Topic: food
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth. Different species of animals have different feeding behaviours that satisfy the needs of their unique metabolisms, often evolving to fill a specific ecological niche within specific geographical contexts.
Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. The industrial food industry supplies most of the food energy required, which produces food with intensive agriculture and distributes it through complex food processing and distribution systems. This conventional agriculture system relies heavily on fossil fuels, which means that the food and agricultural system is one of the major contributors to climate change, accounting for as much as 37% of total greenhouse gas emissions. The food system significantly impacts many other social and political issues, including sustainability, biological diversity, economics, population growth, water supply, and access to food. International agencies like the International Association for Food Protection, World Resources Institute, World Food Programme, Food and Agriculture Organization, and International Food Information Council monitor food safety and food security.
Definition and classification
Food is any substance consumed to provide nutritional support and energy to an organism. It can be raw, processed or formulated and is consumed orally by animals for growth, health or pleasure. Food is mainly composed of water, lipids, proteins and carbohydrates. Minerals (e.g. salts) and organic substances (e.g. vitamins) can also be found in food. Plants, algae and some microorganisms use photosynthesis to make their food molecules. Water is found in many foods and has been defined as a food by itself. Water and fibre have low energy densities, or calories, while fat is the most energy-dense component. Some inorganic (non-food) elements are essential for plant and animal functioning. Human food can be classified in various ways, either by related content or by how the food is processed. The number and composition of food groups can vary. Most systems include four basic groups that describe their origin and relative nutritional function: Vegetables and Fruit, Cereals and Bread, and Dairy and Meat. Studies that look into diet quality often group food into whole grains/cereals, refined grains/cereals, vegetables, fruits, nuts, legumes, eggs, dairy products, fish, red meat, processed meat, and sugar-sweetened beverages. The Food and Agriculture Organization and World Health Organization use a system with nineteen food classifications: cereals, roots, pulses and nuts, milk, eggs, fish and shellfish, meat, insects, vegetables, fruits, fats and oils, sweets and sugars, spices and condiments, beverages, foods for nutritional uses, food additives, composite dishes and savoury snacks.
Food sources
Food forms a web of interlocking chains in a given ecosystem, with primary producers at the bottom and apex predators at the top. Other aspects of the web include detrivores (that eat detritus) and decomposers (that break down dead organisms). Primary producers include algae, plants, bacteria and protists that acquire their energy from sunlight. Primary consumers are the herbivores that consume the pants, and secondary consumers are the carnivores that consume those herbivores. Some organisms, including most mammals and birds, diets consist of both animals and plants, and they are considered omnivores. The chain ends with the apex predators, the animals with no known predators in their ecosystem. Humans are often considered apex predators. Humans are omnivores finding sustenance in vegetables, fruits, cooked meat, milk, eggs, mushrooms and seaweed. Cereal grain is a staple food that provides more energy worldwide than any other crop. Corn (maize), wheat, and rice account for 87% of worldwide grain production. Just over half of the world's crops are used to feed humans (55 per cent), with 36 per cent grown as animal feed and 9 per cent for biofuels. Fungi and bacteria are also used to prepare fermented foods like bread, wine, cheese and yoghurt.
Sunlight
Photosynthesis is the ultimate energy source and food for nearly all life on earth. It is the main food source for plants, algae and certain bacteria. Without this, all organisms which depend on these organisms further up the food chain would be unable to exist, from coral to lions. Energy from the sun is absorbed and used to transform water and carbon dioxide in the air or soil into oxygen and glucose. The oxygen is released, and the glucose is stored as an energy reserve.
Plants
Plants as a food source are often divided into seeds, fruits, vegetables, legumes, grains and nuts. Where plants fall within these categories can vary with botanically described fruits such as the tomato, squash, pepper and eggplant or seeds like peas, commonly considered vegetables. Food is a fruit if the part eaten is derived from the reproductive tissue, so seeds, nuts and grains are technically a fruit. From a culinary perspective, fruits are generally considered the remains of botanically described fruits after removed grains, nuts, seeds, and fruits used as vegetables. Grains can be defined as seeds that humans eat or harvest, with cereal grains (oats, wheat, rice, corn, barley, rye, sorghum and millet) belonging to the Poaceae (grass) family and pulses coming from the Fabaceae (legume) family. Whole grains contain all the elements of the original seed (bran, germ, and endosperm). Nuts are dry fruits distinguishable by their woody shell. Fleshy fruits (distinguishable from dry fruits like grain, seeds and nuts) can be further classified as stone fruits (cherries and peaches), pome fruits (apples, pears), berries (blackberry, strawberry), citrus (oranges, lemon), melons (watermelon, cantaloupe), Mediterranean fruits (grapes, fig), tropical fruits (banana, pineapple). Vegetables refer to any other part of the plant that can be eaten, including roots, stems, leaves, flowers, bark or the entire plant itself. These include root vegetables (potatoes and carrots), bulbs (onion family), flowers (cauliflower and broccoli), leaf vegetables (spinach and lettuce) and stem vegetables (celery and asparagus). Plants have high carbohydrate, protein and lipid content, with carbohydrates mainly in the form of starch, fructose, glucose and other sugars. Most vitamins are found in plant sources, with the notable exceptions of vitamin D and vitamin B12. Minerals are also plentiful, although the presence of phytates can prevent their release. Fruit can consist of up to 90% water, contain high levels of simple sugars that contribute to their sweet taste and have a high vitamin C content. Compared to fleshy fruit (except Bananas), vegetables are high in starch, potassium, dietary fibre, folate and vitamins and low in fat and calories. Grains are more starch-based, and nuts have a high protein, fibre, vitamin E and B content.
Seeds are a good food source for animals because they are abundant and contain fibre and healthy fats, such as omega-3 fats. Animals that only eat plants are called herbivores, with those that mostly eat fruits known as frugivores, and leaves, while shoot eaters are folivores (pandas) and wood eaters are termed xylophages (termites). Frugivores include various species, from annelids to elephants, chimpanzees and many birds. About 182 fish consume seeds or fruit. There are many types of grasses, adapted to different locations, that animals (domesticated and wild) use as their main source of nutrients. Humans only eat about 200 out of the world 400 000 plant species, despite at least half being edible. Most human plant-based food comes from maize, rice, and wheat. Plants can be processed into bread, pasta, cereals, juices and jams, or raw ingredients such as sugar, herbs, spices, and oils can be extracted. Oilseeds are often pressed to produce rich oils - sunflower, flaxseed, rapeseed (including canola oil) and sesame. Many plants and animals have coevolved so that the fruit is a good source of nutrition for the animal, which then excretes the seeds some distance away, allowing greater dispersal. Even seed predation can be mutually beneficial as some can survive digestion. Insects are major eaters of seeds, with ants being the only real seed dispersers. Birds, although major dispersers, only rarely eat seeds as a source of food and can be identified by their thick beak used to crack open the seed coat. Mammals eat a more diverse range of seeds as they can crush harder and larger seeds with their teeth.
Animals
Animals are used as food either directly or indirectly. This includes meat, eggs, shellfish and dairy products like milk and cheese. They are an important source of protein and are considered complete proteins for human consumption as they contain all the essential amino acids the human body needs. One 4-ounce (110 g) steak, chicken breast or pork chop contains about 30 grams of protein. One large egg has 7 grams of protein, a 4-ounce (110 g) serving of cheese of about 15 grams and 1 cup of milk of about 8. Other nutrients found in animal products include calories, fat, essential vitamins (including B12) and minerals (including zinc, iron, calcium, and magnesium). Food products produced by animals include milk produced by mammary glands, which in many cultures is drunk or processed into dairy products (cheese, butter, etc.). In addition, birds and other animals lay eggs, often eaten, and bees produce honey, a reduced nectar from flowers, a popular sweetener in many cultures. Some cultures consume blood, sometimes in the form of blood sausage, as a thickener for sauces, or in a cured, salted form for times of food scarcity, and others use blood in stews such as jugged hare. Some cultures and people do not consume meat or animal food products for cultural, dietary, health, ethical, or ideological reasons. Vegetarians choose to forgo food from animal sources to varying degrees. Vegans do not consume any foods that are or contain ingredients from an animal source.
Taste perception
Animals, specifically humans, have five tastes: sweet, sour, salty, bitter, and umami. As animals have evolved, the tastes that provide the most energy (sugar and fats) are the most pleasant to eat, while others, such as bitter, are not enjoyable. Water, while important for survival, has no taste. Fats, on the other hand, especially saturated fats, are thicker and richer and thus considered more enjoyable to eat.
Sweet
Generally regarded as the most pleasant taste, sweetness is almost always caused by simple sugar, such as glucose or fructose or disaccharides, such as sucrose, a molecule combining glucose and fructose. Complex carbohydrates are long chains and thus do not have a sweet taste. Artificial sweeteners such as sucralose mimic the sugar molecule, creating the sensation of sweetness without calories. Other types of sugar include raw sugar, known for its amber colour, as it is unprocessed. As sugar is vital for energy and survival, the taste of sugar is pleasant.
The stevia plant contains a compound known as steviol which, when extracted, has 300 times the sweetness of sugar while having minimal impact on blood sugar.
Sour
The taste of acids, such as vinegar, in alcoholic beverages, causes sourness. Sour foods include citrus, specifically lemons, limes, and to a lesser degree, oranges. Sour is evolutionarily significant as it signifies food that may have gone rancid due to bacteria. Many foods, however, are slightly acidic and help stimulate the taste buds and enhance flavour.
Salty
Saltiness is the taste of alkali metal ions such as sodium and potassium. It is found in almost every food in low to moderate proportions to enhance flavour, although eating pure salt is highly unpleasant. There are many different types of salt, each with a different degree of saltiness, including sea salt, fleur de sel, kosher salt, mined salt, and grey salt. Besides enhancing flavour, its significance is that the body needs and maintains a delicate electrolyte balance, which is the kidney's function. Salt may be iodized, meaning iodine has been added to it, a necessary nutrient that promotes thyroid function. Some canned foods, notably soups or packaged broths, tend to be high in salt to preserve the food longer. Historically salt has long been used as a meat preservative as salt promotes water excretion. Similarly, dried foods also promote food safety.
Bitter
Bitterness is a sensation often unpleasant and characterized by a sharp, pungent taste. Unsweetened dark chocolate, caffeine, lemon rind, and some types of fruit are known to be bitter.
Umami
Umami has been described as savoury and is characteristic of broths and cooked meats. Foods with a strong umami flavour include meats, shellfish, fish (including fish sauce and preserved fish such as Maldive fish, sardines, and anchovies), tomatoes, mushrooms, hydrolyzed vegetable protein, meat extract, yeast extract, cheeses, and soy sauce.
See also
References
Sources
Further reading
Collingham, E.M. (2011). The Taste of War: World War Two and the Battle for Food
Katz, Solomon (2003). The Encyclopedia of Food and Culture, Scribner
Nestle, Marion (2007). Food Politics: How the Food Industry Influences Nutrition and Health, University Presses of California, revised and expanded edition, ISBN 0-520-25403-1
Mobbs, Michael (2012). Sustainable Food Sydney: NewSouth Publishing, ISBN 978-1-920705-54-1
The Future of Food (2015). A panel discussion at the 2015 Digital Life Design (DLD) Annual Conference. "How can we grow and enjoy food closer to home, further into the future? MIT Media Lab's Kevin Slavin hosts a conversation with food artist, educator, and entrepreneur Emilie Baltz, professor Caleb Harper from MIT Media Lab's CityFarm project, the Barbarian Group's Benjamin Palmer, and Andras Forgacs, the co-founder and CEO of Modern Meadow, who is growing 'victimless' meat in a lab. The discussion addresses issues of sustainable urban farming, ecosystems, technology, food supply chains and their broad environmental and humanitarian implications, and how these changes in food production may change what people may find delicious ... and the other way around." Posted on the official YouTube Channel of DLD
External links
The dictionary definition of food at Wiktionary
Media related to food at Wikimedia Commons
Food Timeline
Wikibooks Cookbook
Food, BBC Radio 4 discussion with Rebecca Spang, Ivan Day and Felipe Fernandez-Armesto (In Our Time, 27 December 2001)
