs from different countries. The library serves a purpose beyond any company’s interests. Furthermore, it helps educate younger generations about the beautiful world of sourdough.

Many bakers refer to sourdough as “going back to the basics.” This ancient breadmaking technique encompasses the craft, art and science behind baking and fermentation. Making sourdough is a practice that was partially lost after the introduction of commercial yeast.1

Now, over 150 years later, sourdough is recovering its old glory. Furthermore, many people are starting to see its real value. Sourdough adds things such as better flavors and aromas, enhanced nutritional value and superior texture and shelf-life.1


  1. Corsetti, A. Handbook on Sourdough Biotechnology, Springer Science+Business Media New York, 2013, pp. 1–103.