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An education in taste

Yale Medicine Magazine, 1999 - Spring


A conversation with Linda Bartoshuk, an expert on the physiology of taste, and Jacques Pépin, celebrity chef and cookbook author, explores the many facets of taste.

Taste is one of the most fundamental yet most complex of all human experiences. It of course begins on the tongue, but it also embraces all of the other senses as well as each individual’s genetic makeup and life experience. In many ways, taste is as unique as the individual. Nonetheless, there are certain universally appreciated tastes. But what does taste mean for two people who have devoted their professional lives to studying it from very different perspectives? On behalf of Yale Medicine, contributing editor Marc Wortman invited renowned chef and author Jacques Pépin and Linda Bartoshuk, a leading authority on the biology of taste and on the treatment of oral pain, to share their views on taste over lunch at the Union League Café, one of Connecticut’s most noted French restaurants.

Born in France, Jacques Pépin, M.A., was raised around fine food at his parents’ restaurant near Lyon. He was the personal chef to three French heads of state, including Charles de Gaulle. He is the author of a number of groundbreaking books on French culinary technique, as well as cookbooks published in conjunction with the cooking shows he has hosted on public television over the past 10 years. Holder of a master’s degree in 18th-century French literature, he is a faculty member at Boston University. He lives near New Haven and has provided the School of Medicine and Yale-New Haven Hospital with frequent fund-raising and other assistance.

Born in South Dakota, Linda Bartoshuk, Ph.D., has been a member of the faculty since 1971. Her research has opened up broad new avenues in the study of the physiology and genetics of taste. Her more than 100 articles on the subject have established the importance of the genetic basis of taste preference and its impact on health in many areas. She has demonstrated the significant anatomical differences, most importantly taste bud density, underlying taste preferences. Her work with taste has also improved the treatment of oral pain in cancer patients and people with neurological damage resulting in loss of taste. Bartoshuk was a contributor to The Yale Guide to Children’s Nutrition [Yale University Press, 1997].

The following excerpt from their two-hour conversation begins with a discussion of the artistry that goes into exceptional cooking and its parallels in the realm of science.

Not on the menu

LB: Part of being a great chef is obviously learning and experiencing and repeating dishes over and over.

JP: Exactly. It’s never using the recipe. That’s why a chef must understand the food. If you’re able to taste a dish somewhere, and you say, “Gee, that’s a really good idea,” that’s all you need to know. But if I do a recipe for the New York Times or a new cookbook, then I have to say how long it stays in the oven and how hot the oven should be, because the editors ask. They’ll say, “How long was it in the oven?” “Well, 35 minutes,” I answer. Now I am stuck with those 35 minutes, and it will probably never happen to be 35 minutes for someone else. The fact of writing the recipe down destroys the recipe by definition. Because as you write it down, you tell people, “This is the way it has to be done.” It’s never the way it has to be done. It just happened to be the way I did it this time because the chicken looked a certain way and I reacted to its look. And then I increased or reduced the heat or I added a cup of water because the situation demanded it. And yet the chicken will never react exactly this way the next time, and the adjustments will be different. The important thing is the taste at the end of cooking.

It is hard to get someone to understand that this is what professional chefs do. You have to change the recipe each time to get to the same taste, because nothing is ever the same. You have to go beyond the recipe to understand how the food works.

LB: That’s why it’s an apprenticeship to learn to be a good cook.

JP: Sure. In the laboratory, how could you give somebody the formula for science? I mean, could you provide a recipe for thinking through a problem?

LB: In a sense, it’s the same thing. The difficulty with doing basic research is you tend to want to purify the experience to the point where you can study it in a laboratory under great control. And that’s all well and good. But you then take the richness out of it, and it’s no longer like real experience. On the other hand, the expert uses judgment at every step in order to make certain that you get to something at the end. For example, suppose I am testing a group of patients and I want to learn something about them. The nature of the patient determines how I’m going to interact with the patient. I might have someone who’s extremely anxious or cognitively impaired and really can’t follow what I’m trying to do. And I’m going to change the whole way I behave. Some of my students will get upset because I’m not rigidly doing it the same every time. They’ve learned in books that to do science you have to be rigidly the same. And I say, “No, you have to make sure that people comprehend at essentially the same level.”

JP: To understand, you have to interpret. You have to recognize an innate pattern in the making of each recipe. And I suppose, to a certain extent, what you do is the same—because even after you’ve tested a group of patients, you have some data that applies directly to each person on that particular day, but will not be the same on another day with the same person, and it will be different with someone else. So to a certain extent, the result of those tests has to be looked at with an open mind and as a guideline.

LB: That’s right. What makes one expert better than another is the ability to have insight about what variables are going to really matter, and to control the ones that are really going to matter. And that’s one of the reasons why you get inferior science. Genuinely inferior science occurs because people don’t have a feel for what needs to be controlled.

JP: That’s why you get inferior dishes, also, because cooks believe too much in a structured recipe. It’s never the way it has to be done.

The varieties of taste

LB: Can you imagine a particular flavor in your mind? That is a rare gift. Most people cannot do that.

JP: As a professional chef, I believe I can do that. I can formulate a recipe in my head and “taste” it on my tongue. I know it’s going to taste this way. After 50 years of cooking professionally, I am technically good enough to control the food, although you never control it entirely. I did three recipes at home last night. And I knew more or less what they would taste like. After a bit of a correction here and there, I got pretty close to what I imagined.

Shall we order? I think I’m going to have that tuna. It looks great.

LB: I’m having what you’re having. Can I suggest since the artichoke induces a taste effect in some people, that we have that artichoke bisque? Some people are genetically sensitive, so that after they eat artichokes things taste intensely sweetened for a period of time. I get it incredibly, which is why I started working on it.

JP: It’s interesting, because we shouldn’t serve wine with artichoke, likewise we shouldn’t serve it with asparagus.

LB: The same compound is found in asparagus; it’s an isomer of chlorogenic acid. There is tremendous genetic variation in our ability to taste. One thing that we’ve learned in the last few years is that these genetic variations are much greater than we suspected before. For example, a supertaster has many times the number of taste buds and is tasting two or three times the intensity of sweetness from ordinary sugar as a nontaster, like me. The supertaster can find broccoli too bitter and hot peppers too spicy. The nontaster won’t react to these tastes nearly as much.

You also have some genetic variation in olfaction. But even more important than the genetic variation, you have life-span variation. Olfaction begins to decline at about 40 years of age, and it declines quite steadily. We don’t know if that’s a true age effect or if it’s due to pathology, because your olfactory system is so exposed to viral illness.

In any case, as you age, your ability to smell is lessening steadily. And your ability to taste is not, not nearly so much. The main effect of aging on taste, we think, happens to women at menopause. The ability to taste bitter is a poison detection system. And it looks as if the body has arranged it so that women vary in their ability to taste bitter, depending on whether they are protecting a fetus. There’s variation with the menstrual cycle, and it appears to make women heightened responders to bitter early in pregnancy so that they become very good poison detectors. Once you’ve been pregnant, you’re always a little more sensitive to bitter than you were before. At menopause, it falls off a cliff, and women become much less sensitive to bitter than they were.

JP: Would that be what they call species adaptive behavior?

LB: Yes. It is very adaptive for the species. Then you might ask, “Why would you want genetically different groups of bitter tasters?” As a nontaster, I can barely taste some bitters, and a supertaster, as I suspect you are—we’ll find out—is exquisitely sensitive to bitters. The answer appears to be that there’s a selective advantage to either group, depending on the environment you find yourself in. If you’re in a really dangerous environment with a lot of poisons, the supertaster has the advantage. The supertasters will survive and the nontasters are likely to die off. But in a safe environment, where you have a lot of plants that are actually safe, but taste bitter, like certain mushrooms, the nontaster has the advantage, because the nontaster will eat that mushroom and have a bigger food world. The supertaster will avoid it. In the modern world, we suspect that this might be a health risk. For example, right now, one of my colleagues, Adam Drewnowsky, believes that women are at greater risk for breast cancer if they’re supertasters because they avoid certain bitter-tasting fruits and vegetables that protect them from cancer. We think the same thing might be true in colon cancer. In the modern era, we have to reassess.

Eating through the nose

LB: This soup is wonderful.

JP: As a nontaster, are you missing something that a supertaster might be experiencing when tasting this soup?

LB: No. This is primarily olfactory. There’s very little genuine taste here. Maybe a little salt. But for the most part, this is entirely olfactory. Notice that as you swallow, you get the bouquet. This is the second biological function of the nose. It’s called retronasal olfaction. You swallow and chew, and the air, with all the odors in it, is pumped up into your nose. Your nose is perceiving the odor the entire time you’re eating. The brain uses smell and taste together to create flavor. Perceptually, you believe the olfactory experience is coming from your mouth, because taste and smell are both perceptually localized by touch. If your mouth is feeling the food, the olfactory sensation will seem to be localized in the mouth.

JP: I see the world of smell affecting memory. That’s very important, because the effect of memory improves the taste of a glass of wine or a soup. It’s much more powerful when the memory of an event comes through the senses, particularly smell. If you asked me, “Where were you on such and such a date in 1978?” my brain may be able to recall the details, but the recall will be dry and unemotional. On the other hand, the memory of the senses has the element of surprise; it affects you deeply in an intimate way, when you don’t expect it at all. You walk through a room, and all of a sudden you smell something and you’re 5 years old again. That smell enables you to relive something through your senses in a much deeper and clearer way than something that is brought about deliberately by your brain. For a chef, and certainly for food critics, this memory of taste and smell is important. Affective memories are more important for us than the memories of the brain.

LB: Let me step back for a minute, because there are many things going on there. Taste is very different. The emotional effect of taste is not acquired at all. It’s all present at birth. In fact, it’s present before birth. You’re born loving sweet and hating bitter. And your experience has very little to do with that. Taste is first of all sweet, salty, bitter and sour. These are what we perceive through the taste buds. The taste buds also have another sensory role. They’re surrounded by nerve fibers responding to pain, temperature and touch.

If you’re a supertaster you are born with a different anatomy. You have fungiform papillae, which are the little structures that hold taste buds. You have many, many more of them if you are a supertaster. It is like reaching up and feeling something with 500 fingers as opposed to 50. The texture that a supertaster feels is quite different.

Then there’s smell. Smell is iced tea, lemon, roast beef—much more complex and subtle than taste. The way we learn smells is particularly interesting in the light of what you’ve been talking about. When you’re born, you have the capacity to smell a tremendous number of different molecules, but they don’t mean anything to you. Perhaps the mother wears a certain perfume, and so the baby learns to recognize that particular mixture of odors, because the perfume is complex, as many things are. The baby recognizes it after repeated pairings, and now that perfume takes on tremendous positive valence, because it’s associated with comfort, with the mother.

That memory, once learned, will stay in your brain for your lifetime. If you were to walk into a room years after you ever smelled it and smell it again, you’d be flooded with the feelings associated with that memory of when you were young. And with your exquisite experience as a chef, you’ve built up a library of experiences far more complex and subtle than I have. You learn those things when you’re very young, and they’re very powerful. They control your pleasure.

JP: Taste can be experienced in different ways. I always say that food critics should be blind, so they can tell you what’s good or not good. But, unfortunately, very often they are influenced by many other things: the presentation of the food, the setting and so on, which make it so subjective. On the other hand, the food can be many things. It can be something simple, straightforward and tasty, or it can be a symphony of different tastes. For example, when you do a pork chop, you want it to taste like pork, and it’s good. Now if I take that pork and grind it and put cognac, white wine and shallots with it and different types of seasonings, too, I do a paté. The paté now is delicious. But it does not taste like pork any longer. It’s more of a mixture of different tastes, culminating in the taste that we call paté.

If, as they do in France, you cook apple with butter and sugar on top of a dough, you have an apple tarte. If you make an apple pie in the American style, with cinnamon, nutmeg, mace and butter, you have lost the taste of apple but have created another taste with this combination. So you have transcended the taste of apple and created a symphony by combining different ingredients.

LB: We know a lot about the pleasure that is associated with those experiences, believe it or not. One of the amazing things about olfaction is it has this ability to take components and relearn them in combination. An apple, cinnamon. Your brain learns a template that’s a holistic sort of map of this, and you learn it as a new whole. The apple pie is a new template. It’s not the same as the apple template mixed with the spice template.
Here’s the important property of olfaction: Those templates acquire pleasure. The more templates you have, the more pleasure you can acquire. Because of the way olfaction works, as soon as you can identify an odor, you acquire the emotional valence—that is, it’s either good or bad—based on your experience. The acquisition of affect to olfaction is very vivid, very powerful and very hard to lose.

The love of calories

JP: One way of learning about food is to go to have the real McCoy—a dish the way it is supposed to be prepared—so that you can put that in your taste memory and draw from it eventually. You learn that’s the way it should taste. I remember going to China many, many years ago. I knew a fair amount of Chinese cooking at that time, but when I was in China I was exposed to ingredients and tastes that I had never experienced, and some of these tastes were pretty weird. So I asked, “Is it supposed to taste this way? Is this for real?” I tasted these dishes several times, trying to put them somewhere in my taste memory so I could draw from them at a later time. Often, tastes that are not pleasant to start with eventually grow on you.

LB: But see, that taste to the Chinese has been paired with all kinds of reinforcing experiences, including calories. One of the main ways to make something loved is to pair it with calories. It’s a survival mechanism. And that’s why we all love high-fat food. The problem is that, in the short term, eating calories, salt and sugar is very good for you. In the long term, it leads to chronic disease. We live in a culture that has learned they’re bad for us, but our brains are living in a world where they are good for us.

JP: And there’s a paradox there.

LB: That’s a paradox. And you can’t solve it. There’s no free lunch here. One of the problems our culture has to solve is, “Are we really going to ask people to eat foods that they were not evolved to love and tell them they are healthy?” That’s not easy. So how do you do it? How do you trick people into learning to like things that have less fat, less sugar, less salt? Part of it has to be social conditioning.

JP: I feel that the conditioning is extremely important when you are small, because it will stay with you for the rest of your life. I like asparagus fresh and lightly steamed. My wife was born in New York City, and as a child she was served canned asparagus by her mother. She now loves fresh asparagus, too, but she still has that taste for canned asparagus because that taste is associated with her youth.

Likewise for me, a Frenchman who’s now an American, I learned how to make an apple pie with cinnamon, nutmeg and mace, and I now like it. But it will never have the same resonance for me that it does for my wife, because it’s something she had when she was a child. For me, a piece of crunchy baguette with dark chocolate, which is what I ate as a snack after school as a child, is still a true delight. While my wife likes bread and chocolate now, it will never mean the same thing for her as it does for me because she never had it as a child.

LB: You know, there’s a name for that. It’s called comfort food.

JP: Yes, of course.

LB: See, ordinarily I wouldn’t try this type of food, a tuna tartare or an artichoke soup. But because you know it’s interesting and you ordered it, it takes on very special positive characteristics for me. I look at it and say, oh, this is going to be interesting. I approach it with a completely different attitude.

JP: It’s true. And it works both ways. When I had a restaurant, many people came because they knew me and liked me. For these people, even if I screwed up and the food was ordinary, they still loved it. They were conditioned; they liked me, and I could do no wrong. Then we had the reverse. We had a guest who would say, “Let’s see what the big famous chef can do. Let’s see what the big deal is.” Each time he tasted something, regardless of how good it was, he would question it and find fault with it. There’s nothing you can do.

The PROP test

LB: We need to find out if you’re a supertaster. Let’s try this simple test we’ve devised. This piece of filter paper has 1.6 milligrams of a chemical called propylthiouracil, or PROP, on it. If you were being treated for thyroid disease, you would take 200 milligrams per day of this chemical, so this paper contains really a trivial amount. Let me demonstrate. What will happen when I taste it is absolutely nothing. I don’t have enough taste buds. It will taste just like paper to me, and, if we photograph my tongue, we will see that my fungiform papillae are so widely spaced that they look like polka dots.

I am going to guess that you are going to taste this paper as bitter, and that, if we photograph your tongue, your fungiform papillae are going to be just side by side.

JP: You just put it on your tongue?

LB: Just put it in your mouth.

JP: Oh boy! Very bitter.

LB: See, I told you. You have all the earmarks of a supertaster.

JP: It’s disgusting.

LB: Absolutely nothing for me.

JP: Oh boy, it was really bitter.

LB: No taste. It’s genetic, purely genetic. You are probably carrying two dominant genes for this characteristic and I carry two recessive.

JP: There is also a recessive gene?

LB: Yes, yes. Not surprisingly, it seems to have a big effect on people’s lives. For instance, we visited the culinary school at Johnson & Wales and tested students. They were virtually all supertasters. Men are more likely to be nontasters; it is women who are more likely to be supertasters—probably to protect the fetus. Yet most of the students were men. Finding all these male supertasters who are experts at food is extremely interesting, and this is not an accident. You were born to it.

JP: And learned to love the experience of taste.

LB: And to share that love.