Table sugar is a simple carbohydrate known scientifically as sucrose, a disaccharide molecule composed of one unit of glucose bonded to one unit of fructose. This molecule is produced by nearly all green plants through photosynthesis. While many plants contain sucrose, only a few accumulate it in high enough concentrations to make commercial extraction economically viable. The vast majority of the world’s granulated sugar comes from just two sources: a tall tropical grass and a temperate root vegetable.
Sugarcane: The Tropical Source
Sugarcane, classified as Saccharum officinarum, is a giant perennial grass belonging to the Poaceae family. This tropical plant is cultivated primarily in warm, humid regions globally, with stalks that can reach heights of up to 24 feet. Sugarcane has an ancient history as a cultivated crop, tracing back to the East Indies. The plant stores high concentrations of sucrose, ranging from 7 to 18 percent of its weight, within the fibrous stalks. After a growth period of 8 to over 20 months, the stalks are harvested and processed immediately to prevent decomposition.
Sugar Beet: The Temperate Source
The sugar beet (Beta vulgaris) is a root crop grown in cooler, temperate zones like Europe and North America. It is a biennial plant harvested after one growing season for its large, subterranean taproot. The plant concentrates sucrose in this root at levels ranging from 8 to 22 percent by weight, a concentration comparable to that found in sugarcane. Developed as a commercial crop in 19th-century Europe, sugar beets provided a domestic supply. Cultivation requires fertile, well-drained soil and a sunny growing season, with roots planted in the spring and harvested in the autumn when sugar content peaks.
Converting Plants to Granulated Sugar
The industrial process for extracting and refining sucrose differs based on the plant source, though both result in the same final product.
Sugarcane Processing
For sugarcane, the harvested stalks are washed, shredded, and crushed through heavy rollers to press out the juice. This raw juice is clarified and boiled down to a thick syrup, from which “raw sugar” crystals are separated. This raw sugar is then shipped to a refinery for final purification.
Sugar Beet Processing and Refining
Sugar beet processing avoids the intermediate raw sugar stage, converting the root directly into refined white sugar. After washing, the roots are sliced into thin strips called cossettes, and the sucrose is extracted by soaking them in hot water through diffusion. The resulting sugar solution from both sources undergoes purification, involving filtering and boiling the syrup under a vacuum to promote crystallization. The mixture is then centrifuged to spin off residual liquid, leaving behind pure, dried white sucrose crystals. Since refining removes all plant matter, the final granulated sugar is chemically pure sucrose, making cane sugar and beet sugar indistinguishable.
Sweetness Beyond Cane and Beet
While sugarcane and sugar beets dominate global production, other plants also serve as commercial sources of sweeteners. Maple syrup is primarily sucrose extracted from the sap of maple trees. Coconut sugar is produced from the sap of the coconut palm flower, which is boiled down to create a granular product that is also mostly sucrose.
Agave nectar, derived from the agave plant, is another popular plant-based sweetener, although its main sugar component is fructose rather than sucrose. Other alternatives come from plants that produce intensely sweet, non-carbohydrate compounds, such as Stevia, extracted from the leaves of the Stevia rebaudiana plant. The compounds in Stevia, called steviol glycosides, can be hundreds of times sweeter than sucrose without adding calories.