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 and East Asia, and the northeastern regions of South Asia, which has opaque grains, very low amylose content, and is especially sticky when cooked. It is widely consumed across Asia.
"Sticky rice" redirects here. For the Chinese rice dish, see Chinese sticky rice.It is called glutinous (Latin: glūtinōsus)[1] in the sense of being glue-like or sticky, and not in the sense of containing gluten (which it does not). While often called sticky rice, it differs from non-glutinous strains of japonica rice, which also become sticky to some degree when cooked. There are numerous cultivars of glutinous rice, which include japonica, indica and tropical japonica strains.
History[edit]
The origins of glutinous rice is difficult to ascertain due to its long-standing cultural importance across a wide geographical region in Asia. It is most prevalent in the highland regions in Southeast Asia where it is a staple, while it also serves as occasional festival food in East Asia (mainly for desserts) and parts of South Asia. Glutinous rice is particularly associated with the upland agriculture of the Kra–Dai-speaking peoples of Mainland Southeast Asia. A region of around 200,000 km2 (77,000 sq mi) that includes Laos, Myanmar, Thailand, Cambodia, and Vietnam is sometimes known as the "glutinous rice zone."[2][3]
A 2002 genetic study discovered that the waxy mutation that disrupted amylose synthesis likely has a single origin. This is supported by the fact that all glutinous rice accessions in the study contain the same mutation. From comparisons of subsequent mutations in the different accessions in the study, it was found that the progenitor haplotype is highest among Southeast Asian glutinous rice cultivars, indicating strongly that the waxy mutation first arose in Southeast Asia, likely in the upland regions of Mainland Southeast Asia, before spreading to the rest of Asia.[2]
The waxy mutation is also known to have first arose in temperate japonica rice, where it is far more common, before spreading to tropical japonica rice (javanica) and indica cultivars via gene flow.[2][4]
Cultivation[edit]
Glutinous rice is grown in Laos, Thailand, Cambodia, Vietnam, Malaysia, Indonesia, Myanmar, Nepal, Bangladesh, Bhutan, Northeast India, China, Japan, Korea, Taiwan, and the Philippines. An estimated 85% of Lao rice production is of this type.[5]
As of 2013, approximately 6,530 glutinous rice varieties were collected from five continents (Asia, South America, North America, Europe, and Africa) where glutinous rice is grown for preservation at the International Rice Genebank (IRGC).[6] The International Rice Research Institute (IRRI) has described Laos as a "collector's paradise".[7] Laos has the largest biodiversity of sticky rice in the world. IRRI-trained collectors gathered more than 13,500 samples and 3,200 varieties from Laos alone.[7]
Composition[edit]
Glutinous rice is distinguished from other types of rice by having no (or negligible amounts of) amylose and high amounts of amylopectin (the two components of starch). Amylopectin is responsible for the sticky quality of glutinous rice. The difference has been traced to a single mutation that farmers selected.[2][8]
Like all types of rice, glutinous rice does not contain dietary gluten (i.e. does not contain glutenin and gliadin) and should be safe for gluten-free diets.[9]
Glutinous rice can be used either milled or unmilled (that is, with the bran removed or not removed). Milled glutinous rice is white and fully opaque (unlike non-glutinous rice varieties, which are somewhat translucent when raw), whereas the bran can give unmilled glutinous rice a purple or black colour.[10] Black and purple glutinous rice are distinct strains from white glutinous rice. In developing Asia, there is little regulation, and some governments have issued advisories about toxic dyes being added to colour adulterated rice. Both black and white glutinous rice can be cooked as discrete grains or ground into flour and cooked as a paste or gel.
Non-food uses[edit]
In construction, glutinous rice is a component of sticky rice mortar for use in masonry. Chemical tests have confirmed that this is true for the Great Wall of China and the city walls of Xi'an.[41][42] In Assam also, this rice was used for building palaces during Ahom rule.
Glutinous rice starch may also be used to create wheatpaste, an adhesive material.[43]
In Vietnam, glutinous rice is made into flour and used to make To he, a figurine.