In this episode, you're invited to the fermentation party! Join us as we learn about the funk-filled process behind making sauerkraut, sourdough and sour beer. Plus, no fermentation episode is complete without a lil history of our boy, yeast.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What role does fermentation play in breakfast foods?
You're listening to Shortwave from NPR. Hey, Shortwavers, it's Regina Barber. And we're starting today's episode with breakfast. Because regardless of what you had for breakfast today, chances are at least part of it was made by fermentation. Yogurt and granola, fermentation. Eggs with cheese, fermentation. Bread, fermentation. It's even key in coffee.
When a coffee bean is harvested, you know, in the jungles of Costa Rica or Colombia or wherever it might be, those berries, which look like little tiny cherries or almost like crab apples, they get hauled into baskets or trucks and then like thrown onto the ground. And there's either like dry or wet fermentations.
But in both cases, just whatever endemic microbes are in the jungle, on the fruit, start to acidify and metabolize all of the fruit flesh. And all those metabolites, all the acids that are produced, all the organic molecules seep into the actual coffee bean itself and change its flavor.
This is David Zilber, chef, reality TV show host, and former director of the Fermentation Lab at the world-famous Danish restaurant Noma. And he told me, if fermentation wasn't part of my coffee, it wouldn't even be good.
If you took a fresh coffee bean and completely stripped it of the fruit and dried it immediately and went through the same roasting process, you would end up with the most like... flat, cardboardy, acrid coffee compared to what happens post-fermentation. So fermentation is an incredibly important step in coffee production.
To make it taste delicious.
Yeah. Complex.
Okay, I'm convinced. Fermentation is important. But what exactly is it?
Fermentation is the transformation of one food into another with the help of microbes.
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Chapter 2: How does fermentation affect coffee flavor?
And it's your job to suppress those microbes immediately by using things like oxygen or an absence of oxygen, more specifically, or salt to make sure that they are tamped down and you give center stage to those lactic acid bacteria.
Right, right. And so what do they do, like those lactic acid bacteria?
They will start to... release enzymes into their environment that will break up the carbohydrates in the plant cells themselves and allow them to digest these sugars. Carbohydrates and starch and lots of plant fibers are just stitched together chains of simple sugar molecules like glucose. And so...
In the great tree of life, lots of organisms have devised enzymes that snip those daisy chains into their constituent molecules.
Then they can grab an easily handable portion of chemical energy in the form of sugar, eat it, and through the process of fermentation, which going back to the textbook microbiology definition, is the metabolism in the absence of oxygen of a sugar molecule into either ethanol or lactic acid.
Okay, so just to review, the microbes take the sugar, like from the carbs and starches and whatever food they're given, and they start to break it down. They start to eat it, right? And that process of microbes eating sugars and turning it into energy, that's fermentation.
Yeah. And then when it harvests the chemical energy, energy for its own purposes, what's left over is lact gas.
Okay. That's the byproduct.
That's the byproduct. That's like microbial poop, basically.
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