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TERRY GROSS, HOST:
This is FRESH AIR. I'm Terry Gross. If you heard our interview last week about how fermentation changes milk to yogurt and cabbage to sauerkraut, you may have felt cheated that we didn't talk about how the process of fermentation creates wine, beer, cheese and salami, which is why we now present part two of that interview.
Sandor Katz is the author of "The Art of Fermentation," and has taught hundreds of fermentation workshops around the country. His book explains how and why bacteria transform beverages in the fermentation process, and why some of these foods have probiotic qualities that are good for the digestive track. He also offers advice about how to make fermented foods. Katz grew up in New York and now lives in Tennessee, where he ferments many vegetables from his garden.
Let's talk about wine, which is fermented fruit. Why are grapes such a natural for fermentation?
SANDOR KATZ: Well, grapes have a really great balance of sugars and acids and tannins, so that they are a, you know, particularly good nourishment for yeast. I mean making wine from grapes is incredibly easy. It's easy to get the juice out of grapes. I mean "I Love Lucy," I think, you know, sort of showed us all how to make wine. I mean if you stomp on grapes it releases the juices.
And, you know, when I was on a farm in Italy a couple of years ago at the grape harvest, well, we weren't stomping with our feet but they had this very clever little set of rollers that crushed the grapes a little bit. And so we picked the grapes and crushed them into grape juice with the grapes and stems floating in it, then we went to eat lunch and by the time we came back from eating lunch, the crushed grape juice was bubbling vigorously. The fermentation had begun immediately. So grapes are really easy to ferment. But any fruit can be fermented.
And like where I live in Tennessee, we have this great tradition called Country Wines. And so actually, yesterday I was driving on the road and saw a plum tree dropping plums all over the road. And I stopped my car and I picked a big bag of plums, and then when I got home, we mixed up some sugar water and poured sugar water over the plums - we'll have plum wine shortly. So you really can make wine out of any kind of a fruit or even you can make flower-flavored wines or vegetable-flavored wines or herb-flavored wines. You know, the idea of, you know, fermenting a sugary liquid into alcohol, you know, can be applied with, you know, all sorts ingredients beyond the most famous ones, like grapes.
GROSS: So what is it that turns the juice into alcohol? Is it the yeast?
KATZ: Yes. Yes. I mean, you know, yeast consumes sugar and transform it into alcohol and carbon dioxide.
GROSS: OK. And is there a certain kind of yeast that you use to make wine?
KATZ: Well, you know, all fruits are covered with yeast. Yeast is really everywhere, so certainly...
GROSS: Oh, so you're not adding yeast. It just has the yeast in it - for the grapes, anyways.
KATZ: Yes. Yes. Yes. Really, I mean all sweet foods have yeast. Yeast are just everywhere and they find their way to all the sweet things. The skins of grapes and plums and blueberries and other really dark-colored fruits, you can actually see a little white film and that white film includes lots of different types of microorganisms, including yeast.
Usually when people talk about yeast in relation to the fermentation of fruit into wine, they're talking about saccharomyces cerevisiae, that's the most famous yeast. If you go to buy a packet of yeast, that's what you're buying. And so that's the yeast that, you know, people have been cultivating for thousands of years. But, you know, all sweet fruits have yeast on them. All honey incorporates yeast. Yeast is very easy to, you know, find on any of the, you know, foods that you might be fermenting, and it's just a matter of, you know, kind of working with it to develop the yeast that's there. So what I'm doing with these, you know, plums sitting in sugar water is stirring it frequently, and this basically distributes yeast activity and the stirring introduces oxygen which can really stimulate the yeast growth and proliferation.
GROSS: Once you've made wine you have to, you know, bottle it and make sure there's no air in it. That, you know, that the wine is exposed to the air because if it's exposed to the air for a period of time it's going to turn to vinegar.
KATZ: Well, yeah. I mean you really have a number of options. I mean one way you can do it is enjoy it fresh. You know, ferment it for two weeks and you already have, you know, more than half of the potential alcohol has been produced and you can just have a party and enjoy your wine without ever bottling it or aging it. That would be a green or young wine, partially developed and, you know, in a lot of the ancient indigenous traditions of making alcohol, people had no means for fermenting it to dryness so people drank, you know, fresher, more lightly fermented beverages.
But, yes, you're correct. If you want to ferment it for dryness, you know, meaning to the point where all of the sugars are converted into alcohol, then once your bubbling peaks and begins to slow down, then you need to transfer it to a bottle - a different type of vessel where it won't be exposed to oxygen. So typically, we move it into a vessel that's called a carboy, which is a narrow-neck vessel that looks like what's on a water cooler, and then you put this device in it that's called an airlock that enables carbon dioxide that's being produced to escape but doesn't allow air with oxygen from outside the vessel, you know, in to allow for vinegar formation. Then once the bubbling stops, typically people will siphon it into a second vessel, which can restart stuck fermentation and get the last of the sugars to be fermented. And only then after it stops again would you bottle it and cork it for long-term storage. And, you know, as we all know, you know, storing wine can really allow the flavors to mature and become, you know, much more refined and wonderful.
GROSS: OK. If you're just joining us, my guest is Sandor Katz. He's the author of the new book "The Art of Fermentation." Let's take a short break here, then we'll talk some more.
This is FRESH AIR.
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GROSS: If you're just joining us, my guest is Sandor Katz. He's the author of the new book "The Art of Fermentation." Fermentation is his thing. It's what he writes about. It's what he spends a lot of his time doing is making fermented foods and teaching people how to do it.
We've talked a little bit about making wine. Now beer is made out of grain, not fruit. So what's the difference in how you would ferment grain to make an alcoholic beverage?
KATZ: Grain-based alcoholic beverages, they're much more technically demanding than fruit-based or honey-based alcoholic beverages, because fruit and honey will really spontaneously ferment into alcohol, whereas grains, which are complex carbohydrates, long chains of carbohydrates rather than simple carbohydrates, need to be predigested. They need to have those complex carbohydrates broken down into simple carbohydrates.
In the Western tradition of beer making, we do this through malting, which is germination or sprouting and that sets in motion enzymatic changes that breaks down the starches into sugars. In the Asian tradition molds are used, which accomplish the same kind of enzymatic breakdown. And really, the most ancient method of doing this is chewing, using our human saliva and the enzymes that are in our saliva to break down starches into sugars, and then you brew the beer from the grains that have already been malted or otherwise enzymatically broken down into starches.
Beer is wonderful and, you know, there's a thriving movement of home brewers all around the United States of people making beers themselves. Just last night, I had some Nepalese-style millet beer. That's a warm beer. You know, beers are made out of every kind of grain in every part of the world and, you know, in my limited explorations, they are all delicious.
GROSS: So you said that sometimes with beer you can chew the grain?
GROSS: Like chew the barley to like mash it up? Like has anybody really made beer that way, where there is a lot of people like chewing the grain and spitting it out? Like that doesn't sound really appetizing.
KATZ: Well, I mean this is a traditional method in the Andes Mountains of South America for making a corn beer called chicha. There are also examples of, you know, beers that have been made in other parts of the world using this process. It's generally regarded as the most ancient form of enzymatic transformation of starches and grains and tubers into sugars that are fermentable into alcohol. So I don't think that there are a lot of people doing it these days. I've done a number of, you know, experiments, you know, in my own practice and, you know, gotten people to sit around and, you know, chew corn or in my most recent experiment, chew potatoes with me, you know, to produce an alcoholic beverage out of them. And it's fun and some people get really, really freaked out at the suggestion of it.
GROSS: I could see why.
KATZ: Well, then you cook - I mean...
GROSS: But it's...
KATZ: ...then you brew it after that.
GROSS: Oh, oh, oh, you cook it after that?
KATZ: Yeah. Then you brew it after that. You cook it for a really long time so, you know, I mean I understand how, you know, conceptually that it's difficult for people but, you know, really, you know, anything that would be alive in the saliva that chewed it gets, you know, gets destroyed during the cooking. So I don't think it's, you know, any kind of, you know, danger.
GROSS: I feel better already. OK. Very good.
KATZ: And chicha is really delicious.
GROSS: Mm-hmm. OK.
GROSS: Let's talk about cheese, which is also a fermented food. What's the difference between making cheese and making yogurt?
KATZ: Well, with yogurt you're typically not removing any liquid. You're just, you know, it's kind of this magical process where you're transforming the liquid into a solid. With cheeses, typically you're removing some of the liquid. You know, most often this is done with a group of enzymes that we call rennet, and the rennet curdles the milk. The milk solids and fats all come together and then there is a byproduct, which is this thin, yellow, liquid that's still really quite nutritious called the whey. But part of what preserves cheese is the removal of liquid from the milk so it becomes more solid. I mean we could really think of, you know, a chunk of cheddar or Parmesan cheese as, you know, a form of preserved milk. I mean think how stable that is, you know, the cheese compared to the milk. And one reason for this is the removal of liquid. Another reason for this is the acidification. So just as with sauerkraut, the acidification makes it impossible for bacteria that we would regard as pathogenic or threatening to us to develop, because they can't tolerate an acidic environment.
GROSS: So how does fermentation apply to meat?
KATZ: Well, I mean meat is certainly the most perishable of all the foods that people eat - meat and fish. And so, you know, it has really been, you know, imperative for people to, you know, figure out ways of preserving meat. And people use a range of techniques to preserve meat without refrigeration, including drying, salting and smoking. And, you know, sometimes it's been a little bit elusive, you know, which cured and preserved meat products are products of fermentation. But in most of them there's at least some incidental fermentation that enhances the flavor of the meat, but I think that the clearest example of a fermented meat process would be salami. So basically salami is ground meat that is mixed with salt and curing salts and spices and a little bit of sugar. And what the little bit of sugar does is it supports a lactic-acid fermentation. The nutrient for lactic-acid bacteria that meat lacks is carbohydrate. So by adding some carbohydrate, you promote lactic-acid development, and so the lactic acid becomes part of what enables that salami to just hang on a string in a delicatessen for months and months.
GROSS: So how did you become, as you describe it, a fermentation fetishist?
KATZ: Well, the development of my interest in fermentation has a few stages. When I was in my 20s I did quite a bit of dietary experimentation, and for a while I was following a macrobiotic diet, and that was when I first became aware that there was some association with eating these, you know, live fermented foods and digestion. And I started noticing that whenever I would eat sauerkraut or pickles that the flavor of the lactic acid, even the smell of it would make my salivary glands start secreting. And so I just started really feeling how these foods got my digestive juices flowing. But it wasn't until I moved from New York City to a community in rural Tennessee and got involved in keeping a garden that I ever actually tried fermenting anything myself. And what motivated me was, you know, the practical desire to make use of the bounty of the garden, you know. It came as a little bit of a surprise to me that all the cabbages are ready at the same time and all of the radishes are ready at the same time. So this is really a practical dilemma that, you know, gardeners and people who grow food have always faced.
And, you know, this is really - has been the incentive for people to, you know, develop fermentation methods. I mean, really, agriculture makes no sense without fermentation and, you know, that's what got me to look in "The Joy of Cooking" and learn how to make sauerkraut for the first time.
GROSS: You're very public about this so I feel comfortable asking. But I know you've had HIV for many years and, you know, you're on one of the drug regimens which has really helped you a lot. Does your - does having HIV connect at all with the kind of emphasis on fermented foods that you've had?
KATZ: Well, living with HIV has just forced think a lot about, you know, what I can do in my life to, you know, help keep myself healthy. You know, think of it as, you know, rituals of self-care and, you know, these have to go beyond, you know, popping pills. It's, you know, thinking about good nutrition. It's thinking about, you know, things that reduce stress and, you know, just, you know, observing how fermented foods improve my digestion.
And, you know, learning about how, you know, probiotic bacteria really stimulate immune function, you know, and, you know, generally feeling good day to day has really, you know, confirmed the idea that these foods are part of a strategy for keeping healthy. I mean, I am very suspicious of, you know, miracle cures, panaceas, you know, promises of specific benefit from specific foods.
But, you know, as a group, you know, these foods really can help people digest their food better, get more nutrients out of their food and have, you know, better overall immune functioning. And these are great benefits, you know, regardless of whether they cure any particular disease.
GROSS: So what did you have for breakfast today?
KATZ: I had eggs and toast.
GROSS: OK. Very plain.
KATZ: Well, OK. But I mean, I would just point out that, you know - and I had coffee. I mean, most people eat fermented foods every day. I mean, not all fermented foods...
GROSS: Wait, wait. What's fermented in that list there?
KATZ: All bread is fermented and coffee is fermented.
GROSS: Oh, see, I don't think of them as fermented foods. I'm not thinking correctly.
KATZ: Well, you know, it's like, you know, you need to, you know, in typical contemporary breadmaking, you know, you add your yeast and the yeast activity is what rises the bread, the carbon dioxide that's produced by the fermentation. In traditional breadmaking, you use natural leavens, which are mixed communities of yeast and lactic acid bacteria that are really found on all grains.
And so it's a slightly slower process, but actually improves the bread's nutritional profile, introduces more complex flavors and makes the bread storable for a much longer period of time. But either way, the bread is definitely fermented because the microbial activity is, you know, sort of key to the bread not being a dense brick.
GROSS: And now you're going to tell me coffee is fermented?
KATZ: Yeah. Coffee is. Coffee, as well as chocolate, are fermented on the harvesting end so we really never see it. But, you know, with coffee, it's just the freshly picked beans are moistened and, you know, held together, you know, in some sort of a box or vessel and they are fermented for a few days before they are dried and roasted.
GROSS: All right. Well, Sandor Katz, thank you for telling me a lot that I didn't know about fermented food. Much appreciated. Thank you so much.
KATZ: Well, thanks for having me. It's an honor to be on your show.
GROSS: Sandor Katz is the author of "The Art of Fermentation." You can read an excerpt on our website, freshair.npr.org.
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