Coffee starts its life as the seed of a cherry. You wouldn't think that when you look at a bag of beans, but there's a whole process that coffee goes through before it gets to you. It's picked, it's washed, it's milled, it's shipped, it travels across the globe—and that's all before it's roasted, packaged, and brewed by your favorite barista. Somewhere in the middle of all that, coffee hangs out with a bunch of yeast.

Lucia Solis is a coffee fermentation expert—probably not a job you dreamed about in school or even knew existed, but her job can make a coffee go from just OK to excellent. She started her career studying viticulture at the University of California, Davis, and was a winemaker before jumping into the world of coffee. She was able to use her training to explore a big gap in the coffee industry.

Solis is interested in "processing," which refers to how the layers around a coffee seed are removed, and how the sugars and starches surrounding the bean interact with yeasts and other bacteria. She visits coffee farms around the world and helps producers control consistency and cup quality through understanding what's happening on the micro level—and investigating how yeasts can transform the flavor of coffee.

It's a scary topic, thinking about yeasts in your coffee, but there are a lot of similarities between the role of yeasts in both beer and coffee. Solis was one of my main sources in an article I wrote for our Uppers and Downers series on lactic acid fermentation, a series that explores big topics relevant to both the beer and coffee industries, and her insights helped elucidate just how important microbiology is to the future of coffee.

Solis is continuing to expand her scope, and recently gave a talk called "Worms and Germs," which discussed how soil health can improve fermentation. We sat down to chat after one of these talks, and in our conversation, we dive deep into chemistry, the fundamentals of coffee farming, and how we're constantly interacting with the microscopic world around us.

This is Lucia Solis, coffee fermentation expert. Listen in.