도서] why people like junk food

조미, 요리 ≫ 미식 ≫

미식이론 : why people like junk food

미식 평론, 평론가
- 그루망디즈, 맛 컬럼리스트
- 미식 평론가의 역할
- 샤바랭 : You are what you eat 의미변질
- 미식의 단계, 맛집 = 맛쇼
- 한국 차문화가 중국에 밀리는 이유
- 신경미식학,  분자 미식학

Fundamental Principles of Food Perception and Pleasure
Chapter 1: Food Pleasure Theories and Principles

Why We Like Our Favorite Foods
Chapter 2: Why We Like Corn Tortilla Chips
Chapter 3: Why We Like Sandwich Cookies
Chapter 4: Why We Like Vanilla Ice Cream
Chapter 5: Why We Like Butter
Chapter 6: Why We Like Gourmet Coffee
Chapter 7: Why We Like Popcorn
Chapter 8: Why We Like Donuts
Chapter 9: Why We Like Garlic
Chapter 10: Why We Like Toasty Sandwiches
Chapter 11: Why We Like Hamburgers
Chapter 12: Why We Like Southern Fried Chicken
Chapter 13: Why We Like Diet Vanilla Soda
Chapter 14: Why We Like French Fries
Chapter 15: Why We Like Spices
Chapter 16: Why We Like Chocolate
Chapter 17: Why We Like Artichokes
Chapter 18: Why We Like Pizza
Chapter 19: Why We Like To Eat Dessert Last

Secrets of Great Cooking and Cuisine Design
Chapter 20: Secret-Weapon Pleasure Foods
Chapter 21: Culinary Secrets of the Top Chefs
Chapter 22: Eight Most Common Cooking Mistakes
Chapter 23: Tasty Home Cooking and Healthy Fast Food: a Summary


Major Food Perception Theories
1. Food Pleasure Equation (Hyde/Witherly)
   Sensation Plus Calories
   Taste Hedonics
   Emulsion Theory
   Salivation Response
2. Dynamic Contrast (Hyde/Witherly)
   Ping-Pong Pleasure Contrast (Hyde)
   Tostada Effect (Witherly)
   Meatloaf Effect (Witherly)
3. Sensory Specific Satiety (Rolls) or “Variety Effect”
4. Supernormal Stimulus (E. O. Wilson)
5. Evoked Qualities (Hyde) a/k/a Emeril “BAM!” Effect
6. Flavor-Flavor Learning (Pliner)
7. Mere Exposure Effect (Pliner)
8. Taste-Aversion Learning (Bernstein/Rozin)
9. P. Rozin’s Principles of Food Likes and Dislikes
   Disgust Theory
   E. Rozin’s Flavor Principles
10.  Energy Density Theory (Drewnowski)
11. Vanishing Caloric Density (Hyde)
12. Post-Ingestional Conditioning (Booth, Capaldi)
13. Human “Cookivore” Theory (Wrangham)
14 Aroma and Essential-Nutrient Encoding (Goff and Klee)
15. “Liking” Versus “Wanting” Theory
16. The Stomach: the Second “Taste” System

Six Most Important Food Theories:
- Taste Hedonics (salt, sugar, and umami)
- Dynamic Contrast (food arousal and surprise)
- Evoked Qualities (when food sensory properties evoke past memories)
- Food Pleasure Equation (Food Pleasure = sensation + macronutrients)
- Caloric Density (humans like food with a CD of about 5.0)
- Emulsion Theory (taste buds love foods in emulsified forms)

 

Food Perception Theories

The reality is that scientists know very little about food choice or preference.4 Food pleasure appears to involve both the opioid and cannabinoids reward circuitry that interact in complex ways.5 Moreover, if we wish to understand the nature of overeating and obesity we must explore the science behind what makes food taste good.6

1. The Food Pleasure Equation

Food Pleasure = Sensation (Taste, Aroma, Orosensation) + Calories (Macronutrients)
Food pleasure is a combination of sensory factors (sensation) and caloric stimulation by the macronutrients (protein, carbohydrate, and fat). Sensory factors that most contribute to pleasure are salty taste, sweet taste, umami taste, and orosensation from the oral cavity (feeling). Aroma is important in food discrimination but not a primary hedonic driver like taste. Dynamic Contrast in the food plays a major role in food pleasure (texture and taste contrasts, food meltdown, and temperature changes).
The body regulates all three macronutrients with intricate feedback mechanisms—but uses the total amount of calories as the general sensor. And as we will learn, high caloric density foods are preferred over lower—brain scans show a reduced hedonic response when subjects view a plate of vegetables versus a higher calorie alternative. Depressing, isn’t it?
The Food Pleasure Equation postulates that the brain has the ability to quantify the pleasure contained in an eating experience as performed by certain dopamine neurons in the brain and the sensing of calories by the gut. When you have a food choice, the brain actually calculates how much pleasure will be generated during the eating and digestion of a particular food. The goal of the brain, gut, and fat cell is to maximize the pleasure extracted from the environment, both in food sensation and macronutrient content. If a food is lowered in calories for health reasons, the gut has the ability to sense this, and the food will become less palatable over time (think frozen yogurt or light potato chips). To keep the food pleasure elevated, one must add additional sensation, e.g., more taste, greater dynamic contrast, or added orosensation. The biggest mistake I see in the commercial marketplace is creating a light food (that tastes and looks exactly like the original) without adding more pleasure sensation(s). Given the choice of two foods exactly alike in sensory terms, the brain, with instructions from the gut and fat cell, will always choose the higher-calorie original.

B. Taste Hedonics
As mentioned above, certain solutes (salt, sugar, MSG, and the 5’-nucleotides in solution) in foods contribute most to food pleasure. In numerous studies, we find that the taste of sugar, particularly sucrose, and salt drive taste hedonics and ingestion. Monosodium glutamate (MSG) taste, or “umami,” is now firmly entrenched as the fifth hedonic taste. Umami means “deliciousness” in Japanese and is believed to signal the presence of protein in your mouth. Protein, by itself, does not have much taste (try chewing on a raw steak if you are a skeptic). MSG, interestingly, does not have that much taste on its own either; kind of brothy and a little salty, but add sodium chloride to it, and the hedonic flavors just explode!

C. Emulsion Theory

Taste buds (and higher-order brain structures) like the taste of emulsions, whether they are salt-fat or sugar-fat combinations. The most agréable foods are true emulsions, whether they are butter, chocolate, salad dressings, ice cream, hollandaise sauce, mayonnaise, or crème. One major reason for this is the concentration effect of the hedonic taste solutes when made into an emulsion. For example, butter is about 2.5 percent salt by weight, but this level of salt is concentrated into the 15 percent water phase of the butter emulsion. In effect, the true salt concentration is 10 percent—a true hedonic salt rush.
French chefs are masters of emulsion creation, and the humble mashed potato is no exception. In the French Laundry Cookbook (p. 86), Thomas Keller describes the exacting technique of using a chinois (cone strainer) to create the perfect emulsification of potatoes, butter, and cream—or pomme purée. Chef Rowley Leigh, food columnist for the Financial Times USA, writes about the extraordinary (unctuous) mashed potatoes of French chef Joel Robuchon—finest ratte waxy potatoes emulsified with equal parts of unsalted Normandy butter.7  

D. Salivation Response
My salivation theory states that we prefer foods that are moist or evoke saliva during the mastication process. Saliva is critical for hedonic solute contact with taste buds; simply put, no taste, no pleasure. Saliva also fosters food lubrication and enhances the entire eating experience. Even dry foods like saltines have salt on top and a flaky texture that fosters salivation as it melts down in the mouth. Add fat to a dry food (potato chips are 50 percent fat calories), and you have additional oral lubrication—the perfect “salivation” food. Thin potato chips have a texture that melts down very quickly and stimulates salivary flow. The tastiest foods should evoke saliva or at least provide lubrication and moistness. Culinologists and great chefs know this secret. French chefs are masters of food saucing; Chinese (and Asian food in general) and Indian cuisines are almost entirely finished with a sauce or glaze.
We have all experienced “mouth watering” when presented with tasty food, especially when we are hungry. Salivation is tied into the whole experience of eating. And Temple et al. (2006) found that as we eat more of the same food, we secrete less saliva—we are actually habituating to the food in a manner similar to Sensory Specific Satiety.8 This amazing response actually means the food becomes less pleasurable as you continue to eat it, and you salivate less! Taken to another level, this means that superior cuisine that keeps you stimulated with texture, colors, and taste will not allow this salivation habituation response to occur. In fact, salivation to a food may be an independent measurement of how much you like it. (Dr. Robert Hyde and I performed a number of salivation experiments under the direction of Professor Rose Marie Pangborn at UC Davis.)

2. Dynamic Contrast (DC)

“So because you are lukewarm, and neither hot nor cold, I will spit you out of My mouth.” Revelation 3:16 (NASB)

The Witherly and Hyde theory of DC states that people prefer foods with sensory contrasts—light and dark, sweet and salty, rapid meltdown in the mouth, crunchy with silky, and so on. Temperature changes in the mouth are also highly arousing and pleasurable. “Ping-Pong Pleasure” refers to an ingestion pattern, in which people tend to alternate between foods that cleanse the palate, like drinking beer (which is low sodium) with salty snacks, or wine with food (wine is very low sodium and acidic). Studies indicate that the brain has a craving for novelty, which produces a “thrilling effect” via the release of brain opioids (endorphins).9 In fact, we used to call our theory “dynamic novelty,” wherein the mouth delights in texture, flavor, and orosensory novelty. In 2006, Biederman and Vessel proposed that humans are “infovores”; where pleasure systems (using mu-opioids) actually guide human behavior for learning (and preference for novelty) in a constantly changing or challenging environment—hence, the addictiveness of video and Internet gaming.9 In the same way, gustation and orosensation excite mu-opioids in the medial and forebrain sections (our pleasure centers), guiding our pleasures of ingestion.
Many foods with high DC have the same feature, which I call the Tostada Effect—an edible shell that goes crunch followed by something soft or creamy and full of taste-active compounds. This rule applies to a variety of our favorite food structures—the caramelized top of a crème brûlée, a slice of pizza, or an Oreo cookie—the brain finds crunching through something like this very novel and thrilling. No doubt, higher-order brain mechanisms release opioids—and probably a separate population of neurons distinct from the activation of the classic taste centers. This phenomenon name is derived from the only dish that I cooked in college that was popular with my roommates—sometimes we would eat it once a week. (Cooking the tostada shells can be hazardous; one roommate, while trying to deep-fry the corn tortilla, ignited the paper-towel rack with the hot oil. A well-aimed dousing with beer saved the apartment.)
The exact opposite of adding contrasting flavors, textures, and tastes is what I call the “meatloaf effect”, affectionately named after this most quintessential American dish that evokes sensory yawns and feelings of apathy—a taste bud dud. Top French chefs know this effect well and take great lengths to reduce or eliminate it entirely. Thomas Keller is one of the best at this—he crafted the French Laundry and Bouchon Cookbook recipes to eliminate the accidental blurring of sensation and diminution of pleasure. (See my chapter on secrets of the chefs). The meatloaf effect is very prominent in canned foods or in stews and soups that sit around for a long period. The intense heating called retort processing or, to a lesser extent, aseptic processing, transforms fresh and bright looking ingredients into muted colors and unidentifiable flavors. Not only does the meatloaf effect reduce food pleasure, but consuming such foods creates a bad-food memory complex. To this day, the taste and smell of a tinny, canned vegetable evokes the sensory shudders of my youth. Julia Child writes of this effect as well and provides culinary guidance on how to eliminate it.10 She describes culinary techniques that transform ordinary canned beef bouillon into a tasty brown sauce. I often use Thomas Keller’s favorite (fresh thyme and bay leaf) flavoring complex to revitalize sauces that use canned chicken or beef broths.

3. Sensory Specific Satiety (SSS)

SSS is a very important theory in food pleasure appreciation. It states that as we eat food, the pleasure response to the sensory properties of the food decreases within minutes. This involves parts of the brain (orbitofrontal cortex) that sense the taste, aroma, texture, and even visual aspects of foods.11 A decrease in pleasure response is the body’s way of encouraging the intake of a wide variety of foods—differing in flavors and textures. The opposite or reciprocal of SSS has been called the “variety effect” or the “smorgasbord effect,” wherein we eat more when presented with food variety. The SSS effect is quite rapid (as little as ten minutes) and has culinary implications for creating the most interesting and pleasurable food. Thomas Keller (of French Laundry fame), understands this effect, he calls it the law of diminishing returns, and specifically designs his tasting courses to counteract this negative effect on food pleasure.12

4. Super Normal Stimulus or Super Size Me

This is a long-held biology principle stating that rare and important stimuli in the environment (like energy-dense foods) become magnified and more desirable (or Super Normal) if made larger than expected—like a supersized order of French fries or the 1,400 kcal Monster Thickburger. Meat is a valuable and precious macronutrient in our evolutionary past, and half a heifer on a bun is visually exciting and stimulates the overall ingestive response. Several studies indicate that big portions excite the palate, and people just eat more. Although the super size phenomenon is waning, big portions are still the norm in many restaurants. Many of our favorite foods are supernormal combinations of salt, fat, and sugar that exceed anything available to our wandering ancestors. We evolved to crave these valuable and rare nutrients. Hence, we respond with an exaggerated eating response (hyperphagia) to the super normal sundae.
Super normal stimuli exist in other avenues, such as the entertainment world. The cartoon drawing of Jessica Rabbit (from the movie Who Framed Roger Rabbit) and, to a more limited extent, Barbie, are popular examples of obvious accentuation of physical attributes beyond normal physiological probability, with the intent of enhancing female desirability. For a discussion on this phenomenon, see E. O. Wilson’s book Consilience: The Unity of Knowledge.
Brian Wansink, marketing professor at Cornell and author of Mindless Eating, has studied this phenomenon and found that portion size can even supersede taste as a driver of ingestion.13 Similar to the supersize phenomenon in fast food, he found moviegoers given popcorn in large buckets ate 34 percent more. I can’t wait to read his book.

5. Evoked Qualities (EQ)

Dr. Robert Hyde’s hypothesis states that the act of eating food creates memories, not only the sensory properties of that food, but the event of eating, and even the people you ate with. This food-environmental experience creates a permanent memory engram. Later on, this memory can be “evoked” or relived by exposure to the sensory properties of the food or one’s mere presence in the same environment. Food cravings are often triggered by sight, smell, and caloric memories of restaurants past. One EQ example is Emeril’s ubiquitous use of his excellent “Original Essence” seasoning—or “BAM!” spice blend. It contains a number of culinary spices (onion, garlic, Italian herbs) whose aromas evoke past memories of food ingestion and happy times. And, according to the theory, one does not need to be consciously aware of the underlying memories being recalled. Neuroscientist Sarah Leibowitz has also noted that every food experience creates a sensory memory response to the food, the caloric level, and the social surroundings.14 Another example is Chef Thomas Keller, who reminisced that every time he prepares onion soup it brings back memories of every bowl of soup he has ever consumed.12

6. Flavor—Flavor Learning

This theory states that food preference to a neutral stimulus that is paired with a preferred flavor or taste, will increase liking for the previous neutral or even disliked food.15 An example would be adding sugar to oatmeal to induce preference or the use of garlic in a vegetable to induce liking (works well with kids). This should not be confused with post-ingestional conditioning, which is caloric-induced liking to a food after digestion.

7. Mere Exposure Effect

In studies on food preference, the mere exposure to a sensory stimulus (so-called neutral stimuli) will increase familiarity and liking.16 Familiarity actually increases liking more than contempt as we acquire tastes for things over time with repeat exposure. As an example, kids may not like broccoli, but if you keep exposing them to it, for instance, by just placing it on their plates, liking will occur even without ingestion. In time they will at least try it; and if it is made tasty (butter, garlic, and salt), kids will be enticed to consume it. Once consumed, the calories (butter or cheese sauce) will help burn-in permanent liking. We call this post-ingestional conditioning (see below).

8. Taste-Aversion Learning

This principle states that food ingestion with negative gastrointestinal side effect creates a permanent flavor or taste-aversion to that food.17 It is likely that all of us have about half a dozen of these aversions buried in our brain stems. An easy way to acquire one (and I have not, of course, done this personally) is to drink too much, get sick, and throw up—alcohol is a gastric irritant, and all those interesting flavors and tastes on the way up become instant food aversions. Also known as the “Southern Comfort Effect” in the not-so-scientific food intake literature, certain sweet liquors, or drinks with umbrellas, can slow gastric emptying, allowing alcohol a longer and more damaging gastric contact time—with sometimes unpleasant results (vomiting). Once during a lecture on food aversions, an executive came to the podium and confided that his company is aware of this sugar-gastric-irritation phenomenon and is developing a line of less sweet alternatives.

9. Rozin’s Fundamental Principle

Food psychologist Paul Rozin suggests that it is easier to dislike a food than to learn to like it. His observation is an important protective feature of the human omnivore, where we eat anything and can be poisoned by everything! Children, with lower body weights and less developed detoxification systems, become very picky and prone to eat the same foods over and over. Pregnant women, with a developing fetus, must be very selective with foods—especially novel ones, where even small amounts of ingested food can have lasting biological effects.
Disgust. This is a powerful motivation to reject food because the food tastes bad or is considered dangerous (a worm in an apple).18 A basic, core emotion, disgust involves the sense of taste, perhaps gastric nausea, and stereotypical facial (disgust) expressions—yuck! This factor is probably largely overlooked in food likes and dislikes—most of which are based on texture and animal products. My favorite examples of disgust from Rozin’s research include his attempt to get adults and kids to consume a cockroach-in-a-drink (after the cockroach has been removed) or his request for people to drink apple juice from a bed pan—now that’s disgusting.
Elisabeth Rozin’s Flavor Principle. An outstanding cook and food anthropologist, Ms. Rozin observes that cuisines have core techniques and flavors that define their character (sensory signature). Cuisine-curious cooks may want to check out her cookbooks (The Flavor Principle Cookbook, now known as Ethnic Cuisine; and Crossroads Cooking) and try preparing the flavor signatures of various cuisines. The function of Flavor Principles is to allow people to experience novel foods in their diet without inducing neophobia, or rejection. In Asian cuisine, for example, adding soy sauce to a new dish brings back the familiar and encourages food exploration. Here is an example of a flavoring principle: Indonesian cuisine is characterized by a combination of soy sauce, brown sugar, peanut, and chile. So by recreating this combination of flavors and ingredients you have formed the flavor “signature” of that cuisine. (For college students and serious foodies, reading anything from Paul and Elisabeth Rozin will advance your culinary and sensory knowledge.)

10. Energy Density (ED) Theory
Adam Drewnowski (nutrition and sensory expert) has discovered in his research that high energy density food is associated with high food pleasure. In addition, energy-dense foods are tasty but not filling, whereas foods with low energy density are more filling but less tasty.19 Although humans never evolved in an energy-rich food environment (with the exception of nuts), but we crave the calorically dense foods when we see or sense them—we call this modern fast food. Even French cuisine techniques increase the tastiness and density of foods with butter and cream—visit the mashed potatoes recipe of Puree de Pomme de Terre in the Bouchon cookbook (page 250) to get the idea. His preparation technique is worth noting; it creates an emulsified potato mixture with rapid meltdown on the palate.
Energy density is a number from 0–9, and it is calculated by dividing calories (kcals) by the gram weight of a food. Foods’ ED ranges from water (0) to pure vegetable fat (9). Most vegetables are near 1, meats climb to 2–3, fast and junk foods hover around 4.0–5.0, and butter climbs to 7.2.

Vanishing Caloric Density
A hypothesis by Dr. Robert Hyde states that we tend to like foods with high oral impact, plenty of taste and dynamic contrast, but with low satiating ability or immediate gastric feedback. Now, few foods qualify (meringues, diet soda, cotton candy, and pretzels), but popcorn is perhaps the best example. Buttered, salted popcorn is very tasty, and you can eat a lot of it, repeat oral stimulation, since it isn’t that filling. In fact, I’ve seen some people actually accelerate their eating rate due to the absence of gastric satiety. Eating a whole bowl of popcorn for dinner is not a rare occurrence. Foods that exhibit this rapid (oral) meltdown response may actually signal the brain that the food being ingested is lower in calories than it really is. The reduced satiety response to high dynamic contrast foods (ice cream, chocolate, and French fries) may partially explain Dr. Drewnowski’s observation that energy dense foods that meltdown rapidly in the mouth, often lack satiety. Hence, foods that quickly “vanish” in the mouth are more rewarding, reduce gastric satiety, and encourage over ingestion.

12. Post-Ingestional Conditioning

“The belly rules the mind.” Old Spanish proverb
Consuming the macronutrients (fat, protein, and carbohydrate) will quickly condition the human (and animals) to prefer the taste of that food. Sweet foods condition readily, sometimes after one pairing—sweet taste is a reliable and potent inducer of mu-opioid in the brain reward center. Foods high in fat calories also condition readily; studies reveal that feeding people yogurts with higher fat content will condition the food flavor faster and stronger. This is part of the problem with junk food—unusually rich in taste-active components like salt, fat, sugar, and umami, with high caloric density, they readily create potent food preferences. As food is digested, receptors in the stomach and intestines relay information on the food to the brain via direct contact with the vagus nerve, resulting in the release of many different peptide hormones. High-fat foods are particularly bienvenue; specific hormones relay fatty acid information (calories) to the brain and the fat cells. There are plenty of peptides in the brain that respond to the presence of fat. Such peptides include orexin, galanin, leptin, and insulin. In the appetite center, certain peptides are released that can stimulate the taste for fat (opioids, galanin) and carbohydrate (neuropeptide Y) and encourage hyperphagia (overeating).20

13. Human Cookivore Theory
Richard Wrangham, professor of anthropology at Harvard University, noticed the close evolutionary relationship between humans and fire over the past five hundred thousand years.21 Cuisine may be in our genes. Cooking made modern man and influenced gastronomy, nutrient assimilation, and flavor preferences. There is much evolutionary support for this theory: human stomachs are smaller than primate herbivores, and we prefer nutrient-dense foods. Although our olfactory receptors have degenerated over the past hundreds of thousands of years, our higher-order aroma brain processing (secondary and tertiary areas) has actually increased. Aroma perception touches more parts of the brain than any other sense. The use of fire greatly expanded what we could digest and eat safely. This, in part, explains our seemingly built-in liking for the smell of smoke and BBQ—it’s the smell of survival! To this day, hickory smoke can give me pleasure chills—similar to a favorite piece of music.
Scientists have discovered “meat-adaptive” genes in humans that were a very important nutritional adaptation to meat eating. Human ancestors ate meat as long as 2.5 millions years ago, and despite what we currently think about meat and bad health; these gene changes protected us against the adverse consequences of a higher protein diet (high cholesterol and iron). Chimps and other apes that are fed our type of fast food diet clog their arteries very quickly—while we are relatively resistant.22 I’ve also expanded Wrangham’s cookivore theory a bit to include fermentation aromas. Fermented foods and their aromas can also signal survival, whether it is in the form of cheese, beer, wine, miso, or Kimchi.
Further evidence for the cookivore theory comes from researcher Peter Lucas, author of Dental Functional Morphology, who suggested that cooking makes food softer and easier to chew, and the use of utensils makes cutting food much easier, thus reducing the need for a huge jaw.23 Bernard Wood, a paleoanthropologist at George Washington University, believes we are evolving to eat mushy food.24 Actually, we are evolving to eat cooked foods, prepared in ways to increase caloric density.
Zoologist Desmond Morris in the now-classic Naked Ape, says that humans are meat-eating carnivores, but have kept their plant-eating ways (like all other primates) for the pleasures of food variety and the hedonic taste of sugar.25 Typical primates have a wide and diversified palate of tastes and flavors from plant foods, consuming roots, leaves, flowers, shoots, and fruits with deliberate and obvious relish. Desmond also suggested that we prefer warm or hot food, primarily to increase food flavor generation—a strict meat diet is simply too boring. Hence, humans are mostly meat-eating omnivores, who like to consume plant foods for variety, flavor, and sweet taste (energy). Most importantly, we like to cook these foods together. This is, in effect, the foundation of modern cuisine (it’s in our genes).

14. Aroma and Essential Nutrient Encoding (Goff and Klee)
This novel theory states that human olfaction and the perception of essential nutrients in plants co-evolved in a mutually beneficial way.26 Many plants derive their volatiles from essential nutrients such as vitamins, minerals, and fatty acids. Their detection and perception may have helped guide human olfaction—fine-tuning the olfactory system to detect useful aromas. This fits in well with the cookivore theory. As we have seen, over hundreds and thousands of years of evolution our olfactory discrimination may have degenerated, but higher-order olfactory pathways were fine-tuned to pay attention to survival aromas in the environment: detecting food, foes, and sex. The authors suggest that volatiles that signal nutritional significance (Vitamin C, B-vitamins, and carotenoids) are epigenetically (pre-programmed) preferred—and this has very important food pleasure implications—especially in flavor manufacture and cuisine design.


15. “Liking” Versus “Wanting” Theory
Neurophysiologist Kent Berridge suggests (with strong scientific support) that our desire for food (and drugs) must be distinguished into two separate phenomena: liking, or pleasure induced during eating, and wanting, the (non-hedonic) desire to choose that food.27 Berridge’s work is tough reading and difficult to understand because it is not biologically intuitive. (But the good doctor is always quick to answer my e-mails when I need further clarification.) In an article on liking vs. wanting, scientist David Mela (2006) explains that the key to understanding food behavior involves physiological cues, anticipated pleasure, and external cues (conscious and unconscious).28 He says that oral pleasure is not the only food-purchase criteria; the other dimension is a desire for “wanting” that food based on a non-hedonic choice. He suggests that wanting may be related to the experience of food boredom—we simply want food with differing sensory properties. Low calorie foods, he hypothesizes, must be optimized for both wanting and liking. Why is this important? Well, it is fairly easy to measure and to manipulate how much you like something, but measuring how much you want something, especially when you are not aware of it, is quite another matter! Mela believes that this new dimension of wanting is a major factor in purchase intent and deserves much more serious study. In the future, manipulation of food “wanting” may be a major product development endeavor.
Berridge and his colleagues disclose that the intense liking of sweetness is due to mu-opioid stimulation localized in the rostrodorsal region of the nucleus accumbens shell (a pleasure circuit in the limbic brain) and the ventral pallidum.29 Dopamine was widely believed to be the major pleasure neurotransmitter in the brain, but this may not be the case at all. Mice that are bred to have no brain dopamine still experience pleasant taste, however, they lack the will to work for it.27 Shimura et al. (2006) also found that GABA, opioid, and D1 receptors in the ventral pallidum (brain pleasure structure) are involved in the consumption of hedonically positive taste stimuli.30 The authors suggest that many common motivated behaviors activate the ventral pallidum such as consuming food, mating behavior, sexual activity, and in the liking for number of drugs such as alcohol, heroin, and cocaine. The brain pleasure response, it appears, likes to share a final common pathway.

16. The Stomach: the Second “Taste” System
Many chefs and food scientists have focused on the oral cavity as the major dictator of what we eat. The tongue does contain many thousands of taste buds and chemoreceptors that constantly monitor the gustatory and orosensations of the food we eat, and they certainly guide food selection and pleasure. But this view of oral fixation changed when researchers found that the stomach and small intestine have the great ability to sense what we eat as well—in fact, these organs contain many more “sensing receptors” than our taste buds! The stomach, small (and even the large) intestines’ major roles are to evaluate incoming food (called a bolus), facilitate digestion, and prevent you from ingesting potentially toxic compounds. I became aware of the importance of “stomach sensing” from a presentation in Geneva by the physiologist N. Mei in 1986. He was one of the first to note the amazing richness and complexity of the sensory information arising from the digestive territory.31
The stomach and small intestine have the following systems to evaluate what is consumed:
Mechanoreceptors. These receptors located in the mucosa and muscular layers sense the distention or contraction of the digestive wall.
Chemoreceptors. These receptors are sensitive to all three main types of nutrients: carbohydrate, amino acids, and lipids. In addition, they are pH responsive to acids or alkali substances.
Thermoreceptors. The stomach can sense the temperature (and the intensity) of the nutrients and the water of the food eaten.
Osmoreceptors. The stomach can sense “osmolality” or the number of dissolved particles in solution. If one consumes a very high sugar and fat food, the stomach secretes water in an effort to dilute the contents to lower the osmolality back to normal. This can stress the stomach lining, and cause a feeling of malaise (upset).
The wall of the gut has an impressive array of sensors that can relay information to the brain stem and ultimately to the sensory cortex of the brain (right next door to the taste areas). The gut has nutrient receptors for: sodium chloride, amino acids, fats, fatty acids, glucose (especially rich), and other simple sugars. In fact, the intestine may have more taste receptors than the oral cavity, and non-nutrient receptors abound as well. These receptors sense the volume of food, osmotic pressure, the temperature of food, the size and shape of food particles, and mucosal touch. All these sensors have the following main functions—to sense what was eaten, prepare the gut for digestion, create a gastro-sensory memory, and alter food selection in future meals. This is accomplished by direct neural intervention with other body organs and a large number of hormonal signals released by gut tissue. For example, the stomach and intestine may “taste” glucose and amino acids and relays this information (via nerves) to the pancreas and the liver to increase blood insulin and other post-digestive hormones.32
The gastrointestinal tract and nervous system, both central and enteric, are involved in a complicated, two-way communication by both parasympathetic and sympathetic nerves, cholinergic fibers, and dozens of peptides and hormones. We will not deal with details here, but suffice it to say that sensors in the gut relay information during food digestion via vagal and sympathetic spinal nerves to the central nervous system. This input is affected by the nature of the food stimuli (protein, fat, and carbohydrate) and neuro-hormonal stimuli such as gut hormones, neurotransmitters, and modulators as well as cytokines and microbial end products. The stomach and intestine, therefore, are the body’s second chance to evaluate the taste, volume, osmolality, and nutrient composition of chewed food and relay this information to the brain. In addition, the stomach secretes hormones such as ghrelin, a powerful appetite stimulant that slows metabolism and inhibits fat burning as well. Dieting causes a rise in this appetite-stimulating hormone, and the more weight you lose the greater the rise. The body doesn’t want you to lose weight; this is just one protective mechanism against starvation.

Importance of Stomach Sensing
For years food scientists have created a whole new category of foods that are light in fat, salt, or sugar (or all three). Despite the unpopularity of some of these foods, they still proliferate in the marketplace. And they certainly have their place in our society, as healthier alternatives to junk food. But making a light version of a nutrient-dense food is sensorially difficult, due to the ability of the stomach and intestinal to sense calories. Once you eat a food, the vast array of sensors in the intestine calculate the taste and macronutrient content and relays that information to the brain via vagal afferents to the nucleus of the solitary tract (among others) and then to higher-order brain centers. In essence, the gut-brain axis knows the nutrient density of that food; and if you try to fool the stomach by creating the exact same taste but with reduced calories, the body’s natural reaction is to lower food hedonics and, over time, food selection. Remember the craze over low-fat yogurt? Shops popped up everywhere, until the stomach-learning mechanism dropped the food preference and forced us back to ice cream (read that: Cold Stone!). Of all the nutrients that condition food preference, the strongest associations are made from fat- and sugar-containing foods, preferably in the emulsified form.
A number of years back, I was giving a lecture on food preference, and a food scientist in the audience asked what I thought about the new Border Lights menu, developed to great fanfare at Taco Bell in 1995. In a move that made the food police happy (including Michael Jacobson, Center for Science in the Public Interest), the taco giant, owned by PepsiCo, introduced fat- and calorie-reduced versions of tacos, burritos, and taco salads, a healthy alternative for more than half of all their offerings. Two years of development and $75 million in advertising went along with the food revisions. At the time, John Martin, the chairman and chief executive of Taco Bell, suggested the move would transform the fast-food industry. He even suggested that the menu would become a $5 billion opportunity in ten years (quite the optimist).35
So what did I think? Well, I visited the local Taco Bell and tried each one of the foods; I noticed that they were good copies of the regular menu items, but in each and every case, the foods were lower in dynamic contrast and hedonic solutes. The company made three very serious mistakes. First, the brain and gut have a memory of the foods eaten in the past, including the taste and the calories. Second, by removing the fat and modifying the ingredients, there was less meltdown, less aroma, less flavor, and increased rubberiness and cardboard notes. (For example, starches replaced milk fat, cheese became nonfat, and the tortillas were baked—ugh!) Finally, I could not find any increased sensation to make up for the calories lost, as should occur based on the food pleasure equation. I told the audience that Taco Bell would lose 50 million bucks. I was wrong; it was double that. Now, don’t get me wrong; I like Taco Bell food (it sustained me in college), and I don’t wish to be too harsh (their Mexican pizza is high in dynamic contrast and quite tasty).  But an awareness of the basic principles of food perception, appreciation, and digestion would have helped enlighten the product development process and increased the probability of success.

Summary: The Big Six

Foods that are considered delicious and desirable have the following characteristics; look for the application of these pleasure qualities in the chapters that follow. Our favorite foods usually combine most, or all, of the following in a single food.
Taste Hedonics. Foods must contain salt, sugar, MSG, and flavor-active compounds. Preferably all of the above at the physiologically correct amounts: salt at 1.0–1.5 percent, MSG at 0.15 percent, and 5’-nucleotides at 0.02 percent. In sugar systems, salt will always improve the overall taste hedonics; 0.25 percent salt is usually sufficient. Taste is a major driver of ingestion and pleasure in food, but it only accounts for less than 10 percent of all the sensation from the mouth to the brain. Food must also excite thermal (hot and cold), tactile, texture, fatty acid, and pain receptors. And there are many lesser known hedonic solutes yet to be discovered.
Dynamic Contrast. Tastiest foods must contain texture and/or flavor contrasts; the more the merrier—rapid food meltdown with snap, crackle, and pop. Next to taste hedonics, this is the most important contributor to food pleasure. Since humans are visual animals (almost 40 percent of the brain cortex is devoted to vision), contrasts must include color and appearance as well.
Evoked Qualities. Food must evoke or bring forth previously conditioned pleasure memories—food content, environs where ingested, and prior physiological state. Emeril’s “BAM!” blend is a good example: the spices (garlic, onions, etc.) evoke memories and pleasures of past meals. The key is to add these “qualities” in a subtle and balanced way.
Food Pleasure Equation. Food pleasure is a function of sensation and macronutrient stimulation. The tastiest foods maximize both dimensions. For example, if a food is lowered in calories, to increase the pleasure, you must add more sensation.
Caloric Density. The gut-brain axis senses CD and makes it good. A CD of 4–5 is most preferred, often found in junk foods. (0 is the score for water and 9 is for pure fat.) Exceptions to this preference rule are those foods with big volumes that melt down quickly in the mouth (vanishing caloric density), such as popcorn.
Emulsion Theory. Taste buds like emulsions, especially salt-fat or sugar-fat combinations. Many of our tastiest foods are in liquid or solid phase emulsions, whether they are butter, chocolate, salad dressings, ice cream, hollandaise sauce, mayonnaise, or crème. The making of an emulsion concentrates the hedonic taste solutes (salt, sugar, and MSG) into the water phase. We have discussed that butter is about 2.5 percent salt, but in the emulsified state, the actual salt content presented to the taste bud is 10 percent salt because all of the salt is in the 18 percent water phase. Ice cream is a frozen emulsified “foam” that concentrates the sugar (sucrose) in the water phase, enhancing the perception of sweetness.