Your sourdough jar is one of a kind. And science has just proven it.

You may not have thought of it this way, but that jar in your fridge, which you feed weekly with a spoonful of flour and a bit of water, contains a universe. This universe is made up of microorganisms that exist in that precise combination nowhere else on the planet—not in your neighbor's kitchen, not in that of a professional baker, nor in a scientific laboratory. Only in your jar, only in your environment, only between your hands.

This is not poetry. It’s what a major international scientific research project has demonstrated, involving hundreds of bakers from around the world, both professionals and home enthusiasts alike, in a collaborative effort that has produced one of the most comprehensive catalogs ever created on the biodiversity of sourdough.

When science knocks on the doors of home kitchens

The idea behind this study was simple yet revolutionary: instead of analyzing sourdough only in the laboratory, why not directly involve the people who use it every day? Thus began a global collection. Bakers from every corner of the world submitted samples of their sourdough, filled out detailed questionnaires about their habits, shared how they refresh the starter, at what temperature they keep it, and how long they have been using the same starter.

The result was an extraordinary map of microbial diversity, a kind of living library of sourdough in the world. And what researchers found within all these samples surprised even them.

Each sourdough is its own ecosystem. The lactic acid bacteria and wild yeasts that inhabit it do not distribute themselves evenly in two different jars, even if they were prepared with the same flour and in the same city. Differences depend on the water used, the temperature of the kitchen, the frequency of refreshments, the age of the starter, and even the microbial flora present on the hands of those who work with it daily.

What professionals do differently than we do

One of the most interesting aspects to emerge from the study concerns the differences between professional bakers and home bakers. Professionals generally use older sourdough, with years or even decades of history behind it. They refresh it much more often, sometimes even twice a day, and keep it at higher temperatures than we typically do at home.

This doesn’t mean that your homemade sourdough is worth less. On the contrary, it means that your sourdough has its specific characteristics, which arise from the way you manage it. If you refresh it once a week and keep it in the fridge, you will have a colony of microorganisms that is different from someone who refreshes it every day at room temperature. Both produce good bread—just different bread.

If you want to do a little experiment, try...