'Fermentation': When Food Goes Bad But Stays Good

iStockphoto.com Yogurt is produced by the bacterial fermentation of milk. "Bacteria in our gut enable us to live," says author Sandor Katz. "We could not survive without bacteria."

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June 13, 2012

The list of fermented food in our lives is staggering: bread, coffee, pickles, beer, cheese, yogurt and soy sauce are all transformed at some point during their production process by microscopic organisms that extend their usefulness and enhance their flavors.
The process of fermenting our food isn't a new one: Evidence indicates that early civilizations were making wine and beer between 7,000 and 8,000 years ago — and bread even before that.
But was exactly is fermentation? And how does it work? Those were the questions that fascinated Sandor Katz for years. Katz calls himself a "fermentation revivalist" and has spent the past decade teaching workshops around the country on the ancient practice of fermenting food.
Katz collects many of his recipes and techniques in a new book, The Art of Fermentation, in which he describes fermentation as "the flavorful space between fresh and rotten."
"If you walk into a gourmet food store and start thinking about the nature of the foods that we elevate on the gourmet pedestal, almost all of them are the products of fermentation," he tells Fresh Air's Terry Gross. "Fermentation creates strong flavors. But they're not always flavors that everybody can agree on."

The Art of Fermentation

An In-Depth Exploration of Essential Concepts and Processes from Around the World

by Sandor Ellix Katz

Hardcover, 498 pages |

Take cheese, for instance. Cheese exists in a variety of flavors, including the extra-stinky varieties Katz says he fancies. "But once in a while I'll buy cheese and I've learned that some friends will smell the cheese and walk out of the room," he says. "They'll never think about putting that in their mouths. ... So around the world, you find these iconic foods created by fermentation that create strong, strong flavors that become strong markers of cultural identity and in many cases, people who have not been raised within the culture find these foods very challenging."
In addition to enhancing flavors, fermentation also allows food items to be preserved well past their shelf-life date, says Katz.
"It's not forever like canned foods that you can put into a pantry or storm cellar and forget about for 10 years and still eat it," he says. "These foods are alive, they're dynamic, but they're extremely effective strategies for preserving food through a few seasons, which is really the point."
Starting With Sauerkraut
For fermentation newbies, Katz recommends starting with sauerkraut because it's particularly easy to make. To begin, take a cabbage and any additional vegetables you want and chop it up. Put your chopped veggies in a large bowl and lightly salt them. (Katz notes that he never measures the salt because there's really no "magic number for how much salt to use.")
After salting the veggies, which helps get rid of excess water, Katz squeezes them for a few minutes to release their juices, so that they can be submerged under their own liquid. (Katz says he hardly ever adds water to his kraut, because the flavor is more concentrated if you use only the vegetable juice.) He then stuffs the veggies and the juices they've released into a jar.

Enlarge Courtesy of the author Sandor Katz is the author of Wild Fermentation and lectures extensively on topics related to fermentation.

"You want to press really hard to force out any air bubbles," he notes. "And you want to make sure that the vegetables are pressed down under their juices. And then just seal the jar — but be aware that pressure will be produced, so you don't want to leave it for days and days."
Katz recommends checking the jar on a daily basis to release the pressure — and then after maybe 3-5 days, enjoying your new creation.
"The flavors transform very quickly," he says. "The bacteria proliferate, the texture changes, and what I recommend to people experimenting for the first time, is just to taste it at periodic intervals. And then you're getting a sense of whether you're liking it more and more as the flavor gets more acidic or whether it's acidic enough and you want to move it into your fermentation-slowing device, which is your refrigerator."
Once you've mastered the simple kraut, Katz says you can add spices and/or other items like apples or cranberries to your jar. "You can basically use any season you like," he says.