Sugar Manufacture

Extracting sugar from beet

24 hours a day seven days a week -  the campaign in full swing

Each year's crop yields around seven million tonnes of sugar beet. Around 2,500 lorry loads of sugar beet are delivered daily to British Sugar's factories which take in around 350,000 tonnes of beet each week during the processing season (campaign), this is completed by the end of February.

Sampling

On arrival, a sample of the sugar beet is taken from the load and tested to measure the sugar content and to determine the amount of soil, tops or leaves present in the load.

These analyses, combined with the weight of the vehicle entering and leaving the factory, enables the calculation of the quantity of sugar delivered and hence the payment due.

Cleaning

Sugar beet floats in water and in the cleaning stage of the process it is moved around in large quantities of water, allowing the beet to pass through machinery which 'catches' stones but allows the beet to float over the top. Weeds and other trash are also removed before the beet enters the factory, where it is sliced into thin slices called 'cossettes'.

Slicing

The slicing machines work in a similar manner to a kitchen grater and the cossettes they produce have a 'V' cross section. This ensures the largest possible surface area is presented to maximise the sugar extraction stage.

Diffusion

Sugar is extracted from the beet by diffusion. This process takes place in a large vessel and in simple terms is akin to brewing tea in a teapot.

The cossettes are mixed with hot water at around 70°C for a period of time and the sugar simply passes from the plant cells into the surrounding water by the diffusion process.

The vegetable material left behind from this stage is mechanically pressed to extract as much remaining sugar and water as possible and, after the addition of molasses, is dried to produce animal feed products. It is this drying process which gives rise to the familiar plume of steam rising from the factory. The liquid resulting from the diffusion process is dark in colour and is called raw juice.

Purification

This juice is passed through an important purification stage called carbonatation. This involves mixing the juice with milk of lime and adding carbon dioxide gas. During this process, the carbon dioxide and the milk of lime re-combine to produce calcium carbonate which precipitates out, taking most of the impurities from the juice with it. This lime which contains important trace elements is sold as a soil improving agent under the LimeX brand.

Evaporation

The pale yellow juice which remains is called thin juice and while much purer it is still relatively low in sugar content. It passes to the next stage of the process - evaporation - where the water is boiled off in a series of evaporator vessels to increase the solids content of the juice from the previous 16 per cent in thin juice to 65 per cent in the thick juice.

The concentrated juice passes through filters, after which it is ready for the final stage of the process; or it can be stored and brought back into the factory during the summer to produce crystal sugar.

Crystallisation

The crystallisation process takes place in vacuum pans which boil the juice at lower temperatures under vacuum. When the juice reaches a predetermined concentration it is 'seeded' with tiny sugar crystals which provide the nucleus for larger crystals to form and grow.

When the crystals reach the desired size the process is stopped and the resultant mixture of crystal sugar and syrup - known as massecuite - is spun in centrifuges to separate the sugar from the 'mother liquor'. The sugar crystals are washed and after drying and cooling, are conveyed to storage silos.

Some sugar remains in the separated liquid so it is boiled again in a further set of vacuum pans to produce raw sugar. This process is repeated a third time resulting in final product sugar and molasses. Raw and final product sugars are redissolved into the thick juice.

Quality

All British Sugar manufacturing sites work to a well established business management system which is registered to ISO9001 and which encompasses the entire operation from buying the raw materials, through manufacturing and packaging to delivery.

A specific and important element of business management is to uphold and champion food safety. As part of the company's strategy to continuously improve product quality and customer focus, food safety systems have been accredited to the British Retail Consortium's Global Food Standard. This, and other initiatives, clearly demonstrate that British Sugar is committed to not only maintaining but also advancing its reputation as a quality company at the forefront of the British food industry.