This does not involve the use of any additives. The sugar is purified by means of several recrystallisation processes to obtain pure, clear crystals which appear white due to the refraction of light. The sucrose content of these crystals is nearly 100%. Sugar is therefore a high-purity foodstuff with an almost unlimited shelf life if stored appropriately.
The smallest sugar factory
THE SUGAR BEET PLANT (beta vulgaris saccharifera)
is a biennial plant belonging to the goosefoot family. The taproot, the so-called beet, which is used to produce sugar, forms during the growing phase in the first year. A flower and seeds form during the growing phase of the second year. This relies on the sugar stored in the beet. With a sugar concentration of 16 to 20%, the sugar beet offers the highest yield among sugar-producing plants (sugar beet and sugar cane). The water content is around 75%.
LEAVES OF THE SUGAR BEET
With the aid of solar energy and the chlorophyll in its leaves, the sugar beet plant converts carbon dioxide from the air, water and minerals in the soil into sugar. This process is called photosynthesis. The sugar beet foliage are left on the fields during harvesting.
HEAD OF THE SUGAR BEET
The head of the sugar beet plant, from where the leaves branch off, contains many non-sugar materials and therefore needs to be removed during harvesting.
ROOT OF THE SUGAR BEET
The sugar produced during photosynthesis is stored in the root of the sugar beet. The lighter areas are those in which the concentration of sugar is particularly high.
After being washed carefully and temporarily stored in the beet bunker, the sugar beet are subsequently processed.
Slicing machines cut the beets into strips known as cossettes which have an average sugar content of between 16 and 20%.
2. Raw Juice Production
The sugar is extracted from the cossettes by means of hot water (around 70 °C) in a diffuser, with the cossettes moving in the opposite direction to the water flow (counter-flow-principle), in a process known as extraction. The raw juice or liquor obtained contains around 98% of the sugar in the sugar beet as well as organic and inorganic constituents (so-called non-sugars) from the beet.
3. Juice Purification
The non-sugars in the raw juice are bound and extracted by means of the natural substances lime (CaO) and carbonic acid gas (CO2) which are produced in the site‘s own lime kiln.
The flocculatable insoluble non-sugars and the lime are filtered off in filter units. The filtrate is known as thin juice and the filter residue as carbonation-lime. This is an important soil improver and fertilizer which is spread on the fields.
5. Thick Juice Production
The thin juice is evaporated in hour-long steaming process to produce thick juice. The operation of on-site power plants provides the considerable quantities of energy needed for sugar production. The steam produced in the high-pressure boilers is used in the turbogenerators to produce electricity. The waste steam from the turbines is used as process heat (cogeneration) in order to heat the evaporator station.
The thick juice is thickened further in the boiling-pans under vacuum. The crystallisation process is triggered by adding (spiking) the thick juice with finely ground sugar. Further evaporation allows the crystals to grow to the desired size.
The sugar crystals are separated from the syrup by means of centrifuging. The separated syrup is subjected to a further two crystallisation process.
The pure, crystal-clear sugar appears white when subjected to white light. White sugar contains at least 99.7% sucrose. The remainder is in effect moisture.
9. Sugar Drying
White sugar is dried in an air stream, cooled and stored in silos. In its many forms and packaged in numerous different household and industrial volumes, sugar is an important nutritional and semi-luxury foodstuff which then makes its way to the end consumer.
The syrup separated off during the final crystallisation step is known as molasses. The molasses contains the non-crystallised sugar (6-9% of the sugar content of the beet) as well as the soluble non-sugars from the sugar beet. Molasses is a valuable ingredient for the baking yeast and animal feed industry as well as for the production of alcohol.
The cossettes from which the sugar juice is derived in the extraction tower are mechanically pressed and, following the addition of molasses, dried in a drying tunnel before being pelleted and sold as animal feed.