Rice
, commonly known as Asian rice, is a semi-aquatic annual grass species whose edible seeds serve as a primary cereal grain and staple food for more than half of the world's population, particularly in Asia where it supplies up to 80% of caloric intake for billions.[1][2] The plant features erect, hollow culms reaching 80-120 cm in height, flat sessile leaves, and terminal panicles bearing spikelets that develop into grains after pollination, with cultivation typically requiring flooded fields to suppress weeds and optimize yields.[3] Domesticated from wild progenitors around 10,000 years ago in China's Yangtze River valley, rice agriculture spread globally, enabling dense populations in tropical and subtropical regions through its high productivity and adaptability to diverse ecosystems.[4][5] Global production exceeds 520 million metric tons of milled rice annually, with China and India accounting for roughly half, driven by yield improvements from hybrid varieties and intensive farming practices amid rising demand from population growth and dietary preferences.[6][7] Despite its nutritional role—providing carbohydrates, proteins, and micronutrients—challenges include water-intensive irrigation, vulnerability to pests like the rice blast fungus, and methane emissions from anaerobic soil conditions, which contribute to greenhouse gases but are mitigated through alternate wetting-drying techniques in modern systems.[8] Varieties such as indica (long-grain, tropical) and japonica (short-grain, temperate) reflect eco-geographical adaptations, with ongoing breeding efforts focusing on drought resistance and nutritional enhancement to sustain food security.[9]
Botanical Characteristics
Morphology and Growth Habit
Oryza sativa, the Asian cultivated rice, is an erect annual grass in the Poaceae family, typically reaching heights of 1 to 1.5 meters, though varieties range from 30 cm to over 5 meters under varying environmental conditions.[10] The plant develops a fibrous root system comprising seminal roots from the seed, nodal adventitious roots emerging from the lower stem nodes, and lateral roots that extend into the soil for anchorage and nutrient uptake.[11] These roots are primarily confined to the top 30 cm of soil in flooded conditions but can penetrate deeper in upland cultivation.[12] The stem, known as the culm, is hollow, cylindrical, and segmented into internodes by nodes, from which leaves and tillers arise; mature culms measure 0.5 to 1 cm in diameter.[12] Leaves are alternate, linear-lanceolate, and sheathing at the base, with blades up to 60 cm long and 12 mm wide, featuring a ligule and auricles at the junction with the sheath.[10] The growth habit is characterized by profuse tillering, where basal shoots (tillers) emerge from the lower nodes of the main culm, each capable of developing independent roots, stems, leaves, and potentially a panicle; tiller number varies from 5 to 20 per plant depending on genotype and management.[13] This tillering phase, occurring 20-40 days after sowing, enables vegetative proliferation before the reproductive stage, with primary tillers forming first adjacent to the main stem.[13] Reproductive morphology includes a terminal panicle inflorescence, 15-50 cm long, bearing spikelets in raceme-like branches; each spikelet contains one fertile floret with two lodicules, three stamens, and a pistil, facilitating self-pollination.[14] Post-anthesis, the caryopsis (grain) develops within the hull, comprising the pericarp, seed coat, endosperm, and embryo.[14] Varietal differences influence habit, with traditional indica types exhibiting taller, longer-duration growth and japonica types showing more compact stature, though semi-dwarf cultivars predominate in modern agriculture for lodging resistance.[15]Taxonomy and Phylogeny
Rice (Oryza sativa L.) is classified within the kingdom Plantae, phylum Tracheophyta, class Liliopsida, order Poales, family Poaceae, subfamily Ehrhartoideae, tribe Oryzeae, and genus Oryza.[16][17] The species was formally described by Carl Linnaeus in 1753, with its common name referring to the Asian cultivated rice.[17] The genus Oryza includes 23 recognized species, encompassing two cultivated taxa—O. sativa (Asian rice) and O. glaberrima (African rice)—alongside diverse wild relatives adapted to aquatic or semi-aquatic habitats across tropical and subtropical regions.[18][19] These species are categorized into 9–10 distinct genome types (AA, BB, CC, DD, EE, FF, GG, HH, II, JJ), determined by meiotic chromosome pairing stability in interspecific hybrids, which reflects varying degrees of genetic divergence and reproductive isolation.[18][20] The AA genome group, shared by O. sativa, O. glaberrima, and wild progenitor O. rufipogon, exhibits the closest relatedness among diploids, enabling gene flow and facilitating breeding applications.[18] Phylogenetic analyses, drawing from chloroplast genes like matK and nuclear markers, confirm the monophyly of tribe Oryzeae, which divides into two primary clades corresponding to subtribes Oryzinae (including Oryza) and Zizaniinae (encompassing genera like Zizania and Luziola).[21][22] Within Oryza, evolutionary divergence traces back approximately 15 million years to the Miocene, marked by genomic rearrangements, polyploidy events, and adaptive radiations in response to environmental pressures such as flooding and salinity.[23][24] Molecular phylogenies reveal polyphyletic origins for O. sativa subspecies indica and japonica, with evidence of multiple independent domestication events from perennial and annual wild O. rufipogon variants, supported by phylogeographic patterns in nucleotide diversity.[25][26] Interspecific relationships highlight closer affinities among AA-genome diploids, while allotetraploids like those in the FF and HH genomes arose from ancient hybridizations, contributing to genomic complexity over evolutionary timescales.[27][20]Origins and Domestication
Evolutionary History
The genus Oryza, which includes the progenitors of cultivated rice, encompasses approximately 23 wild and cultivated grass species distributed across Africa, Asia, Australia, and the Americas, with its evolutionary divergence estimated at around 15 million years ago based on molecular clock analyses.[28] The AA-genome diploids within this genus, including Oryza sativa and its wild relatives, represent the primary lineage relevant to Asian rice cultivation, characterized by adaptations to wetland environments that facilitated the transition from wild perennial forms to domesticated annuals.[29] Phylogenetic studies reveal that O. rufipogon, a perennial, shattering-seeded wild rice native to tropical and subtropical Asia, serves as the closest progenitor to domesticated O. sativa, with genetic continuity evidenced by shared nucleotide diversity and chromosomal synteny.[30][31] Domestication of O. sativa from O. rufipogon involved selective pressures favoring non-shattering rachides, reduced seed dormancy, and enlarged grains, traits governed by mutations in genes such as sh4 (for shattering) and rc (for pericarp coloration), which emerged through human-mediated selection rather than neutral drift.[32] Archaeological and genetic evidence places the initial domestication events around 9,000–8,000 years before present (BP), with early sites in the Yangtze River basin yielding proto-domesticated grains exhibiting partial shattering loss.[5][33] Phylogeographic data from wild O. rufipogon populations indicate multiple independent domestication origins, rather than a single bottleneck followed by gene flow, as distinct ecotypes in southern China diverged into temperate japonica lineages while tropical strains contributed to indica and aus varieties in regions like the Ganges plain and Southeast Asia.[34][35] This polyphyletic model aligns with observed genome-wide variation, where indica shows admixture from Oryza nivara (an annual wild relative) alongside O. rufipogon, contrasting with purer japonica ancestry.[36] Post-domestication evolution featured recurrent gene flow between wild progenitors and cultivars, driving adaptation to diverse agroecosystems, but also leading to feral "weedy" forms that hybridized back into wild populations, as documented in Southeast Asian O. rufipogon stands.[37] Genetic divergence between wild and cultivated forms stabilized around 3,000–3,500 years BP for certain varietal subgroups, coinciding with expanded cultivation and trait fixation under artificial selection.[38] While earlier single-origin hypotheses relied on limited markers, comprehensive population genomic analyses reject them in favor of repeated trait evolution across geographies, underscoring how ecological variation in progenitor populations—such as perennial vs. annual habits—causally shaped varietal divergence without requiring extensive hybridization post-domestication.[39][40]Early Cultivation and Spread
Archaeological evidence indicates that rice cultivation originated in the Lower Yangtze River region of China during the early Holocene, with the earliest phytolith remains from the Shangshan site dating to approximately 9,400 years before present (cal BP), marking the initial stages of domestication from wild Oryza rufipogon.[4] Stone tools from southern China, analyzed for use-wear patterns consistent with rice harvesting, provide evidence of systematic collection and processing as early as 10,000–8,200 cal BP in the Shangshan culture, suggesting a gradual transition from gathering wild stands to managed cultivation.[41] This process was protracted, involving morphological changes such as non-shattering rachides, and occurred amid a broader Neolithic agricultural revolution in the region around 8,000 years ago.[42] The primary domesticated form, Oryza sativa japonica, emerged in the Yangtze basin, with synchronous evidence of managed fields appearing around 7,600 years ago in the South Hangzhou Bay area during the Kuahuqiao Culture.[43] Genetic studies support an initial domestication event for japonica from local wild progenitors, followed by dispersal and adaptation, though debates persist on whether indica varieties arose independently in the Ganges plains from proto-indica populations or through later gene flow and selection from japonica introductions.[42] Evidence for multiple origins includes distinct genetic clusters for indica, japonica, and aus subpopulations, each tracing to separate wild O. rufipogon ecotypes in southern and southeastern Asia, with indica domestication likely postdating japonica by several millennia.[44] Rice cultivation spread from the Yangtze core to the middle and upper reaches by 6,000 BCE, reaching the Sichuan Plains around 4,000 years ago via overland routes.[45] Maritime adaptations facilitated early Neolithic expansion along the South China coast by 8,000 cal BP, with rapid dissemination into mainland Southeast Asia and westward across India and Nepal occurring in the late third millennium BCE, driven by human migration and trade networks rather than solely environmental diffusion.[46][47] By the second millennium BCE, rice had reached the Korean Peninsula and Japanese archipelago, establishing wet-paddy systems that supported population growth in these regions.[48]Agronomic Practices
Environmental Requirements and Planting
Rice cultivation requires warm temperatures, with optimal daytime ranges of 25–33°C and nighttime temperatures of 15–20°C for vegetative growth and development.[49] Germination occurs between 10–41°C, ideally around 30°C, while temperatures above 35°C can stress the crop, reducing photosynthesis and yield.[50] As a short-day plant, Oryza sativa exhibits photoperiod sensitivity, where flowering is promoted under day lengths shorter than 12–14 hours, influencing varietal adaptation to tropical latitudes.[51] Soils for rice must retain water effectively, favoring clayey or loamy textures rich in organic matter to support flooded conditions.[52] Optimal pH ranges from slightly acidic to neutral, approximately 5.5–7.0, to facilitate nutrient uptake, though acidic soils below 5.5 can limit phosphorus availability and require amendments.[53] Fertility demands include 90–150 pounds of nitrogen per acre, with applications timed before flooding to maximize availability.[54] Water is critical, with seasonal requirements of 1,100–1,250 mm, including rainfall or irrigation to maintain 5–10 cm flood depths during key growth stages for weed suppression and oxygen exclusion from soil.[55] Total inputs can reach 2,000 mm in coarse-textured soils with low groundwater, equating to 6–10 mm daily evapotranspiration.[56] Planting typically occurs at the onset of the monsoon in tropical regions, from May to July, aligning with adequate rainfall for establishment.[57] Traditional transplanting involves raising seedlings in nurseries for 20–30 days before manual or mechanical transfer to puddled fields, enhancing tillering and weed control through flooding but increasing labor demands.[58] Direct seeding, either dry or wet, bypasses nurseries, saving water by 20–30% and labor while accelerating maturity, though it risks higher weed pressure without proper herbicide use.[59] Seeding rates vary by method, with 80–100 kg/ha for direct broadcasting to achieve uniform stands.[60]Harvesting, Processing, and Yield Optimization
Rice harvesting typically occurs when grains reach physiological maturity, indicated by a moisture content of 20-25% in the paddy, to minimize shattering losses while ensuring quality. Manual harvesting, prevalent in smallholder farms across Asia, involves cutting panicles with sickles or knives, often followed by bundling and field drying, but can lead to 5-15% yield losses from improper timing or weather exposure. Mechanical harvesting using combine harvesters, common in mechanized regions like Japan and Australia, cuts, threshes, and cleans grains in one pass, reducing labor needs by up to 90% but requiring fields with uniform maturity to avoid grain damage. Post-harvest processing begins with drying paddy to 12-14% moisture content to prevent mold and facilitate storage, achieved through sun drying on mats or mechanical dryers in humid climates, where improper drying causes 10-20% quality deterioration. Milling removes the husk (dehusking) via rubber roll hullers, yielding brown rice, followed by polishing to produce white rice by abrading the bran layer, a process that retains 90-95% of the grain but discards nutrient-rich bran and germ. Parboiling, practiced in parts of India and Bangladesh, steams paddy before milling to improve milling recovery by 10-15% and nutrient retention, though it increases processing time and energy use. Yield optimization integrates precise harvesting and efficient processing to curb losses, which globally average 15-20% post-harvest in developing countries due to manual methods and inadequate infrastructure. Timely harvesting within 10-14 days of maturity can boost yields by 5-10% by avoiding lodging or pest damage, while mechanical threshing reduces grain breakage to under 2% compared to 5% in manual methods. Adopting hybrid varieties with strong stems for direct seeding and mechanized systems, as in China's Yangtze River basin, has elevated average yields to 7-8 tons per hectare, supported by integrated pest management and balanced fertilization to sustain soil health without yield plateaus. Advanced processing technologies, such as color sorting machines, eliminate defective grains post-milling, improving market quality and reducing waste by 1-3%, particularly in export-oriented producers like Thailand. However, over-polishing depletes vitamins, prompting fortification programs in deficient regions, though efficacy depends on consumer adoption rates below 50% in some areas. Causal factors in yield gaps include varietal resilience to asynchronous ripening, which mechanical harvesters address better than manual cuts, and infrastructure investments yielding 20-30% loss reductions in pilot programs by the International Rice Research Institute.Varieties and Breeding
Major Ecotypes and Cultivars
Oryza sativa, the predominant cultivated rice species, is differentiated into major ecotypes primarily through genetic, morphological, and physiological traits adapted to diverse agroecological conditions. These ecotypes encompass two main subspecies—indica and japonica—with japonica further divided into temperate japonica and tropical japonica subgroups, alongside the aus ecotype often classified under or closely related to indica. These groupings reflect adaptations to water availability, photoperiod sensitivity, and grain quality, with indica dominating tropical irrigated systems and japonica prevailing in temperate or rainfed uplands.[35][61] Genetic analyses indicate that indica and japonica diverged from distinct wild progenitors, with aus representing an early-maturing lineage suited to short-season, drought-prone environments in South Asia.[62][63] Indica ecotypes, characterized by tall stature, long slender grains, and non-sticky cooked texture, comprise over 70% of global production and thrive in flooded lowland conditions with high photoperiod sensitivity. Key cultivars include IR8, a semi-dwarf variety released by the International Rice Research Institute (IRRI) in 1966, which revolutionized yields through responsiveness to nitrogen fertilizers and lodging resistance, achieving up to 10 tons per hectare under optimal conditions. Basmati varieties, such as Basmati 370 and Pusa Basmati 1, originate from the Indo-Gangetic plains and are prized for elongated grains and aromatic compounds like 2-acetyl-1-pyrroline, though yields average 2-3 tons per hectare due to photo-periodism limiting mechanization. Jasmine rice (Oryza sativa subsp. indica cv. Hom Mali), cultivated mainly in Thailand, features soft texture and fragrance, with annual production exceeding 1 million tons from Northeast Thai soils.[64][65] Japonica ecotypes exhibit shorter, bolder grains that cohere when cooked, with lower tillering and greater cold tolerance, adapting to upland or rainfed systems. Temperate japonica, prevalent in East Asia (e.g., Japan, Korea), includes Koshihikari, a high-quality variety occupying 30% of Japan's paddy area since its 1956 release, yielding 5-6 tons per hectare with superior eating quality due to high amylose content. Tropical japonica, found in upland Latin America and parts of Africa, shows intermediate traits like drought tolerance; representative cultivars include those from the CIRAD breeding programs, with yields varying from 1-4 tons per hectare in rainfed conditions.[61][66] The aus ecotype, distinct for its early maturity (90-100 days) and adaptation to rainfed, heat-stressed uplands in the Indian subcontinent, features small grains and high shattering, with genetic markers linking it to proto-indica lineages. Prominent aus cultivars like those from Bangladesh's BRRI series (e.g., BRRI dhan28) yield 4-5 tons per hectare in short seasons, supporting food security in flood-vulnerable regions. Hybrid rice cultivars, crossing indica and japonica parents, emerged in China in the 1970s via three-line systems, boosting yields by 15-20% over inbreds; examples include Shanyou 63, which covered millions of hectares by the 1980s, though heterosis depends on cytoplasmic male sterility maintenance. Oryza glaberrima, the African rice ecotype domesticated independently around 3,000 years ago in the Niger River delta, persists in weedy forms with shattering and red hulls but has been largely supplanted by sativa hybrids for higher yields.[35][67] Ecotypic classifications inform breeding, as indica-japonica hybrids often suffer hybrid sterility from chromosomal differences, limiting gene flow.[68]Conventional and Hybrid Breeding Advances
Conventional rice breeding has relied on methods such as mass selection, pedigree breeding, and backcrossing to develop inbred varieties with improved yield potential, grain quality, and resistance to biotic stresses. These techniques, applied since the early 20th century, progressively enhanced varietal performance by exploiting genetic variation within Oryza sativa.[69] A pivotal advance came with ideotype breeding during the Green Revolution, targeting semi-dwarf stature to prevent lodging under high fertilizer inputs while maintaining high tillering and harvest index.[70] The International Rice Research Institute's IR8 variety, released in 1966 through conventional crosses, exemplified this by achieving yields up to 10 tons per hectare under optimal conditions, doubling traditional outputs and enabling fertilizer-responsive cultivation across Asia.[69] Hybrid rice breeding emerged as a breakthrough in exploiting heterosis, or hybrid vigor, to surpass inbred variety limits. Chinese agronomist Yuan Longping initiated systematic research in the 1960s after observing male-sterile plants, leading to the three-line system: cytoplasmic male-sterile (CMS) lines maintained by fertile counterparts and restored by restorer lines for seed production.[71] The first viable hybrid, Nanyou 2, developed in 1973, demonstrated 20% yield superiority over leading inbreds due to enhanced biomass and grain filling.[72] Commercialization accelerated post-1976, with hybrids covering over 50% of China's rice area by the 1990s, contributing to an average national yield increase of 1-2 tons per hectare in adopting regions.[73] Further refinements in hybrid systems addressed limitations of the three-line approach, including CMS source dependency and photoperiod sensitivity. Two-line hybrids, utilizing environment-sensitive genic male sterility (EGMS) lines responsive to temperature or photoperiod, simplified parental line propagation and broadened adaptable germplasm since the 1990s.[74] These yielded comparably or higher, with some super hybrids reaching 15-21 tons per hectare in trials, though at higher seed costs limiting adoption outside Asia.[70] Empirical data confirm hybrids' edge, with field studies showing 10-20% yield gains over elite inbreds under similar management, attributed to superior photosynthesis and sink capacity, though milling quality often lags.[75] Despite biases in state-promoted Chinese reports favoring hybrids, independent assessments validate heterosis benefits while noting environmental and input sensitivities.[76]Global Production and Economics
Current Production Statistics and Leading Producers
Global rice production reached a record 533.8 million metric tons on a milled-equivalent basis during the 2024/25 marketing year, driven primarily by expanded acreage and yields in key Asian producers.[77] This figure reflects paddy production processed to account for milling recovery rates, with Asia accounting for over 90 percent of output.[6] India emerged as the top producer in 2024/25, with an estimated 150 million metric tons, surpassing China due to favorable monsoon conditions and increased hybrid variety adoption.[6] China followed closely at 145.28 million metric tons, supported by state-backed irrigation improvements and high-yield cultivars despite localized weather challenges.[6] Bangladesh, Indonesia, and Vietnam ranked next, contributing 36.6 million, 34.1 million, and 26.75 million metric tons, respectively, with production concentrated in irrigated lowlands.[6] The following table summarizes the leading producers for the 2024/25 marketing year:| Country | Production (million metric tons, milled basis) |
|---|---|
| India | 150 |
| China | 145.28 |
| Bangladesh | 36.6 |
| Indonesia | 34.1 |
| Vietnam | 26.75 |
| Thailand | 20 (estimated) |
| Myanmar | 15 (estimated) |
Trade Dynamics and Market Influences
Global rice trade volume reached approximately 57 million metric tons in 2024, with export values totaling around $39 billion, reflecting a 12% increase from 2023 driven by expanded production in key exporting nations.[77][79] India dominates as the leading exporter, capturing about 30% of the global market share through high-volume shipments of basmati and parboiled varieties, followed by Thailand, Vietnam, Pakistan, and the United States, which accounts for roughly 5-6% of trade.[80][81] On the import side, Indonesia led with $2.71 billion in purchases, trailed by the Philippines at $2.52 billion and Saudi Arabia, while China emerged as the volume leader in 2023 with nearly 5 million metric tons amid domestic supply shortfalls.[82][83]| Top Rice Exporters (2024) | Share/Volume | Top Rice Importers (2024) | Value (USD Billion) |
|---|---|---|---|
| India | 30% market share | Indonesia | 2.71 |
| Thailand | Significant volume | Philippines | 2.52 |
| Vietnam | Key player | Saudi Arabia | N/A |
| Pakistan | Major supplier | Iraq | N/A |
| United States | 5-6% global | China (2023 volume lead) | N/A |
Food Security Implications
Rice constitutes a staple food for over half the world's population, particularly in Asia where it supplies more than 76% of caloric intake in regions like Southeast Asia, underscoring its central role in global food availability and stability.[92][93] Production must expand by 15-20% to match rising demand amid population growth, yet constraints like land scarcity and resource limits threaten this expansion without efficiency gains.[94] Climate variability amplifies risks, with floods causing annual losses of about 4 million tons in countries like Bangladesh and India, while droughts tied to events such as El Niño reduce yields in rainfed systems.[95][93] Projected temperature rises could diminish global yields by 3.4-10.9% by 2100 under sustained warming, though elevated CO2 levels and warmer nights might offset declines in some tropical areas, highlighting model-dependent outcomes.[96][97] Pests like rice blast fungus further endanger supplies, capable of devastating fields and posing economic threats equivalent to billions in losses.[98] High water demands—accounting for 40% of global agricultural freshwater use—exacerbate scarcity in irrigated systems, where over 3 billion people depend on rice for nutrition, straining resources in water-stressed basins.[99] Trade dependencies compound vulnerabilities; many Asian importers face price spikes and shortages from export curbs, as seen in India's July 2023 ban on non-basmati varieties, which tightened global supplies and elevated risks for net importers like Bangladesh and the Philippines.[100][101] Mitigation through resilient breeding addresses these challenges, with varieties tolerant to biotic stresses and abiotic extremes enabling sustained output; for instance, flood-resistant lines have preserved production in flood-prone deltas.[102][95] Sustainable practices, including alternate wetting-drying irrigation, reduce emissions while maintaining yields, supporting long-term security without yield trade-offs.[103] Policy efforts to diversify imports and boost domestic productivity remain essential to buffer against shocks, though geopolitical tensions, such as those between India and Pakistan, could disrupt regional flows.[104]Nutritional Profile and Culinary Applications
Biochemical Composition and Health Effects
Rice grains primarily consist of starch in the endosperm, comprising 70-80% of dry weight and serving as the main caloric source for billions. Protein content ranges from 7-8%, predominantly glutelin (60-80%) and prolamin (20-30%), while lipids account for 2-3%, concentrated in the bran and germ layers. The bran layer contains dietary fiber, minerals such as magnesium and phosphorus, and antioxidants like ferulic acid, whereas the germ is rich in B vitamins, particularly thiamin (vitamin B1).[105][106][107] Milling to produce white rice removes the bran and germ, resulting in lower nutrient density compared to brown rice. Brown rice retains approximately 4-6 times more fiber, double the phosphorus and manganese, and significantly higher magnesium and B vitamins than white rice per equivalent serving. For instance, uncooked brown rice provides about 3.5g fiber per 100g versus 1.6g in white rice, alongside elevated levels of selenium, zinc, and iron. White rice, often enriched with iron and B vitamins post-milling, still lacks the natural fiber and antioxidants present in whole-grain forms. Phytic acid, an anti-nutritional factor concentrated in the bran, binds minerals like iron, zinc, and calcium, potentially reducing their bioavailability by up to 50-80% in brown rice diets without processing interventions like soaking or germination.[108][109][110]| Nutrient (per 100g uncooked) | Brown Rice | White Rice |
|---|---|---|
| Calories | 370 | 365 |
| Carbohydrates (g) | 77 | 80 |
| Protein (g) | 7.9 | 7.1 |
| Fiber (g) | 3.5 | 1.3 |
| Magnesium (mg) | 143 | 25 |
| Phosphorus (mg) | 333 | 115 |
| Manganese (mg) | 3.7 | 1.1 |
Preparation Methods and Regional Consumption
Rice preparation begins with milling, which removes the inedible husk and varying amounts of bran and germ to produce different forms such as brown rice, which retains the bran layer, or white rice, where the bran and germ are polished away.[117] Dry milling grinds the grains mechanically after husking, while wet milling involves soaking and grinding into flour, and semi-dry methods combine elements of both for specific textures in products like rice noodles.[118] Parboiling, a pre-milling steam treatment, gelatinizes starches to improve nutrient retention and texture, commonly used in regions like India and parts of Africa.[119] Cooking methods vary by rice type and cultural preference, with the absorption technique predominant: rice is rinsed, combined with water at a 1:2 ratio for long-grain varieties, brought to a boil, then simmered covered until liquid is absorbed, typically 15-20 minutes.[120] Steaming follows soaking for sticky or glutinous rice in East and Southeast Asia, enhancing adhesiveness for dishes like sushi or mochi.[121] In some traditions, such as Indonesian nasi, rice is boiled until water evaporates, then steamed briefly to fluff grains without clumping.[122] Asia accounts for approximately 90% of global rice consumption, serving as the dietary staple providing 50-80% of calories for over half the world's population in the region.[123] Per capita consumption peaks in Myanmar at 279 kg annually, followed by Vietnam (228 kg), Laos (227 kg), and Bangladesh, where it constitutes up to 70% of caloric intake.[124][125] In China and India, the largest total consumers, rice is often steamed plain or paired with stir-fries and curries, though per capita rates are lower at around 80-100 kg due to diverse diets.[126]| Country | Per Capita Consumption (kg/year) |
|---|---|
| Myanmar | 279 |
| Vietnam | 228 |
| Laos | 227 |
| Philippines | 194 |
| Bangladesh | ~200 (estimated high) |