Hello and welcome to Sourdough and stories beyond

I am your host Mykola Nevrev and I am a sourdough expert, cookbook author and owner of The Midnight bakery, soon to be Bloom bakery in Bratislava, Slovakia 

In each episode of this podcast, I am going to share a story from the wonderful, and sometimes strange world of sourdough baking and beyond.

Today’s story is about the things that most of us don’t realize, but they exist and influence the taste of our bread and wine.

If you are listening to this podcast, you probably like sourdough bread, either as a baker or consumer. The products of sourdough baking are often claimed to be produced without yeast, but this statement is not completely true, as sourdough is a symbiosis of different kinds of yeasts and bacteria, so technically, there is yeast in sourdough too. But in contrast to the products baked with bakers’ yeast, which is essentially just one type of fungus called Saccharomyces cerevisiae, good sourdough is produced with a whole team of yeasts (including a much smaller amount of bakers’ yeast) and bacteria.

And although the technical process of bread baking is more or less the same all around the world, the taste of bread can be very different. This is not only due to the variety of flours used for baking, but also because of differences between the starters. All sourdough starters in the world share some identical bugs, and some of them are specific to certain regions. 

Yeasts and bacteria get to the starter through water, air and flour and what is also interesting, is that some of them are specific to certain bakers or bakeries.

During a famous experiment that took place in Belgium in 2017, a group of 15 bakers from 14 countries were given samples of the same exact flour as well as instructions on how to create a sourdough starter. The goal was to see if their bread would turn out any differently. Long story short, each came out differently, and this was not only due to a different approach to proofing and baking. When scientists took a closer look under the microscope, they discovered differences in the starters themselves.

A few months later, a group of participants met in Belgium to bake bread and get their hands swabbed by the team of scientists.

I personally love the results of this experiment: it turns out that the hands of bakers are literally colonized with yeasts and bacteria from sourdough. Of course, we often wash our hands with soap and water, which is a good thing, but because water and soap only wash away parts of germs that are not a part of our skin microbiome, our hands are far from sterile. If bakers put their hands on sourdough bread often, their skin microbiome actually start to include Lactobacteria and some yeast species as well.

So if you are a passionate baker who spends a lot of time touching sourdough, then you have what’s called “fermented touch” and can perform a sort of magical trick—starting fermentation just by touching an object with your bare fingers.

The starters from this experiment also showed the influence of the bakery environment. What does this mean for your every day baking life? I think that the more air in the bakery and the more fresh organic flour used, the more bugs will be inside the starter, which could actually benefit the taste of your bread.

All of these experiments have been described in the wonderful book “Never home alone” by Rob Dunn, which reminds me of another book that influenced my understanding of food: “Eating to extinction” by Dan Saladino, in particular the chapter about cheese.

Before industrial production, the cheese was closely connected to the place it was produced. This is because it was made of local unpasteurized milk, whose taste was influenced by the grasses growing in the fields and also specific and unique sets of bacteria that were living in the place where the cheese was produced and stored.

After the start of industrial food production, this is not a common story anymore. For example, To create Dutch style cheese, you just need to take your local and probably most pasteurized milk and mix it with cultures that were grown in laboratories. The result will be cheese and it might even taste good, but it won’t be even close to the original version made from raw local milk with the help of wild fermentation.

The same thing can happen in baking as well. Sourdough bread, hand shaped and made with locally grown stone milled population wheat, will taste not like yeasty bread made from white flour that you find in the supermarket. While Every bread deserves respect and admiration, I would definitely choose the first option as my daily bread choice.

Bakers yeast is now produced in specialized facilities, that produce hundreds of millions of identical fungi every hour. But what about wild yeast, where can they be found, and can we use them in fermentation as well?

The short answer is that wild yeasts are everywhere and yes, we could use them for making bread, wine or beer. Some sources of wild yeasts are surprising and might not make you feel very hungry, but they’re fun to talk about.

Wild yeast, including wild forms of bakers yeast, can be found in all kinds of different places, including on the skin of grapes in late summer. Do you know the layer of coating on grapes? That’s actually pure yeast. The life cycle of these yeasts is fascinating and shows the beauty of nature and its logic.

Yeast cells thrive on sweet and ripe grapes, happily consuming sugars and making an amazing layer of coating, which actually begins the fermentation process in wine. The question is: when the warm months are over and the cold sets in, how does the yeast survive?

Nature provides the smartest answer possible. In the summer, ripe grape juice attracts wasps and hornets, whose bodies become contaminated with yeast. This yeast can then survive the long winter months in wasp nests, where the temperature is acceptable. The next year the cycle begins again: yeast is spread outside by wasps, on grapes and other fruits, the fruits become ripe, attracts insects and then survives winters in their company.

To be more specific, yeast actually lives inside wasp intestines and this relationship is a true symbiosis, as yeast can help the digestion of sugars and other nutrients. In return, the yeast benefits from the nutrient rich environment of the wasp nest.

What is also fascinating is that yeasts in general prefer wasps to bees, as wasps have less specific eating habits: while bees are mostly consuming nectar from flowers, wasps have a more varied diet that includes ripe sugary fruits also favored by wild yeasts. 

And despite bees being more accepted by humans, the much less pleasant wasps play a more significant role in keeping yeast alive during the winter.

Scientists do a variety of strange things, so when I found that a group of scientists were examining wasp guts for new kinds of yeast, It didn’t surprise me at all. Reportedly they found and extracted a new yeast variety which was used to brew a new beer with an amazing taste. 

They also found yeasts that made a very bad beer. The experiment was not limited to wasps, though. The same group of scientists found new yeasts inside hornet intestines, and managed to add it to sourdough starter and bake bread with it.

I don’t think that these experiments will end the world dominance of Saccharomyces cerevisiae, but they might add some new taste profiles to well known products, and I think that is very exciting.

This episode was recorded in the beautiful downtown of Bratislava Slovakia.

You can find the text version on my website mykolanevrev.com 

Many thanks to Mandy Jones and Pilota Creative for producing this podcast.

I’m looking forward to sharing another story in two weeks. Until then, please don’t kill any wasps to extract wild yeast from their guts.

Sources
https://www.youtube.com/watch?v=XqWIHDPmmQ4
https://www.npr.org/sections/thesalt/2018/11/12/665655220/sourdough-hands-how-bakers-and-bread-are-a-microbial-match
https://www.nature.com/articles/s41598-023-43541-9
https://www.science.org/content/article/brewer-s-yeasts-mate-inside-guts-hibernating-wasps
https://pubmed.ncbi.nlm.nih.gov/27168222/