The Homogenous History of Processed Cheese

17:23 minutes

An example of the slice-on slice manufacturing process. Credit: Lloyd Metzger
An example of the slice-on slice manufacturing process. Credit: Lloyd Metzger

“Processed cheese” probably conjures visions of those cellophane-wrapped slices from lunchbox days. But it was originally dreamed up by inventor James L. Kraft as a way to keep blocks of cheese fresh on his Chicago cheese wagon. And it’s not a uniquely American invention—Europeans, too, were experimenting with cheese processing at the same time. Lloyd Metzger, a dairy scientist at South Dakota State University, unwraps the history of processed cheese, and the simple chemistry that DIY chefs can use to make it at home.

Plus, this week Wisconsin hosted the World Championship Cheese Contest, where 2,959 cheeses from 23 countries and 31 states competed for first place. We sent Wisconsin Public Radio producer Christie Taylor along with Metzger to give us an inside taste of how professionals sample and judge cheese.

Segment Guests

Lloyd Metzger

Lloyd Metzger is a Professor and the Alfred Chair in Dairy Education at South Dakota State University in Brookings, South Dakota.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. If you heard our show last week, you know that we’re celebrating the science of cheese. Oh, we love cheese. I certainly do. From the gooey, the viscous physics of melted mozzarella, to the microbial mayhem behind your favorite fermented flavors, it’s our spotlight this month, with lots of stories for you to nibble on. And you can find it at sciencefriday.com/cheese.

So, what better way to celebrate than a trip to– where else– the world championship cheese contest. That championship happened this week in, of course, Madison, Wisconsin. And the judges had to taste nearly 3,000 different cheeses, from 23 countries and 31 states. Christie Taylor of Wisconsin Public Radio tagged along with the judges on their tasting tour.

LLOYD METZGER: So, my name’s Lloyd Metzger, I’m a professor at South Dakota State University.

TIM CZMOWSKI: Tim Czmowski and Tim Cheese-mouski, is what my alias is.

CHRISTIE TAYLOR: All right. So walk me through what you do to sample this cheese.

LLOYD METZGER: So, you need a device called a trier. That’s what I’ve got my hands. Basically a curved, stainless steel knife essentially. And since we’ve got a 40 pound block, we have to try to get a representative sample of that cheese. So in the middle of the cheese, I’ll push the trier through. And what it’s going to allow me to do is remove a plug of cheese. Go ahead and smell that. You should get a nice–

CHRISTIE TAYLOR: That is a really strong cheddar smell.

LLOYD METZGER: Now, you’ll take the plug, and one of the first things you do is look for any cracks in the cheese, or any holes in the cheese, that would be an indicator of gas development because we don’t expect that in this cheese variety. In Swiss, we’d want a whole bunch of holes in there. The next thing we’re going to do is bend it. And we want it to bend and then tear before it actually breaks, and not snap. And it did that really well. So really an ideal texture for this cheese. And we’ll take a piece of cheese and we’ll squeeze it. And I want to squeeze it four times and see if it goes into a ball. And if it goes into a ball and doesn’t fall apart, it’s considered an ideal texture.

TIM CZMOWSKI: Before you even taste it, you’ve already felt it and have a bit of a relationship with what it’s probably going to taste like.

LLOYD METZGER: You’ve already got this opinion that you’re starting to form. Sometimes you’re very disappointed when you finally put it in your mouth, when things have looked really good up to that point.

CHRISTIE TAYLOR: So we’ve been talking about putting the cheese in our mouths, why don’t we do that?

TIM CZMOWSKI: You put the cheese in the back your mouth, along the sides of your tongue. You look for bitterness, you look for acid, you look for fruity, fermented, unclean flavors, sanitizer, all of those things. And there’s a hundred other flavors that you could look for. After you’ve worked it into a ball, now you’re starting to warm it up and that’ll actually help you detect the fine flavors. Some of the volatiles will come out.

LLOYD METZGER: And with this cheddar, it’s so clean. It’s got that mild, cheesy, nutty note, but then there’s no bitterness, there’s no excessive salt. Is just a very smooth, clean aftertaste, in a cheddar cheese, which is very desirable.

CHRISTIE TAYLOR: You just spit out that piece of cheese, Lloyd.

LLOYD METZGER: That’s the crime in all this, is you have to spit all the cheese out. You don’t actually get to eat any of it. And you do that because, if you follow the cheese, that’s all you’re going to taste for the next several cheeses as you try to evaluate them. So you spit the cheese out, wash your mouth out several times, and then you can go on to the next sample.

ANNOUNCER: All right. The finalists– the final two of the sweet 16. It is the surface mold ripened sheep’s milk–

There you go. That I was Christie Taylor of the WPR, with cheese judges Tim Czmowski and Lloyd Metzger. And if you’re wondering what cheese won the championship, well, I’m going to have Professor Metzger tell us himself all about it. He truly a jack of all trades. He joins us from South Dakota Public Broadcasting today, welcome to Science Friday.


IRA FLATOW: Are there enough cheese puns to go around for everything?

LLOYD METZGER: It has not “Oc-CURD” to me that they’re done yet. Did you catch that one?

IRA FLATOW: I did. Got a whole bunch in once. You’ve been practicing.

LLOYD METZGER: Yeah. No “whey”. You really shouldn’t encourage me because I just keep going.

IRA FLATOW: Well, don’t be afraid because we’re open to that. Well tell us, who won the cheese championship this year.

LLOYD METZGER: The Grand Champion cheese was a smear ripened hard cheese from Roth, USA. So it was a very unique cheese, and a cheese that’s very difficult to make. So when it’s a smear ripened cheese, you’re going to put a smear consortium of bacteria on the surface of that cheese that’s going to provide unique flavor. When it’s a hard cheese, it’s similar to what you would think of a Parmesan cheese. So it has some very nutty, unique flavors.

And then it’s in a category there called alpine cheeses, where you like to have a particular feed for the cows that produce the milk to make the cheese, that provides kind of a floury taste to the cheese. So you have this whole combination of flavors from the smear ripened, from the milk source, and then from the organisms that were used to make that cheese. And you get this floury, nutty, slightly rancid combination of flavors that’s really a nice bouquet of flavors, and really almost hard to describe.

IRA FLATOW: Send some over would you?

LLOYD METZGER: I’ll get right on it.

IRA FLATOW: One of the things that you’ve written about, and one of the reasons we first got in touch with you was to find out what exactly is processed cheese? We’ve seen it on so many ingredients, we’ve seen it as cheese food, processed– give us the summary. What is processed cheese? What’s the difference?

LLOYD METZGER: The age old question. I really wish I could simply answer that, but it really gets down to the details of, is it really processed cheese and what category is it? So I would love it if consumers would go to the grocery store and actually read what it says on their labels. And you’ll see terms like pasteurized processed cheese, pasteurized processed cheese food, pasteurized process cheese spread, and pasteurized process cheese product. And all of those products will be in the same category in the store. They’ll look very much alike. But the ingredients and how those cheeses were made will vary dramatically. So it’s a really hard question to answer.

IRA FLATOW: Well, people get the impression that it’s sort of synthetic.

LLOYD METZGER: Yeah. And that’s clearly not the case. So, when you make a processed cheese, you actually start with a natural cheese. And actually, this goes back to the early 1900s, J.L. Kraft– and I’m sure you recognize the Kraft name– had a cheese cart that he would take around Chicago and sell cheese. And his cheddar cheese that he was using would spoil. And so he started to pursue a technique where he could pasteurize the cheese, that would allow him to have it for an extended period and it wouldn’t immediately spoil. And that’s kind of where processed cheese started in America.

At the same time in Switzerland, they were starting to make fondues. And if you took certain types of cheese and added a particular type of wine to the cheese, you would make a very nice, smooth, creamy, fondue-type cheese that was the earliest processed cheeses that were being developed in Europe at the time. So bottom line, to make a processed cheese, you need to start with a natural cheese, and then you have to add some type of ingredient called an emulsifying salt. And that can be something as simple as a wine or a lemon juice and some baking soda. Because basically what you need is a chelator that will bind the calcium and cause this cheese to actually form a nice smooth, velvety, creamy texture.

And I guess I’ll try to explain it with a picture. So, everybody’s had spaghetti, and you can imagine a bowl of spaghetti were all the strands are interacting with each other. It’s in a great big pile in a bowl. You got that picture in your head?

IRA FLATOW: I got it. I’m eating it, but I got it.

LLOYD METZGER: Now, what we do when we add an emulsifying salt, is we make all those strands of spaghetti unravel and be individual strands. And when we do that and unravel all those strands, those strands will actually interact with any fat and any water that are present in that cheese, and then the cheese will no longer leak oil, and it won’t have water that comes out of it. And with a little mixing and heating, you very make this very nice smooth, creamy product. So that’s basically what you do when you’re making processed cheese.

IRA FLATOW: So what I’m hearing is that cheese is processed milk to begin with, right, so you’re just processing it a little differently?

LLOYD METZGER: Exactly. And it’s really about extending the shelf life of the product. That’s why processed cheese was developed, was trying to get cheese to stop where it was. Because everybody knows this, if you take a cheese and put it in your refrigerator, it’s alive. And it keeps changing over time. And the characteristics of that cheese rapidly change over time. And it can be a good change, if it’s a very nice aged cheddar, or it can spoil in your refrigerator. So processed cheese was designed to try to arrest and stop that ripening process.

IRA FLATOW: Let’s talk a little bit about cheese chemistry and food, for example. American cheese melts so well on a burger, but why doesn’t cheddar melt like that? What’s going on there?

LLOYD METZGER: OK. So when you make cheddar cheese, you use an enzyme to form the coagulum that produces that curd, and it very loosely entraps the milk fat that’s present in the milk. And so, when you heat that product up, the fat actually leaks out of the cheese and you get this kind of oily, gloppy mess that you get with a natural cheese like cheddar. With a processed cheese, we took those spaghetti strands and deaggregated them, took them all apart, and now they hold onto that water and fat, and make it very smooth and creamy. Just like you would if you made a cream sauce on a stove top.

IRA FLATOW: And then you have cheeses, like fontina, that aren’t processed, right?

LLOYD METZGER: Correct. And if you get the cheese to ripen to exactly the right amount and have the right level of the protein being broken down, it will actually make a smooth and creamy cheese. But you have to have the age of the cheese exactly right, and it’ll only do it for a short period of time. With processed cheese, we give it that heat treatment and then it’s going to stay that way for a much longer period of time.

IRA FLATOW: Now, I understand that it’s actually not that hard to make melty nacho cheese without it separating into an oily mess. And this is something that people can try at home.

LLOYD METZGER: Yeah. Just go buy some mild cheddar cheese, or even a medium cheddar cheese, and put that on a saucepan on your stove top. Add some water to it, and then also add some lemon juice and a little bit of baking soda. And just stir it up with a whisk, and you’ll get this very smooth, creamy product. If you want to be thinner, add a little bit more water to it. And you can really get your nice nacho cheese sauce at home.

IRA FLATOW: And in fact, we have a recipe at sciencefriday.com/nachocheese on our website. And while we’re on the subject of American cheese– I asked about it before melting on a burger– is there really any fundamental difference between a mild American cheddar and something like a Jack?

LLOYD METZGER: Yeah. You will use a slightly different make procedure and different cultures to produce those two cheeses. And then they’ll have a different moisture content as well. So you use a slightly different bacteria, slightly different manufacturing process to change the composition of that cheese.

IRA FLATOW: If anybody has any questions about cheese they want to get in in the last few minutes, our phone number, phone lines are open, 8-4-4-7-2-4-8-2-5-5. 8-4-4-S-C-I-T-A-L-K. 4 Do you have a favorite cheese of your own?

LLOYD METZGER: I have– that’s like asking if one of my children is my favorite.

IRA FLATOW: I know, I was going to preface that with that exact phrase.

LLOYD METZGER: So, I like several of them equally well. So I really like a very highly aged cheddar cheese, just because I’ve done so much research on them over the years. I actually had a cheese that I made when I was in graduate school, 25 years ago, that I carried with me from University to University, until it was 15 years old. And that was quite a good cheese by them. But I also like blue cheese as well.

IRA FLATOW: When you had that tour of the contest, what happens to all those cheeses? I mean, are they just available there? Can we get them? What happens to them?

LLOYD METZGER: So, there is the top 16 cheeses in the contest actually are auctioned to raise money for scholarships for students that are in various food and dairy science programs in the United States. Then the remaining portion of the cheeses are actually donated to a food pantry in Madison, Wisconsin.

IRA FLATOW: And is there a wrong way to eat cheese?


IRA FLATOW: I, mean should you let it all come to room temperature? It’s like, I’m going to go into your dairy subjects like ice cream, they say you should let it melt a little bit so it doesn’t freeze your taste buds, you can get the flavor of the– is the same thing with cheese?

LLOYD METZGER: Well, no. Cheese, it’s nice if it’s warmed up a little bit toward room temperature, but your mouth is going to continue to warm it up. The big thing is to don’t be the typical American pig and chew it twice and swallow it. You’ve got to give it a little bit of time in your mouth and let that product melt. It really is good to breathe a little bit because actually some of the flavors will go up retro-nasally, and you’ll actually get a better sense of the cheese if you breathe in a little bit.

IRA FLATOW: Yes. Keep breathing. Talking with Lloyd Metzger, The Cheese Baron. He’s professor in the dairy education department, South Dakota State University in Brookings, on Science Friday, from PRI, Public Radio International. What question do you get most about cheese?

LLOYD METZGER: The one you just asked, what’s your favorite cheese. And then the second one really is about processed cheese. Is it really cheese? I mean, you can go on YouTube and watch videos about fake cheese, and people really wonder what’s in it.

IRA FLATOW: Right. All right. Let’s go to the phones. John now, he’s got a question for you. Go ahead. Welcome to Science Friday. Let’s– come on. We lost him. All right. Let’s go to Lori in Malden, Massachusetts. Hi Lori.


IRA FLATOW: Hey there.

CALLER: Thanks for taking my call. Conversation was very interesting, and I wanted to ask how it could apply to macaroni and cheese, by trying to use real cheddar cheese comes out grainy usually.

LLOYD METZGER: Yes, exactly.

IRA FLATOW: How do you do it? What’s the secret?

LLOYD METZGER: So, the cheese used in macaroni and cheese really needs to be a processed cheese to not have that grainy texture. So if you wanted to do that, you could follow that nacho cheese recipe that’s on the website, and then use that cheese in macaroni and cheese. But if you use just a straight cheddar, you’ll get a very gloppy, oily product that really doesn’t have that desirable velvet, melty characteristic that you’re after in your macaroni and cheese.

IRA FLATOW: What, Doctor Metzger, is the holy grail for cheese scientists?

LLOYD METZGER: Well, 10 to 15 years ago it was could we make cheese that had less fat in it and less salt in it, and still taste good? And why would you want to do that, first of all.

IRA FLATOW: My question exactly.

LLOYD METZGER: It tastes so wonderful. But really, the holy grail of cheese is trying to get the flavor that you want every time. So there’s so many steps that go into the cheese manufacturing process, and the ripening stages, that if you screw any one up, it will magnify any bad flavors that you have and negate all the good flavors in that cheese. So, if there was a way to more consistently get the flavor that you want, every time, it’d sure make cheese manufacturers happier, and I think consumers too because they’d more likely get the cheese that they want every time.

IRA FLATOW: If you wanted to try cheese making at home, what would be the easiest, best way to learn?

LLOYD METZGER: The easiest, best way is to probably do– you could do a fresh mozzarella type cheese that you can stretch, and then make fresh mozzarella balls out of. That’s an easy cheese to make, and you can use lemon juice as your acidulant, to actually help coagulate the milk. So a pretty easy one to do is mozzarella.

IRA FLATOW: I’m glad you brought that up because we have that on our website. We actually visited a great mozzarella cheese maker in the Bronx, and so it’s up on our website at sciencefriday.com/cheese. Yeah. And this gentleman we had was putting his hand in boiling water for 30 years, pulling them up–

LLOYD METZGER: Yes. You need to be a really old Italian with these ready red hands. When I do it, I put rubber gloves on because I’m a sissy from South Dakota.

IRA FLATOW: Well, your Wisconsin people appreciate hearing that, I’m sure. All the cheese makers. Well, thank you very much for taking time to be with us. Give me a pun to end with. What your best pun?

LLOYD METZGER: My best pun. I’ll tell you a cheese joke, I guess.

IRA FLATOW: Quickly.

LLOYD METZGER: There was an explosion in the French cheese factory. What was left?

IRA FLATOW: I give up.


IRA FLATOW: Oh. I love it. All right, everybody’s heard that one for this evening. Lloyd Metzger, a pun artist, is Professor in the Alfred Chair in Dairy Education at South Dakota State University in Brookings.

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  • John Stimson

    In the radio segment, Dr. Metzger suggested making smooth nacho cheese sauce using mild cheddar by adding “some water, some lemon juice, and a little bit of baking soda”. I was interested in how much of each, so I visited the URL that was mentioned, http://www.sciencefriday.com/nachocheese. That recipe calls for more exotic ingredients which I would have to mail order: sodium citrate and hexametaphosphate. If I want to use lemon juice and baking soda, how much should I put in per pound of cheddar? What is the minimum amount of liquid (milk or water) to add?

  • Amanda P

    I tried and failed, it got all foamy but the cheese never incorporated into the liquid. My google-searching didn’t find any other mentions of this, but I figured it was worth a try anyway. The taste was fine, but it looked gloppy and was the wrong consistency.

  • Willow Johnson

    I was also disappointed not to find a recipe here. Decided to try anyway. Here is what I did, it could use a bit of tweaking but turned out ok for a first try… and worlds better than any nacho cheese I’ve tried to make before.

    2 Tbs Lemon juice
    3/4 tsp baking soda
    1Tbs water
    2 Tbs milk
    1lb medium cheese
    Add ins:

    I mixed the lemon juice and baking soda until it stopped foaming then added the water and one Tbs of milk. Used a small pot on the stove on medium/low temp. I added one handful at a time of shredded cheddar. Whisked the first handful like crazy and just when I was getting disheartened suddenly it all came together. Kept adding cheese until it was too thick then added some salsa to loosen it up. This is when I added the rest of the milk.
    Turned out really tasty and cheesy with none of the floury taste like other recipes. Next time I might try 3Tbs lemon juice and a full tsp of baking soda and see if that made a smoother texture.
    Good luck making your own nacho cheese!