Exploring spontaneous ferments in the UK

Liana’s interest in spontaneous fermentation takes her across Ireland and southeast England to meet her microbiology hero and explore a variety of cheeses, sourdoughs, fermented wild garlic and more. 

I arrived in Ireland on April 6 and spent the first two weeks traveling and arranging lab placements. I also met with two lab PIs working on fermentation research. I was keen to sit with them, get their advice on my project, and figure out how my work could complement theirs. I also wanted to find out which fermented products I should sample from Ireland that hadn’t already been studied.

I first met with Professor Jens Walter at the Food Science Department at University College Cork. His research lab focuses on evolutionary biology and how communities develop over time. I was particularly interested in discovering more about their study, looking into the origins of Lactobacillus in sourdough. Their research has shown that it came from the mouse gut microbes, potentially fecal matter from mice. This is how I predict some of my spontaneous fermentations are happening, so it’ll be interesting to see if this is the case. For example, I expect to see many skin microbes making their way into home ferments where producers aren’t wearing gloves in preparation.

In the following days, I met with Professor Paul Cotter at the Teagasc research institute. The institute is located on an idyllic farm, and on the way there, you drive through all these tiny quaint towns on the outskirts of Cork. While I was there, we discussed how to perform metagenomic sequencing on fermented foods, and one of the PhD students, John Leech, gave me samples of his home-fermented okra, chilies, kombucha and kefir. They also told me about this fantastic project they’re working on called Kefir for All, where they send kefir samples to students across Europe and ask them to send back samples of their home-brewed kefir. It reminded me of a class I co-taught during my undergraduate studies, which involved sending my kombucha starter to students across the US. They would brew kombucha and send back samples for analysis. I like the idea that a lot of the diversity in fermented foods is happening in homes. It’s fascinating to see the interaction between fermentation and citizen science.

When I started this project, I envisioned coming across many starters passed down for generations and finding unique microbes from old starters, because that was exciting to me. I was also hoping to make a case for why industrial starters potentially lose much of the diversity that fermentation has taken thousands of years to develop. However, throughout this project, it’s become more apparent to me that, especially in Europe, there’s a lot less spontaneous or non-starter-based fermentation happening, with many companies using industrial starters for safety and consistency.

During my last week in Ireland, I visited Limerick, where I sampled some local raw milk cheeses, including the most famous of the region, Cais Dubh. I also went to the Milk Market, one of the largest farmer’s markets in the area, where I was fortunate enough to meet the owner, Mimi, of Crawford's farm, a small-scale micro-dairy. She explained how they use raw cow milk to make kefir and cultured butter.

I met with Edward, who ferments foraged vegetables from around Ireland. He adds a small amount of salt to the vegetables and leaves them to spontaneously ferment in jars for over two years. I’m looking forward to analyzing these samples as I expect to see a lot of diverse soil microbes from all the different locations.

While in Limerick, I visited a charcuterie specialist. The owner, Oliver, had a deep interest in the yeast on the salami because although he could predict the taste of the salami by looking at the white powder on the surface, he didn’t know what microbes were causing the difference. A big theme among producers I meet with is they have a gut sense of how different fermentation conditions affect the taste, texture, and outcome of the product, and many are interested in knowing the microbes that are driving these changes.

Before leaving Ireland for London, I visited a farm in Ennistimon, where I met the producers and collected samples of raw goat milk cheeses at different stages of the fermentation process. 

I was only in London for 10 days, so time was tight! The day after I arrived, I headed straight to Neal's Yard Dairy in Bermondsey to meet Bronwen Percival, a cheese buyer and co-founder of the website microbialfoods.org. Her site helped kickstart my interest in fermentation, so I was excited to meet her in person. I only had one day at the dairy, so I mainly focused on sampling raw milk cheeses where we could get multiple time points during maturation. We also took samples from the core and rind as Bronwen was interested to see how they differ. One cheese, in particular, had a rind with so many different morphologies, so I tried to sample as many different sections to see if I could capture the diversity.

There was also an ingot that had been maturing over the past year, so it had some really wild molds growing on it. I’m excited to see what's on there.

In the following days, I went to Cambridge to visit Professor Kiran Patil’s lab, which had recently published an exciting paper on water kefir. I visited Fen Farm Dairy in Bungay, where they make raw cow milk cheeses. It was great to follow the cheese-making process and see how scientific it can be – from measuring pH over time to calculating the precise amount of salt to add to the outside of the cheese.

On my last day in London, I went to the Fermentary, where they produce different varieties of kraut and water kefir. During my visit, the lead fermentation expert scooped a bit of the water kefir and placed it on a microscope slide for us to take a look. In fact, the fermenters were using a host of lab equipment – pH meters and spectrophotometers. They were also hoping to do some metabolite screenings of the ferments soon. It was one of the most exciting cases of blending science with traditional fermentation methods that I had seen.

Seeing kefir bacterial cells floating around the microscope slide reminded me of my first time really appreciating the vastness of biology. In my freshman bioengineering lab course at university, we looked at the contents of the termite gut under the microscope. Even though magnification is 100X, we could only resolve the outlines of the bacteria and could only imagine the thousands of cell processes that were happening inside.