Sugar beet

Two sugar beets. The one on the left has been selectively bred to be smoother than the traditional beet, so that it traps less soil.

Sugar beet, a cultivated plant of Beta vulgaris, is a plant whose root contains a high concentration of sucrose. It is grown commercially for sugar production.

The sugar comes from the bulb of the beetroot plant, chard and fodder beet, all descended by cultivation from the sea beet.

The European Union, the United States, and Russia are the world's three largest sugar beet producers,^[1] although only the European Union and Ukraine are significant exporters of sugar from beets. The U.S. harvested 1,004,600 acres (4 065 km²) of sugarbeets in 2008 alone.^[2] Beet sugar accounts for 30% of the world's sugar production.

In the United States, genetically modified sugar beets resistant to glyphosate (marketed by Monsanto Company as Roundup), an herbicide, were planted for the first time in the spring of 2008. Sugar from the biotechnology-enhanced sugarbeet has been approved for human and animal consumption in the European Union. This action by the EU executive body allows unrestricted imports of food and feed products made from (H7-1) glyphosate-tolerant (Roundup Ready) sugarbeets. On September 21, 2009, a federal court ruled that the USDA had violated federal law in deregulating Roundup Ready sugar beets without adequately evaluating the environmental and socio-economic impacts of allowing commercial production, and will be considering an appropriate injunction.^[3][4]

Culture

Sugar beet is a hardy biennial plant that can be grown commercially in a wide variety of temperate climates. During its first growing season, it produces a large (1–2 kg) storage root whose dry mass is 15–20% sucrose by weight. If the plant is not harvested at this time, then during its second growing season, nutrients in the root will be used to produce flowers and seeds and the root will decrease in size. In commercial beet production, the root is harvested after the first growing season.

Sugar beet output in 2005

In most temperate climates, beets are planted in the spring and harvested in the autumn. At the northern end of its range, growing seasons as short as 100 days can produce commercially viable sugarbeet crops. In warmer climates, such as in California's Imperial Valley, sugarbeets are a winter crop, planted in the autumn and harvested in the spring. In recent years, Syngenta AG has developed the so-called tropical sugar beet. It allows the plant to grow in tropical and subtropical regions. Beets are planted from a small seed; 1 kg of beet seed comprises 100,000 seeds and will plant over a hectare of ground (1 lb will plant about an acre).

Until the latter half of the 20th century, sugarbeet production was highly labor-intensive, as weed control was managed by densely planting the crop, which then had to be manually thinned with a hoe two or even three times during the growing season. Harvesting also required many workers. Although the roots could be lifted by a plough-like device which could be pulled by a horse team, the rest of the preparation was by hand. One laborer grabbed the beets by their leaves, knocked them together to shake free loose soil, and then laid them in a row, root to one side, greens to the other. A second worker equipped with a beet hook (a short-handled tool between a billhook and a sickle) followed behind, and would lift the beet and swiftly chop the crown and leaves from the root with a single action. Working this way, he would leave a row of beets that could be forked into the back of a cart.

Worldwide sugar beet production

Top Ten Sugar Beet Producers - 2005 (million metric tons)
France	29
Germany	25
United States	25
Russia	22
Ukraine	16
Turkey	14
Italy	12
Poland	11
United Kingdom	8
Spain	7
World Total	242
Source: UN Food & Agriculture Organisation (FAO)[5]

Today, mechanical sowing, herbicide application for weed control and mechanical harvesting have removed this reliance on numerous workers.

Harvesting is now entirely mechanical. A roto beater uses a series of blades to chop the leaf and crown (which is high in non-sugar impurities) from the root. The beet harvester lifts the root, and removes excess soil from the root in a single pass over the field. A modern harvester is typically able to cover six rows at the same time. The beets are dumped into trucks as the harvester rolls down the field and delivered to the factory. The conveyor then removes more soil.

If the beets are to be left for later delivery, they are formed into clamps. Straw bales are used to shield the beets from the weather. Provided the clamp is well built with the right amount of ventilation, the beets do not significantly deteriorate. Beets that freeze and then defrost produce complex carbohydrates that cause severe production problems in the factory. In the UK, loads may be hand examined at the factory gate before being accepted.

In the US, the fall harvest begins with the first hard frost, which arrests photosynthesis and the further growth of the root. Depending on the local climate, it may be carried out over the course of a few weeks or be prolonged throughout the winter months. The harvest and processing of the beet is referred to as "the campaign", reflecting the organization required to deliver the crop at a steady rate to processing factories that run 24 hours a day for the duration of the harvest and processing (for the UK the campaign lasts approx 5 months). In the Netherlands this period is known as "de bietencampagne", a time to be careful when driving local roads in the area the beets are grown. The reason for this is the naturally high clay content of the soil, causing slippery roads when soil falls from the trailers during transport.

Sebewaing, Michigan is known (to Americans) as the sugar beet capital of the world. Sebewaing lies in the Thumb region of Michigan; both the region and state are major sugar beet producers. Sebewaing is home to one of three Michigan Sugar Company factories. The town sponsors an annual "Michigan Sugar Festival".

Arthur Stayner, because of his energetic work in experimenting with the growing of sugar beets in alkali soils, is regarded as the "father and founder of the movement that made the manufacture of sugar in Utah a success."^[6]

Processing

Reception

A beet harvester

A sugar refinery located in Shropshire, England.

After they are harvested, beets are hauled to a factory. In the U.K., beets are transported by a hauler, or by a tractor and a trailer by local farmers. Railways and boats are no longer used. Some beets were carried by rail in the Republic of Ireland, until the shutdown of sugar beet production in 2006 after the end of the government subsidies.

Each load is weighed and sampled before it gets tipped onto the reception area, typically a "flat pad" of concrete, where it is moved into large heaps. The beet sample is checked for

• soil tare - the amount of non beet delivered
• crown tare - the amount of low sugar beet delivered
• sugar content ("pol") - amount of sucrose in the crop
• nitrogen content - for recommending future fertilizer use to the farmer.

From these elements, the actual sugar content of the load is calculated and the grower's payment determined.

The beet is moved from the heaps into a central channel or gulley, where it is washed towards the processing plant.

Diffusion

After reception at the processing plant, the beet roots are washed, mechanically sliced into thin strips called cossettes, and passed to a machine called a diffuser to extract the sugar content into a water solution.

Diffusers are long vessels of many metres in which the beet slices go in one direction while hot water goes in the opposite direction. The movement may either be by a rotating screw or the whole unit rotates, and the water and cossettes move through internal chambers. There are three common designs of diffuser: the horizontal rotating 'RT' (Raffinerie Tirlemontoise, manufacturer), inclined screw 'DDS' (De Danske Sukkerfabrikker), or vertical screw "Tower". Modern tower extraction plants have a processing capacity of up to 17,000 metric tons per day.^[7] A less common design uses a moving belt of cossettes, with water pumped onto the top of the belt and poured through. In all cases the flow rates of cossettes and water are in the ratio one to two. Typically cossettes take about 90 minutes to pass through the diffuser, the water only 45 minutes. These are all countercurrent exchange methods that extract more sugar from the cossettes using less water than if they merely sat in a hot water tank. The liquid exiting the diffuser is called raw juice. The colour of raw juice varies from black to a dark red depending on the amount of oxidation, which is itself dependent on diffuser design.

The used cossettes, or pulp, exits the diffuser at about 95% moisture but low sucrose content. Using screw presses, the wet pulp is then pressed down to 75% moisture. This recovers additional sucrose in the liquid pressed out of the pulp, and reduces the energy needed to dry the pulp. The pressed pulp is dried and sold as animal feed, while the liquid pressed out of the pulp is combined with the raw juice, or more often introduced into the diffuser at the appropriate point in the countercurrent process. The final byproduct, Vinasse, is used as fertilizer or growth substrate for yeast cultures.

During diffusion, there is a degree of breakdown of the sucrose into invert sugars. These can undergo further breakdown into acids. These breakdown products are not only losses of sucrose but also have knock-on effects reducing the final output of processed sugar from the factory. To limit (thermophilic) bacterial action, the feed water may be dosed with formaldehyde and control of the feed water pH is also practiced. There have been attempts at operating diffusion under alkaline conditions, but the process has proven problematic. The improved sucrose extraction in the diffuser is offset by processing problems in the next stages.

Carbonatation

Carbonatation is a procedure which removes impurities from raw juice before it undergoes crystallization. First, the juice is mixed with hot milk of lime (a suspension of calcium hydroxide in water). This treatment precipitates a number of impurities, including multivalent anions such as sulfate, phosphate, citrate and oxalate, which precipitate as their calcium salts and large organic molecules such as proteins, saponins and pectins, which aggregate in the presence of multivalent cations. In addition, the alkaline conditions convert the simple sugars, glucose and fructose, along with the amino acid glutamine, to chemically stable carboxylic acids. Left untreated, these sugars and amines would eventually frustrate crystallization of the sucrose.

Next, carbon dioxide is bubbled through the alkaline sugar solution, precipitating the lime as calcium carbonate (chalk). The chalk particles entrap some impurities and absorb others. A recycling process builds up the size of chalk particles and a natural flocculation occurs where the heavy particles settle out in tanks (clarifiers). A final addition of more carbon dioxide precipitates more calcium from solution; this is filtered off, leaving a cleaner, golden light-brown sugar solution called thin juice.

Before entering the next stage, the thin juice may receive soda ash to modify the pH and sulphitation with a sulfur-based compound to reduce colour formation due to decomposition of monosaccharides under heat.

Evaporation

The thin juice is concentrated via multiple-effect evaporation to make a thick juice, roughly 60% sucrose by weight and similar in appearance to pancake syrup. Thick juice can be stored in tanks for later processing, reducing load on the crystallization plant.

Crystallization

Thick juice is fed to the crystallizers. Recycled sugar is dissolved into it, and the resulting syrup is called mother liquor. The liquor is concentrated further by boiling under vacuum in large vessels (the so-called vacuum pans), seeded with fine sugar crystals. These crystals grow, as sugar from the mother liquor forms around them. The resulting sugar crystal and syrup mix is called a massecuite, from "cooked mass" in French. The massecuite is passed to a centrifuge where the liquid is removed from the sugar crystals. Remaining syrup is rinsed off with water and the crystals dried in a granulator using warm air.

The remaining syrup is fed to another crystallizer from which a second batch of sugar is produced. This sugar ("raw") is of lower quality with a lot of color and impurities and is the main source of the sugar that is dissolved again into the mother liquor. The syrup from the raw is also sent to a crystalliser. From this a very low-quality sugar crystal is produced (known in some systems as "AP sugar") that is also redissolved. The syrup separated is molasses, which still contains sugar but contains too much impurity to undergo further processing economically.

Actual procedure may vary from the above description, with different recycling and crystallisation processes.

Other uses

Beverages

In a number of countries, most notably the Czech Republic, sugar from sugar beet is used to make a type of "rum" which is now known as tuzemak. On the Åland Islands, a similar drink is made under the brand name Kobba Libre. In some European countries, especially in the Czech Republic and Germany, sugar beet is also used to make rectified spirit and vodka.

Sugar beet syrup

An unrefined sugary syrup can be produced directly from sugar beet. This thick, dark syrup is produced by cooking shredded sugar beet for several hours, then pressing the resulting sugar beet mash and concentrating the juice produced until it has the consistency similar to that of honey. No other ingredients are used. In Germany, particularly the Rhineland area, this sugar beet syrup (called Zuckerrüben-Sirup in German) is used as a spread for sandwiches, as well as for sweetening sauces, cakes and desserts.

Commercially, if the syrup has a Dextrose Equivalency above 30 DE, the product has to be hydrolyzed and converted to a high-fructose syrup, much like high-fructose corn syrup, or iso-glucose syrup in the EU.

In Saint John, New Brunswick, sugar beet molasses is used as a de-icing product on the Harbour Bridge. The molasses has a lower melting point (-34 Celsius) than road salt and reduces corrosiveness.^[8]

Betaine

Betaine can be isolated from the by-products of sugar beet processing. Production is chiefly by chromatagraphic separation, using techniques such as the "simulated moving bed".

Uridine

Uridine can be isolated from sugar beet. Uridine in combination with omega 3 fatty acids has been shown to alleviate depression.^[9]

Alternative fuel

There are plans by BP and Associated British Foods to use agricultural surpluses of sugar beet to produce biobutanol in East Anglia in the United Kingdom.

History

A geneticist evaluates sugar beet plants resistant to the fungal disease Rhizoctonia root rot for pollen fertility.

A large root vegetable in 4000-year-old Egyptian temple artwork may be a beet. Although beets have been grown as vegetables and for fodder since antiquity, their use as a sugar crop is relatively recent. As early as in 1590, the French botanist Olivier de Serres extracted a sweet syrup from beetroot, but the practice was not widely used. The Prussian chemist Andreas Sigismund Marggraf used alcohol to extract sugar from beets (and carrots) in 1747, but the methods did not lend themselves to industrial scale production.

His former pupil and successor Franz Karl Achard began selectively breeding sugar beet from the White Silesian fodder beet in 1784. By the beginning of the 19th century, his beet was approximately 5–6 percent sucrose by weight, compared to around 20 percent in modern varieties. Under the patronage of Frederick William III of Prussia, he opened the world's first beet sugar factory in 1801, at Cunern in Silesia.

The beet sugar industry in Europe rapidly developed after the Napoleonic Wars. In 1807, the British began a blockade of France, which prevented the import of sugarcane from the Caribbean. Partly in response, in 1812 Frenchman Benjamin Delessert devised a process of sugar extraction suitable for industrial application. In 1813, Napoleon instituted a retaliatory embargo. By the end of the wars, over 300 sugar beet mills operated in France and central Europe.

The first sugar beet mill in the U.S. opened in 1838, and the first commercially successful mill was established by E. H. Dyer in 1879.

Agriculture

Sugar beet is an important part of a rotating crop cycle.

Sugar beet plants are susceptible to rhizomania ("root madness") which turns the bulbous tap root into many small roots making the crop economically unprocessable. Strict controls are enforced in European countries to prevent the spread, but it is already endemic in some areas.

Continual research looks for varieties with resistance as well as increased sugar yield. Sugar beet breeding research in the United States is most prominently conducted at various USDA Agricultural Research Stations, including one in Fort Collins, Colorado, headed by Linda Hanson and Leonard Panella; one in Fargo, North Dakota, headed by John Wieland; and one at Michigan State University in East Lansing, Michigan, headed by J. Mitchell McGrath.

Other economically important members of the Chenopodioideae subfamily:

• Beetroot
• Chard
• Mangelwurzel or Fodder Beet

See also

• Sugar cane
• Sugar refinery

References

External links

• Sugar Process at the American Crystal Sugar Company website
• How Beet Sugar is Made
• Growing Sugar Crystals
• CSM sugar
• Guardian (UK) article on how sugar beet can be used for fuel
• Sugar beet culture in the northern Great Plains area hosted by the University of North Texas Government Documents Department