Rice is a cereal foodstuff which forms an important part of the diet of many people worldwide and as such it is a staple food for many.
Domesticated rice comprises two species of food crops in the Oryza genus of the Poaceae ("true grass") family: Asian rice, Oryza sativa is native to tropical and subtropical southern Asia; African rice, Oryza glaberrima, is native to West Africa. The name wild rice is usually used for species of the different but related genus Zizania, both wild and domesticated, although the term may be used for primitive or uncultivated varieties of Oryza.
Rice is grown as a monocarpic annual plant, although in tropical areas it can survive as a perennial and can produce a ratoon crop and survives for up to 20 years. Rice can grow to 1–1.8 m tall, occasionally more depending on the variety and soil fertility. The grass has long, slender leaves 50–100 cm long and 2–2.5 cm broad. The small wind-pollinated flowers are produced in a branched arching to pendulous inflorescence 30–50 cm long. The edible seed is a grain (caryopsis) 5–12 mm long and 2–3 mm thick.
Rice is a staple food for a large part of the world's human population, especially in tropical Latin America, and East, South and Southeast Asia, making it the second-most consumed cereal grain. A traditional food plant in
Africa, Rice has the potential to improve nutrition, boost food security, foster rural development and support sustainable landcare. Rice provides more than one fifth of the calories consumed worldwide by humans. In early 2008, some governments and retailers began rationing supplies of the grain due to fears of a global rice shortage.
Rice cultivation is well-suited to countries and regions with low labor costs and high rainfall, as it is very labor-intensive to cultivate and requires plenty of water for cultivation. On the other hand, mechanized cultivation is extremely oil-intensive, more than other food products with the exception of beef and dairy products. Rice can be grown practically anywhere, even on a steep hill or mountain. Although its species are native to South Asia and certain parts of Africa, centuries of trade and exportation have made it commonplace in many cultures.
The traditional method for cultivating rice is flooding the fields whilst, or after, setting the young seedlings. This simple method requires sound planning and servicing of the water damming and channeling, but reduces the growth of less robust weed and pest plants that have no submerged growth state, and deters vermin. While with rice growing and cultivation the flooding is not mandatory, all other methods of irrigation require higher effort in weed and pest control during growth periods and a different approach for fertilizing the soil.
There are two species of domesticated rice, Oryza sativa (Asian) and Oryza glaberrima (African).
Oryza sativa contains two major subspecies: the sticky, short-grained japonica or sinica variety, and the non-sticky, long-grained indica variety. Japonica are usually cultivated in dry fields, in temperate East Asia, upland areas of Southeast Asia and high elevations in South Asia, while indica are mainly lowland rices, grown mostly submerged, throughout tropical Asia.
Rice is known to come in a variety of colors, including: white, brown, black, purple, and red.
A third subspecies, which is broad-grained and thrives under tropical conditions, was identified based on morphology and initially called javanica, but is now known as tropical japonica. Examples of this variety include the medium grain “Tinawon” and “Unoy” cultivars, which are grown in the highelevation rice terraces of the Cordillera Mountains of northern Luzon, Philippines. Glaszmann (1987) used isozymes to sort Oryza sativa into six groups: japonica, aromatic, indica, aus, rayada, and ashina. Garris et al (2004) used SSRs to sort Oryza sativa into five groups; temperate japonica, tropical japonica and aromatic comprise the japonica varieties, while indica and aus comprise the indica varieties.
According to the Microsoft Encarta Dictionary (2004) and the Chambers Dictionary of Etymology (1988), the word 'rice' has an Indo-Iranian origin. It came to English from Greek óryza, via Latin oriza, Italian riso and finally Old French ris (the same as present day French riz).
It has been speculated that the Indo-Iranian vrihi itself is borrowed from a Dravidian vari (< PDr. *warinci) or even a Munda language term for rice, or the Tamil name arisi (¬¬¬¬¬) from which the Arabic ar-ruzz, from which the Portuguese and Spanish word arroz originated.
The seeds of the rice plant are first milled using a rice huller to remove the chaff (the outer husks of the grain). At this point in the process, the product is called brown rice. The milling may be continued, removing the 'bran' (i.e. the rest of the husk and the germ), thereby creating white rice.
White rice, which keeps longer, lacks some important nutrients; in a limited diet which does not supplement the rice, brown rice helps to prevent the deficiency disease beriberi.
White rice may be also buffed with glucose or talc powder (often called polished rice, though this term may also refer to white rice in general), parboiled, or processed into flour. White rice may also be enriched by adding nutrients, especially those lost during the milling process. While the cheapest method of enriching involves adding a powdered blend of nutrients that will easily wash off (in the United States, rice which has been so treated requires a label warning against rinsing), more sophisticated methods apply nutrients directly to the grain, coating the grain with a water insoluble substance whichis resistant to washing.
Despite the hypothetical health risks of talc (such as stomach cancer), talc-coated rice remains the norm in some countries due to its attractive shiny appearance, but it has been banned in some and is no longer widely used in others such as the United States. Even where talc is not used, glucose, starch, or other coatings may be used to improve the appearance of the grains; for this reason, many rice lovers still recommend washing all rice in order to create abetter-tasting rice with a better consistency, despite the recommendation of suppliers. Much of the rice produced today is water polished.
Rice bran, called nuka in Japan, is a valuable commodity in Asia and is used for many daily needs. It is a moist, oily inner layer which is heated to produce oil. It is also used as a pickling bed in making rice bran pickles and Takuan.
Raw rice may be ground into flour for many uses, including making many kinds of beverages such as amazake, horchata, rice milk, and sake. Rice flour does not contain gluten and is suitable for people on a gluten-free diet. Rice may also be made into various types of noodles. Raw wild or brown rice may also be consumed by raw-foodist or fruitarians if soaked and sprouted (usually 1 week to 30 days), see also Gaba rice below.
Processed rice seeds must be boiled or steamed before eating. Cooked rice may be further fried in oil or butter, or beaten in a tub to make mochi.
Rice is a good source of protein and a staple food in many parts of the world, but it is not a complete protein: it does not contain all of the essential amino acids in sufficient amounts for good health, and should be combined with other sources of protein, such as nuts, seeds, beans or meat.
Rice, like other cereal grains, can be puffed (or popped). This process takes advantage of the grains' water content and typically involves heating grains in a special chamber. Further puffing is sometimes accomplished by processing pre-puffed pellets in a low-pressure chamber. The ideal gas law means that either lowering the local pressure or raising the water temperature results in an increase in volume prior to water evaporation, resulting in a puffy texture. Bulk raw rice density is about 0.9 g/cm³. It decreases more than tenfold when puffed.