Rice

Rice (Oryza sativa) is one of the most important staple foods for more than half of the world's population. Its origins and subsequent development as a vital crop have profoundly influenced agriculture, culture, and economies across the globe.       

Origins of Rice


The cultivation of rice dates back thousands of years. Archaeological evidence suggests that rice was domesticated independently in at least two primary regions: the Yangtze River Valley in China around 7000 BCE and the Ganges Valley in India approximately 3000 BCE. These early domestication processes of selecting seed from desirable plants transformed wild rice species into cultivated varieties, suitable for human consumption (Zhang & Zhang, 2014).

Development and Spread
Initially concentrated in Asia, rice cultivation expanded eastward, reaching Southeast Asia and Japan. In tandem, it spread westward into the Middle East and Africa through trade routes and migration. The development of irrigated rice farming systems and advanced cultivation techniques in Asia greatly increased yield and efficiency (Liu et al., 2017). During the medieval period, rice cultivation reached Europe through Moorish influence, though it remained a minor crop there. The Columbian Exchange in the 15th and 16th centuries further facilitated the spread of rice to the Americas, especially to Brazil and the Caribbean, where it thrived in tropical climates (Naylor, 2004).

Modern Developments


In the 19th and 20th centuries, scientific advances led to the development of high-yielding rice varieties through hybridization and selective breeding. The Green Revolution of the mid-20th century which improved the stem strength and helped ensure that the grain could be harvested, significantly increased rice production globally, especially in Asia, alleviating hunger in many regions (Khush, 2005). Furthermore, advancements in irrigation, pest control, and farming practices have continued to bolster rice productivity. Today, rice is cultivated on every continent except Antarctica, with major producers including China, India, Indonesia, and Bangladesh (International Rice Research Institute [IRRI], 2020).

Global Rice Production


Rice is cultivated extensively across many countries, with certain nations dominating global production due to their favorable climates, extensive paddy fields, and established agricultural practices. The top rice-producing countries are primarily located in Asia, which accounts for more than 90% of the world's rice production.

Global Rice Production

Note: Data approximates based on recent statistics from FAO (2022) and IRRI reports.

Rice Production in the United States 


Although on the global scale, the United States produces a relatively small amount of rice, about half of the crop is exported, contributing to 5% of the rice in world trade (USDA-ERS, Jan. 7, 2025). There are two primary modern growing regions in the United States, California and the southern states of Arkansas, Mississippi, Texas, Missouri and Louisiana where most of the commodity grade rice is grown.  These states have favorable climates and extensive irrigation infrastructure that support large-scale rice farming.

Historically, rice first was grown in the American continent in the Carolinas prior to the Civil War.  Since early in the 21^st century efforts have been made to re-establish specific antebellum varieties (Carolina Gold Rice) and to integrate them as artisanal rice varieties into the culinary arsenal of chefs and food conscious consumers.

                               State-Level Rice Production in the United States (USDA-ERS 2024)                                  

Source: USDA, Economic Research Service using data from USDA, National Agricultural Statistics Service, Quick Stats.     

Updated March 11, 2025. Hundredweight (cwt) = 100 pounds.

Primary Types and Varieties of Rice


There are two main subspecies of cultivated rice: Oryza sativa indica and Oryza sativa japonica. Although, these have been generally referred to as long and medium grains, respectively, there is a wide diversity of plant and grain types and areas of adaption that both of these sub-species include. Thus, for marketing or culinary purposes and for consumers, market classes which refer to the grain dimensions: long, medium, and short grains, are more relevant. Within each of these classes, there are other cooking, grain appearance, and flavor traits that are very important. Generally, long-grain rice is  slender, and remains separate and fluffy when cooked whereas medium and short grain rice have round grains that are sticky and moist when cooked.

Aromatic vs. Non-Aromatic Varieties


Rice varieties can also be categorized based on their aroma. Aromatic rice varieties are prized for their distinctive, fragrant smell and flavor, primarily due to the presence of natural compounds like 2-acetyl-1-pyrroline. These varieties are highly valued in culinary traditions worldwide. 

• Aromatic varieties include Basmati and Jasmine rice. Basmati, mainly cultivated in India and Pakistan, is known for its very slender long grains, fragrant aroma, and fluffy texture. Jasmine rice, primarily from Thailand, is famous for its sweet aroma and soft, sticky texture when cooked.
• Non-aromatic varieties are generally neutral in flavor and aroma, used in a broad spectrum of cuisines and daily dishes. Examples include most US commodity long, medium and short grain rice, as well as, Calrose, Koshihikari, and Arborio rice.

Rice Production Systems


Rice production employs various systems tailored to different ecosystems, climates, and socio-economic contexts. The main rice production systems include: 

• Lowland Rice Cultivation: The most widespread system, where rice is grown in irrigated or flooded fields which takes advantage of local water resources (high rainfall, rivers, tidal areas) and requires significant infrastructure (levees, canals, irrigation control) (Sweeney et al., 2011). In many parts of the world this type of rice is transplanted by hand but labor-saving mechanically seeded fields are increasing as well as the use of water-saving alternate wetting and drying practices.
• Upland Rice Farming: Grown on dry, non-flooded lands, often in hilly or mountainous regions. Upland rice relies on rainfall and is common in parts of Southeast Asia and Africa, but yields are lower than in lowland systems (Matsuno et al., 2015).
• System of Rice Intensification (SRI): An agro-ecological method that promotes water-saving, reduced disturbance, and higher plant density to increase productivity with fewer inputs. SRI has gained popularity for its sustainability and resilience (Uphoff & Randriamiharisoa, 2012).

Each system responds to local environmental and socio-economic conditions and plays a vital role in ensuring food security for millions.

Rice Processing - Milling and Its Products


After harvesting, rice must undergo milling to remove inedible husks and bran layers, producing edible rice grains. The rice milling process involves several critical steps:

• Cleaning and husking: The “rough or paddy rice” that is harvested from the field first goes through a cleaning process to remove stones, stems, and foreign material. It then goes through a huller that removes the husks that cover the grain. The product at this stage is whole grain (brown) rice which still contains the outer bran layer and germ.
• Milling: White rice is what is most commonly consumed, and it is produced by a friction mill that removes the bran layer. The degree of milling determines how white is the final milled product.  During the milling process some of the grain breaks into pieces called brokens or “middlins”. The amount of milled whole grains that is produced during the milling process largely determines its value.
• Polishing: An optional step that further refines the appearance of the grain by removing surface defects or residual bran streaks resulting in a shiny grain luster.

Milled Rice Products 

• White rice: The most common form, produced after removing the husk, bran, and germ. It has a mild flavor, bright appearance, and longer shelf life, but fewer nutrients compared to brown rice.
• Brown rice: Retains the bran and germ layers which are the most nutritious part of the grain, rich in vitamins, proteins, and lipids, The higher oil content as compared to milled rice is why brown rice has a shorter shelf life. The bran layer is also a barrier to water absorption which is why cooking time for brown rice takes longer than milled rice.
• Pigmented rice is whole grain rice which has a purple (i.e. “black”) or red bran rather than brown. These rice varieties are high in natural anti-oxidants which have health beneficial properties. Converted (parboiled) rice: Paddy rice that has undergone soaking, steaming under pressure, and drying before milling. This process helps retain nutrients, reduces the glycemic index, and improves cooking consistency.

In addition, milled rice can be processed into various products such as rice flour, rice bran oil, rice bran, rice flakes, and rice noodles, catering to diverse culinary and industrial uses.

Rice Cooking Properties

Amylose Content – The milled rice grain is primarily composed of starch which is made up of two molecules: amylose and amylopectin. Amylose content is the primary determinant of cooked rice texture and can vary from 0% in waxy or sweet rice, to low amylose (12-18%) in typical short and medium grains, and intermediate to high (20-28%) in typical long grains. Rice varieties with higher amylose content have firmer texture, are less sticky, and have less starch solids loss during cooking. When cooked rice is cooled, the amylose molecules recrystallize due to retrogradation which changes the texture of the rice. Varieties with lower amylose contents will undergo less retrogradation and will stay soft when refrigerated, like for use in salads.

Gelatinization Temperature – Starch in the rice grain is concentrated in microscopic starch granules. When rice is cooked, these starch granules absorb water and swell to the point of bursting as the crystalline structure of the starch melts. This gelatinization temperature (GT) is an indicator of when the rice is “cooked” with the greater the GT, the longer the cooking time. Short and medium grain varieties typically have low (<70C) GT whereas conventional long grain varieties have intermediate (70-74C) GT. Very few varieties have a high (74-80C) GT. Amylose content and GT are important cooking quality traits selected for in rice breeding programs, so that different rice varieties can be co-mingled by mills but be expected to have the same cooking properties.     

Landrace and Heirloom Varieties of Rice

Landrace and heirloom varieties represent some of the most culturally significant and genetically diverse examples of rice. Landraces are traditional varieties developed by local farmers over generations, adapted to specific climates and soils. Heirloom varieties are specific types of landraces that have been preserved over time, often within families or communities. These varieties hold immense value in preserving biodiversity, cultural heritage, and culinary traditions.

• Examples of Predominant Landraces and Heirloom Varieties:
  • Carolina Gold Rice