The sugar beet, Beta vulgaris, is cultivated extensively worldwide as a major source of table sugar. Its root contains high levels of sucrose, which is chemically identical to the sugar derived from sugarcane, making it the second-largest global source of this common household ingredient. German chemist Andreas Marggraf demonstrated in 1747 that sweet crystals could be extracted from beets. Commercial production gained momentum in Europe during the Napoleonic Wars when a British blockade cut off the supply of cane sugar. This stimulated the construction of factories and the selective breeding of the plant, establishing the sugar beet as a staple crop in temperate regions.
The Plant’s Anatomy and Origin
The sugar beet is a member of the Amaranthaceae family, related to the common table beet and Swiss chard. The plant’s leaves use photosynthesis to convert sunlight into sucrose, a disaccharide sugar. This sugar is then transported and stored in a large, white, conical taproot. A mature taproot typically contains a high sugar concentration, ranging between 15% and 20% sucrose by weight, depending on the cultivar and growing conditions.
The plant’s origin traces back to the sea beet (Beta vulgaris subsp. maritima), a wild relative found in the coastal regions of the Mediterranean. For centuries, various forms of Beta vulgaris were grown for fodder or as a garden vegetable. Following the discovery of sucrose in the root, selective breeding began in the late 18th century to increase the sugar content. This process transformed a root with only about 6% sucrose into the high-yield varieties used in commercial production today.
Transforming Beets into Table Sugar
Extracting sucrose begins with thoroughly cleaning the sugar beet root, followed by slicing the beets into thin strips called “cossettes.” These cossettes are moved into a diffuser and treated with hot water in a process called diffusion. The hot water draws the sugar out of the plant cells, producing a raw juice high in sucrose but containing non-sugar impurities.
This raw juice undergoes purification where calcium hydroxide (lime) and carbon dioxide are added. This chemical treatment causes the non-sugar solids to coagulate and precipitate out of the liquid, known as carbonation. The clarified juice is then sent through evaporators, where excess water is boiled off to create a concentrated, thick syrup that is about 60% sucrose by weight.
The final stages involve crystallization and separation. The thick syrup is boiled under reduced pressure, encouraging sucrose molecules to form solid crystals. This mixture of sugar crystals and residual liquid, or molasses, is fed into a high-speed centrifuge. The centrifugal force separates the white sugar crystals from the dark, viscous molasses. After final drying and cooling, the result is refined, pure white sucrose, ready for packaging and consumption.
Sugar Beet vs. Sugarcane
Sugar beets and sugarcane are the world’s two primary agricultural sources of sucrose, but they are cultivated and processed differently. Sugarcane is a tropical grass, while the sugar beet is a root crop grown in temperate zones like Europe and North America. This difference dictates the initial processing: sugarcane stalks are crushed to squeeze out the juice, while sugar beets are sliced and use hot water diffusion to leach out the sucrose.
Despite the distinct agricultural and extraction processes, the resulting final product is chemically identical. The refining process for both crops yields pure white crystalline sucrose. Table sugar derived from beets is therefore indistinguishable from table sugar derived from cane, as both sources produce the exact same disaccharide molecule.
Valuable Materials Beyond Sugar
The sugar beet is considered a highly efficient crop because nearly all parts of the harvested plant can be utilized commercially, minimizing waste. After the sugar is extracted and crystallized, the remaining liquid is dark, concentrated sugar beet molasses. This molasses still contains 40% to 50% sugar, along with minerals and other compounds.
Sugar beet molasses is a valuable co-product used in various fermentation applications, including yeast production and alcohol distillation. The exhausted beet pulp, the fibrous material remaining after sugar extraction, is dried and repurposed. This dried pulp is widely used as a high-value animal feed for livestock. The sugar beet’s high carbohydrate yield also makes it a promising feedstock for sustainable biofuel production, such as ethanol.