workshop : what’s for dinner tonight? introduction · the explanation for distribution of these...

Mediation workbook - « What’s for dinner tonight ? » - Provided by The Cité des sciences et de l’industrie - Universcience Direction de la médiation scientifique et de l’éducation (DMSE), 2010

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Workshop : What’s for dinner tonight? Introduction

Product and objectives Title: What do we eat? (school version) / Flavors and humankind (general public version) Programme of special events: Workshop presented at the Cité des sciences et de l’industrie as of end January 2010, in parallel with the "Bon Appétit!" exhibition Type: Workshop Target groups: § Groups of schoolchildren aged 9 to 14 § Families with children, adults § Accessible to the disabled Hosting capacity: 30 people Duration: 45 mins Objectives: • Examine the concept of the pleasure of eating, and examine cultural differences based on taste § Present the diversity of diets throughout the world, and demonstrate that what we in the US might view

as a "balanced" diet is not at all the same for all the Earth's inhabitants, yet they continue to survive any particular health problem.

The aim of the workshop is to raise awareness of cultural diversity in terms of diet. It takes place in several parts, punctuated by tastings:

- What are the foundations of the human diet? - What do other people eat? Who eats what? - What are the different perceptions of taste on the individual level?

Summary of the special activity One must eat to live. Throughout the world, humankind typically has a staple diet comprised of cereals, vegetables, tubers, and legumes, depending on the region. The explanation for distribution of these staple foods can be traced back to the Neolithic Revolution. These staple foods have certain points in common: they are inexpensive, plant-based, calorie-rich, and storable. Although highly nourishing, staple foods are generally insufficient to provide the full range of nutritional elements. The staple diet, therefore, has to be supplemented by other foods. These other foods take multiple forms, and humans do not all eat the same things. This part will be reinforced by spotlighting five remarkable foods, each presented in an original recipe. This diversity of taste is also personal in nature since humans are conditioned throughout our lifetimes by genes, upbringing and learning.


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Resources: Plan Part 1: Staple food crops

1. Why agriculture and why choose cereals? § The environmental model (determinist) § The cultural model

2. Diet after the birth of agriculture: development and new

revolutions § Major discoveries: the second dietary revolution § Advent of the mass-consumption society

3. Examples of staple foods

§ Cereals § Tortilla § Taro § Lentil cake (Papad)

Part 2: Diverse diets: original culinary creations

§ Ants § Crickets § Swift nests § Snails § Corn smut

Part 3: Physiological and molecular bases of taste

Part 4: What is taste?


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Part 1: Staple food crops There are thousands of plants which humans can grow. Yet there are only several hundred plants for which there is genuine demand as a food source (now or in the past). Currently, only thirty or so plants suffice to cover over 95% of calories of plant origin. These staple foods include grass plants (wheat, rice, millet, corn, and sorghum) and tubers and root vegetables (yam, manioc, taro, potatoes, and sweet potatoes). Although used in smaller quantities, a third group of staple food plants termed legumes (lentils, peas, and beans) are also grown, and these play a key role due to their nutritional quality (rich in protein) and their diversity.

Most plants which feature in our diets today are domesticated forms of wild plants that our ancestors ate thousands of years ago. Why agriculture and why choose cereals? It's not so simple. There is no validated model explaining the origin of agriculture. Given the scale and the scope of this revolution in human biology, it is quite extraordinary that there is no commonly accepted model for the origin of agriculture. Indeed, a growing number of arguments have been advanced in recent years to the effect that, far from being a normal stage in human progress, agriculture generally leads to a poor quality of life. Hunter-gatherers typically expend less energy for the same quantity of food, and they are healthier and less subject to famine than primitive farmers (Lee and DeVore 1968, Cohen 1977, 1989). Biological evaluation of what has been termed the puzzle of agriculture could express this enigma in simple ethological terms: why did this practice (agriculture) develop (and gain popularity) if it failed to offer appropriate rewards over and above those available to hunter-gatherer type economies or people with nomadic lifestyles? Similarly, archaeological digs in Mehrgarh, a necropolis in Pakistan which is 9,000 years old, have unearthed the vestiges of a profession which is still with us today, dentistry. This work has been conducted by international teams led by the French archaeological mission (CNRS, Musées des arts asiatiques-Guimet). Their findings were published in Nature ("Early Neolithic tradition of dentistry" by A. Coppa et. Al. 6 April 2006). At a time when the beginnings of an agricultural economy founded on the cultivation of cereals and raising livestock were taking root, inhabitants of the first sedentary villages of the Neolithic period suffered a rapid deterioration in their general state of health, particularly on the nutritional level. Dental health worsened. The use of millstones to grind cereals contributed to enamel abrasion and weakening teeth; furthermore, the new sugar-rich diet favored the process of acidification and the development of tooth decay. So, why was agriculture selected?


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A. The environmental model (determinist) Climatechange,endofthelasticeage(Pleistocene)

↓Humans(MiddleEast)becomedependentonwildcereals(easilyharvestedandstored)

↓Inhighlyfavorablezoneshumansadoptasedentarylifestyle(Natufiens)

↓Increasedpopulation:demographicpressure

↓ Migrationtolessfavorablezonesorno/littlewheatandwildbarley

↓Experimentationwithcropsandpropagationofthesecerealstooffsetthisshortfall However, this model does not explain the data observed in the field, particularly:

- The emergence of domestication in regions where wild resources were abundant

- Even after their domestication, cereals represented a low percentage of diets (e.g.: just 3.4% of the remains of plants in the initial phases of introduction ; therefore, they would not have been able to make up for the significant dietary shortfalls caused by the lack of natural resources).

B. The cultural model

Discoveryofnewtechniquesforprocessingfood(seeintroondiversityofrecipes)

Germinationandfermentationofgrains

↙↘

Productionofalcohol(beer)Alternativeconsciousness(rites,socialgatherings)

ImprovednutritionalqualitiesvitaminsB,lysinPhytates:absorptionofCaSelectivebenefits

It is hard to make a clear choice between these two models. We can, however, advance certain arguments in favor of the cultural model. For instance, in America, archaeologists have just discovered traces of domestic green squash which date back as far as the oldest traces of corn. This result challenges theories explaining the birth of agriculture through economic and production necessities, advanced, for instance, by Robert Braidwood of the University of Chicago which state that the first sedentary societies, in a quest for more abundant resources, first domesticated cereals which are prolific and nutritional plants. However, the green squash is not an exception; in the Andes, the oldest known domestic plant is the chilli, traces of which have been found from around 8,500 years ago at the Guitarrero site in Peru. Barbara Pickersgill, from the University of Reading, UK, has explained this domestication by the search for a condiment with


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aphrodisiacal and stimulant qualities that promoted expenditure of energy, both gestural and sexual, during village community gatherings. Does the domestication of marrows, which are less nutritional than cereals, also have a festive origin? Unless they were for a particular ritual which would have created the need for a permanent stock of these vegetables. By way of example, note that the Nuer people in Niger sacrifice cucumbers instead of cattle. (R. Pigeaud La Recherche April 5,2003 ;D. Piperno and K. Stothert, Science 2003)

I. Diet after the birth of agriculture: development and new revolutions

A. Major discoveries: the second dietary revolution

Diet subsequently developed through changes to produce and the dissemination of crops. In Europe, the colonization of America triggered a veritable second dietary revolution. Beginning in the era of Christopher Columbus, a widespread redistribution of plant resources continued through until the 20th century. Only a few species are mentioned below. The only animal brought to Europe was the turkey.

ThedistributionofplantsfromtheAmericasMarrow,beans,corn,peppers,potatoes,tobacco,tomatoesPineapple,peanuts,cocoa,rubbertreeplant,corn,cassava,peppers,cinchona,tobacco,tomatoes,avocados,cottonplants,beansPineapple,peanuts,cocoa,rubbertreeplant,corn,cassava,peppers,cinchona,tobacco,tomatoes

America also greatly benefited from the transfer of plant species: wheat, chickpeas, yam, breadfruit, rice, bananas, citrus fruits, sugarcane, coffee, and, above all, livestock in the form of sheep, cattle, and horses.

Marrow,beans,corn,peppers,potatoes,tobacco,tomatoes

TheDistributionofplantsfromtheAmericas

Pineapple,peanuts,cocoa,rubbertreeplant,corn,cassava,peppers,cinchona,tobacco,tomatoes,avacados,,cottonplants,beans

Pineapple,peanuts,cocoa,rubbertreeplant,corn,cassava,peppers,cinchona,tobacco,tomatoes


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ThetransferofplantstowardstheAmericasCitrusfruits,bananas,sugarcane,rice,soybeansWheat,flax,barley,chickpeas,grapevinesCoffee,yams

B. Advent of the mass-consumption society In the 18th century, two hours of manual labor in an urban environment purchased two pounds of cereals, but today, just five minutes of manual labor can purchase the same amount. But mass consumption does not signify equal diets or even diets which meet nutritional needs. It signifies access by the greatest number to the major food markets, but this great feast of humanity is not evenly shared. Most developing countries are still at the stage of mass poverty. Under-consumption, shortages, and sometimes famine characterize the poorest societies. Even in Western European societies which have reached the stage of mass consumption, hunger has not been totally eradicated, and the situation has worsened with the emergence of long-term unemployment. In affluent societies, 5% to 10% of the population live in a virtually permanent state of dietary under-consumption.

ThetransferofplantstowardstheAmericas

Citrusfruits,bananas,sugarcane,rice,soybeans

Wheat,flax,barley,chickpeas,grapevines

Coffee,yams


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Examples of staple foods A staple diet is generally

- inexpensive - plant-based: the staple foods are plants for virtually the entire population of the world except for

Fula (cow's milk); Inuits (meat and fish); Patagonian Indians, now extinct, (fish). - calorie-rich - easy to store - locally produced for much of the year

Cereals A short history of cereals:

Rice: Rich in starch First grown some 10,000 years ago in China

Wheat: Central component of the typical American diet Rich in starch + gluten

Sorghum: Plant of African origin grown for its grain or as animal feed Originally from Ethiopia

Millet: Food grain grown in dry zones

Corn: Introduced to Europe by Christopher Columbus Easy to grow, higher yields than wheat Grain which is rich in starch Poor in protein Staple food for pre-Columbian civilizations Substitute for millet Base ingredient for tortillas in Mexico

The base of the everyday diet for the Mexican masses, tortillas are prepared with a range of sauces and accompany many traditional dishes. Over 300 million tortillas are consumed every day. The first tortillas have been traced back to around 12,000 years ago.

Tortillas


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Taro

Tubers and root vegetables: Tubers and root vegetables represent the staple diet for over two million people, mainly among the poorest sectors of society, and are the second group of subsistence crops after cereals. The principal tropical root and tuber vegetables are cassava, sweet potato, yam, and taro. Most are grown on tiny plots of land in impoverished regions where production statistics are either non-existent or unreliable.

Tubers:

The tuber is a reserve organ (reserves stored to ensure flowering the following year). Organs transformed into tubers can be the root (e.g. carrots), the rhizome (underground stalk growing roots and shoots above ground like the potato), the stalk base (e.g. kohlrabi), or the root and stalk base together (e.g. beets). The tuber is relatively rich in starch, around 30 to 33%, but poor in proteins (1% to 2%) and fats.

The taro, or Colocasia esculenta, is an ancient and important starchy plant eaten by over 400 million people. It is grown in highly diverse environments for its starch-rich corm tissue, its petioles, and its leaves eaten like spinach. It is also sometimes used as an ornamental plant. The taro is originally from Papua New Guinea. It is a big favorite in West Africa, China, Polynesia, the islands of the Indian Ocean, and the West Indies. The average global harvest is close to 9.2 million tons (Food and Agriculture Organization, 2002), the principal producers being Nigeria, Ghana, China, and the Ivory Coast. For centuries, travellers in China and much of Asia have been packing this tuber in their baggage, whether in dried or smoked form. This same dietary custom can be found among Polynesian seafarers. Sources: https://en.wikipedia.org/wiki/Taro


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Lentils One of the first leguminous plants to be domesticated—some 9,000 to 10,000 years ago, probably at the same time as wheat—lentils originate from the "fertile crescent" of the Middle East. Remains of the plant dating from this era have been discovered on the banks of the Euphrates in northern Syria. Other than as crop breakouts, it is rarely found in its wild form. Its cultivation spread throughout Greece and southern Bulgaria with the development of agriculture in the Neolithic period and reached Crete around 6,000 BC. During the Bronze Age, it was popular in Hungary, the Czech Republic, Switzerland, Germany, and France. The lentil was much appreciated in the Egypt of the pharaohs. Remains of the plant were discovered in the tombs of Thebes dating from 2400 BC while frescos from the time of Ramses II provide evidence that lentil soup was consumed in Egypt. The Assyrians were also fond of it since documents show that it was grown in the legendary hanging gardens of Babylon in the 8th century BC. In ancient Greece, it was considered as a food for paupers. The nouveau riche of the time were euphemistically described as having "gone off their lentils." The lentil rapidly spread eastwards. Vestiges were discovered at an Indian site dating from 2500 BC. Down through the centuries, it became a staple food for populations in the Near East, North Africa, and India. In the 16th century, it was successfully introduced to America, but it was not until the First World War that it was grown in the United States and Canada.


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Part 2: Diverse Diets

1. Original culinary creations "Insects have a high nutritional value. They contain proteins, fats, minerals (especially zinc and iron), vitamins (riboflavin and thiamine) and water. “Eating insects is not merely a dietary curiosity but also a necessity for certain populations. Insects are an abundant source of accessible and cheap food. Some are eaten out of tradition (e.g.: termite queens consumed by African women to boost fertility) while others are eaten for their nutritional properties and flavor. Insects are widely eaten around the world." –Marjolaine Giroux, entomologist at the Montreal Insectarium Ants

§ In China, the Polyrhachis vicina roger species is much coveted for its nutritional qualities and medicinal properties. This ant is considered to be particularly effective in combating rheumatism and immune system disorders including hepatitis B. (Chitin, the main component of ants’ exoskeletons has acknowledged medicinal properties.) § In South America, leaf-cutting ants, whether roasted or coated in chocolate, are a popular substitute for popcorn at the movies.

Crickets When there are large numbers of crickets, some countries sell them for human consumption: Madagascar, the Congo, Cameroon, and, more generally, locales subject to invading hordes. As well as being grilled on embers, crickets are fried, roasted, and boiled for immediate consumption or dried for eating later. Dishes: Tinjiya (a Tswana recipe): Remove the crickets' wings and back legs, boil in water until the crickets go soft. Salt to taste and brown in some fat. Serve with corn. Sikonyane (a Swazi recipe): "Prepare the embers and roast the whole crickets. Remove the head, wings and legs; only the body is eaten. Inhabitants of Lesotho mainly use crickets for food when travelling. The head is removed along with the end segments of the rear legs. The remaining part is then left to roast over embers. The roasted crickets are then crushed with a pestle until a fine power is obtained. They can be stored for some time and carried on journeys. Dried crickets are also prepared for winter. Their dried legs are much appreciated for their flavor." Is it possible to image a trade in crickets? "Hordes invade intermittently. These are one-off events which do not permit a regular trade to develop. All the more so since during invasions there are no means of ensuring a large number of crickets can be caught. But they do, however, represent a dietary supplement. Account should also be taken of the fact that the migrating cricket found in Madagascar, for instance, does not demonstrate the same behavior as the pilgrim cricket. Migrating crickets tend to alight in tall grass and in the morning their wings are heavy with dew. This means that Madagascans merely have to collect them, which is not the case with the pilgrim cricket," says Annie Monard, locust expert at the Food and


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Agriculture Organization. Eating crickets is therefore only a partial solution to the serious problem presented by descending hordes. China: swift nests Information drawn from the following website: https://en.wikipedia.org/wiki/Edible_bird%27s_nest In Asia, the nests of certain species of swift are considered a delicacy by gourmets. These swifts secrete mucilage to build their nests. This mucus is much sought after as a luxury item for traditional cooking in China, Vietnam, and numerous other Southeast Asian countries. It is also believed to possess many health benefits. These translucent nests are whitish and sometimes yellowy with an appearance not unlike rice noodles. History: This expensive delicacy used to be the preserve of kings and mandarins. The Chinese also imported it from Malaysia, Thailand, and Vietnam. Today, Thailand meets 70% of global needs. The nests of various species of swift are consumed but intensive harvesting has probably led to the reduction in species building such nests in south China and certain caves in other Southeast Asian countries. For example, in Vietnam, the nests of the Collocalia Fuchiphaga are collected. Every year, this bird builds a small lightweight nest (weighing tens of grams). It takes the bird around three months to complete it. Nest hunters collect it, forcing the swift to build a second nest before laying its eggs. As soon as the fledglings are big enough, the hunters return to collect the nest. The swallow can then rebuild a third and final nest for the year. This intensive harvesting is a threat for species whose efforts to continually rebuild nests leave them exhausted. Preparing the dish: White mucus fibres are used to make various dishes, for instance, soups or dishes accompanied by a pigeon or chicken cooked in a bain-marie. Prepared with beans or lotus nuts, the swallow's nest can be used to make a compote which is a big favorite in Asia. In taste terms, gourmets described the boiled nest as being tasteless on its own. In fact, the flavor comes from the added ingredients. Virtues: In China and Southeast Asia, these nests are traditionally renowned for being fortifying anti-ageing remedies, which facilitate digestion and assist convalescence (sickness, injuries and post-operative conditions). And they would appear to have many more health virtues, perceived a cure-all for life's ailments. In Indonesia, eating nests is thought to help cool the body's temperature during high temperatures or in cases of fever. This effect could be related to glycoproteins which make up most of the nest's dry material (up to 50%). The mucus which is dried and spun by these swifts is an acknowledged source of amino acids. Some consider that active molecules are at work such as HAD (hexadecanoic acid) which, at low doses, is thought to boost the body's enzymatic activity (by three to five times) through acceleration of the Krebs Cycle.


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Economic importance: 1 kilo of fresh nests trades for $3,000 to $5,000 in Hong Kong. This can exceed $6,000 elsewhere. Hong Kong is the leading importer of swallow nests (just under 100 tons per year). Extensive rearing Due to the decline in swallow numbers noted in recent decades, in some countries (such as Thailand and Indonesia) special air-conditioned bird houses have been built to house hundreds of swallows of the Aerodramus fushipagus species.

Snails When did humans first start eating snails? Archaeology has revealed that snails were consumed in Europe as of the Mesolithic era some 10,000 years B.C. In ancient times, the Greeks and Romans were very fond of snails. In the 16th century, snails returned to favor, being considered a lean meat, and became regular features of the dining table in France. In the 17th century, snails were shunned and only really consumed in the provinces of France. In the 19th century, Parisian restaurants rediscovered the snail and made it popular to eat again. Source: http://www.gireaud.net/histoire.htm Where do the snails eaten today come from? The collection of snails means the species has grown rarer at a time when consumption levels have risen sharply. To satisfy demand, the French specialists import live snails from Germany, Central Europe, the Balkans, and Turkey. Healthy and non-fattening snails Snails are rich in omega-6 fatty acids, and their consumption is highly recommended to combat cholesterol, heart disease, and aging, on condition naturally that they are not consumed dipped in butter sauce. Ancient Roman scholar Pliny the Elder recommended snails for women who had recently given birth while monks in the Middle Ages used them to make cordials and potions to treat coughs. An appealing or repugnant creature? Most legends featuring snails cast them in a positive light while their shape has greatly inspired artists. However, the founders of the Catholic church, in a literal interpretation of the Bible which classifies them among "crawling things," often associated them with the devil. In medieval times, they were viewed as representing the deadly sins of sloth, greed, and lust. Source: Françoise Dieterich-Associate Professor in history-geography


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Corn smut (huitlacoche)

During the rainy season in Mexico, a grey-black fungus grows on ears of corn. Since the pre-Columbian era, the huitlacoche, or cuitlacoche, has been viewed as a delicacy and is sometimes called the Mexican truffle, maize mushroom, or Aztec caviar. Its price can even sometimes soar to almost 20 times that of corn. Harvested before maturity, the huitlacoche is a standard ingredient of Mexican cuisine. To prepare huitlacoche, it is removed from the ears of corn it then minced. The fungus is generally cooked in butter or oil and flavored with

onions, chillies, and epazote (wormwood). It is then served in tacos, quesadillas, stuffed chillies, pancakes, and soups. During the dry season, canned, pre-cooked huitlacoche is used for recipes. Huitlacoche has a higher carbohydrate content than other mushrooms which is what gives it its sweet flavor; other flavors come from the vanillin (vanilla) and sotolon (characteristic of maple syrup).


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Part 3: The genetics of human taste

a. The PROP test: supertasters and non-tasters In 1931, A.L. Fox, a chemist working for DuPont noticed that some people described

Phenylthiocarbamide (PTC) as having a bitter flavor while everyone else thought it was tasteless. Today, PROP (6-n-propylthiouracil, a compound which is similar) has replaced PTC in taste research due to the latter's suffocating sulphurous odor and the risks it posed to health.

These variations in the capacity to "taste" PROP or PTC can be extended to all tasting experiments.

Some people hate eating certain foods that have a strong, bitter taste or that are very spicy, such as chillies. But there are others who happily eat such foods. In fact, some react more than others to a food stimulus. These are the "supertasters." According to research by Linda Bartoshuk, a specialist in experimental psychology who has spent most of her career studying genetic variations in taste, "a supertaster is an individual who has a more intense perception of flavors than the rest of the population. This characteristic is more prevalent among women as well as Asians, Africans, and South Americans. It is estimated that 25% of the American population are supertasters."

b. The physiological and molecular bases of taste

Anatomy of taste In mammals, the test receptors are found at the level of special tasting organs: taste buds which are spread across the surface of the tongue or associated with its protruding papillae

Taste buds and papillae


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Diagram of a taste bud Taste buds are comprised of 50 to 100 cells including support cells and taste cells. Support cells, which are located at the edge of the taste bud, serve to support the structure of the whole. The taste cells are found inside the taste bud and have taste receptors at their ends. We have seen that "supertasters" react more than others when faced with a food stimulus. This different response has an anatomic and biological basis. A supertaster has many taste papillae which allows them to taste food more acutely.

Tongueofasupertaster

Tongueofanontaster


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Telling flavors apart

Humans can distinguish between five different classes of flavor: sweet, bitter, sour, salty, and umami (sensitivity to glutamate). These different flavors are perceived thanks to their specific protein receptors (located in taste cells). For a long time, it was thought that the perception of five flavors by the taste receptors was located differently on the tongue (in other words, that there were specific papillae for each of the five flavors located on the tongue). Based on taste tests, mapping of the tongue was proposed. Recent identification and location of specific receptors for different flavors disproved this model (Nature November 2006). In fact, the cells for the same taste bud present different specific features (bitter, sour, sweet, salty, umami). The papillae are therefore heterogeneous and capable of perceiving different flavors whatever their location on the tongue. Heterogeneity of a taste bud's cells

The flavors perceived by taste receptors (bitter, salty, sweet, umami, sour)

The molecular bases of taste perception

The model proposed by taste physiologists stipulated that: - sour and salty flavors were associated with the activity of ionic channels (H+/sour, Na+/salty) - sweet, bitter and umami flavors were associated with activation of specific membrane receptors

expressed by taste buds' receptor cells. The recent discovery of specific receptors associated with the salty flavor has complicated this simple model.

a.

b.


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c. The genetic bases of sensitivity to bitterness Recognition of the bitter taste seems to occur via a family of receptors T2Rs. Humans have genes encoding 25 different bitter receptors or "T2Rs" (in comparison with the hundreds of olfactory receptors). The same taste receptor cell expresses practically all of the T2Rs which suggests that these receptors all function in the same way and that even very different substances will be perceived as having the same repulsive bitter taste. A study has revealed that T2Rs are also present along the gastro-intestinal wall where they could play a role in respect of the vomiting reflex.

Distribution and prevalence

The proportion of tasters and nontasters varies from one population to another. The degree of non-

taster phenotypes is less than 3% among North American Indians. We can observe proportions of 5% to 10% in numerous populations of sub-Saharan Africa, among Afro-Americans and certain Asian populations. Higher proportions (20% to 30%) are found in Europe (as well as among European descendants in America), North Africa and the Middle East. The highest frequencies are noted on the Indian continent. This particular distribution has been explained by the fact that PTC tasters are also tasters for an entire family of compounds: thiourea, PROP and over forty other products including natural substances with antithyroid properties or which are highly toxic in some cases. The distribution observed could reflect a selection of "taster" genes in an environment where there is a high concentration of products including the N-C=S radical (supposedly harmful bitter tasting substances), particularly in South America.


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Lapons Sami people Japonais Japanese Aborigènes de Malaisie Orang asli Indiens Indians Kenyans Kenyans Berbères Berbers Anglais British Brésiliens (origins euro) Brazilians (of European

origin) Chiliens Chileans Indiens (Quechua, Jivaros, etc.)

Jivaro, Quechua people

Euro-Américains European Americans Afro-Américains African Americans Eskimos d'Alaska Alaskan Eskimos Super Goûteurs Supertasters Goûteurs Tasters Non-Goûteurs Non-tasters

d. Consequences: selective advantages/bias

Having many taste papillae leaves you unable to appreciate certain foods such as alcoholic drinks,

Brussels sprouts, cabbage, coffee, grape juice, green tea, spinach, chillies (the capsaicin is hotter for supertasters), olives (deemed too salty), and soy-based products. Some of these foods cause burning of the taste papillae and others amplify bitterness for supertasters. What's more, they sometimes find products with salt concentrations unpleasant. Other foods are also liable to be appreciated to different degrees: Supertasters are changing. They are learning to appreciate things by tasting them (in normal cases, a individual must taste a new food at least five times before getting used to it) and psychology impacts on this learning process. When your entourage insists that a particular food tastes good, you gradually succumb to their point of view and learn to appreciate it, especially when you are young. So what is the value of being a supertaster? A strong response to taste (particularly bitterness) would make it possible in certain circumstances to avoid consuming plants which are potentially rich in toxic alkaloids but would appear to limit diet diversification in other environments. With alleles presenting advantages, depending on the environment, both are retained. The same polymorphism can be observed in other bitterness receptor genes. In fact, recent human genome sequencing data have shown that the allele of the gene TAS2R16 responsible for reduced sensitivity to bitter substances is favored in zones with high levels of malaria. It is possible that ingestion of (bitter) cyanogenic compounds helps slow the development of P. falciparum. In other regions (without malaria), it is the allele ensuring higher sensitivity to bitterness which is in the majority.


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e. Food neophobia “Genetic and environmental influences on children’s food neophobia” Lucy J. Cooke, Claire MA Haworth and Jane Warldle, 2007. “Development of taste and food preferences in children,” Gillian Harris, 2008 A definition Food neophobia describes the fear felt by an individual (often a child) when tasting an unknown food. This natural response is observed in most children. It emerges as of 18 months of age and diminishes after the age of 8. The most sensitive period for food neophobia is 3 to 6 years of age. An evolutionary role Humans naturally demonstrate a degree of wariness and aversion when it comes to new foods. Similarly, food neophobia is widespread among omnivores (rats, chimpanzees, and capuchin monkeys). It presents an adaptive value by reducing the probability of poisoning through ingestion of unfamiliar and toxic products. But it also has a price in that it restricts the variety of diets. Related problems In the modern world (in which food is generally harmless), neophobia loses its evolutionary benefits and only retains a negative effect in terms of dietary choices. Among children it induces a reduction in the variety of foods consumed, with children often having a particular aversion to fruit and vegetables (whose beneficial role in preventing obesity and cancers is well known). The causes Although universal (neophobia is a normal period in the child's development), neophobia is more marked among certain children (major interindividual differences in the degrees of neophobia). Understanding the mechanisms which underpin food neophobia among children is therefore the subject of extensive public health research. This is making it possible to identify two possible determining factors for neophobia: genetic determinism and environmental determinism. The study and comparison of homozygous and heterozygous twins have revealed the significant hereditary nature of this trait. The genetic contribution therefore plays a key role in food neophobia. However, the environment (particularly, repeated early exposure to new foods in the months following weaning off breast milk) enables this genetic terrain to be modulated. PROP. One of the factors determining the heritability of neophobia could be a genetic predisposition to react strongly to bitter tastes. In fact, experiments have shown that "tasters" reject new foods more often than "nontasters."Research is ongoing.


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Part 4: What is taste? Article in "La recherche," written by Véronique Leclerc, Patrick Mac Leod, and Benoît Schaal,

Does taste have more to do with the nose than the tongue? Surely you have at one time eaten something while you’re suffering from a heavy cold. So you already know how the taste of food can change under such circumstances. Fortunately, this condition is reversible and stops when your nose clears, and you can breathe clearly again. As surprising as it may seem, olfaction has been shown to be an essential sense when it comes to sensing taste. Retro-nasal olfaction, at the back of the nose, is in fact on its own responsible for almost 80% of taste. We owe this discovery to oenologists who in the mid-20th century successively analyzed all the sensations procured by a mouthful of wine. They were able to show that the versatile molecules exhaled by wine or food when swallowing stimulate the olfactory receptors through the direct nasal passage and the retro-nasal passage. Food also releases sapid molecules into the saliva. These molecules are responsible for around 10% of taste. They interact with taste receptors in certain taste papillae spread over the top of the tongue and on the coating of the palate. These receptors, called taste buds, were described in the 1960s by the American and Japanese anatomists Raymond Murray and Masako Takeda, specialists in electronic microscopy. These buds form a cluster of 50 to 100 cells that react to all of the flavors. This means that each flavor is perceived by any taste bud on any part of the tongue. But tasting food is not merely a matter of the nose and tongue since all the senses play their part. Sight shows us the appearance of food and its environment, hearing contributes perceptions such as crunchy and cracking while touch in the mouth defines the texture. Calling on all these sensors prepares our bodies for the arrival of food. Who has not salivated in front of tasty tidbits? And this goes still further since digestive enzymes and hormones like insulin are secreted the moment there is a warning of the imminent arrival of food. In the case of hypoglycemia, merely seeing a sweet-flavored food, for instance, is sufficient enough to boost energy even before the sugar has had a chance to be assimilated by the body! Have you heard of the umami flavor? In the 1950s, a Japanese food processing firm, Ajinomoto, developed industrial quantities of umami, a new flavor. Umami means delicious or tasty in Japanese. This flavor is produced by two amino acids, aspartate and glutamate, present in protein-rich foods such as meat, soy, and mushrooms. Although this industrialized product is a newcomer, the flavor itself is very ancient: the Japanese enjoyed it over 2,000 years ago in a seaweed soup that is extremely rich in sodium glutamate. In fact, it is known in the west under another name. In the late 19th century, a founder of chemistry in Germany, Gustus von Liebig, observed that protein hydrolysates had a very pleasant flavor. The idea was exploited industrially by a Swiss manufacturer, Julius Maggi, who achieved significant commercial success with his famous stock cubes. Why do certain compounds have "flavor"? Certain compounds have flavor either because they are fragrant or because they are sapid. All compounds are organic and belong to the chemical families, without exception. However, they still must meet certain criteria. The first is that they must be small in size in order to vaporize easily and reach the nostrils. In other words, compounds with a molecular weight of between 30 and 300 daltons. This runs from oxygen (32 daltons), fragrant as of a pressure of 1.6 atmosphere, through to musk and steroids (around 300 daltons). They must also be relatively soluble in water in order to be able to cross the aqueous mucous


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lining of the nose. However, it may be that the presence of lipids and proteins in the mucus enables the passage of less soluble compounds. [...]

Fresh, strong, or astringent: tastes, flavors, or sensations? Although the tongue makes it possible to perceive different flavors, the particular taste of a food is also defined by sensations. Strong, fresh, or astringent sensations. In fact, this relates to stimulation of other sensorial receptors in the mouth: those of pain, temperature, and touch. Numerous spices such as the capsaicin in chillies or the piperine in white and grey pepper are capable of activating the nerve endings to register the pain. A refreshing taste comes from stimulation of the low temperature receptors in the mouth. Compounds like menthol or sorbitol dissolve in water by taking energy from their environment. This is called an endothermic reaction. The mouth loses some of its heat, and the cold receptors are alerted to this. Moreover, menthol reinforces the cold sensation, and you only have to open your mouth for the fresh sensation to be multiplied tenfold. Astringency defines the capacity of certain substances to constrict tissues such as tannins in wine. In this case, tactile receptors are called on. Does taste change with age? Yes, especially since age impacts all the senses. With age, deficiencies primarily concern sight and hearing whose sensors are not renewed as they disappear. However, the taste and olfactory receptors continually renew themselves, every ten days and three months, respectively. But, as we grow old, taste and olfactory acuity declines nonetheless with less effective cellular renewal. To feel and taste, more is required. A survey conducted in 1985 by the American psychologist Richard Doty from the University of Pennsylvania showed that olfactory performances diminish from the age of 60 onwards. But, in reality, it is the capacity to understand words which declines. In general terms, the deterioration of the central nervous system is faster than the peripheral deterioration of the senses. But if the brain irremediably loses neurons every day, learning and training of the senses and memory can make up for this loss by multiplying synapses, in other words, the links between neurons. Age is not the only factor capable of modifying the perception of taste. The sexual and hormonal identity of an individual influences their taste capacities, particularly by acting on the secretion and composition of saliva. In fact, during puberty, pregnancy, menopause, andropause and also while taking contraceptives, food will appear to have another taste. For women on the pill for instance, the perception of bittersweet flavors diminishes slightly; whereas, sensitivity to salty tastes increases. Medicinal products, along with anaesthetics and drugs, but also temperature, atmospheric pressure, color, and even noise can disrupt our perception of taste. Above 60 decibels, taste acuity diminishes. And we can all remember eating an ice cream which has suddenly grown too sweet once melted! [...]


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PROP TEST protocol

Objective Determine taste sensitivity to a bitter substance, 6-n-propylthiouracil, named PROP, and classify participants as "supertasters", "tasters," and "non-tasters" of bitterness, using a neutral, simple, and rapid method (Zhao et coll., 2003). Equipment

- Filter paper disk, Whatman no. 1 - 6-propyl-2-thiouracil; Aldrich Chemical Inc.

Preparation Prepare a 50mM solution (example: 1.7g in 200 ml). Mix the powder in pure water (Roucous water at 25 mg/l) boiling, while stirring. Using a tong, dip the paper disks, one after the other, for 10 s then shake them for 10 s and leave on a sheet of aluminium foil without overlaying. Leave overnight to dry. Keep the (stacked) papers in a box in a dry place at room temperature. Before the test, the paper disk is cut up into small pieces of ½ cm2. Reference A paper screening test to assess genetic taste sensitivity to 6-n-propylthiouracil. Zhao L.; Kirkmeyer S.V.; Tepper B.J.1. Source: Physiology and Behavior, Volume 78, Number 4, April 2003, pp. 625-633(9).

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