Misplaced Pages

#977022

83-480: There are two main religions in Lejja, which include Christianity and African tradition worshippers. Lejja is predominantly a community of farmers. Some of the local farm produce grown in the community are yam , cassava , coco yam , Nsukka yellow pepper and many vegetables. The produce is grown on a small to medium scale and thus farmers use mostly human labour for their farming activities. Another common occupation among

166-525: A combination of the two. The resulting fragments are known as dextrins . The extent of conversion is typically quantified by dextrose equivalent (DE), which is roughly the fraction of the glycosidic bonds in starch that have been broken. These starch sugars are by far the most common starch based food ingredient and are used as sweeteners in many drinks and foods. They include: The modified food starches are E coded according to European Food Safety Authority and INS coded Food Additives according to

249-558: A complex molecular event that can be subdivided into four major steps, namely, granule initiation, coalescence of small granules, phase transition, and expansion. Several proteins have been characterized for their involvement in each of these processes. For instance, a chloroplast membrane-associated protein, MFP1, determines the sites of granule initiation. Another protein named PTST2 binds to small glucan chains and agglomerates to recruit starch synthase 4 (SS4). Three other proteins, namely, PTST3, SS5, and MRC, are also known to be involved in

332-519: A dietary AGE is acrylamide . Recent evidence suggests that the intestinal fermentation of dietary AGEs may be associated with insulin resistance , atherosclerosis , diabetes and other inflammatory diseases. This may be due to the impact of AGEs on intestinal permeability. Starch gelatinization during cake baking can be impaired by sugar competing for water , preventing gelatinization and improving texture. Starch can be hydrolyzed into simpler carbohydrates by acids , various enzymes , or

415-497: A few of which are widely grown for their edible tuber but others of which are toxic (such as D. communis ). Yam plants can grow up to 15 metres (49 feet) in length and 7.6 to 15.2 centimetres (3 to 6 inches) high. The tuber may grow into the soil up to 1.5 m (5 ft) deep. The plant disperses by seed . The edible tuber has a rough skin that is difficult to peel but readily softened by cooking. The skins vary in color from dark brown to light pink. The majority, or meat, of

498-513: A fresh-weight basis. Yams, with cassava , provide a much greater proportion of the protein intake in Africa, ranging from 5.9% in East and South Africa to about 15.9% in humid West Africa. As a relatively low-protein food, yam is not a good source of essential amino acids . Experts emphasize the need to supplement a yam-dominant diet with more protein-rich foods to support healthy growth in children. Yam

581-494: A glucose molecule is released. Now, BAM can release another maltose molecule from the remaining chain. This cycle repeats until starch is fully degraded. If BAM comes close to the phosphorylated branching point of the glucose chain, it can no longer release maltose. In order for the phosphorylated chain to be degraded, the enzyme isoamylase (ISA) is required. The products of starch degradation are predominantly maltose and smaller amounts of glucose. These molecules are exported from

664-542: A great potential for increased production. D. hirtiflora subsp. pedicellata , lusala, busala or lwidi, is native to Tropical Africa . It is widely harvested and eaten in Southern Zambia where it grows in open forest areas. In Southern Zambia, it is an important addition to the March–September diets of almost all, and income of over half of rural households. Research on propagation of this subspecies to alleviate

747-671: A higher gelatinization temperature than other types of starch, and retains its resistant starch content through baking , mild extrusion and other food processing techniques. It is used as an insoluble dietary fiber in processed foods such as bread, pasta, cookies, crackers, pretzels and other low moisture foods. It is also utilized as a dietary supplement for its health benefits. Published studies have shown that resistant starch helps to improve insulin sensitivity, reduces pro-inflammatory biomarkers interleukin 6 and tumor necrosis factor alpha and improves markers of colonic function. It has been suggested that resistant starch contributes to

830-456: A lesser extent, sources of refined starch are sweet potato, sago and mung bean. To this day, starch is extracted from more than 50 types of plants. Crude starch is processed on an industrial scale to maltodextrin and glucose syrups and fructose syrups. These massive conversions are mediated by a variety of enzymes, which break down the starch to varying extents. Here breakdown involves hydrolysis, i.e. cleavage of bonds between sugar subunits by

913-416: A mixture of pigments, binders and thickeners. Coated paper has improved smoothness, hardness, whiteness and gloss and thus improves printing characteristics. Corrugated board adhesives are the next largest application of non-food starches globally. Starch glues are mostly based on unmodified native starches, plus some additive such as borax and caustic soda . Part of the starch is gelatinized to carry

SECTION 10

#1732873363978

996-478: A mold in the conventional sense. A tray is filled with native starch and leveled. A positive mold is then pressed into the starch leaving an impression of 1,000 or so jelly beans. The jelly mix is then poured into the impressions and put onto a stove to set. This method greatly reduces the number of molds that must be manufactured. Resistant starch is starch that escapes digestion in the small intestine of healthy individuals. High-amylose starch from wheat or corn has

1079-664: A phosphate at the C-6 position of glucose, close to the chain's 1,6-alpha branching bonds. A second enzyme, phosphoglucan, water dikinase (PWD) phosphorylates the glucose molecule at the C-3 position. After the second phosphorylation, the first degrading enzyme, beta-amylase (BAM) attacks the glucose chain at its non-reducing end. Maltose is the main product released. If the glucose chain consists of three or fewer molecules, BAM cannot release maltose. A second enzyme, disproportionating enzyme-1 (DPE1), combines two maltotriose molecules. From this chain,

1162-760: A practice that complicates harvesting in some cases. In forested areas, tubers grow in areas where other tree roots are present. Harvesting the tuber then involves the additional step of freeing them from other roots. This often causes tuber damage. Aerial tubers or bulbils are harvested by manual plucking from the vine. Yields may improve and cost of yam production be lower if mechanization were to be developed and adopted. However, current crop production practices and species used pose considerable hurdles to successful mechanization of yam production, particularly for small-scale rural farmers. Extensive changes in traditional cultivation practices, such as mixed cropping, may be required. Modification of current tuber harvesting equipment

1245-450: A precursor to myriad organic building blocks such as nucleic acids , lipids , proteins , and structural polysaccharides such as cellulose . Most green plants store any extra glucose in the form of starch, which is packed into semicrystalline granules called starch or amyloplasts . Toward the end of the growing season, starch accumulates in twigs of trees near the buds. Fruit , seeds , rhizomes , and tubers store starch to prepare for

1328-433: A preferred food and a culturally important food security crop in some sub-Saharan African countries. The following table shows the nutrient content of yam and major staple foods in a raw harvested form on a dry weight basis to account for their different water contents. Raw forms, however, are not edible and cannot be digested. These must be sprouted, or prepared and cooked for human consumption. In sprouted or cooked form,

1411-548: A prefix for several carbon compounds related to or derived from starch (e.g. amyl alcohol , amylose , amylopectin ). Starch grains from the rhizomes of Typha (cattails, bullrushes) as flour have been identified from grinding stones in Europe dating back to 30,000 years ago. Starch grains from sorghum were found on grind stones in caves in Ngalue , Mozambique dating up to 100,000 years ago. Pure extracted wheat starch paste

1494-443: A similar type of polysaccharide called floridean starch in their cytosol or periplast . Especially when hydrated, glucose takes up much space and is osmotically active. Starch, on the other hand, being insoluble and therefore osmotically inactive, can be stored much more compactly. The semicrystalline granules generally consist of concentric layers of amylose and amylopectin which can be made bioavailable upon cellular demand in

1577-464: A single large tuber per year, generally weighing 5 to 10 kilograms (11 to 22 pounds). Yams suffer from relatively few pests and diseases. There is an anthracnose caused by Colletotrichum gloeosporioides which is widely distributed around the world's growing regions. Winch et al. , 1984 finds C. gloeosporioides afflicts a large number of Dioscorea spp. Despite the high labor requirements and production costs, consumer demand for yam

1660-535: A typical sheet of copy paper for instance, the starch content may be as high as 8%. Both chemically modified and unmodified starches are used in papermaking. In the wet part of the papermaking process, generally called the "wet-end", the starches used are cationic and have a positive charge bound to the starch polymer. These starch derivatives associate with the anionic or negatively charged paper fibers / cellulose and inorganic fillers. Cationic starches together with other retention and internal sizing agents help to give

1743-409: A vessel of salt water, in cold or hot fresh water or in a stream. The bitter compounds in these yams are water-soluble alkaloids which, on ingestion, produce severe and distressing symptoms. Severe cases of alkaloid intoxication may prove fatal. Aerial or potato yams ( D. bulbifera ) have antinutritional factors. In Asia, detoxification methods, involving water extraction, fermentation, and roasting of

SECTION 20

#1732873363978

1826-434: Is waxy maize , others are glutinous rice and waxy potato starch . Waxy starches undergo less retrogradation , resulting in a more stable paste. A maize cultivar with a relatively high proportion of amylose starch, amylomaize , is cultivated for the use of its gel strength and for use as a resistant starch (a starch that resists digestion) in food products. Plants synthesize starch in two types of tissues. The first type

1909-429: Is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds . This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in staple foods such as wheat , potatoes , maize (corn), rice , and cassava (manioc). Pure starch is a white, tasteless and odorless powder that

1992-492: Is an important dietary element for Nigerian and West African people. It contributes more than 200 calories per person per day for more than 150 million people in West Africa, and is an important source of income. Yam is an attractive crop in poor farms with limited resources. It is rich in starch, and can be prepared in many ways. It is available all year round, unlike other, unreliable, seasonal crops. These characteristics make yam

2075-403: Is from a Germanic root with the meanings "strong, stiff, strengthen, stiffen". Modern German Stärke (strength, starch) is related and refers to the main historical applications, its uses in textiles: sizing yarn for weaving , and starching linen . The Greek term for starch, "amylon" (ἄμυλον), which means "not milled", is also related. It provides the root amyl , which is used as

2158-578: Is high in certain subregions of Africa, making yam cultivation quite profitable to certain farmers. Many cultivated species of Dioscorea yams are found throughout the humid tropics. The most economically important are discussed below. Non- Dioscorea tubers that were historically important in Africa include Plectranthus rotundifolius (the Hausa potato) and P. esculentus (the Livingstone potato); these two tuber crops have now been largely displaced by

2241-481: Is insoluble in cold water or alcohol . It consists of two types of molecules: the linear and helical amylose and the branched amylopectin . Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. Glycogen , the energy reserve of animals, is a more highly branched version of amylopectin. In industry, starch is often converted into sugars, for example by malting . These sugars may be fermented to produce ethanol in

2324-547: Is native to China . The Chinese yam plant is somewhat smaller than the African, with the vines about 3 m (10 ft) long. It is tolerant to frost and can be grown in much cooler conditions than other yams. It is also grown in Korea and Japan . It was introduced to Europe in the 19th century, when the potato crop there was falling victim to disease, and is still grown in France for

2407-838: Is necessary given yam tuber architecture and its different physical properties. In 2020, world production of yams was 75 million metric tons (74,000,000 long tons; 83,000,000 short tons), led by Nigeria with 67% of the total (table). Unlike cassava , most varieties of edible, mature, cultivated yam do not contain toxic compounds. However, there are exceptions. Bitter compounds tend to accumulate in immature tuber tissues of white and yellow yams. These may be polyphenols or tannin -like compounds. Wild forms of bitter yams ( D. dumetorum ) do contain some toxins, such as dihydrodioscorine , that taste bitter, hence are referred to as bitter yam. Bitter yams are not normally eaten except at times of desperation in poor countries and in times of local food scarcity. They are usually detoxified by soaking in

2490-428: Is preferred by most people. However, it is popular in home vegetable gardens because it produces a crop after only four months of growth and continues producing for the life of the vine, as long as two years. Also, the bulbils are easy to harvest and cook. In 1905, the air potato was introduced to Florida and has since become an invasive species in much of the state. Its rapid growth crowds out native vegetation and it

2573-477: Is said that they have also been used for criminal purposes. D. trifida , the cush-cush yam, is native to the Guyana region of South America and is the most important cultivated New World yam. Since they originated in tropical rainforest conditions, their growth cycle is less related to seasonal changes than other yams. Because of their relative ease of cultivation and their good flavor, they are considered to have

Lejja - Misplaced Pages Continue

2656-485: Is second only to white yam. The tuber shape is generally cylindrical, but can vary. Tuber flesh is white and watery in texture. D. alata and D. esculenta (lesser yam) were important staple crops to the seafaring Austronesian cultures. They were carried along with the Austronesian migrations as canoe plants , from Island Southeast Asia to as far as Madagascar and Polynesia . D. polystachya , Chinese yam,

2739-472: Is slow but relatively complete within the small intestine. Widely used prepared foods containing starch are bread , pancakes , cereals , noodles , pasta , porridge and tortilla . During cooking with high heat, sugars released from starch can react with amino acids via the Maillard reaction , forming advanced glycation end-products (AGEs), contributing aromas, flavors and texture to foods. One example of

2822-416: Is storage tissues, for example, cereal endosperm, and storage roots and stems such as cassava and potato. The second type is green tissue, for example, leaves, where many plant species synthesize transitory starch on a daily basis. In both tissue types, starch is synthesized in a plastids (amyloplasts and chloroplasts). The biochemical pathway involves conversion of glucose 1-phosphate to ADP -glucose using

2905-528: Is stored in semi-crystalline granules. Each plant species has a distinctive starch granular size: rice starch is relatively small (about 2 μm), potato starches have larger granules (up to 100 μm) while wheat and tapioca fall in-between. Unlike other botanical sources of starch, wheat starch has a bimodal size distribution, with both smaller and larger granules ranging from 2 to 55 μm. Some cultivated plant varieties have pure amylopectin starch without amylose, known as waxy starches . The most used

2988-438: Is subjected to dry heat, it breaks down to form dextrins , also called "pyrodextrins" in this context. This break down process is known as dextrinization. (Pyro)dextrins are mainly yellow to brown in color and dextrinization is partially responsible for the browning of toasted bread. Starch is the most common carbohydrate in the human diet and is contained in many staple foods . The major sources of starch intake worldwide are

3071-402: Is used in the manufacture of various adhesives or glues for book-binding, wallpaper adhesives , paper sack production, tube winding, gummed paper , envelope adhesives, school glues and bottle labeling. Starch derivatives, such as yellow dextrins, can be modified by addition of some chemicals to form a hard glue for paper work; some of those forms use borax or soda ash , which are mixed with

3154-450: Is very difficult to remove since it can grow back from the tubers, and new vines can grow from the bulbils even after being cut down or burned. D. esculenta , the lesser yam, was one of the first yam species cultivated. It is native to Southeast Asia and is the third-most commonly cultivated species there, although it is cultivated very little in other parts of the world. Its vines seldom reach more than 3 m (10 ft) in length and

3237-756: The Caribbean , Asia, and Oceania . About 95% of yam crops are grown in Africa. A yam crop begins when whole seed tubers or tuber portions are planted into mounds or ridges, at the beginning of the rainy season. The crop yield depends on how and where the sets are planted, sizes of mounds, interplant spacing, provision of stakes for the resultant plants, yam species, and tuber sizes desired at harvest. Small-scale farmers in West and Central Africa often intercrop yams with cereals and vegetables. The seed yams are perishable and bulky to transport. Farmers who do not buy new seed yams usually set aside up to 30% of their harvest for planting

3320-798: The Codex Alimentarius : INS 1400, 1401, 1402, 1403 and 1405 are in the EU food ingredients without an E-number. Typical modified starches for technical applications are cationic starches , hydroxyethyl starch , carboxymethylated starches and thiolated starches. As an additive for food processing , food starches are typically used as thickeners and stabilizers in foods such as puddings, custards, soups, sauces, gravies, pie fillings, and salad dressings, and to make noodles and pastas. They function as thickeners, extenders, emulsion stabilizers and are exceptional binders in processed meats. Gummed sweets such as jelly beans and wine gums are not manufactured using

3403-462: The EU the starch industry produced about 11 million tonnes in 2011, with around 40% being used for industrial applications and 60% for food uses, most of the latter as glucose syrups . In 2017 EU production was 11 million ton of which 9,4 million ton was consumed in the EU and of which 54% were starch sweeteners. The US produced about 27.5 million tons of starch in 2017, of which about 8.2 million tons

Lejja - Misplaced Pages Continue

3486-405: The bulbils which grow at the base of its leaves are the more important food product. They are about the size of potatoes (hence the name "air potato"), weighing from 0.5 to 2.0 kg (1 lb 2 oz to 4 lb 7 oz). Some varieties can be eaten raw, while some require soaking or boiling for detoxification before eating. It is not grown much commercially since the flavor of other yams

3569-747: The cereals ( rice , wheat , and maize ) and the root vegetables ( potatoes and cassava ). Many other starchy foods are grown, some only in specific climates, including acorns , arrowroot , arracacha , bananas , barley , breadfruit , buckwheat , canna , colocasia , cuckoo-pint , katakuri , kudzu , malanga , millet , oats , oca , polynesian arrowroot , sago , sorghum , sweet potatoes , rye , taro , chestnuts , water chestnuts , and yams , and many kinds of beans , such as favas , lentils , mung beans , peas , and chickpeas . Before processed foods, people consumed large amounts of uncooked and unprocessed starch-containing plants, which contained high amounts of resistant starch . Microbes within

3652-450: The Americas and cultivated for the consumption of their starchy tubers in many temperate and tropical regions. The tubers themselves, also called "yams", come in a variety of forms owing to numerous cultivars and related species. A monocot related to lilies and grasses, yams are vigorous herbaceous , perennially growing vines from a tuber . Some 870 species of yams are known,

3735-429: The Americas. Three species were independently domesticated on those continents: D. rotundata (Africa), D. alata (Asia), and D. trifida (South America). Some yams are invasive plants , often considered a noxious weed outside cultivated areas. Yams are cultivated for the consumption of their starchy tubers in many temperate and tropical regions, especially in West Africa, South America and

3818-483: The Asian food market. The tubers are harvested after about 6 months of growth. Some are eaten right after harvesting and some are used as ingredients for other dishes, including noodles, and for traditional medicines. D. bulbifera , the air potato, is found in both Africa and Asia, with slight differences between those found in each place. It is a large vine, 6 m (20 ft) or more in length. It produces tubers, but

3901-532: The Community Primary School Lejja serves the primary education needs of the community. This African archaeology article is a stub . You can help Misplaced Pages by expanding it . Yam (vegetable) Yam is the common name for some plant species in the genus Dioscorea (family Dioscoreaceae ) that form edible tubers (some other species in the genus being toxic). Yams are perennial herbaceous vines native to Africa, Asia, and

3984-553: The Lejja community is trading. Traders sell some of the local produce or they buy other farm produce from neighouring communities. The town has many festivals and traditional events that are celebrated annually. One of such is the new yam festival, which is celebrated every year, following the farm harvest season. Another local cultural event is the masquerade event, which includes the Omaba and Odo only worn by men. Many primary and secondary schools are located in Lejja. The schools serve both

4067-665: The Okinawan purple "yam", which is a sweet potato ), greater yam, winged yam, water yam, and (ambiguously) white yam, was first cultivated in Southeast Asia. Although not grown in the same quantities as the African yams, it has the largest distribution worldwide of any cultivated yam, being grown in Asia, the Pacific islands, Africa, and the West Indies. Even in Africa, the popularity of water yam

4150-413: The addition of water. Some sugars are isomerized. The processes have been described as occurring in two phases: liquefaction and saccharification. The liquefaction converts starch into dextrins . Amylase is a key enzyme for producing dextrin. The saccharification converts dextrin into maltoses and glucose. Diverse enzymes are used in this second phase, including pullanase and other amylases. If starch

4233-695: The enzyme glucose-1-phosphate adenylyltransferase . This step requires energy in the form of ATP . A number of starch synthases available in plastids then adds the ADP-glucose via α-1,4- glycosidic bond to a growing chain of glucose residues, liberating ADP . The ADP-glucose is almost certainly added to the non-reducing end of the amylose polymer, as the UDP-glucose is added to the non-reducing end of glycogen during glycogen synthesis . The small glucan chain, further agglomerate to form initials of starch granules. The biosynthesis and expansion of granules represent

SECTION 50

#1732873363978

4316-405: The flesh is usually white and firm. Yellow yam has yellow flesh, caused by the presence of carotenoids. It looks similar to the white yam in outer appearance; its tuber skin is usually a bit firmer and less extensively grooved. The yellow yam has a longer period of vegetation and a shorter dormancy than white yam. The Kokoro variety is important in making dried yam chips. They are large plants;

4399-422: The formulation, and the process is allowed to heat and cure to form the eventual rigid wall board. The starches act as a glue for the cured gypsum rock with the paper covering, and also provide rigidity to the board. A solution of triiodide (I 3 ) (formed by mixing iodine and potassium iodide ) can be used to test for starch. The colorless solution turns dark blue in the presence of starch. The strength of

4482-452: The fragile tubers; however, wood tools need frequent replacement. Yam harvesting is labor-intensive and physically demanding. Tuber harvesting involves standing, bending, squatting , and sometimes sitting on the ground depending on the size of mound, size of tuber, or depth of tuber penetration. Care must be taken to avoid damage to the tuber, because damaged tubers do not store well and spoil rapidly. Some farmers use staking and mixed cropping,

4565-571: The glucose chains, creating the branched amylopectin. The starch debranching enzyme (DBE) isoamylase removes some of these branches. Several isoforms of these enzymes exist, leading to a highly complex synthesis process. The starch that is synthesized in plant leaves during the day is transitory: it serves as an energy source at night. Enzymes catalyze release of glucose from the granules. The insoluble, highly branched starch chains require phosphorylation in order to be accessible for degrading enzymes. The enzyme glucan, water dikinase (GWD) installs

4648-605: The grated tuber, are used for bitter cultivars of this yam. The bitter compounds in yams also known locally as air potato include diosbulbin and possibly saponins , such as diosgenin . In Indonesia, an extract of air potato is used in the preparation of arrow poison. Raw yam has only moderate nutrient density , with appreciable content (10% or more of the Daily Value , DV) limited to potassium , vitamin B6 , manganese , thiamin , dietary fiber , and vitamin C (table). But raw yam has

4731-473: The health benefits of intact whole grains. A cell-free chemoenzymatic process has been demonstrated to synthesize starch from CO 2 and hydrogen.y. The chemical pathway of 11 core reactions was drafted by computational pathway design and converts CO 2 to starch at a rate that is ~8.5-fold higher than starch synthesis in maize . Papermaking is the largest non-food application for starches globally, consuming many millions of metric tons annually. In

4814-417: The highest potassium levels amongst the 10 major staple foods of the world ( see nutritional chart ). Yam supplies 118 calories per 100 grams. Yam generally has a lower glycemic index , about 54% of glucose per 150 gram serving, compared to potato products. The protein content and quality of roots and tubers is lower than other food staples, with the content of yam and potato being around 2% on

4897-423: The introduction of cassava . D. rotundata , the white yam, and D. cayenensis , the yellow yam, are native to Africa. They are the most important cultivated yams. In the past, they were considered as two separate species, but most taxonomists now regard them as the same species. Over 200 varieties between them are cultivated. White yam tuber is roughly cylindrical in shape, the skin is smooth and brown, and

4980-447: The large intestine ferment or consume the starch, producing short-chain fatty acids , which are used as energy, and support the maintenance and growth of the microbes. Upon cooking, starch is transformed from an insoluble, difficult-to-digest granule into readily accessible glucose chains with very different nutritional and functional properties. In current diets, highly processed foods are more easily digested and release more glucose in

5063-468: The local community and other neighbouring communities. The Federal Government Girls' Collage Lejja was founded in 1995 and only admits girls both for junior and senior secondary schools in boarding school. The school is owned by the Nigerian Federal Ministry of Education. Another secondary school located in the community is the state-owned Community Secondary School, Lejja. For primary education,

SECTION 60

#1732873363978

5146-511: The manufacture of beer , whisky and biofuel . In addition, sugars produced from processed starch are used in many processed foods. Mixing most starches in warm water produces a paste, such as wheatpaste , which can be used as a thickening, stiffening or gluing agent. The principal non-food, industrial use of starch is as an adhesive in the papermaking process. A similar paste, clothing or laundry starch , can be applied to certain textile goods before ironing to stiffen them. The word "starch"

5229-524: The mid eighth century production of paper that was sized with wheat starch started in the Arabic world. Laundry starch was first described in England in the beginning of the 15th century and was essential to make 16th century ruffed collars . Plants produce glucose from carbon dioxide and water by photosynthesis . The glucose is used to generate the chemical energy required for general metabolism as well as

5312-399: The necessary strength properties to the paper web formed in the papermaking process ( wet strength ), and to provide strength to the final paper sheet (dry strength). In the dry end of the papermaking process, the paper web is rewetted with a starch based solution. The process is called surface sizing . Starches used have been chemically, or enzymatically depolymerized at the paper mill or by

5395-404: The next growing season. Young plants live on this stored energy in their roots, seeds, and fruits until they can find suitable soil in which to grow. The starch is also consumed at night when photosynthesis is not occurring. Green algae and land-plants store their starch in the plastids , whereas red algae , glaucophytes , cryptomonads , dinoflagellates and the parasitic apicomplexa store

5478-443: The next year. Yam crops face pressure from a range of insect pests and fungal and viral diseases, as well as nematodes . Their growth and dormant phases correspond respectively to the wet season and the dry season. For maximum yield, the yams require a humid tropical environment, with an annual rainfall over 1,500 millimetres (59 in) distributed uniformly throughout the growing season. White, yellow, and water yams typically produce

5561-429: The physicochemical properties as well as energy release of different types of starches. In addition, cooking and food processing significantly impacts starch digestibility and energy release. Starch has been classified as rapidly digestible starch, slowly digestible starch and resistant starch, depending upon its digestion profile. Raw starch granules resist digestion by human enzymes and do not break down into glucose in

5644-503: The plant. Amylose consists of long chains derived from glucose molecules connected by α-1,4- glycosidic linkage . Amylopectin is highly branched but also derived from glucose interconnected by α-1,6- glycosidic linkages. The same type of linkage is found in the animal reserve polysaccharide glycogen . By contrast, many structural polysaccharides such as chitin , cellulose, and peptidoglycan are linked by β-glycosidic bonds , which are more resistant to hydrolysis. Within plants, starch

5727-470: The plastid to the cytosol, maltose via the maltose transporter and glucose by the plastidic glucose translocator (pGlcT). These two sugars are used for sucrose synthesis. Sucrose can then be used in the oxidative pentose phosphate pathway in the mitochondria, to generate ATP at night. In addition to starchy plants consumed directly, 66 million tonnes of starch were processed industrially in 2008. By 2011, production had increased to 73 million tons. In

5810-477: The process of starch granule initiation. Furthermore, two proteins named ESV and LESV play a role in the aqueous-to-crystalline phase transition of glucan chains. Several catalytically active starch synthases, such as SS1, SS2, SS3, and GBSS, are critical for starch granule biosynthesis and play a catalytic role at each step of granule biogenesis and expansion. In addition to above proteins, starch branching enzymes (BEs) introduces α-1,6-glycosidic bonds between

5893-527: The relative nutritional and antinutritional contents of each of these staples is remarkably different from that of raw form of these staples. raw yellow dent corn raw unenriched long-grain white rice raw hard red winter wheat raw potato with flesh and skin raw cassava raw green soybeans raw sweet potato raw sorghum raw yam raw plantains unofficial Starch Starch or amylum

5976-658: The resulting blue color depends on the amount of amylose present. Waxy starches with little or no amylose present will color red. Benedict's test and Fehling's test is also done to indicate the presence of starch. In the US, the Occupational Safety and Health Administration (OSHA) has set the legal limit ( Permissible exposure limit ) for starch exposure in the workplace as 15 mg/m total exposure and 5 mg/m respiratory exposure over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set

6059-414: The slurry of uncooked starches and prevent sedimentation. This opaque glue is called a SteinHall adhesive. The glue is applied on tips of the fluting. The fluted paper is pressed to paper called liner. This is then dried under high heat, which causes the rest of the uncooked starch in glue to swell/gelatinize. This gelatinizing makes the glue a fast and strong adhesive for corrugated board production. Starch

6142-450: The small intestine - they reach the large intestine instead and function as prebiotic dietary fiber . When starch granules are fully gelatinized and cooked, the starch becomes easily digestible and releases glucose quickly within the small intestine. When starchy foods are cooked and cooled, some of the glucose chains re-crystallize and become resistant to digestion again. Slowly digestible starch can be found in raw cereals, where digestion

6225-414: The small intestine—less starch reaches the large intestine and more energy is absorbed by the body. It is thought that this shift in energy delivery (as a result of eating more processed foods) may be one of the contributing factors to the development of metabolic disorders of modern life, including obesity and diabetes. The amylose/amylopectin ratio, molecular weight and molecular fine structure influences

6308-436: The starch industry (oxidized starch). The size/starch solutions are applied to the paper web by means of various mechanical presses (size presses). Together with surface sizing agents the surface starches impart additional strength to the paper web and additionally provide water hold out or "size" for superior printing properties. Starch is also used in paper coatings as one of the binders for the coating formulations which include

6391-449: The starch solution at 50–70 °C (122–158 °F) to create a very good adhesive. Sodium silicate can be added to reinforce these formula. A related large non-food starch application is in the construction industry, where starch is used in the gypsum wall board manufacturing process. Chemically modified or unmodified starches are added to the stucco containing primarily gypsum . Top and bottom heavyweight sheets of paper are applied to

6474-687: The threat from wild harvest has been successful. D. japonica – known as East Asian mountain yam, yamaimo, or Japanese mountain yam – is a type of yam (Dioscorea) native to Japan (including Ryukyu and Bonin Islands), Korea, China, Taiwan, and Assam. D. japonica is used for food. Jinenjo, also called the wild yam, is a related variety of Japanese yam that is used as an ingredient in soba noodles. Yams in West Africa are typically harvested by hand, using sticks, spades, or diggers. Wood-based tools are preferred to metallic tools as they are less likely to damage

6557-564: The tubers are fairly small in most varieties. The tubers are eaten baked, boiled, or fried much like potatoes. Because of the small size of the tubers, mechanical cultivation is possible, which along with its easy preparation and good flavor, could help the lesser yam to become more popular in the future. D. dumetorum , the bitter yam, is popular as a vegetable in parts of West Africa, in part because their cultivation requires less labor than other yams. The wild forms are very toxic and are sometimes used to poison animals when mixed with bait. It

6640-822: The vegetable is composed of a much softer substance ranging in color from white or yellow to purple or pink in mature yams. The name "yam" appears to derive from Portuguese inhame or Canarian Spanish ñame , which derived from Fula , one of the West African languages during trade. However, in Portuguese, this name commonly refers to the taro plant ( Colocasia esculenta ) from the genus Colocasia , as opposed to Dioscorea . The main derivations borrow from verbs meaning "to eat". True yams have various common names across multiple world regions. In some places, other (unrelated) root vegetables are sometimes referred to as "yams", including: Yams are native to Africa, Asia, and

6723-409: The vines can be as long as 10 to 12 m (33 to 39 ft). The tubers most often weigh about 2.5 to 5 kg (6 to 11 lb) each, but can weigh as much as 25 kg (55 lb). After 7 to 12 months' growth, the tubers are harvested. In Africa, most are pounded into a paste to make the traditional dish of "pounded yam", known as Iyan . D. alata , called purple yam (not to be confused with

6806-425: Was high fructose syrup , 6.2 million tons was glucose syrups, and 2.5 million tons were starch products. The rest of the starch was used for producing ethanol (1.6 billion gallons). The starch industry extracts and refines starches from crops by wet grinding, washing, sieving and drying. Today, the main commercial refined starches are cornstarch , tapioca , arrowroot, and wheat, rice, and potato starches . To

6889-644: Was used in Ancient Egypt , possibly to glue papyrus . The extraction of starch is first described in the Natural History of Pliny the Elder around 77–79 CE . Romans used it also in cosmetic creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat halva . Rice starch as surface treatment of paper has been used in paper production in China since 700 CE. In

#977022