The sugar stored inside the plant is a finished product. In order for it to reach the consumer it must be extracted from the plant. Producing table sugar is about extraction rather than manufacture.
The same principle applies to sugar cane and sugar beet. The sucrose has to be isolated and the other components of the plant removed stage by stage. To extract the sugar from the plant cells it must be cleared of impurities. The sugar juice is then evaporated to obtain crystals. At the end of these processes the sugar will have been extracted, purified, concentrated and crystallised but will not have undergone any chemical change.
Cane and beet must be processed quickly in order to preserve their sugar content. That is why sugar factories are located close to cultivation areas. It is also the reason why the activities of the sugar industry are seasonal, from late September to late December.
Sugar beet has a two-year reproductive cycle. During the first year, or vegetative phase, the plant builds up stores of sugar in its root. After this growth period, during the second year, or reproductive phase, these energy reserves are used to support flowering and production of seeds by cross-fertilisation.
For sugar production, sugar beet is harvested after one year, when the sugar reserves in the root are at their highest (15-20% of total weight).
Over the last 20 years, “soil tare” has dropped from 30% to 20% of net weight on delivery, due mainly to the activities of growers. This means that three million tonnes of earth remain in the fields rather than being transported to sugar processing plants with the sugar beets. This represents a saving in soil transport equal to a line of trucks 3,000 km long!
Sugar professionals are committed to making further improvements. In 2001, they agreed to reduce average French “soil tare” by 7 percentage points over five years. The goal is to ensure that it does not exceed 15% in 2006, representing a reduction of 1.4 percentage points every year.
- A photo slide show
- A short description of the production process
The process of extracting cane sugar is exactly the same as that used for beet sugar - apart from the first stage. Cane sugar juice is extracted by milling, while beet sugar juice is extracted by diffusion.
The pace of work in sugar cane plants is very different depending on the place in which it is grown. The campaign can last between 4 and 11 months.
Red sugar cane crystals or second and third grade beet sugar still contain many impurities, including mineral salts and organic matter. They are removed during the refining process.