Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch, making up approximately 20–25% of it. Because of its tightly packed helical structure, amylose is more resistant to digestion than other starch molecules and is therefore an important form of resistant starch.
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👉 Amylose in the context of Rice
Rice 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 2023, 800 million tons were produced, placing it third after sugarcane and maize. Only some 8% of rice 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 a sustainable way.
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. The composition of starch components within the grain, amylose and amylopectin, gives it different texture properties. Long-grain rice, from the Indica cultivar, tends to stay intact on cooking, and is dry and fluffy. The aromatic rice varieties, such as basmati and jasmine, are widely used in Asian cooking, and distinguished by their bold and nutty flavor profile. Medium-grain rice, from either the Japonica or Indica cultivar, or a hybrid of both, is moist and tender and tends to stick together. Its varieties include Calrose, which founded the Californian rice industry, Carnaroli, attributed as the king of Italian rice due to its excellent cooking properties, and black rice, which looks dark purple due to high levels of anthocyanins, and is also known as forbidden rice as it was reserved for the consumption of the royal family in ancient China. Short-grain rice, primarily from the Japonica cultivar, has an oval appearance and sticky texture. It is featured heavily in Japanese cooking such as sushi (with rice such as Koshihikari, Hatsushimo, and Sasanishiki, unique to different regions of climate and geography in Japan), as it keeps its shape when cooked. It is also used for sweet dishes such as mochi (with glutinous rice), and in European cuisine such as risotto (with arborio rice) and paella (with bomba rice, which is actually an Indica variety). Cooked white rice contains 29% carbohydrate and 2% protein, with some manganese. Golden rice is a variety produced by genetic engineering to contain vitamin A.
In this Dossier
- ⭐ Core Definition: Amylose
- 👉 Amylose in the context of Rice
- Amylose in the context of Polysaccharide
- Amylose in the context of Pseudocereal
- Amylose in the context of Red algae
- Amylose in the context of Amylopectin
- Amylose in the context of Carnaroli
- Amylose in the context of Mochi
- Amylose in the context of Glutinous rice
Amylose in the context of Polysaccharide
Polysaccharides (/ˌpɒliˈsækəraɪd/; from Ancient Greek πολύς (polús) 'many, much' and σάκχαρ (sákkhar) 'sugar') are "Compounds consisting of a large number of monosaccharides linked glycosidically". They are the most abundant carbohydrates in food. Their structures range from linear to highly branched polymers. Examples include storage polysaccharides such as starch, glycogen, and galactogen and structural polysaccharides such as hemicellulose and chitin. The term "glycan" is synonymous with polysaccharide, but often glycans are discussed in the context of glycoconjugates, i.e. hybrids of polysaccharides and proteins or lipids.
Polysaccharides are often heterogeneous, containing slight modifications of the repeating unit. They may be amorphous (e.g. starch) or insoluble in water (e.g. cellulose).
Amylose in the context of Pseudocereal
A pseudocereal or pseudograin is one of any non-grasses that are used in much the same way as cereals (true cereals are grasses). Pseudocereals can be further distinguished from other non-cereal staple crops (such as potatoes) by their being processed like a cereal: their seed can be ground into flour and otherwise used as a cereal. Prominent examples of pseudocereals include amaranth (love-lies-bleeding, red amaranth, Prince-of-Wales-feather), quinoa, and buckwheat. The pseudocereals have a good nutritional profile, with high levels of essential amino acids, essential fatty acids, minerals, and some vitamins. The starch in pseudocereals has small granules and low amylose content (except for buckwheat), which gives it similar properties to waxy-type cereal starches. The functional properties of pseudocereals, such as high viscosity, water-binding capacity, swelling capability, and freeze-thaw stability, are determined by their starch properties and seed morphology. Pseudocereals are gluten-free, and they are used to make 100% gluten-free products, which has increased their popularity.
Amylose in the context of Red algae
Red algae, or Rhodophyta (/roʊˈdɒfɪtə/, /ˌroʊdəˈfaɪtə/; from Ancient Greek ῥόδον (rhódon) 'rose' and φυτόν (phutón) 'plant'), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 recognized species within over 900 genera amidst ongoing taxonomic revisions. The majority of species (6,793) are Florideophyceae, and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, no terrestrial species exist, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.
Red algae form a distinct group characterized by eukaryotic cells without flagella and centrioles, chloroplasts without external endoplasmic reticulum or unstacked (stroma) thylakoids, and use phycobiliproteins as accessory pigments, which give them their red color. Despite their name, red algae can vary in color from bright green, soft pink, resembling brown algae, to shades of red and purple, and may be almost black at greater depths. Unlike green algae, red algae store sugars as food reserves outside the chloroplasts as floridean starch, a type of starch that consists of highly branched amylopectin without amylose. Most red algae are multicellular, macroscopic, and reproduce sexually. The life history of red algae is typically an alternation of generations that may have three generations rather than two. Coralline algae, which secrete calcium carbonate and play a major role in building coral reefs, belong there.
Amylose in the context of Amylopectin
Amylopectin /ˌæmɪloʊˈpɛktɪn/ is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Plants store starch within specialized organelles called amyloplasts. To generate energy, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, an enzyme that assists in breaking down amylopectin, to initiate the hydrolysis of starch.
Amylose in the context of Carnaroli
Carnaroli is an Italian medium-grained rice grown in the Pavia, Novara, and Vercelli provinces of northern Italy. Carnaroli is used for making risotto, differing from the more common arborio rice due to its higher starch content and firmer texture, as well as having a longer grain. Carnaroli rice keeps its shape better than other forms of rice during the slow cooking required for making risotto due to its higher amylose content. It is the most widely used rice in Italian cuisine, and is highly prized.
Amylose in the context of Mochi
Mochi (/ˈmoʊtʃiː/ MOH-chee; Japanese もち, 餅 [motɕi] ) is a Japanese rice cake made of mochigome (もち米), a short-grain japonica glutinous rice, and sometimes other ingredients such as water, sugar, and cornstarch. The steamed rice is pounded into paste and molded into the desired shape. In Japan, it is traditionally made in a ceremony called mochitsuki (餅搗き). While eaten year-round, mochi is a traditional food for the Japanese New Year, and is commonly sold and eaten during that time.
Mochi is made up of polysaccharides, lipids, protein, and water. Mochi has a varied structure of amylopectin gel, starch grains, and air bubbles. In terms of starch content, the rice used for mochi is very low in amylose and has a high amylopectin level, producing a gel-like consistency. The protein content of the japonica rice used to make mochi is higher than that of standard short-grain rice.
Amylose in the context of Glutinous rice
Glutinous rice (Oryza sativa var. glutinosa; also called sticky rice, sweet rice or waxy rice) is a type of rice grown mainly in Southeast Asia and the northeastern regions of South Asia, which has opaque grains and very low amylose content and is especially sticky when cooked. It is widely consumed across Asia.
It is called glutinous (Latin: glūtinōsus) in the sense of being glue-like or sticky, and not in the sense of containing gluten (which, like all rice, it does not). While often called sticky rice, it differs from non-glutinous strains of japonica rice, which also becomes sticky to some degree when cooked. There are numerous cultivars of glutinous rice, which include japonica, indica and tropical japonica strains.