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Beets are grown primarily for their enlarged bulbous root, although the greens can be eaten or used for cattle feed. Beets are a biennial plant, producing leaves and the root one year, and a seed stalk the following year; but, except for seed production, beets are grown as an annual. The plant develops best under cool conditions. The ancestor of Beta vulgaris v. vulgaris is v. maritima, which grows wild along seashores and marshes of Britain, Europe and Asia. Beets and their relatives like it cool, and are able to withstand a mild frost. They grow well in a variety of soils, except clay, and can tolerate a moderately alkaline soil. The plants are machine-harvested and the top of the root and leaves are cut off for livestock feed, while the roots are delivered to the sugar mills where they're stored in piles outside the mill, waiting to be processed into sugar. |
| Sugar beets are the principal source of sugar outside of the tropical areas of the world, where sugarcane is used. Although beets were used for many centuries as food and feed, beets for sugar are a relatively recent development. In 1747, Robert Marggraf, a chemist in Berlin, discovered a small amount of sugar in the juice of beets, but thought that there wasn't enough sugar to warrant developing the techniques needed to extract it. Fifty years later, a student of Marggraf's, Mr. Archard, rekindled the search for extraction techniques, and the development of beets with a higher sugar content. His efforts were effective and he founded the first beet sugar factory, in 1802 in Kunern, Germany. |
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Processing sugar beets separates sucrose from insoluble pulp, soluble non-sugars, and water. A typical sugar beet contains 16.0% sugar, 75.9%water, 2.6% soluble non-sugar, and 5.5% pulp. Separation of sugar from soluble non-sugars is done by adding milk of lime to the beet juice. Many chemical and physical reactions are necessary to extract juice from beets and crystallize the juice to obtain white granulated sugar. First the roots are washed, then cut into strips called cossettes. The cossette mixer mixes beets with hot juice and pumps he mixture into the bottom of the diffusion towers. It is in the diffusion towers where the sugar is released from the beets. As the cossettes are conveyed slowly toward the top of the towers, hot water is added at the top and flows through the cossettes, to the bottom, carrying the sugar from the cells of the beet. Cossettes are discharged as pulp from the upper part of the towers. The sugar-laden juice at the bottom of the diffusion towers, called "raw juice," is heated, pumped through a series of tanks and alkalized to a pH of about 8.9 by adding lime and carbon dioxide gas. The milk of lime and CO2 added to the juice cause the formation of a precipitate or "mud," which is heated and sent to a clarifier where the mud is allowed to settle, leaving clear juice. This juice is run through a series of filters and vacuum evaporators. The final super-saturated solution is "seeded" with sugar crystals to promote crystallization of the sugar. Crystals are separated from the syrup using a centrifuge. The separated molasses is re-boiled and re-centrifuged to remove additional sugar. Finally the molasses is treated with lime and mixed with raw juice to extract still more sugar. The crystallized sugar is dried in granulators, cooled and sold as granulated sugar, blended with flour to make powdered sugar or mixed with molasses to make brown sugar. |
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Sugar is an important source of carbohydrate, the body's primary energy source. Sugar can contribute to the flavor, aroma, texture, color, and body of healthy, but not-very-tasty, foods. It helps bread rise by acting as a food for the yeast. In baked products, it contributes to flavor and crust color as well as prolonged shelf life. Sugar preserves jams, jellies and canned goods against the growth of yeast and molds. Granulated sugar consists of 99.9% sucrose. The sucrose molecule is composed of twelve atoms of carbon, twenty-two atoms of hydrogen, and eleven atoms of oxygen (C12H22O11). Sugar beet processing produces refined sugar and three main byproducts: pulp, molasses and lime. Pulp, the vegetable matter remains of the beet, is pressed and dried to remove water, then formed into pellets. A ton of beets produces 110 pounds of pulp pellets, which are used as a nutritious feed for cattle. Although molasses is about 50% sugar, it is not economically feasible to further process this liquid. However, the high sugar content makes molasses perfect for fermentation processes, where it is used in the production of bakers' yeast, citric acid, pharmaceuticals, and alcohol. Molasses is also used as an animal feed supplement, where it adds nutrient value, texture, and palatability. The lime is used on agricultural land to de-acidify the soil, and balance the pH. |
Links to other sites with information about beets:
| Crop Plant Resources |
| Outreach and Educational
Resources | | Molecular
Biology Program |
Please send comments and suggestions to: moconnel@nmsu.edu
Last Updated: June 5, 1998
