Chile Peppers: The Science Behind The Spice Science Friday broadcasts this week from the heart of the "chili belt" in Tuscon, Ariz. What makes peppers spicy? Why do some people love spicy foods? Researchers explain the chemistry of peppers and the psychology of spice.
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Chile Peppers: The Science Behind The Spice

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Chile Peppers: The Science Behind The Spice

Chile Peppers: The Science Behind The Spice

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IRA FLATOW, host: This is Talk of The Nation: Science Friday. I'm Ira Flatow. We're here in Tucson, Arizona, and if you've ever visited this part of the country, you know it can get really hot. And I'm not talking about the weather, I'm talking about the food from Jalapenos to Anaheim's, to Poblano's, folks in this part of that world have been spicing their food with chilies for centuries.

But something I learned on this trip out West is that chilies don't just make food hot, there are lots of mild ones too that are used in cooking, and chilies have non-food uses too. We'll talk about all the uses for chilies, you know, for example their signature chemical compound, capsaicin.

That stuff that makes them hot is also used for a pain reliever. I see your shaking your head, you knew that. Yes. And their color is used in cosmetics with lipsticks, did you know that too? Well, well, what's about - that's why we're here for, to talk about chilies and everything that you ever wanted to know about chilies, so we're going to kick off the hour talking about chili peppers, what makes them hot and why do we like them.

Why do we like something that's that hot for us, and burns or maybe doesn't burn our tongues? And how are farmers and scientists working together to take the plants from seed to fruit and back to seed, then here we are. In the audience in Tucson, Arizona, talking to folks, and if you'd like to join us please step up to the microphone when the - when it hits you.

The appeal to ask a question? Also, our number, 1-800-989-8255, 1-800-989-TALK, and in Second Life you can find us in Science Friday Island, and look for our seating area there and ask a question to Second Life. Let me introduce my guest. Jeff Silvertooth is a professor and the head of the Plant Scientist Department at the University of Arizona in Tucson. Thanks for talking to us today.

Dr. JEFF SILVERTOOTH (Professor and Head, Plant Scientist Department, University of Arizona, Tucson): Thank you.

FLATOW: Good to have you here. Ed Curry is a farmer and owner of the Curry Seed and Chile Company in Pearce, Arizona. Thank you, Ed.

Mr. ED CURRY (Farmer and Owner, Curry Seed and Chile Company, Pearce, Arizona): Thank you.

FLATOW: And in fact, we have a little bit of a tour of Ed's Chili farm just outside of Tucson. It's sciencefriday.com. Flora Lichtman, our digital producer put it together, and if you'd like to see a little preview of the full-blown version, you can go over to our website at sciencefriday.com, to see a bit of Ed's farm.

Gary Nabhan is a research social scientist at the University of Arizona, he's also the author of "Why Some Like it Hot: Food, Genes, and Cultural Diversity." And he joins us from WMEA in Portland, Maine. Thanks for talking with us today, Dr. Nabhan.

Dr. GARY NABHAN (Researcher Social Scientist, University of Arizona; Author, "Why Some Like it Hot: Food, Genes, and Cultural Diversity"): Happy to be here with you.

FLATOW: Thank you. Ed, when we say chili? What are we talking about? It was a - it encompasses a lot of stuff, doesn't it?

Mr. CURRY: It does. Probably the simplest explanation for chili is obviously as a lot of countries have their own specific chilies, but here in The Southwest, long, green, once termed Anaheim, because they were so popular there around Anaheim, California. They responded to the cool weather and next to the ocean there...

FLATOW: Mm-hm.

Mr. CURRY: But long green chili, Dr. Paul Smith from U.C. Davis gave it that name, suggested that name some years ago. So long, green chili indicates a relatively mild, flavorful chili.

FLATOW: Mm-hm. There are lots of different varieties and brands of things like that, that you can get?

Mr. CURRY: Of the long green?

FLATOW: Yeah.

Mr. CURRY: Of the long green alone, there's several. We - my partner Phil V. and I have bred the several different strands of just the long green alone. But, when you get outside of the long green, the - in the Capsaicum annum species...

FLATOW: Right.

Mr. CURRY: It's huge, there's just all kinds.

FLATOW: Mm-hm. Jeff, South - the Eastern Arizona is part of what is called the Chili Belt, and I don't think I've ever heard that phrase until I got here. What does that mean? Why is this a great spot to grow chilies?

Dr. SILVERTOOTH: Well, I think we kind of gave it that name. Sounded good.

(Soundbite of laughter)

Dr. SILVERTOOTH: But, it really - it depicts some of the unique characteristics associated with the chili plants, particularly this type that Ed was describing, we call the Anaheim or sometimes the New Mexico-type chilies.

And this is a characteristic that is consistent with basically any type of crop, that they have their own environmental parameters, environmental conditions that they best develop and produce under. And whenever we take those kind of plants out of those optimum conditions, they can often times still grow, but they don't opt - they don't grow to an optimum type of condition with regard to yield and quality.

This area is kind of what Ed and I referred to as the Chili Belt, or a lot of us do, is about 3500 to 4500 feet elevation. And it runs along about a 32 degree north-latitude zone, extends in our case from Southeast Arizona across Southern New Mexico, into Far West Texas,, and the Northern part of Chihuahua, Mexico. But, the whole area has those ranges of elevation in common, so it's a climatic and weather-type of conditions that are really, well, suitable.

FLATOW: So the elevation is important?

Dr. SILVERTOOTH: Very much so, and it's really the temperatures and the climate, but elevation changes everything here in this desert.

FLATOW: Yeah.

Dr. SILVERTOOTH: For example, we're at about 2600 feet here in Tucson, from here to go west to the Colorado River, we drop down to about 150 feet anuma(ph), right above sea level. And we go to extend all the way up to about 4500 feet elevations in Southeast Arizona...

FLATOW: Mm-hm.

Dr. SILVERTOOTH: (Unintelligible) farms in the Sulphur Springs Valley. FLATOW: So it's a little cooler, a little wetter up there?

Dr. SILVERTOOTH: Yes, exactly.

FLATOW: Yeah.

Mr. SILVERTOOT: A little higher elevation. Higher elevations mean you get a little bit more precipitation on an annual basis, and a little cooler temperatures.

FLATOW: Mm-hm. Gary Nabhan, where do chilies come from? Chili peppers, are they native here? Were they imported? How did they get here?

Dr. NABHAN: Well, the wild chilies called the chiltepines are right there in Southern Arizona, within about 40 miles of where you're standing. But chilies are all over the Western Hemisphere, from Tucson all the way down into the country of Chile.

And we have four domesticated species, some semi-cultivated things, and some other species, a dozen other wild species. But people have been cultivating them for about 8,000 years in Mexico, we think the origin of Capsicum annuum is somewhere south of Guadalajara.

We don't know whether it was on the Western Coast of Mexico, or the Central Valleys, or the Caribbean Coast, but from there down is a probable center of origin of chilies for the most part that we grow in the United States. We have a few exceptions...

FLATOW: Mm.

Dr. NABHAN: Like the Datil chili pepper in Florida and the Tabasco that are different species, but Ed and Jeff are correct that most of what we grow to United States is this species Capsicum annuum.

FLATOW: And they've been part of people's diets for a longtime. When you dig up ancient sites, yeah...

Dr. NABHAN: Well, the wild chilies predate even agriculture in the Southwest by 4,000 years. We find them in caves, and what are affectionately called coprolites, the human manure remains in caves of prehistoric sites, and people can extract chili seeds out of those going back 8,000 years in the border land...

FLATOW: Mm.

Dr. NABHAN: Right in this chili belt that Jeff and Ed are describing.

FLATOW: Ed, you breed chili peppers. I have to say it's a great name for a chili pepper breeder. Ed Curry.

(Soundbite of laughter)

FLATOW: Chili pepper breeder. What kind of traits do you look for? I mean, give me the ABC's of breeding a chili pepper. I mean, there a lot of different things you could choose for. What do you select at? What are you looking for?

Mr. CURRY: We look for - specifically in the canning industry, we look to make it two wall. I brought one here, obviously radio audience can't see it, but we look for a two-wall, slim-type chili which we've tried to make it a little bigger, a little girthier. Specifically right now we're trying to make the skin thinner, we're looking for thinner skins, so there's less waste product to the canning industry. We're looking for more yield. How we got on the map, Phil V. and myself - Phil's just a renowned pepper breeder around the world. But how we got famous in this, quote unquote "was by stabilizing the heat." And that variety was Arizona 20. As this industry spread to the north and to the east and new connoisseurs of chili were coming in, it needed a standardized heat because you know yourself. If you went to a restaurant one time and got a mild chili and you went the next time...

FLATOW: Right.

Mr. CURRY: And you got your head burned off.

FLATOW: Yeah.

Mr. CURRY: So when we standardized, it may - that was one of the first characteristics we looked for.

FLATOW: Right. Can you tell how hot a chili is by the color? If it's red chili versus a green chili?

Mr. CURRY: Good question. Good question, Ira.

FLATOW: We used to not know anything about chili pepper, so we're...

Mr. CURRY: We Westerners don't either, especially those of us trying to make a living. It - red doesn't mean hotter. Red is only a state of maturity. I said this on a Phoenix TV station some years ago. You know, as a human, when you get old, you turn wrinkled while a chili turns red. It's just, strictly, maturity. The heat is - developed - the capsaicin oil is produced right on the placenta wall of the pepper and it comes down that placenta wall. The further down the placenta wall, obviously, the hotter the pepper. Many people think the seeds are hot. Only true because the capsaicin is rubbed off on the seeds sometimes in processing. The seed in, any of itself, is not hot. It's strictly that oil that is developed along the placenta wall.

FLATOW: So the oil is not in the seed then.

Mr. CURRY: No.

FLATOW: It's in not the seed.

Mr. CURRY: No. That's correct. The oil - if you cut a pepper...

FLATOW: Right.

Mr. CURRY: And I can cut one for the audience for the audience here. If you cut a pepper, you're going to see that oil. A little shiny blisters right along that placenta wall and there is so many uses for that. And you'll probably ask questions later.

FLATOW: Oh, you can tell us whenever you'd like to.

Mr. CURRY: OK.

FLATOW: But let me ask you about this. When you cut the wall, you release that hot oil. How do you measure how hot? Is there a terminology or standard for heat?

Mr. CURRY: Scoville unit.

FLATOW: Is there a guy named Scoville?

Mr. CURRY: A guy named, Scoville, many moons ago that developed it. There's a HPLC tester that measures. The beauty that God gave us in quantification is really neat because we're able to quantify heat. And yesterday, we talked extensively with Annette(ph) about why is that important. When you go to the store and you buy a bottle of salsa and it's more mild, medium or hot. By standardizing that through the HPLC machine, we can actually give the custumer the same heat level in every jar.

FLATOW: What's the range of Scoville units for those three categories? Is there something like five to ten is one heat. Ten to twenty something...

Mr. CURRY: Typically, I don't know if I'll hit this exact. But roughly, probably mild sauce is going to be 50 Scoville units. Medium is probably going to be 150 to 200. Hot is going to be 500. Now, when you get out - when you get over here to New Mexico and Arizona - my friends at New Mexico State will all testify that, you know, it's a much - much, much hotter than that. But typically, like your Pace Picante, your brand name, Picante sauces, are going to be in that range.

FLATOW: All right. We're going to take a break and come back and talk about - some more about chili peppers. Maybe there'll be Scoville units on your menu someday to tell you how hot this stuff is. We could start that instead of those little numbers of chilies lined up how hot it is. Stay with us. We'll be right back and talk more about chili peppers with Jeff Silvertooth, Ed Curry and Gary Nabhan. And right here in Tucson. Don't go away.

(Soundbite of music)

FLATOW: You're listening to Talk of the Nation: Science Friday. I'm Ira Flatow. We're talking this hour about the science of chili peppers with my guest Jeff Silvertooth, professor and head of Plant Sciences at the University of Arizona. Ed Curry, farmer and owner of Curry Seed and Chili in Pearce, Arizona. Gary Nabhan is a research scientist at the University of Arizona and author of "Why Some Like it Hot: Food, Genes, and Cultural Diversity." And Gary mentioned before - talked about a wild chili botanical reserve south of Tucson that is down there. I want to introduce my next guest, Jean England Neubauer. She is with us. Anyway, welcome to Science Friday.

Ms. JEAN ENGLAND NEUBAUER (Owner, Santa Cruz Chili and Spice Company): Thank you. It's great to have you here.

FLATOW: Tell us about this reserve.

Ms. NEUBAUER: Well, actually, my family is head of the grazing rights on the Rock Corral Canyon down south of Tucson since 1900s. And we also have a chili company called Santa Cruz Chili and Spice Company. So when Gary Nabhan came to me and he and some friends, they've been out researching and camping out in the desert and he said, I think up on your grazing reserve. We found some very unusual chiltepins and I'd like to go in to call for cooperation and put together a biological reserve up there. So we were very, very excited and happy to work with Gary.

FLATOW: What do you do on the preserve? What goes on there?

Ms. NEUBAUER: Well basically, it's just - is an effort to protect the environment where these chilies - these chiltepins are actually growing. And one of - part of the research we did is because we have a cattle grazing operation up there. We wanted to be sure that they could be compatible. And Gary came to us and said that they're absolutely were compatible. And essentially, they're just there for us to sort of take care of and make sure that nothing happens to them.

FLATOW: Now chiltepins are some of the hottest chilies you can get.

Ms. NEUBAUER: They're very hot. They're very hot.

FLATOW: They're way over the 500 number that (unintelligible).

Ms. NEUBAUER: You know, I'm not sure what's the Scoville on chiltepins.

Dr. SILVERTOOTH: Chiltepin is probably going to be in 50 to 100,000 range.

Ms. NEUBAUER: There you go.

FLATOW: Wow!

Ms. NEUBAUER: But they're great. They're full of flavor and they are just wonderful. You know, people use them sort of for medicinal purposes...

FLATOW: Right.

Ms. NEUBAUER: In terms of firing up your menudo and things like that. That's very good you.

FLATOW: So you don't want to ever bite into one of these...

Ms. NEUBAUER: Oh, sure you can.

FLATOW: (Unintelligible).

Ms. NEUBAUER: I'm sure you can. Sure you can.

FLATOW: Without a glass...

Ms. NEUBAUER: Yeah. But you have to be careful.

FLATOW: You have to be careful.

Ms. NEUBAUER: Yeah. You have to be really - you really need to love your hot chili.

FLATOW: Thank you very much for taking time to talk with us today.

Ms. NEUBAUER: Sure.

FLATOW: We'll be ready for questions later.

Ms. NEUBAUER: Thank you.

FLATOW: That's a hot chili pepper.

Mr. CURRY: As I think about, I'm not exactly for sure on that. Habanero was 150 to 300,000. But a chiltepin is very hot. I don't know the number. I'll be honest with you. I don't know. It is hot.

Dr. NABHAN: It's 50...

FLATOW: Go ahead.

Dr. NABHAN: It's 50 to 100,000, I think you hit it on the mark. So it's...

Mr. CURRY: Thank you, Gary.

Dr. NABHAN: Several times less than the habanero is, of course, many less than this Bhut Jalokia chili. That's the reigning king of heat, which is up over a million Scoville units now, and it's a chili from India.

FLATOW: And people can eat that. Gary...

Dr. NABHAN: Well...

FLATOW: Gary, are there certain cultures that are able to eat, you know, hotter chilies than others?

Dr. NABHAN: Cultures have become accustomed to this - to eating spicy food. In tropical climates, we have a number of cultures that seem to have a predilection for spicy foods. But there's something in the genes that make people non-tasters of certain bitter and spicy compounds, where other people - largely people from the northern latitudes - may be super tasters. So, the same amount of Scoville units can affect two people, like my wife and I, very differently.

FLATOW: 1-800-989-8255. Let's see if we can - let's see if we can go to the phones. I got a couple of phone calls here. And maybe get some questions about chili peppers. Let's go to Patricio in Chicago. Hi. Welcome to Science Friday.

PATRICIO (Caller): Hi. How are you doing?

FLATOW: Hi, there.

PATRICIO: I was wondering if you could talk about the difference between hot chilies and spicy chilies. It's been my experience that I like spicy because they're full of flavor and the hot ones are just burning.

FLATOW: Hot spot. All right, OK, anybody want to take on that one? Jeff, Ed?

Dr. SILVERTOOTH: Well, probably it's a function of taste and semantics a little bit. Every type of chili has a different flavor with it. They come from the flesh and the structure of the chili itself. And so, a hot chili might just be, you know, let's say, 100 to 500 Scoville units - extremely hot. Spicy chili would be even higher than that. So it's probably just a matter or particular taste and preference.

FLATOW: Gary, any comment?

Mr. CURRY: Well, there's many flavor compounds in chilies. And most good chili breeders like these guys are going for the flavor not just the heat. And so, we tend to spend an inordinate amount of time just talking about where they are on the Scoville scale that clearly, habenero or a jalapeno tastes very different from the fine, spicy chilies that are coming out of southeastern Arizona and New Mexico that I feel have been selected for flavor over decades.

FLATOW: You know, we know that salsa has surpassed ketchup sales in this country. Is that a good thing for bringing back some of these wild chili varieties, Gary, that may be dying up?

Dr. NABHAN: Well, we have fragmented in declining populations of wild chilies where some of the land managers aren't as conscientious as Jean and her husband, and her mother and father before them who had been fine managers of the land where the wild chilies grow. But we also know from our Renewing America's Food Traditions project that we have dozens of traditional heir-loomed chilies like the fish(ph) pepper and the datil chili pepper and chimayo and elwikei(ph) chilies from New Mexico that are now not only in decline, there's fewer and fewer farmers growing them. But we also know that they've been contaminated by accident, out crossing with other varieties, so they don't have the - always a characteristics that they were first bred for and known for. Their skin thickness may change or their flavor may change due to this accidental out crossing with other varieties. So, Renewing America's Food Traditions based at Slow Food U.S.A., is trying to get local communities to champion these different chili varieties as part of our cultural heritage, not just our natural heritage.

FLATOW: Ed, are you more interested in looking for some of these wild chilies or breeding your own? Are you breeding them, you know, in a new way or using the old Mendeleev sort of...

Mr. CURRY: Oh, definitely the old way.

FLATOW: Yeah.

Mr. CURRY: Definitely. Dr. Steve Hansen in New Mexico States works with this on possibly doing some transgenic things. But it's - chili is very diverse genetically so, it's very difficult. That has been a long process. But let me back up on that flavor profile just a minute.

FLATOW: Sure.

Mr. CURRY: To hit the nail on the head. Thank you, Gary. There's many flavor compounds. Dr. Benvy, alone at Texas A&M, spent years working on flavor compounds and then Philby and myself - Phil made many crosses. We took them to the farm, grew them out, segregated them, isolated them. For instance, a chili ancho - if you're familiar with ancho or flavano(ph) - tends to have a high rate of chlorophyll in it. It has a chlorophyll retainer gene. That in itself causes it to be a deep dark green, gives it a different flavor. But then there's starch genes or sugar genes that when you start combining those - the fellow that called in and asked about flavor versus heat, that's exactly - one of our challenges is, years ago when Arizona 20 that Phil bred became the standard of the industry, that was a great yielder, a great canner, and the heat level was very stable in it. But the flavor was very bland.

So, then they came back and he said, hey, can you guys improve the flavor? So, through crossing - there's many, many ties. But for instance, the wahil(ph). The wahil chili is a high-oil content chili, dry and has a much different flavor than it does green. We crossed the wahil with an Anaheim type, the Mexico 6 type, if you will. And we got a complete different set of flavors out of that thing than we ever expected. So breeding is so fun. I feel so blessed to be able to work with Phil because through the years, we made so many crosses and seen so many different things. But that flavor profile thing is really, really an interesting subject. It is not just heat. Heat is important.

FLATOW: Right.

Mr. CURRY: But it's not just heat.

FLATOW: Jeff, we're here in the desert southwest and you mentioned that there was a - the chili belt. But what if - if you had to depend just on the rain for growing chili here, would you be able to do that or you have to depend on irrigation?

Dr. SILVERTOOTH: We could probably keep a few plants alive, but we wouldn't do well with regard to yield and production from an agricultural standpoint. You know, farmers like Ed would have a hard time making a living on what they would produce just from natural rainfall, which across the chili belt, there's approximately about 10 to 12 inches a year in terms of annual precipitation. And these chilies actually require - and that's one of the projects we have right now, to find out how much water do they require, how do they - when do they require that water and what are the different rates of consumptive use that they have over the course of season. It's about 32 to 35 inches of water that the plant actually uses as we call it through (unintelligible) transpiration or consumptive use out of the system.

FLATOW: Uh huh.

Dr. SILVERTOOTH: Much more - a quite a bit more than what natural rainfall would provide.

FLATOW: Oh yeah. OK. Question in the audience here, sir.

Unidentified Man (Audience): I've always wondered what is - why do the wild chili plants have that heat? What advantage does it have for them? Does it attract fruit eating wild animals or detract them before the seeds are ripe? Or what's the deal there?

FLATOW: Gary, do you want to tackle that?

Dr. NABHAN: Well, I've spent about 15 years of field time on that one with my buddy Jack Stutchbury who's been on Science Friday before. And what we found is that those capsaicinoids pick one compounds in chilis repel mammals who would consume the seeds. And also they repel or resist molding in the fruits, so that the seeds don't die that way, but ironically the seed dispersers of chilis, which are a number of birds including cardinals and pyrrhuloxias don't taste that heat. So, ironically birds like some people are non-tasters of the capsaicinoids and so, they readily seek the chilis out for their oils and their flavor compounds that they do pick up. And they benefit from the many rich vitamin compounds in chilis. So, essentially I say, when my little son asked me why chilis are hot, I say so birds can disperse them to nurse trees and other critters will not.

FLATOW: I tell you my squirrels have no problem with them and I've grow hot chilis I thought - in my pots on my backyard, and I thought this will keep the squirrels out. But, boy, this is - they're chomping on the green chili just laugh at me as it's coming off the flask.

Unidentified Man: Can I interrupt your...

FLATOW: Sure.

Unidentified Man: Gary, I tell you an interesting story in our cayenne breeding blocks. We had a problem with a particular cayenne that was too mild, and one year my farm manager came by and he said man, did you see the deer really ate riddle that cayenne blocks. Well, upon closer notice we found that the deer did us a great favor from a breathing stand point. We were looking for hot. They ate every mild cayenne plant out there and they left every hot one. It saved us three or four years in breeding work.

(Soundbite of laughter)

FLATOW: Wow.

Dr. NABHAN: Well, let me tell you another story about this interaction between mammals and chilis. When I worked at the Arizona-Sonora Desert Museum, the great natural history zoo outside at Tucson, we had tremendous bills for bird feed in the aviary out there. And we realized that most of that bird seed wasn't being eaten by the birds at all that we are trying to interpret and present to the public, but that desert mice and house mice, and rats had gotten into the aviary and they were eating most of the food.

So, we laced the birds seed with food and the next night and for the next week, the rats and mice just disappeared from that aviary and it was like chorus lines of mice and rats back in the desert again trying to find food because they've grown sort of accustomed to the bird seed. And we basically reduced the desert museum bird seed budget by several hundred dollars a month by using the capsaicin to repel the small mammals.

FLATOW: Uh huh. You're listening to Talk of The Nation, Science Friday from NPR News. I'm Ira Flatow in Tucson. And up the microphone, sir.

MATTHEW (Audience): Hi, there. My name is Matthew, and I've live in Tucson now for four and a half years. And this year, I tried to plant in my garden and only chilis because I wanted something easy. And they're trickier than I would have thought that - I had a hard time making it through the summer heat, and like I have bunches of wilted ones now. I think I over watered them. I mean, I - what I would like to do is to take you to my house and get you theā€¦

(Soundbite of laughter)

FLATOW: Well, let me (unintelligible).

MATTHEW: But, my question generally is what's good for chilies and I mean how do I get them as big as the ones you brought in. And I mean, but just generally what kind of conditions or other tricks that I can use to grow better chilies?

FLATOW: Jeff.

Dr. SILVERTOOTH: Actually, that's you've got - he had a good point there. They are really sensitive plants, very sensitive plants. We talked about the climate conditions that they like and they're kind of particular about not too high and not too low, not too hot air conditions, but just hot enough. And they're also very particular about their water requirements as well. So in this case we described a while ago they use about 30 or 32 inches of water of over the year. But, we call of (unintelligible) to its fill capacity, it's full of its water like after you irrigate and the water drains away, we call it fill capacity. And as a soil it begins to dry. It drops in as what we called plant available water level.

Now, chilies are sensitive. They'll only ever grow when it gets a little drier, but they like that range about 75 to 80 percent plant available level to fill capacity. And now, you take another plant like say, squash plants or zucchini or tomatoes that you put in your garden as one they'll tolerate - a drier soil. The chili plants are sensitive to too much stress, when you over water them and they're sensitive to that. They have kind of - not really -what I call - I kind of make fun of them sometimes. So they have kind of a little weak little root system. They're hard working plants if you actually can get them to fruit and do well, and that's what this is really kind of cool about watching guys like Ed and the good farmers that are dealing this - they walk that fine line. That kind of razors edge between not too much water, but just enough.

FLATOW: Yeah.

Dr. SILVERTOOTH: And they're also sensitive to disease.

FLATOW: I've only got one minute to get - to go. Ed, I want to ask you what would be the perfect chili that you're looking for. I'll give you a blank check. What would you like to and how can you make it?

Mr. CURRY: Well, I brought that.

(Soundbite of laughter)

FLATOW: Well, describe them. What makes it so perfect?

Mr. CURRY: Two-walled, six, seven, eight inches long, a rounded shoulder, it needs to de-stem quite easily. It needs - for the canning industry it needs to have a Scoville unit of 100 - a 50 to 150 no more that needs to be the range. And a high yield for the farmer. They will be able to set 15 to 25 peppers on one plant. That would be the perfect pair for them - for the canning industry.

FLATOW: So you're pretty happy with the industry now.

Mr. CURRY: Oh my goodness. We have so much left work to do. We've got to live to be 150 years old to solve this thing, you know.

(Soundbite of laughter)

Dr. NABHAN: And the issues I think is that we now we have all these other uses for chilies like you've said the pigments and my closing thought is that you can put pepper pigments on the pig, but it's still carne adobada.

FLATOW: OK. I can't top that. I can't touch that, unless Jeff you want to weigh in. But, we'll - quick, ten seconds.

Dr. SILVERTOOTH: Well, I would say that any kind of corporate production system is a function of art and science. And this is a good example of what we've discussed today as an art to walk that fine line and the management, and kind of get a feel of the personality of the plant. And what we're trying to do is find a little more science and bring the science into - and quantify the process.

FLATOW: There you have, Jeff Silvertooth, professor and head of the Plant Sciences Department at the University of Arizona in Tucson. Ed Curry Farmer and owner of the Curry Seed and Chile Company in Pearce and Gary Nabhan, Social - Research Social Scientist at the University of Arizona, author of "Why Some Like it Hot: Food, Genes, and Cultural Diversity." Gentlemen, thank you all.

(Soundbite of music)

Mr. CURRY: Thank you very much for taking to visit us.

FLATOW: You're welcome. Stay with us we're going to shift gears and come back and talk about astronomy and why Arizona's sky is so great for it. We'll be right back after this short break.

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FLATOW: I'm Ira Flatow, this is Talk of The Nation, Science Friday from NPR News.

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