Play Live Radio
Next Up:
Available On Air Stations
Arts & Culture

Food Fermentation: The Science of Sausage and Cheese


This is SCIENCE FRIDAY. I'm Ira Flatow. We're here at the Wisconsin Science Festival at the Institute for Discovery in Madison and talking about a trip to America's dairy land, of course. Inevitably you're going to talk about food and fermentation. In the form of Wisconsin, it's famous for fermentation, one of the oldest ways of preserving food. It's also a way to get really unique flavors.

You've got your beer, you've got your yogurt, your cheese. They all taste better with a little bit of bacteria in them all. And why spoil your food by cooking it when you can ferment it, right? So what better place to talk about the science behind two of Wisconsin's favorite fermented foods, cheese and sausage.

My guests are John Lucey, director of the Wisconsin Center for Dairy Research, professor of food science at the University of Wisconsin in Madison; and Jerry Traczyk is the plant manager at Underground Meats here in Madison. Welcome to SCIENCE FRIDAY. What do you do at Underground Meats?

JERRY TRACZYK: I get to experiment with different types of sausages, butchering whole animals and creating dry cured products, be it fermented and dry cured or whole muscles. I work with a lot of farmers and try to use every bit of that animal and create new and interesting products with that.

FLATOW: What is the definition of a sausage? For we hotdog eaters and whatever back East, what is a sausage?

TRACZYK: That's interesting. I've never really looked up the actual definition of it, but in my terms in the work that I do I would consider a sausage to be, you know, any type of ground meat, being varying species, pork, beef, veal, lamb, goat, et cetera, something that's ground and stuffed into a casing, be it natural or a synthetic casing and then either fermented, cooked or dry cured all on its own.

FLATOW: So you make a lot of salami in one week?

TRACZYK: I do. It'll vary, but anyone from 800 to 1200 pounds in some weeks. That's about our capacity right now.

FLATOW: How do you make a salami? Give us an idea of the process and the chemistry that goes in.

TRACZYK: It all starts with bringing in the animals. We do - most salami is made with pork, a resource, the heritage pre-pork from small local farms down here near Madison. We also use goat for one of our salamis too, which is becoming one of our most popular salamis. So it all starts with sourcing the right animals from the farms, bringing those in and then we take in the whole animal and butcher them down.

Certain parts of the animals, be it the ham or the shoulder of the pork, will be used for different types of salami. They have different characteristics, being it either lean or a little more fat mixed in with that, so we'll butcher the animals out and separate the meat into various tubs so we know what type of salami we want to make from there.

And then from there we have our spice profiles, so we'll grind that salami and during that grinding process we're also introducing lactic acid starter cultures.

FLATOW: Cultures?


FLATOW: Made out of what? What's in a culture?

TRACZYK: They're freeze-dried cultures we buy that are commercially produced.

FLATOW: What's in it?

TRACZYK: The strain we use is a strain of lactobacillus and staphylococcus bacteria and what happens with that is through the fermentation process, which is stuffing that sausage after it's ground and it's mixed together, we go into a fermentation chamber which, for our purposes, we have it around 85 degrees and that takes about 24 to 36 hours for that salami to ferment.

TRACZYK: And what happens is those cultures come alive and they feed on the dextrose that we add in there. Part of the spice blends is dextrose and that's actually the food that the starter cultures feed on. So the byproduct of them eating that dextrose is lactic acid, so throughout that process the pH is starting somewhere around 5.9 to 6.1 with most raw meat, talking about pork.

And we're looking for a target of somewhere below 4.8 and that takes somewhere 24 to 36 hours for that to occur with the cultures that we use.

FLATOW: So pH is important?

TRACZYK: Very important. It's one of the most important steps in the production of salami.

FLATOW: John Lucey, how different is it to make cheese than it is to make a sausage?

JOHN LUCEY: Well, you start with the animal, but you don't start with meat. So of course you have some very different types of milks out there, but the majority is coming from cow's milk, but there's goat and sheep as well. But I would say that the key ingredients in it, there is a fermentation in it, but the key first step is actually the addition of an enzyme called rennet.

FLATOW: Right.

LUCEY: And rennet actually has its origins as coming from the stomach lining of calves, so I always like to tell students that we borrowed the cheese-making process from the cow and the calf. So when the calf suckles the cow and drinks the milk, the milk actually curdles in the stomach of the calf and it seems to be some biological-driven reason for this to slow down the passage of milk through the digestive system of the calf by having this kind of slow clot that we call cheese, but they call it like a little curd that forms inside in the stomach of the calf.

Probably in our early origins of domesticating cows, we didn't have plastic buckets and we didn't have stainless steel, so we actually used to carry our milk around in the stomachs or bladders of animals and they discovered that after a while, holding in these stomachs of these young calves or mammals that they then clotted, and we discovered it was this rennet enzyme came from that lining and it didn't happen if you put it in a pot, for example, earthenware pot, so after a while they extracted that with salt solutions out of it and that's - up to about 100 years ago, that's how we made cheese.

We took the stomach linings of young calves and extracted this rennet enzyme out of it, and then added it to milk and low and behold, 20 minutes later you had a curd.


LUCEY: That was the key first step, is to make this soft gel. Then (unintelligible) for a long time we didn't add any culture. There was enough bacteria in the milk or got in from the milking process or was in the environment coming from the milker or the farm or the environment, and if you just held it for a period of time it would ferment naturally itself, so-called natural starter or raw malt(ph) type starter.

But then, apart from that, everything else varies depending on which variety you want to make, whether you heat it, cut it, or add salt to it, or stir it, or cook with the high temperatures. This basically took on a life of its own, depending on which variety you're making, so we have everything from cheeses where they don't cook at all, or ones where they actually cook at very high temperatures and actually boil it in the milk.

So diversity has taken over. Now we have literally hundreds, maybe even thousands of cheese varieties all made in slightly different ways.

FLATOW: Let me ask you, Jerry, to talk about making a spreadable sausage. How do you make the sausage spreadable?

TRACZYK: So there's - I believe what you're referring to is I brought a little bit of it with me today...

FLATOW: Yes, I've got some on the plate here, I'm waiting...

TRACZYK: Which is Nduja. It's actually made in the same fashion...

FLATOW: What's it called?



TRACZYK: N-D-U-J-A and it's a fermented, dry-cured salami maintaining a spreadable texture as you had mentioned, and it started in the very southern part of Italy in...

FLATOW: I'm going to taste it while you're talking.

TRACZYK: Just to warn you, it's made with Calabrian peppers and it's meant to be very spicy. The spreadable texture comes between - throughout the grinding process and the emulsification that happens between the fat and the proteins and the lean meat that's used in there. So it goes through the same process as the hard salami. It ferments, the pH is going to drop. It also will go into a drying chamber and lose moisture and it will actually turn into a dry product...

FLATOW: That's good.

TRACZYK: But because of the level of fat, it still maintains a spreadable texture, and there's a lot of spice in it too. It's close to a quarter of the weight.

FLATOW: Yeah, there is. But it's good. I like spicy food.

TRACZYK: It's a flavorful spice, but it's does carry quite a bit of heat.

FLATOW: Here in our audience, you know, you come from Wisconsin, you want to know about cheeses and sausage, please step up to our mike and you can ask a question about what's going on there. Let me talk a little bit about salamis more because you see, you see a lot of mold on the outside of salamis. What does the mold do? What's it there for?

TRACZYK: The mold's there for several different reasons. We use mold, it's a benign mold that you see on most salamis. It's most often a bright white color. If you're going over to Italy, France, you might see some stuff with a little varying color differentiation, but we buy freeze-dried mold cultures and we actually inoculate them and put them onto the salami during the fermentation step.

And what that does is there's three different things that mold helps with. One is it outcompetes any harmful molds from growing, so we want a benign, the proper type of mold to grow on that salami, so no harmful molds do. And during that process too, that mold actually raises the - takes the acidity, you know, kind of away a little bit, so if you're at like a 4.0 pH, by the time that salami finishes, that pH comes up a little bit to give it a little more pleasant flavor instead of being, you know, quite so like tangy.

The third thing it does is it's kind of an extra layer besides the casing the casing to kind of help ensure that that salami's going to dry out evenly, so it doesn't dry out really rapidly on the outside and in effect it would rot from inside out because there would be nowhere for the moisture to go.

FLATOW: Let me ask you, John. I have a plate of cheese here I understand that you invented this cheese. It's your own cheese. What do you mean? How do you invent cheese?

LUCEY: It's a creative act, isn't it? It's basically we have these hundreds of varieties because somebody wanted to make it different another day and decided to use a different culture or a different way of making it. So this cheese you're tasting in front of you is called Dubliner Cheese and actually a long time ago, it's probably 20 plus years ago, when I was doing my PhD back in Ireland, I had to make cheese a very different way because I needed that for my experiment.

It was driven more by the needs of an experiment than anything else, but we tasted the cheese after it ripened for a while and thought it had an interesting or different or unique flavor and it didn't seem like it was similar to other cheeses we tasted.

FLATOW: It's delicious. Yeah.

LUCEY: So after repeating it - like all good science, you have to go back and repeat it and see if it was just a one-off. After repeating it for a while, we approached a local company and said: Would you be interested in this? We think it's a new variety that you might be interested in making. And they did. And after marketing for a while, it became a very popular cheese. Actually, it's now exported to the U.S. So we got it - I got this locally here in Madison. So...

FLATOW: It's called the Dubliner.

LUCEY: Dubliner.

FLATOW: But it's not made in Dublin.


FLATOW: It goes to Dublin, though.

LUCEY: It goes to Dublin.


LUCEY: And I'm from Cork, which is not Dublin.

FLATOW: Right.


LUCEY: And the company that makes it is actually also based in Cork, and not in Dublin. So...

FLATOW: Wow. Wow.

LUCEY: was a marketing idea.

FLATOW: It's hard to swallow in Dublin, then.

LUCEY: Well, I think Dublin - the reason it got Dublin, there's a very popular Irish traditional folk band called Dubliners.


LUCEY: And they thought this would go well with the marketing campaign for this traditional Irish cheese with this name of the traditional Irish folk band, and having the two of them together (unintelligible).

FLATOW: Did I hear you say you can get a degree on cheeseology or something like...

LUCEY: No, not quite.

FLATOW: cheese-making, or...

LUCEY: Not quite. You can get a degree here at the university in food science.

FLATOW: Right.

LUCEY: But we have different programs for people who are interested in becoming experts in cheese. Actually, we - here in Wisconsin, we have what is called a master cheesemaker program. So it's like a traditional guild or art program, skilled programs like you get in Europe. And it's a program that lasts about three years.

FLATOW: Right.

LUCEY: And it's - the prerequisites would probably eliminate everybody here in the audience. You have to be a licensed cheesemaker here in Wisconsin for 10 years.

FLATOW: Anybody in the audience, raise their hand, a licensed...

LUCEY: So...

FLATOW: Not yet.

LUCEY: So that...


LUCEY: It's really for the cream of the crop of existing cheesemakers who want to blend a lot more science with their skill and tradition of making cheese.

FLATOW: You've got every food metaphor in that sentence that I could think of.


FLATOW: That was very good.

LUCEY: That's because we're in the food science department.


FLATOW: I won't get into the jokes that we tell among cheesemakers yet.


FLATOW: Let's go to the audience, here. Yeah.

UNIDENTIFIED WOMAN #1: OK. I have a cheese question. You mentioned that we have cheeses made from cow's milk, goat's milk, sheep's milk, all of which I enjoy, but I think we all find that they taste somewhat different. I've also had the opportunity to travel in Mongolia, where I had yak's milk yogurt, which I thought was delicious, and reindeer's milk, which I thought was disgusting. And my question is: Why all these differences? Is it the milk itself? Is it something about the process of making - the fermentation process and so on? What...

LUCEY: It's a combination of all of the above, because even for a breed just like cow's milk or bovine milk, we have, literally, hundreds of different varieties that all taste different. So, partly, it's how - the recipe of making it, but there are unique differences between breeds. For example, goat and sheep have a lot more of certain short, medium chain fatty acids. That gives it that spicy, peppery flavor. No matter how you make it, you'll always get that spicy, peppery flavor. So it also is - there's some differences in the protein and other compositions of it that either would make a soft gel or a firm gel. So there are compositional things, but there's also a lot of differences in how they're made, as well.

FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY, from NPR.

Jerry, what about sausages? The same thing, that - if you can make a sausage out of any meat and it will taste differently or...

TRACZYK: You can. We - I mean, we do experiment with quite a bit of different meats, whether it be veal, beef, pork, goat, lamb...


TRACZYK: Deer, of course, during hunting season. We don't do it in our - facility. But I definitely do like to experiment in my own in making venison sausage. And each one of those animals does have a different flavor profile. If you're getting into stuff like deer and goat, let's say, they're a really lean animal. There's not a lot of fat on there. And a big part of making sausage is having some of that fat there. So making some of that leaner-type sausage, you're going to be using some kind of a pork product, usually using that nice fatback off of pork and folding it in with the grind with some of those other animals.

FLATOW: I have a nice piece of some salami slices here. What am I eating?

TRACZYK: That's some of our goat salami, there. And it's got goat - goat - well, 75 percent goat, 25 percent pork, and it has a little bit of cinnamon and rosemary are the...

FLATOW: Right, and it's different.

TRACZYK: ...spice profile you're going to get there.

FLATOW: Mm. (unintelligible) well, you can go on, and I'm going to eat.


FLATOW: Let me go to the audience here for this question. Did you have a question?


FLATOW: Go ahead. Thank you.

UNIDENTIFIED MAN: I have a question for Mr. Traczyk. So, I was wondering: Do you actually consider kosher and halal methods of making salami, as in other dietary restrictions for making your meat?

TRACZYK: We don't make, really, a kosher-style salami or a sausage. You know, we're utilizing all parts of the animal. And being it mostly pork is - as salami is all mostly pork...

FLATOW: Tough getting the kosher and the halal on the pork.

TRACZYK: It's kind of tough to get that. And even with the goat salami, we do need to use some of that pork for some texture and add some of that fat in. So it would be very difficult to try to do that. It could be possible, but it would probably be a slightly unpleasant texture to make a salami in that fashion.

FLATOW: Mm. But there is - there are - kosher salami. Hebrew National has a kosher salami...


FLATOW: ...salamis, like, out there. Yeah. Let's go over here. Yes, ma'am.

UNIDENTIFIED WOMAN #2: So, I believe that Wisconsin, in Monroe, Wisconsin is the only place that produces Limburger cheese in the United States. And I think I heard on SCIENCE FRIDAY that it was partially that the bacterial culture comes from the monks' feet...


UNIDENTIFIED WOMAN #2: ...the original. And just wondered if you knew anything about that in Limburger cheese.


LUCEY: Well, it's belonged to a class what is called smear-ripened cheeses.

FLATOW: Smear...

LUCEY: Smear-ripened.

FLATOW: ...ripened.

LUCEY: So that tastes nice, doesn't it?


LUCEY: Smear-ripened cheeses. So...

FLATOW: You lost half the audience on that one.

LUCEY: Yeah, they didn't like that.


LUCEY: And the Brevibacteria are related to the bacteria that give you body odor, as well. So, you know, lost the other half, I think, as well. But it does belong to a class of cheeses that were worked on by the monks in medieval times. So it probably does date back to having some relationship back to - I don't know if they use their feet.


LUCEY: (unintelligible) Because, literally, what the smear means is that you constantly wash the cheese in, you know, it's kind of a salt solution. But what you do is you take some of the good stuff you made before, wipe your cloth on the good stuff, and wipe it over the new stuff to transfer some of the bacteria. And it's basically what we call a smear or surface-ripened type of variety.

FLATOW: I learned more about cheese and sausage today than I ever thought we would know. Thank you, gentlemen...


FLATOW: ...we ran out of time - for taking time to talk with us. John Lucey, director of Wisconsin Center for Dairy Research, professor of food science in the University of Wisconsin here in Madison. Jerry Traczyk is the plant manager at Underground Meats here in Madison. Good luck to both of you.

TRACZYK: Thank you.

FLATOW: Thanks for coming. After the break, we're going to take a tour of nearby Waukesha, Wisconsin, home of legendary music inventor, Les Paul. We're going to talk about him, one of my favorite persons to talk about. So stay with us. We'll be right back after this break. Transcript provided by NPR, Copyright NPR.