93-649: Black rice , also known as purple rice or forbidden rice , is a range of rice types of the species Oryza sativa , some of which are glutinous rice . There are several varieties of black rice available today. These include Indonesian black rice, Philippine heirloom balatinaw black rice and pirurutong black glutinous rice , and Thai jasmine black rice. It is also known as chak-hao in Manipur , India and as “kavuni arisi” or “kavuni rice” in Tamil Nadu , India. The bran hull (outermost layer) of black rice contains one of
186-401: A covalent bond known as a glycosidic linkage formed via a dehydration reaction , resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C 12 H 22 O 11 . Although there are numerous kinds of disaccharides, a handful of disaccharides are particularly notable. Sucrose , pictured to the right,
279-416: A sustainable way. Many varieties of rice have been bred to improve crop quality and productivity. Biotechnology has created Green Revolution rice able to produce high yields when supplied with nitrogen fertiliser and managed intensively. Other products are rice able to express human proteins for medicinal use; flood-tolerant or deepwater rice ; and drought-tolerant and salt-tolerant varieties. Rice
372-413: A balanced diet that includes six one-ounce servings of grain foods each day, at least half from whole grain sources and the rest are from enriched . The glycemic index (GI) and glycemic load concepts have been developed to characterize food behavior during human digestion. They rank carbohydrate-rich foods based on the rapidity and magnitude of their effect on blood glucose levels. Glycemic index
465-403: A branched inflorescence which arises from the last internode on the stem. There can be up to 350 spikelets in a panicle, each containing male and female flower parts ( anthers and ovule ). A fertilised ovule develops into the edible grain or caryopsis . Rice is a cereal belonging to the family Poaceae . As a tropical crop, it can be grown during the two distinct seasons (dry and wet) of
558-517: A component of DNA , is a modified version of ribose ; chitin is composed of repeating units of N-acetyl glucosamine , a nitrogen -containing form of glucose. Carbohydrates are polyhydroxy aldehydes, ketones, alcohols, acids, their simple derivatives and their polymers having linkages of the acetal type. They may be classified according to their degree of polymerization , and may be divided initially into three principal groups, namely sugars, oligosaccharides and polysaccharides. Monosaccharides are
651-399: A form of carbohydrate storage in animal livers, was discovered by French physiologist Claude Bernard . Formerly the name "carbohydrate" was used in chemistry for any compound with the formula C m (H 2 O) n . Following this definition, some chemists considered formaldehyde (CH 2 O) to be the simplest carbohydrate, while others claimed that title for glycolaldehyde . Today,
744-467: A goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates). A 2017 Cochrane Systematic Review concluded that there was insufficient evidence to support the claim that whole grain diets can affect cardiovascular disease. Nutritionists often refer to carbohydrates as either simple or complex. However, the exact distinction between these groups can be ambiguous. The term complex carbohydrate
837-479: A monosaccharide often coexists with a closed ring form where the aldehyde / ketone carbonyl group carbon (C=O) and hydroxyl group (–OH) react forming a hemiacetal with a new C–O–C bridge. Monosaccharides can be linked together into what are called polysaccharides (or oligosaccharides ) in a large variety of ways. Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed. For example, deoxyribose ,
930-411: A role in various religions and traditions, such as in weddings . The rice plant can grow to over 1 m (3 ft) tall; if in deep water, it can reach a length of 5 m (16 ft). A single plant may have several leafy stems or tillers . The upright stem is jointed with nodes along its length; a long slender leaf arises from each node. The self-fertile flowers are produced in a panicle ,
1023-506: A single domestication event for O. sativa . Both indica and japonica forms of Asian rice sprang from a single domestication event in China from the wild rice Oryza rufipogon . Despite this evidence, it appears that indica rice arose when japonica arrived in India about 4,500 years ago and hybridised with another rice, whether an undomesticated proto- indica or wild O. nivara . Rice
SECTION 10
#17328590376541116-468: A symmetric molecule with no stereo centers. The assignment of D or L is made according to the orientation of the asymmetric carbon furthest from the carbonyl group: in a standard Fischer projection if the hydroxyl group is on the right the molecule is a D sugar, otherwise it is an L sugar. The "D-" and "L-" prefixes should not be confused with "d-" or "l-", which indicate the direction that the sugar rotates plane polarized light . This usage of "d-" and "l-"
1209-421: A wide variety of metabolic pathways across species: plants synthesize carbohydrates from carbon dioxide and water by photosynthesis storing the absorbed energy internally, often in the form of starch or lipids . Plant components are consumed by animals and fungi , and used as fuel for cellular respiration . Oxidation of one gram of carbohydrate yields approximately 16 kJ (4 kcal) of energy , while
1302-471: A wide variety of natural and processed foods. Starch is a polysaccharide and is abundant in cereals (wheat, maize, rice), potatoes, and processed food based on cereal flour , such as bread , pizza or pasta. Sugars appear in human diet mainly as table sugar (sucrose, extracted from sugarcane or sugar beets ), lactose (abundant in milk), glucose and fructose, both of which occur naturally in honey , many fruits , and some vegetables. Table sugar, milk, or honey
1395-440: A wide variety of pests including insects, nematodes, rodents such as rats, snails, and birds. Major rice insect pests include armyworms, rice bugs , black bugs , cutworms, field crickets, grasshoppers, leafhoppers, mealybugs, and planthoppers. High rates of nitrogen fertiliser application may worsen aphid outbreaks. Weather conditions can contribute to pest outbreaks: rice gall midge outbreaks are worsened by high rainfall in
1488-691: Is O -β-D-galactopyranosyl-(1→4)-D-glucopyranose. Other notable disaccharides include maltose (two D-glucoses linked α-1,4) and cellobiose (two D-glucoses linked β-1,4). Disaccharides can be classified into two types: reducing and non-reducing disaccharides. If the functional group is present in bonding with another sugar unit, it is called a reducing disaccharide or biose. Oligosaccharides are saccharide polymers composed of three to ten units of monosaccharides, connected via glycosidic linkages , similar to disaccharides . They are usually linked to lipids or amino acids glycosic linkage with oxygen or nitrogen to form glygolipids and glycoproteins , though some, like
1581-436: Is rainfed like wheat or maize. Across Asia, unmilled rice or "paddy" (Indonesian and Malay padi ), was traditionally the product of smallholder agriculture, with manual harvesting . Larger farms make use of machines such as combine harvesters to reduce the input of labour. The grain is ready to harvest when the moisture content is 20–25%. Harvesting involves reaping , stacking the cut stalks, threshing to separate
1674-661: Is 69% water, 29% carbohydrates , 2% protein , and contains negligible fat (table). In a reference serving of 100 grams (3.5 oz), cooked white rice provides 130 calories of food energy , and contains moderate levels of manganese (18% DV), with no other micronutrients in significant content (all less than 10% of the Daily Value ). In 2018, the World Health Organization strongly recommended fortifying rice with iron , and conditionally recommended fortifying it with vitamin A and with folic acid . Golden rice
1767-732: Is a cereal grain and in its domesticated form is the staple food of over half of the world's population , particularly in Asia and Africa . Rice is the seed of the grass species Oryza sativa (Asian rice)—or, much less commonly, Oryza glaberrima (African rice). Asian rice was domesticated in China some 13,500 to 8,200 years ago; African rice was domesticated in Africa about 3,000 years ago. Rice has become commonplace in many cultures worldwide; in 2021, 787 million tons were produced, placing it fourth after sugarcane , maize , and wheat . Only some 8% of rice
1860-613: Is a major food staple in Asia, Latin America, and some parts of Africa, feeding over half the world's population. However, a substantial part of the crop can be lost post-harvest through inefficient transportation, storage, and milling. A quarter of the crop in Nigeria is lost after harvest. Storage losses include damage by mould fungi if the rice is not dried sufficiently. In China, losses in modern metal silos were just 0.2%, compared to 7–13% when rice
1953-624: Is a measure of how quickly food glucose is absorbed, while glycemic load is a measure of the total absorbable glucose in foods. The insulin index is a similar, more recent classification method that ranks foods based on their effects on blood insulin levels, which are caused by glucose (or starch) and some amino acids in food. Low-carbohydrate diets may miss the health advantages – such as increased intake of dietary fiber – afforded by high-quality carbohydrates found in legumes and pulses , whole grains , fruits, and vegetables. A "meta-analysis, of moderate quality," included as adverse effects of
SECTION 20
#17328590376542046-483: Is a structural component of the cell wall of plants and many forms of algae. Ribose is a component of RNA . Deoxyribose is a component of DNA . Lyxose is a component of lyxoflavin found in the human heart. Ribulose and xylulose occur in the pentose phosphate pathway . Galactose , a component of milk sugar lactose , is found in galactolipids in plant cell membranes and in glycoproteins in many tissues . Mannose occurs in human metabolism, especially in
2139-498: Is a variety produced through genetic engineering to synthesize beta-carotene , a precursor of vitamin A, in the endosperm of the rice grain. It is intended to be grown and eaten in parts of the world where Vitamin A deficiency is prevalent. Golden rice has been opposed by activists, such as in the Philippines . In 2016 more than 100 Nobel laureates encouraged the use of genetically modified organisms , such as golden rice, for
2232-428: Is an aldopentose (a five-carbon aldehyde), and fructose is a ketohexose (a six-carbon ketone). Each carbon atom bearing a hydroxyl group (-OH), with the exception of the first and last carbons, are asymmetric , making them stereo centers with two possible configurations each (R or S). Because of this asymmetry, a number of isomers may exist for any given monosaccharide formula. Using Le Bel-van't Hoff rule ,
2325-441: Is an important component of coenzymes (e.g., ATP , FAD and NAD ) and the backbone of the genetic molecule known as RNA . The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system , fertilization , preventing pathogenesis , blood clotting , and development . Carbohydrates are central to nutrition and are found in
2418-581: Is based on four principles: biodiversity, host plant resistance, landscape ecology, and hierarchies in a landscape—from biological to social. Farmers' pesticide applications are often unnecessary. Pesticides may actually induce resurgence of populations of rice pests such as the brown planthopper , both by destroying beneficial insects and by enhancing the pest's reproduction. The International Rice Research Institute (IRRI) demonstrated in 1993 that an 87.5% reduction in pesticide use can lead to an overall drop in pest numbers. Farmers in China, Indonesia and
2511-526: Is calculated in the USDA database and does not always correspond to the sum of the sugars, the starch, and the "dietary fiber". Carbohydrate metabolism is the series of biochemical processes responsible for the formation , breakdown and interconversion of carbohydrates in living organisms . The most important carbohydrate is glucose , a simple sugar ( monosaccharide ) that is metabolized by nearly all known organisms. Glucose and other carbohydrates are part of
2604-504: Is from Asia. The average world yield for rice was 4.7 metric tons per hectare (2.1 short tons per acre), in 2022. Yuan Longping of China's National Hybrid Rice Research and Development Center set a world record for rice yield in 1999 at 17.1 metric tons per hectare (7.6 short tons per acre) on a demonstration plot. This employed specially developed hybrid rice and the System of Rice Intensification (SRI), an innovation in rice farming. Rice
2697-449: Is limited evidence to support routine use of low-carbohydrate dieting in managing type 1 diabetes . The American Diabetes Association recommends that people with diabetes should adopt a generally healthy diet, rather than a diet focused on carbohydrate or other macronutrients. An extreme form of low-carbohydrate diet – the ketogenic diet – is established as a medical diet for treating epilepsy . Through celebrity endorsement during
2790-474: Is most common in biochemistry , where it is a synonym of saccharide (from Ancient Greek σάκχαρον ( sákkharon ) 'sugar' ), a group that includes sugars , starch , and cellulose . The saccharides are divided into four chemical groups: monosaccharides , disaccharides , oligosaccharides , and polysaccharides . Monosaccharides and disaccharides, the smallest (lower molecular weight ) carbohydrates, are commonly referred to as sugars. While
2883-421: Is no longer followed in carbohydrate chemistry. The aldehyde or ketone group of a straight-chain monosaccharide will react reversibly with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal , forming a heterocyclic ring with an oxygen bridge between two carbon atoms. Rings with five and six atoms are called furanose and pyranose forms, respectively, and exist in equilibrium with
Black rice - Misplaced Pages Continue
2976-454: Is not clear how low-carbohydrate dieting affects cardiovascular health , although two reviews showed that carbohydrate restriction may improve lipid markers of cardiovascular disease risk. Carbohydrate-restricted diets are no more effective than a conventional healthy diet in preventing the onset of type 2 diabetes , but for people with type 2 diabetes, they are a viable option for losing weight or helping with glycemic control . There
3069-496: Is often added to drinks and many prepared foods such as jam, biscuits and cakes. Cellulose , a polysaccharide found in the cell walls of all plants, is one of the main components of insoluble dietary fiber . Although it is not digestible by humans, cellulose and insoluble dietary fiber generally help maintain a healthy digestive system by facilitating bowel movements . Other polysaccharides contained in dietary fiber include resistant starch and inulin , which feed some bacteria in
3162-464: Is prepared, individual differences in metabolism, and the chemistry of the carbohydrate. Carbohydrates are sometimes divided into "available carbohydrates", which are absorbed in the small intestine and "unavailable carbohydrates", which pass to the large intestine , where they are subject to fermentation by the gastrointestinal microbiota . The USDA's Dietary Guidelines for Americans 2010 call for moderate- to high-carbohydrate consumption from
3255-463: Is required in the early steps of glycolysis to phosphorylate Glucose to Glucose 6-Phosphate ( G6P ) and Fructose 6-Phosphate ( F6P ) to Fructose 1,6-biphosphate ( FBP ), thereby pushing the reaction forward irreversibly. In some cases, as with humans, not all carbohydrate types are usable as the digestive and metabolic enzymes necessary are not present. Carbohydrate chemistry is a large and economically important branch of organic chemistry. Some of
3348-797: Is sister to the bamboos, Bambusoideae , and the cereal subfamily Pooideae . The rice genus Oryza is one of eleven in the Oryzeae; it is sister to the Phyllorachideae . The edible rice species O. sativa and O. glaberrima are among some 300 species or subspecies in the genus. other grasses (inc. the C4 grasses , maize , sorghum ) Streptogyneae Ehrharteae Phyllorachideae Wild rices inc. Zizania other rice species and subspecies O. sativa (Asian rice) O. glaberrima (African rice) Bambusoideae (bamboos) Pooideae (grasses and cereals inc. wheat , barley ) Oryza sativa rice
3441-685: Is stickier, and is used for sweet dishes, and in Italy for risotto ; and sticky short-grain rice is used in Japanese sushi as it keeps its shape when cooked. White rice when cooked contains 29% carbohydrate and 2% protein, with some manganese . Golden rice is a variety produced by genetic engineering to contain vitamin A . Production of rice is estimated to have caused over 1% of global greenhouse gas emissions in 2022. Predictions of how rice yields will be affected by climate change vary across geographies and socioeconomic contexts. In human culture, rice plays
3534-438: Is subjected to a steaming process before it is milled. This makes the grain harder, and moves some of the grain's vitamins and minerals into the white part of the rice so these are retained after milling. Rice does not contain gluten , so is suitable for people on a gluten-free diet . Rice is a good source of protein and a staple food in many parts of the world, but it is not a complete protein as it does not contain all of
3627-438: Is the metabolic reaction which cells undergo to break down larger molecules, extracting energy. There are two major metabolic pathways of monosaccharide catabolism : glycolysis and the citric acid cycle . In glycolysis, oligo- and polysaccharides are cleaved first to smaller monosaccharides by enzymes called glycoside hydrolases . The monosaccharide units can then enter into monosaccharide catabolism. A 2 ATP investment
3720-450: Is the most abundant disaccharide, and the main form in which carbohydrates are transported in plants. It is composed of one D-glucose molecule and one D-fructose molecule. The systematic name for sucrose, O -α-D-glucopyranosyl-(1→2)-D-fructofuranoside, indicates four things: Lactose , a disaccharide composed of one D-galactose molecule and one D-glucose molecule, occurs naturally in mammalian milk. The systematic name for lactose
3813-699: Is three or more. A typical monosaccharide has the structure H–(CHOH) x (C=O)–(CHOH) y –H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group . Examples of monosaccharides are glucose , fructose , and glyceraldehydes . However, some biological substances commonly called "monosaccharides" do not conform to this formula (e.g., uronic acids and deoxy-sugars such as fucose ) and there are many chemicals that do conform to this formula but are not considered to be monosaccharides (e.g., formaldehyde CH 2 O and inositol (CH 2 O) 6 ). The open-chain form of
Black rice - Misplaced Pages Continue
3906-406: Is to flood the field to a depth of 5 cm (2 in), then to let the water level drop to 15 cm (6 in) below surface level, as measured by looking into a perforated field water tube sunk into the soil, and then repeating the cycle. Deepwater rice varieties tolerate flooding to a depth of over 50 centimetres for at least a month. Upland rice is grown without flooding, in hilly or mountainous regions; it
3999-509: Is traded internationally. China, India, and Indonesia are the largest consumers of rice. A substantial amount of the rice produced in developing nations is lost after harvest through factors such as poor transport and storage. Rice yields can be reduced by pests including insects , rodents , and birds , as well as by weeds , and by diseases such as rice blast . Traditional rice polycultures such as rice-duck farming , and modern integrated pest management seek to control damage from pests in
4092-471: Is used as a model organism in biology. Dry rice grain is milled to remove the outer layers; depending on how much is removed, products range from brown rice to rice with germ and white rice. Some is parboiled to make it easy to cook. Rice contains no gluten ; it provides protein but not all the essential amino acids needed for good health. Rice of different types is eaten around the world. Long-grain rice tends to stay intact on cooking; medium-grain rice
4185-525: The empirical formula C m (H 2 O) n (where m may or may not be different from n ), which does not mean the H has covalent bonds with O (for example with CH 2 O , H has a covalent bond with C but not with O). However, not all carbohydrates conform to this precise stoichiometric definition (e.g., uronic acids , deoxy-sugars such as fucose ), nor are all chemicals that do conform to this definition automatically classified as carbohydrates (e.g., formaldehyde and acetic acid ). The term
4278-440: The essential amino acids in sufficient amounts for good health. World trade figures are much smaller than those for production, as less than 8% of rice produced is traded internationally. China, an exporter of rice in the early 2000s, had become the world's largest importer of rice by 2013. Developing countries are the main players in the world rice trade; by 2012, India was the largest exporter of rice, with Thailand and Vietnam
4371-535: The glycosylation of certain proteins. Fructose , or fruit sugar, is found in many plants and humans, it is metabolized in the liver, absorbed directly into the intestines during digestion , and found in semen . Trehalose , a major sugar of insects, is rapidly hydrolyzed into two glucose molecules to support continuous flight. Two joined monosaccharides are called a disaccharide , the simplest kind of polysaccharide. Examples include sucrose and lactose . They are composed of two monosaccharide units bound together by
4464-1078: The lac operon will express enzymes for the digestion of lactose when it is present, but if both lactose and glucose are present the lac operon is repressed, resulting in the glucose being used first (see: Diauxie ). Polysaccharides are also common sources of energy. Many organisms can easily break down starches into glucose; most organisms, however, cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans . These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites , for example, use microorganisms to process cellulose. Even though these complex carbohydrates are not very digestible, they represent an important dietary element for humans, called dietary fiber . Fiber enhances digestion, among other benefits. The Institute of Medicine recommends that American and Canadian adults get between 45 and 65% of dietary energy from whole-grain carbohydrates. The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set
4557-486: The microbiota of the large intestine , and are metabolized by these bacteria to yield short-chain fatty acids . In scientific literature , the term "carbohydrate" has many synonyms, like "sugar" (in the broad sense), "saccharide", "ose", "glucide", "hydrate of carbon" or " polyhydroxy compounds with aldehyde or ketone ". Some of these terms, especially "carbohydrate" and "sugar", are also used with other meanings. In food science and in many informal contexts,
4650-769: The raffinose series and the fructooligosaccharides , do not. They have roles in cell recognition and cell adhesion . Carbohydrate consumed in food yields 3.87 kilocalories of energy per gram for simple sugars, and 3.57 to 4.12 kilocalories per gram for complex carbohydrate in most other foods. Relatively high levels of carbohydrate are associated with processed foods or refined foods made from plants, including sweets, cookies and candy, table sugar, honey, soft drinks, breads and crackers, jams and fruit products, pastas and breakfast cereals. Lower amounts of digestible carbohydrate are usually associated with unrefined foods as these foods have more fiber, including beans, tubers, rice, and unrefined fruit . Animal-based foods generally have
4743-687: The scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose , which was originally taken from the word glucose (from Ancient Greek γλεῦκος ( gleûkos ) 'wine, must '), and is used for almost all sugars (e.g., fructose (fruit sugar), sucrose ( cane or beet sugar), ribose , lactose (milk sugar)). Carbohydrates perform numerous roles in living organisms. Polysaccharides serve as an energy store (e.g., starch and glycogen ) and as structural components (e.g., cellulose in plants and chitin in arthropods and fungi). The 5-carbon monosaccharide ribose
SECTION 50
#17328590376544836-445: The -OH substituent on the anomeric carbon rests on the opposite side ( trans ) of the ring from the CH 2 OH side branch. The alternative form, in which the CH 2 OH substituent and the anomeric hydroxyl are on the same side (cis) of the plane of the ring, is called the β anomer . Monosaccharides are the major fuel source for metabolism , being used both as an energy source ( glucose being
4929-478: The 21st century as people in Asia and elsewhere ate less grain and more meat. An exception is Sub-Saharan Africa, where both per capita consumption of rice and population are increasing. Rice is a commonly-eaten food around the world. The varieties of rice are typically classified as short-, medium-, and long-grained. Oryza sativa indica varieties are usually long-grained; Oryza sativa japonica varieties are usually short- or medium-grained. Short-grain rice, with
5022-688: The Americas by the Spanish. In British North America by the time of the start of the American War of Independence , rice had become the fourth most valuable export commodity behind only tobacco, wheat, and fish. In 2021, world production of rice was 787 million tonnes , led by China and India with a combined 52% of the total. This placed rice fourth in the list of crops by production, after sugarcane , maize , and wheat . Other major producers were Bangladesh , Indonesia and Vietnam . 90% of world production
5115-460: The Philippines have traditionally managed weeds and pests by the polycultural practice of raising ducks and sometimes fish in their rice paddies. These produce valuable additional crops, eat small pest animals, manure the rice, and in the case of ducks also control weeds. Rice plants produce their own chemical defences to protect themselves from pest attacks. Some synthetic chemicals, such as
5208-401: The aldohexose D-glucose, for example, has the formula (C·H 2 O) 6 , of which four of its six carbons atoms are stereogenic, making D-glucose one of 2 =16 possible stereoisomers . In the case of glyceraldehydes , an aldotriose, there is one pair of possible stereoisomers, which are enantiomers and epimers . 1, 3-dihydroxyacetone , the ketose corresponding to the aldose glyceraldehydes, is
5301-419: The amount of fat vs carbohydrate in the diet." In the long term, effective weight loss or maintenance depends on calorie restriction , not the ratio of macronutrients in a diet. The reasoning of diet advocates that carbohydrates cause undue fat accumulation by increasing blood insulin levels, and that low-carbohydrate diets have a "metabolic advantage", is not supported by clinical evidence . Further, it
5394-465: The benefits these could bring. In 2022, greenhouse gas emissions from rice cultivation were estimated at 5.7 billion tonnes CO2eq, representing 1.2% of total emissions. Within the agriculture sector, rice produces almost half the greenhouse gas emissions from croplands , some 30% of agricultural methane emissions , and 11% of agricultural nitrous oxide emissions. Methane is released from rice fields subject to long-term flooding, as this inhibits
5487-433: The carbonyl group is an aldehyde , the monosaccharide is an aldose ; if the carbonyl group is a ketone , the monosaccharide is a ketose . Monosaccharides with three carbon atoms are called trioses , those with four are called tetroses , five are called pentoses , six are hexoses , and so on. These two systems of classification are often combined. For example, glucose is an aldohexose (a six-carbon aldehyde), ribose
5580-506: The crop would be lost under these conditions. In the Po Valley in Italy, the arborio and carnaroli risotto rice varieties have suffered poor harvests through drought in the 21st century. The Ente Nazionale Risi [ it ] is developing drought-resistant varieties; its nuovo prometeo variety has deep roots that enable it to tolerate drought, but is not suitable for risotto. Rice yield can be reduced by weed growth, and
5673-401: The diet halitosis , headache and constipation . Carbohydrate-restricted diets can be as effective as low-fat diets in helping achieve weight loss over the short term when overall calorie intake is reduced. An Endocrine Society scientific statement said that "when calorie intake is held constant [...] body-fat accumulation does not appear to be affected by even very pronounced changes in
SECTION 60
#17328590376545766-413: The early 21st century, it became a fad diet as a means of weight loss, but with risks of undesirable side effects , such as low energy levels and increased hunger, insomnia , nausea, and gastrointestinal discomfort. The British Dietetic Association named it one of the "top 5 worst celeb diets to avoid in 2018". Most dietary carbohydrates contain glucose, either as their only building block (as in
5859-425: The exception of Spanish Bomba, is usually sticky when cooked, and is suitable for puddings. Thai Jasmine rice is aromatic, and unusually for a long-grain rice has some stickiness, with a soft texture. Indian Basmati rice is very long-grained and aromatic. Italian Arborio rice , used for risotto , is of medium length, oval, and quite sticky. Japanese sushi rice is a sticky short-grain variety. Cooked white rice
5952-425: The field where they will grow, or seedlings can be grown in a seedbed and transplanted into the field. Direct seeding needs some 60 to 80 kg of grain per hectare, while transplanting needs less, around 40 kg per hectare, but requires far more labour. Most rice in Asia is transplanted by hand. Mechanical transplanting takes less time but requires a carefully-prepared field and seedlings raised on mats or in trays to fit
6045-503: The grain, and cleaning by winnowing or screening . The rice grain is dried as soon as possible to bring the moisture content down to a level that is safe from mould fungi. Traditional drying relies on the heat of the sun, with the grain spread out on mats or on pavements. The edible rice species are members of the BOP clade within the grass family, the Poaceae . The rice subfamily, Oryzoideae ,
6138-431: The great diversity and continuous evolution of pests. Resistance genes are being sought from wild species of rice, and genetic engineering techniques are being applied. Carbohydrate A carbohydrate ( / ˌ k ɑːr b oʊ ˈ h aɪ d r eɪ t / ) is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with
6231-575: The herbicide 2,4-D , cause the plant to increase the production of certain defensive chemicals and thereby increase the plant's resistance to some types of pests. Conversely, other chemicals, such as the insecticide imidacloprid , appear to induce changes in the gene expression of the rice that make the plant more susceptible to certain pests. Plant breeders have created rice cultivars incorporating resistance to various insect pests . Conventional plant breeding of resistant varieties has been limited by challenges such as rearing insect pests for testing, and
6324-513: The highest levels of anthocyanin pigment found in food. The grain has a similar amount of fiber to brown rice and like brown rice, has a mild, nutty taste. Black rice has a deep black color and usually turns deep purple when cooked. Its dark purple color is primarily due to its anthocyanin content, which is higher by weight than that of other colored grains. It is suitable for creating porridge , dessert , traditional Chinese black rice cake, bread , and noodles . Rice Rice
6417-410: The later years of the 20th century decreased rice yield by between 10% and 20% across 200 farms in seven Asian countries. This may have been caused by increased night-time respiration. IRRI has predicted that Asian rice yields will fall by some 20% per 1°C rise in global mean temperature. Further, rice is unable to yield grain if the flowers experience a temperature of 35 °C or more for over one hour, so
6510-409: The lowest carbohydrate levels, although milk does contain a high proportion of lactose . Organisms typically cannot metabolize all types of carbohydrate to yield energy. Glucose is a nearly universal and accessible source of energy. Many organisms also have the ability to metabolize other monosaccharides and disaccharides but glucose is often metabolized first. In Escherichia coli , for example,
6603-417: The machine. Rice does not thrive if continuously submerged. Rice can be grown in different environments, depending upon water availability. The usual arrangement is for lowland fields to be surrounded by bunds and flooded to a depth of a few centimetres until around a week before harvest time; this requires a large amount of water. The "alternate wetting and drying" technique uses less water. One form of this
6696-476: The main organic reactions that involve carbohydrates are: Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. This can include the synthesis of monosaccharide residues or structures containing more than one monosaccharide, known as oligosaccharides . Selective formation of glycosidic linkages and selective reactions of hydroxyl groups are very important, and
6789-459: The most important in nature as it is the product of photosynthesis in plants) and in biosynthesis . When monosaccharides are not immediately needed, they are often converted to more space-efficient (i.e., less water-soluble) forms, often polysaccharides . In many animals, including humans, this storage form is glycogen , especially in liver and muscle cells. In plants, starch is used for the same purpose. The most abundant carbohydrate, cellulose ,
6882-428: The other largest exporters. As of 2016, the countries that consumed the most rice were China (29% of total), India, and Indonesia. By 2020, Bangladesh had taken third place from Indonesia. On an annual average from 2020-23, China consumed 154 million tonnes of rice, India consumed 109 million tonnes, and Bangladesh and Indonesia consumed about 36 million tonnes each. Across the world, rice consumption per capita fell in
6975-547: The oxidation of one gram of lipids yields about 38 kJ (9 kcal). The human body stores between 300 and 500 g of carbohydrates depending on body weight, with the skeletal muscle contributing to a large portion of the storage. Energy obtained from metabolism (e.g., oxidation of glucose) is usually stored temporarily within cells in the form of ATP . Organisms capable of anaerobic and aerobic respiration metabolize glucose and oxygen (aerobic) to release energy, with carbon dioxide and water as byproducts. Catabolism
7068-588: The polysaccharides starch and glycogen), or together with another monosaccharide (as in the hetero-polysaccharides sucrose and lactose). Unbound glucose is one of the main ingredients of honey. Glucose is extremely abundant and has been isolated from a variety of natural sources across the world, including male cones of the coniferous tree Wollemia nobilis in Rome, the roots of Ilex asprella plants in China, and straws from rice in California. ^A The carbohydrate value
7161-439: The position of the hydroxyl group (red or green) on the anomeric carbon relative to the CH 2 OH group bound to carbon 5: they either have identical absolute configurations (R,R or S,S) (α), or opposite absolute configurations (R,S or S,R) (β). Monosaccharides are classified according to three different characteristics: the placement of its carbonyl group, the number of carbon atoms it contains, and its chiral handedness. If
7254-406: The simple vs. complex chemical distinction has little value for determining the nutritional quality of carbohydrates. Some simple carbohydrates (e.g., fructose ) raise blood glucose rapidly, while some complex carbohydrates (starches), raise blood sugar slowly. The speed of digestion is determined by a variety of factors including which other nutrients are consumed with the carbohydrate, how the food
7347-533: The simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. They are aldehydes or ketones with two or more hydroxyl groups. The general chemical formula of an unmodified monosaccharide is (C•H 2 O) n , literally a "carbon hydrate". Monosaccharides are important fuel molecules as well as building blocks for nucleic acids. The smallest monosaccharides, for which n=3, are dihydroxyacetone and D- and L-glyceraldehydes. [REDACTED] [REDACTED] The α and β anomers of glucose. Note
7440-1011: The soil from absorbing atmospheric oxygen, resulting in anaerobic fermentation of organic matter in the soil. Emissions can be limited by planting new varieties, not flooding continuously, and removing straw. It is possible to cut methane emissions in rice cultivation by improved water management, combining dry seeding and one drawdown, or executing a sequence of wetting and drying . This results in emission reductions of up to 90% compared to full flooding and even increased yields. Predictions of climate change's effects on rice cultivation vary. Global rice yield has been projected to decrease by around 3.2% with each 1°C increase in global average temperature while another study predicts global rice cultivation will increase initially, plateauing at about 3°C warming (2091–2100 relative to 1850–1900). The impacts of climate change on rice cultivation vary across geographic location and socioeconomic context. For example, rising temperatures and decreasing solar radiation during
7533-401: The straight-chain form. During the conversion from straight-chain form to the cyclic form, the carbon atom containing the carbonyl oxygen, called the anomeric carbon , becomes a stereogenic center with two possible configurations: The oxygen atom may take a position either above or below the plane of the ring. The resulting possible pair of stereoisomers is called anomers . In the α anomer ,
7626-533: The strict sense, " sugar " is applied for sweet, soluble carbohydrates, many of which are used in human food. The history of the discovery regarding carbohydrates dates back around 10,000 years ago in Papua New Guinea during the cultivation of sugarcane during the Neolithic agricultural revolution. The term "carbohydrate" was first proposed by German chemist Carl Schmidt (chemist) in 1844. In 1856, glycogen ,
7719-438: The term "carbohydrate" (or "carbohydrate by difference") is used for everything other than water, protein, fat, ash, and ethanol. This includes chemical compounds such as acetic or lactic acid , which are not normally considered carbohydrates. It also includes dietary fiber which is a carbohydrate but which does not contribute food energy in humans, even though it is often included in the calculation of total food energy. In
7812-496: The term "carbohydrate" often means any food that is particularly rich in the complex carbohydrate starch (such as cereals, bread and pasta) or simple carbohydrates, such as sugar (found in candy, jams , and desserts). This informality is sometimes confusing since it confounds chemical structure and digestibility in humans. Often in lists of nutritional information , such as the USDA National Nutrient Database ,
7905-456: The term complex carbohydrate to refer to any sort of digestible saccharide present in a whole food, where fiber, vitamins and minerals are also found (as opposed to processed carbohydrates, which provide energy but few other nutrients). The standard usage, however, is to classify carbohydrates chemically: simple if they are sugars ( monosaccharides and disaccharides ) and complex if they are polysaccharides (or oligosaccharides ). In any case,
7998-714: The term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons and includes many biological carbohydrates which deviate from this formula. For example, while the above representative formulas would seem to capture the commonly known carbohydrates, ubiquitous and abundant carbohydrates often deviate from this. For example, carbohydrates often display chemical groups such as: N -acetyl (e.g., chitin ), sulfate (e.g., glycosaminoglycans ), carboxylic acid and deoxy modifications (e.g., fucose and sialic acid ). Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH 2 O) n where n
8091-628: The voyage to the rest of the Pacific. It reached Austroasiatic and Kra-Dai -speakers in Mainland Southeast Asia and southern China by 5000 years ago. Rice spread around the rest of the world through cultivation, migration and trade, eventually to the Americas as part of the Columbian exchange after 1492. The now less common Oryza glaberrima (African rice) was independently domesticated in Africa around 3,000 years ago, and introduced to
8184-785: The wet season, while thrips outbreaks are associated with drought. Rice blast , caused by the fungus Magnaporthe grisea , is the most serious disease of growing rice. It and bacterial leaf streak (caused by Xanthomonas oryzae pv. oryzae ) are perennially the two worst rice diseases worldwide; they are both among the ten most important diseases of all crop plants. Other major rice diseases include sheath blight (caused by Rhizoctonia solani ), false smut ( Ustilaginoidea virens ), and bacterial panicle blight ( Burkholderia glumae ). Viral diseases include rice bunchy stunt, rice dwarf, rice tungro , and rice yellow mottle. Crop protection scientists are developing sustainable techniques for managing rice pests. Sustainable pest management
8277-539: The year provided that sufficient water is made available. It is normally an annual, but in the tropics it can survive as a perennial , producing a ratoon crop. Like all crops, rice depends for its growth on both biotic and abiotic environmental factors. The principal biotic factors are crop variety, pests , and plant diseases . Abiotic factors include the soil type, whether lowland or upland, amount of rain or irrigation water, temperature, day length , and intensity of sunlight. Rice grains can be planted directly into
8370-465: Was first domesticated in China 9,000 years ago, by people of Neolithic cultures in the Upper and Lower Yangtze , associated with Hmong-Mien -speakers and pre-Austronesians , respectively. The functional allele for nonshattering , the critical indicator of domestication in grains, as well as five other single-nucleotide polymorphisms , is identical in both indica and japonica . This implies
8463-545: Was first used in the U.S. Senate Select Committee on Nutrition and Human Needs publication Dietary Goals for the United States (1977) where it was intended to distinguish sugars from other carbohydrates (which were perceived to be nutritionally superior). However, the report put "fruit, vegetables and whole-grains" in the complex carbohydrate column, despite the fact that these may contain sugars as well as polysaccharides. This confusion persists as today some nutritionists use
8556-559: Was introduced early into Sino-Tibetan cultures in northern China by around 6000 to 5600 years ago, and to the Korean peninsula and Japan by around 5500 to 3200 years ago. It was also carried into Taiwan by the Dapenkeng culture by 5500 to 4000 years ago, before spreading southwards via the Austronesian migrations to Island Southeast Asia , Madagascar , and Guam , but did not survive
8649-439: Was stored by rural households. The dry grain is milled to remove the outer layers, namely the husk and bran . These can be removed in a single step, in two steps, or as in commercial milling in a multi-step process of cleaning, dehusking, separation, polishing, grading, and weighing. Brown rice only has the inedible husk removed. Further milling removes bran and the germ to create successively whiter products. Parboiled rice
#653346