I spent several years writing a book about the value of biological diversity to agriculture, Never Out of Season. In doing so, I gained a deep appreciation for the role farmers and consumers can play in helping to save the biological diversity of crops and the species they depend on. I also, however, realized that the biological diversity of our food does not end at the farm field. We also have biological diversity living in our kitchen, in our fermented foods. Or at least we used to. Over the last hundred years the diversity of microbes used to make foods was homogenized. We mostly now use the same yeasts to make beer, bread, wine and much more. It is possible that many of the microbes once used to make traditional fermented foods have gone extinct. If they haven’t, it is because of what one might call “kitchen farmers,” people who still make fermented foods in the traditional ways and, in doing so, help to pass along heritage bacteria and fungi. One of the things then that we will be looking for as we study the sourdoughs that have been shared with from around the world is which of those sourdoughs are most likely to have truly unique microbes or mixtures of microbes found nowhere else.

We have four key predictions, but want to hear your ideas too.

We predict that sourdough starters are most likely to have unique microbes if they…

  1. Are from extreme climates. A century of study of the distribution of life in general, be it birds, mammals or ants, suggests that hot, wet and or isolated regions are likely to host unusual species found nowhere else (think the finches of the Galapagos Islands or the unique orchids of the Amazon). Is the same true for sourdough microbes?
  2. Are part of very old sourdough starters, passed generation to generation. Such starters may be sufficiently isolated from other sources of microbes (and perhaps also hard to colonize) that they become dominated by unusual microbes found nowhere else, whether microbes characteristic of another time, or microbes that have actually evolved in the sourdough itself.
  3. Are made using unusual ingredients. Perhaps the uniqueness of the microbes in a starter really depends on what you feed the starter. Maybe the special microbes only turn up when one adds a bit of wild barley and kumquat (for example).
  4. Are part of unique food cultures and histories. We won’t be able to test this hypothesis fully with our first data, but it is possible that microbial cultures become different from one and other not just across the short history of an individual starter but also across the longer history of a human culture. We might imagine in this case that the longer two human cultures have been separate the more different their starters might be expected to be.

But share your ideas too. Remember that there are many ways we can look at the differences among starters. We won’t consider them all at once. We can consider which kinds of bacteria and fungi are present (our first step). We can consider for those bacteria and fungi which genes they have (what toolkits). We can also consider what the starter is able to do, how it affects the resulting bread. We will do all of this in turn. Meanwhile, remember that if you are a teacher interested in working with sourdough in your science class (or art for that matter) to let us know.



Photo Credit: Lea Shell