Cheese: Chemistry Rolled Into Every Wheel

Can science explain what makes Stilton stinky and goat cheese gooey? Liz Thorpe, vice president of Murray's Cheese in New York and author of the book The Cheese Chronicles, talks about the science and business of making cheese in America. Originally broadcast Aug. 14, 2009.

Copyright © 2009 NPR. For personal, noncommercial use only. See Terms of Use. For other uses, prior permission required.

IRA FLATOW, host:

This is SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

If you're still hungry after yesterday's meal, we have one more recipe for you. Here's what to do this evening as - before we eat dinner maybe. Take some milk, add some bacteria - that's to spoil the milk - then inject some mold into the brew. Don't forget to add rennet. That comes from the stomach lining of livestock. I'm sure you have some of that lying around. Then heat the mixture so it's warm, drain out some of the liquid and let us sit around for a few months. Hungry yet? You might try getting a little bit of salt to that mixture.

It might sound better if I call it by another name, and that would be� Yes; cheese. That's how it's made; by turning that concoction into something safe, let alone tasty, requires a lot of science. And that's what we're going to be talking about for the rest of the hour. Cheese is one of my vices, oh, I'm sitting here looking at all this cheese - no crackers.

(Soundbite of laughter)

I wish I had a green apple, a Granny Smith. My next guest is a cheese expert. She's Liz Thorpe, vice president of Murray's Cheese here in New York. If you know what Murray's Cheese is, it's New York's - like Zabar's other places, very famous in town here. She's author of a new book called �The Cheese Chronicles.�

Welcome to the program.

Ms. LIZ THORPE (Vice President, Murray's Cheese; Author, �The Cheese Chronicles�): Thanks so much.

FLATOW: What cheese have you got on the plate here?

Ms. THORPE: Oh, I actually - I've brought five cheeses. No, six cheeses. And I actually - I did not bring a good representative cheese plate. We have primarily cow's milk cheeses today because I thought it would be good to taste and talk through how cheese making, bacteria, molds and cultures can turn out five, six so different cheeses.

FLATOW: Do all the cheeses have the basic, same recipe today?

Ms. THORPE: I mean all cheese has the basic same recipe, so it's really just tweaks on a few simple steps and you wind up with completely different things.

FLATOW: Mm-hmm. And so you have the bacteria, the mold, the stomach lining and�

Ms. THORPE: Rennet, rennet.

FLATOW: The rennet.

(Soundbite of laughter)

Ms. THORPE: Yeah. And I have to say, it's a coagulant. It's what's used to make the proteins and milk basically form of web or a matrix. And animal rennet does come from the stomach lining of an unweaned ruminant. But you can also have rennet that's microbial - mold or yeast derived.

FLATOW: Microbial. So what does the - what's going on in the chemistry as you start the process? You take some milk and then you add?

Ms. THORPE: The first thing you want to do is acidify milk. So, you were�

FLATOW: Why?

Ms. THORPE: Because you're going to try to turn a liquid into a solid.

FLATOW: Ah.

Ms. THORPE: So, you want to add bacteria; and this is variation number one. There are several hundred thousand strains of starter bacteria that you can put in your milk. And what they're going to do is they're going to convert lactose into lactic acid. They're going to take the sugar�

FLATOW: (Unintelligible) cheese, while you're at it.

Ms. THORPE: Yeah. That's good. We'll start on the first one. They're going to eat the sugar. They're going to convert it into lactic acid, and you're going to get an increasingly thickening mass that sort of starts to look like yogurt. TEXT: FLATOW: And next step?

Ms. THORPE: And the next step, you're going to want to seal the deal. You're going to really want to coagulate your milk, and by doing that, by adding rennet or microbial rennet, you get the proteins to knit together. They form a web that traps water and it traps fat. And your yogurty-puddingy stuff becomes like well-set Jell-o, if you will. And from there, it's all about how much water you want to keep and how much water you want to get rid of.

FLATOW: let me just remind everybody that this is SCIENCE FRIDAY from NPR News. I'm Ira Flatow, talking with Liz Thorpe, author of �The Cheese Chronicles: A Journey Through the Making and Selling of Cheese in America, From Field to Farm to Table.� Everything you wanted to know about cheese is�

Ms. THORPE: Hopefully. Cheese in America, so it's�

FLATOW: Cheese in America.

Ms. THORPE: The focus of the book.

FLATOW: Well, let's talk about - well, cheese didn't start in America, did it?

Ms. THORPE: No, definitely not. And yeah, not at all. But we actually - we have real cheese in America, folks. And it's not Velveeta. And it's not made out of vegetable oil. It's actually made by all kinds of farmers and crafts people and small cooperatives and factories that are, you know, owned and run by family dairy farmers. And they're making really good cheese.

And so, the book is about my career in cheese and my travels, and some of my 90 favorite American cheese makers.

FLATOW: Ninety.

Ms. THORPE: Yeah. I think there's 88 maybe, but.

FLATOW: I think that was - 88. Wow, let's not argue - quibble about two.

(Soundbite of laughter)

What are some of the variables? How come we see some cheeses have that purple inside? How do you get that into the cheese?

Ms. THORPE: Meaning, like a blue mold?

FLATOW: Blue mold.

Ms. THORPE: Yeah, sure. I used to think you made a cheese and you shot it up like, you know, injected it with mold.

FLATOW: Right.

Ms. THORPE: Doesn't work that way.

FLATOW: Doesn't?

Ms. THORPE: No. Actually mold is - can be really important if you think about Brie, probably the best-known cheese out there, that white, soft rind. That's also mold. It gets added to the milk during cheese making. In the case of blue cheeses, mold is added to the milk, it's powdered. And its oxygen loving, it won't grow without oxygen. So in the case of blue cheese, you make it and you have a very blue wheel and nothing else. It's not until you're pierce holes in it that you get that veining inside.

FLATOW: Oh, is that right? You can decide where the veining happens?

Ms. THORPE: Absolutely. Most cheese makers don't actually pierce for at least a week. Some wait as long as three or four. And they scrape the blue off the outside but they let it grow in the inside.

FLATOW: Can you make little designs if you know how to poke it?

Ms. THORPE: If you're really good, you (unintelligible) Ira was here.

(Soundbite of laughter)

FLATOW: Well, what about - there are different kinds of molds, as to the Gruyere and there's other colored cheeses, right?

Ms. THORPE: Yeah. Mold is pretty critical for soft ripened cheese. That's what it's called. In here, let's taste. The first two are�

FLATOW: Which one?

Ms. THORPE: The first two are�

FLATOW: That one? That one?

Ms. THORPE: Either one.

FLATOW: I'll take this one.

Ms. THORPE: What you're looking for out there when you're shopping for cheese is a white, soft skin on the outside.

FLATOW: Talk amongst yourselves while I'm eating.

Ms. THORPE: That's - you're having Sweet Grass Dairy Green Hill. That's from Thomasville, Georgia. And�

FLATOW: It tastes different? Is it the grass?

Ms. THORPE: Well, actually, yes. Sweet grass is a pastured operation. They do a rotational grazing.

FLATOW: Wow.

Ms. THORPE: So it's a great opportunity to taste a really floral, grassy profile. But that white, soft mold breaks down fats and proteins and you get an increasingly kind of runny thick buttery texture and often a little bit of mushroomy flavor.

FLATOW: Wow.

Ms. THORPE: So, all that work is happening from the outside in.

FLATOW: Wow. Apologies to Faith Middleton and (unintelligible) this is delicious stuff.

(Soundbite of laughter)

How do you stay so thin eating all the cheese here?

(Soundbite of laughter)

Ms. THORPE: Oh, yeah, I mean, my - someone asked me that last night at the book signing. And the answer was: I'm wearing Spanx.

(Soundbite of laughter)

But I'm not right now. I stay relatively thin because real cheese is real food and it's not processed. And my body knows what to do with it. So�

FLATOW: When you said real cheese, you're making a distinction between these pasteurized products over, this whole�

Ms. THORPE: No, no. Pasteurized, I mean�

FLATOW: �these cheese food things

Ms. THORPE: Well, yeah. Definitely, cheese food. Pasteurized isn't a bad thing. Pasteurized simply means the milk has been heat-treated prior to cheese making. And, in fact, in this country, if you're going to have a cheese that's less than 60 days, it has to be pasteurized. So, that's not necessarily a bad thing. It's - the difference between having something that's made of milk, salt, and rennet, versus vegetable oil, coloring, whey powder, those things are junk and fillers and�

FLATOW: Hmm.

Ms. THORPE: �I mean, I think they - you pack it on on your hips.

FLATOW: There you go. Well, we have to pack a break in here.

I'm talking with Liz Thorpe. She's vice president of Murray's Cheese here in New York. And author of the new book - I'm sorry - for the - �The Cheese Chronicles.�

(Soundbite of laughter)

FLATOW: Now, it's everything you want to know about cheese. We're going to take a break and come back and take your questions: 1-800-989-8255. Maybe you want to do it a Vermont, Wisconsin cheddar battle. You can try that. And we'll talk about - well, we'll talk about why one color is different than the other. Maybe it's made differently. Stay with us and find out. We'll be right back.

(Soundbite of music)

FLATOW: You're listening to SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

We're talking with Liz Thorpe, author of �The Cheese Chronicles: A Journey Through the Making and Selling of Cheese in America, From Field to Farm to Table.�

Let's talk about cheese warfare.

Ms. THORPE: Okay.

FLATOW: Okay. You know, because you mention in your book that there is a big warfare going on about cheddar, let's concentrate on cheddar.

Ms. THORPE: Yeah. Cheddar is the first chapter of the book that's not sort of an introduction and - because to me that's sort of the quintessential American cheese. And I went to visit the Amish to try and learn about the history of cheddar and it was a dismal failure. They've really only been making cheese for about 35 years. And they said, well, we don't know. Thanks for coming.

(Soundbite of laughter)

Ms. THORPE: But I've done a lot of research. I'm actually writing an article on cheddar right now. And so, I brought a block cheddar, which is the cheddar I grew up with, you know, think Cracker Barrel. It's square and it doesn't have any kind of rind on the outside. And then, I brought what's called a clothbound cheddar which is an English - traditional English style. It's made in a wheel, not a block. And it's got cloth, cheesecloth, that's wrapped around the outside and it's aged not in plastic Cryovac packaging, but in a clothbound wheel, aged in a cave, a temperature and humidity-controlled room. So, I don't know -you've already eaten them�

FLATOW: I can't wait. I can't wait.

Ms. THORPE: I was going to have you do a smell comparison.

FLATOW: I did the smell.

Ms. THORPE: Did you?

FLATOW: Yeah, I did.

Ms. THORPE: So I hope what you noticed, what I notice when I smell them side by side, is that the block one smells tart and kind of lemony, almost, and the second one, the clothbound one, smells like macaroni and cheese from a box, which is a smell I really love, and also kind of butterscotch-y, kind of broth-y. And it's interesting because it's the difference between sharp, white, American cheddar or even sharp, yellow, American cheddar, which is the block kind that most of us know, and this clothbound style, which has a totally different texture. It's drier. It's dense and dry.

FLATOW: I can see that.

Ms. THORPE: And it kind of gets messy. It gets lodged in your teeth a little, and it tends not to be sharp but much more complex. And it's got these awesome, butterscotch-y, candied notes to it. So it's my favorite thing to feed people because they think they know cheddar, and then they try a clothbound style -and this is, by the way, Cabot clothbound cheddar made by Cabot, the folks who you find in the supermarket, and aged by the cellars at Jasper Hill Farm, which is the first true aging facility built in the U.S. It's 22,000-square-foot caves for aging cheese.

FLATOW: I'm glad you took a long time to describe that.

Ms. THORPE: You got them both down.

FLATOW: Yeah, that was good. What's the difference between a white cheddar that they sell in Vermont and the yellow cheddar�

Ms. THORPE: That the sell in Wisconsin.

FLATOW: Yes.

Ms. THORPE: So, the coloring of cheddar is a totally regional thing. And the only thing between white cheddar and yellow cheddar is the addition of something called annatto, which is a plant-derived coloring that makes cheese orange. You know, orange �American� cheese, quote-unquote, the slicing deli stuff, that's colored with the same thing, and it has no effect on flavor or texture. It's, as I said, a natural, plant-derived thing.

FLATOW: But you said you could not sell a Vermont cheddar in Wisconsin. What do you mean? They wouldn't touch it.

Ms. THORPE: Yeah, no, they'd think you were crazy. We have some shops that we operate in Cincinnati, Ohio, and when we brought up white cheddar, everyone looked at us like we had 14 heads, so�

FLATOW: What is American cheese?

Ms. THORPE: American cheese is cow's-milk-derived, processed cheese. And it can be sort of - by processed, it goes through - it's sort of extruded. It's pushed through a tube, if you will, to get that kind of, sort of slightly floppy, slippery texture that we all know, and more and more, a lot of it has a lot of the additives I was talking about. You know, it's not just milk anymore.

FLATOW: How do you smoke a cheese? Is there artificial smoke added to it?

Ms. THORPE: Yeah, in that cheese, there is. I think the point for me again is that smoked gouda, okay, we've all had it. I love smoked gouda, it melts really well, but I want my smoked gouda over real smoke. You know, different woods give different intensities. But yeah, you usually smoke a fire in the other room, and you let the cold smoke sort of drift over the wheels of cheese. You don't put it on top of a fire.

FLATOW: And it permeates into the - no, yeah.

Ms. THORPE: Yeah, and it does. It permeates.

FLATOW: Like a smokehouse?

Ms. THORPE: Absolutely, yeah, it's just like meat.

FLATOW: We have to take a quick break, but we'll continue with this cheese chat with Liz Thorpe when we come back.

(Soundbite of music)

FLATOW: This is SCIENCE FRIDAY from NPR News. I'm Ira Flatow. Time for a SCIENCE FRIDAY flashback.

(Soundbite of music)

FLATOW: Thinking you may need a little less souffl� and a little more crudit�s in your diet? Here's Richard Wrangham, author of "Catching Fire: How Cooking Made Us Human," talking about the raw food diet - food for thought this holiday season.

Mr. RICHARD WRANGHAM ("Catching Fire: How Cooking Made Us Human"): Nowadays, we look at people, and we find that if people go onto a diet of raw food, then something peculiar happens, which is that unlike every other animal, they do not thrive in terms of getting really adequate energy. And there is a pretty clear reason for this, which is that our species has a very odd type of digestive system.

It's less than two-thirds of the size of the digestive system if we were a great ape - like a chimpanzee or a gorilla - in relationship to our body size. And so we have somehow, and for some reason, adapted to having a small gut, and we also have small teeth and small mouths, all of which indicates that we, as a species, have adapted to a diet which is very high quality. And we don't have to put large amounts through our gut and retain them and ferment them for many, many hours.

Well, what kind of diet is that? It seems very clear that cooking is responsible for increasing the quality of our diet in this way. So then one can say, well, okay, when did we get these adaptations: the small gut, the small teeth, the small mouth? And the answer is 1.8, 1.9 million years ago with the evolution of Homo erectus.

(Soundbite of music)

FLATOW: If a raw food diet doesn't appeal, what about a cheese diet? Could get expensive, but what if you made it yourself? Liz Thorpe is a cheese expert and author of "The Cheese Chronicles." She is here to chat cheese. Liz, what about people who want to make their own cheese? How do you make sure you're not going to kill yourself with the bacteria you're putting in?

Ms. THORPE: You know, I'm not a cheese maker. I've made cheese several times, and I talk about in the book how miserably I've failed in my attempts.

(Soundbite of laughter)

Ms. THORPE: But I'll tell you that fresher styles are going to be the most perishable. They're the highest moisture and the most likely to have something to go awry but the easiest to tell if there's a problem. You'll get clear sour, rancid smells like an old carton of milk, and if you see that, you want to junk your experiment and start over. But the harder styles that you're talking about, particularly ones where you have to cook the milk, those are going to be the most durable and the least likely to go awry. So you might want to try some of the cooked styles. Cheddar sort of falls into that camp, but think more Grana Padano, Parmesan, Gruyere, the Swiss Alpine styles, and get prepared to wait a while for it to be ready.

FLATOW: A lot of cheese are very stinky. I like - do you have one?

Ms. THORPE: Yeah, I brought one.

FLATOW: What have you got there?

Ms. THORPE: Number three here on the plate - and actually, you can always tell what we'll call a stinky cheese, colloquially. They'll be orange on the outside.

FLATOW: Oh really?

Ms. THORPE: Orange on the outside, you're looking at what's technically called a washed-rind cheese. And these guys are salt, brine-washed, salt-water-washed to develop a certain bacteria, brevibacterium linens and B-linens are - make the cheese orange, sticky, stinky, and they are some of the same bacteria found in human perspiration.

FLATOW: That's what I was going to say�

Ms. THORPE: Which is why they smell sort of like damp feet and other bodily things. Sounds gross, tastes amazing.

FLATOW: Why does Swiss cheese have those big holes?

Ms. THORPE: Oh, I love that. I talked about this with Time magazine, and it sort of was summarized in a funny way. So I'd love to clarify. Swiss cheese�

FLATOW: That's what we're here for.

Ms. THORPE: I appreciate it because I really was like oh, no. Swiss cheese has big holes in it thanks to these little guys called propionic bacteria. And this is an example of bacteria living on in cheese, when I talked about it being a living thing. A lot of those hard cheese are being broken down from the inside by various kinds of bacteria that are added during cheese-making. And propionic bacteria like warm temperatures, and as they multiply, and they continue to convert sugar into acid, they make gas. And the gas is actually what creates those big holes in Swiss cheese. And thanks to the cheese-making style, the paste of the cheese is a little more bendable and elastic. So you get holes instead of big cracks.

You can probably go to YouTube and find some hysterical videos of Swiss cheese wheels blowing off the shelves, and these are sort of - it's sort of out-of-control fermentation going on.

FLATOW: Oh, is that right? So they're not�

Ms. THORPE: But they literally will - if the paste is not elastic, and the paste can't bend around the gas, they kind of, like, blow up, and they'll fall off the shelves, which is dangerous because they all weigh about 140 pounds.

FLATOW: Yeah, I hate it when they fall on you. We're talking about cheese this hour on SCIENCE FRIDAY from NPR News. I'm sampling the cheese. I hope you're not eating your cheese heart out there. Talking with Liz Thorpe, author of "The Cheese Chronicles: A Journey Through the Making and Selling of Cheese in America, from Field to Farm to Table."

Is there a cheese that you'd like to get that you can't have? Is there an ultimate cheese, some other kind of cheese that you'd like to sell in your store or talk about?

Ms. THORPE: I mean, yeah, sure, the thing that everyone in this country, I think, who's into cheese wants to have that they can't have is raw milk cheese under 60 days. You know, a farmer can't sell it on their farm. It's just completely not allowed. And I don't know many cheese makers - I don't know any cheese makers at this point that mess around with that because you get caught once, and you get shut down.

FLATOW: But you could have it for yourself, if you're a cheese maker?

Ms. THORPE: Yeah, totally.

FLATOW: Like people who have raw milk for themselves.

Ms. THORPE: Yeah, but raw milk, even, there you can have raw milk legally in this country. It depends on what state you're in, and the laws differ from state to state, but with cheese, it's just - under 60 is not legal. And you know, I'd love to see what American cheese makers could do if they were allowed to work with raw milk and sell their product at 20 or 30 or 40 days. I think we could be turning out some really superlative, you know, softer cheeses.

FLATOW: What cheeses were invented in this country?

Ms. THORPE: There are a couple of American originals that I talked about in the book: Monterey Jack being one that is actually a cheese that most of us are pretty familiar with. It originated in Monterey, California, but back then, in the early 1900s, jack cheese was not sort of the creamy, the melting sort of milky, mild thing we know now. It was a more-aged, table cheese. Colby is another American original. And brick cheese, originally pressed under bricks, which is why it's called brick cheese, but also, that's another stinker, and some great producers of brick out in Wisconsin in particular.

FLATOW: How do you think the first cheese person stumbled on it?

Ms. THORPE: On cheese in general?

FLATOW: On how to make cheese. Hey, I have this milk that's going bad. Let's try to�?

Ms. THORPE: Yeah, well, actually, the theory is - and it's a good theory, it makes a lot of sense - that somebody four or 5,000 years ago, was transporting milk in a stomach. I mean, bladders and stomachs were used as, you know, in lieu of canteens. And a baby animal's stomach lining, that fourth stomach of an unweaned animal, has this enzyme, rennin, in the lining. So rennin turns milk -knits the proteins together, and they reached their destination and had this sort of chunky stuff and not milk anymore. And from there, experimentation began, so�

FLATOW: So we don't know who that first�

Ms. THORPE: We don't know who that guy was, no.

FLATOW: Have we traced it back as far as we can?

Ms. THORPE: To my knowledge, the earliest known sort of proof of cheese-making was about 4,000 years ago, and that was in the French Pyrenees. And I have to just point out that they're making the same aged sheep-milk cheese they were making 4,000 years ago.

FLATOW: Wow.

Ms. THORPE: So when people point out to me that, you know, American cheese isn't as good as European cheese, they do have a rather significant jump on us.

FLATOW: They have a little head start.

Ms. THORPE: I think we've come pretty far pretty fast.

FLATOW: They obviously are very happy the way it's turning out.

Ms. THORPE: Yeah, they don't mess with a good thing.

FLATOW: If it ain't busted, don't fix it.

Ms. THORPE: Don't fix it.

FLATOW: So it's just - simple cheeses can be just as good as those fancy cheeses?

Ms. THORPE: Oh yeah, absolutely. I think the hardest thing to do well is make a fresh cheese. Fresh cheese is literally - it's, like, just crossed the line from milk into cheese, and you can't hide behind anything. There's no rind, there's no aging. It's just, you know, how good is your milk, and how fresh is your cheese and how well have you made it because texture is so important. And it's really - it's hard to find really superlative fresh cheese.

FLATOW: Well, you brought some great cheeses, which we're going to consume in a few minutes, while we're off the air. Thank you very much.

Ms. THORPE: Yeah, you've got it.

FLATOW: Good luck to you. Liz Thorpe, who is author of "The Cheese Chronicles: A Journey Through the Making and Selling of Cheese in America, from Field to Farm to Table."

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