Two sugar beets - the one on the left has been cultivated to be smoother than the traditional beet, so that it traps less soil.
Sugar beet Beta vulgaris L., one of the Amaranthaceae family, is a plant that contains a very high concentration of sucrose, and is grown commercially for sugar.
Sugar beets are grown mainly in Europe, the United States, and China  (http://www.fao.org/es/ess/top/commodity.jsp?lang=EN&commodity=157&CommodityList=157&year=2003&yearLyst=2003). Beet sugar accounts for 30% of the world's sugar production.
The beets are harvested in the autumn, washed carefully, peeled and cut into chips known as cossettes, which are placed in a machine called a diffuser to extract their sugar content into a water solution. The diffuser is a large horizontal or vertical tank in which the beet slices slowly work their way from one end to the other while water is agitated in the opposite direction. This is called a counter-current flow, and it extracts more sugar from the chips than if they were merely sitting in a hot water bath. Once the beet chips have passed through the diffuser they still contain sugary liquid, so they are pressed in a screw press to extract the last juices. The remaining beet pulp is turned into animal feed, and the beet juice is further processed.
The next stage in processing is carbonation or carbonatation. The sugar juice contains many impurities that must be removed before it can be dehydrated. To do so, the raw juice is mingled with milk of lime and carbon dioxide gas in carbonation tanks. The carbon dioxide bubbles through the mixture forming calcium carbonate. The non-sugar particles attach themselves to the calcium carbonate as small clusters of chalk and settle to the bottom of the tanks. The chalk extracts the impurities from the mix, leaving a pure, if weak, sugar solution.
This sugar solution is then filtered, leaving a golden light brown clarified thin juice. To concentrate the juice, it is boiled under vacuum in a multi-stage evaporating machine where much of the water is evaporated, forming a thicker juice similar to pancake syrup.
Finally, this syrup is once again boiled under vacuum in large vats and crystals begin to form. The resulting sugar crystal and syrup mix is called massecuite. These crystals are removed from the liquid in a centrifuge and dried out using hot air.
A geneticist evaluates sugar beet plants for resistance to the fungal disease Rhizoctonia root rot
Beets (and carrots) were identified as potential sources of sugar by the Prussian chemist Andreas Sigismund Marggraf in 1747, but he thought that commercial extraction would be uneconomic. His former pupil and successor Franz Carl Achard began selectively breeding sugar beet from the White Silesian fodder beet in 1784.
Achard was the first to start producing beet sugar commercially in 1802, following the opening of the world's first beet sugar factory in Kunern, Germany in 1801. At the time his beet was approximately 5% to 6% sugar, compared to around 20% in modern varieties. The development spread rapidly in France and Germany, encouraged by the imposition in 1807 of a blockade by the English in the Napoleonic Wars, which prevented the import of cane sugar.
Other economically important members of the Chenopodioideae subfamily:
- Sugar Process at the Crystal Sugar website (http://www.crystalsugar.com/products/products6.sprocess.asp)
- How Beet Sugar is Made (http://www.sucrose.com/lbeet.html)
- Growing Sugar Crystals (http://www.crystalgrowing.com/recipes/sugar/sugar.htm)
- CSM sugar (http://www.csm.nl)