Introduction

What we call sugar, the chemist knows as sucrose, one of the family of sugars otherwise known as saccharides in the grouping called carbohydrates. Carbohydrates, as the name implies, contain carbon and hydrogen plus oxygen in the same ratio as in water. The saccharides is a large family with the general formula C_nH_2nO_n. The simplest of the sugars is glucose, C₆H₁₂O₆, although its physical chemistry is not that simple because it occurs in two distinct forms which affect some of its properties. Sucrose, C₁₂H₂₂O₁₁, is a disaccharide, a condensation molecule made up of two glucose molecules.

The process whereby plants make sugars is photosynthesis. The plant takes in carbon dioxide from the air though pores in its leaves and absorbs water through its roots. These are combined to make sugar using energy from the sun and with the help of a substance called chlorophyll. Chlorophyll is green which allows it to absorb the sun's energy more readily and which, of course, gives the plants' leaves their green colour. The reaction of photosynthesis can be written as the following chemical equation when sucrose is being made:

This shows that oxygen is given off during the process of photosynthesis.

Historically, sugar was only produced from sugar cane and then only in relatively small quantities. This resulted in it being considered a great luxury, particularly in Europe where cane could not be grown. The history of man and sugar is a subject in its own right but suffice to say that, even today, it isn't easy to ship food quality sugar across the world so a high proportion of cane sugar is made in two stages. Raw sugar is made where the sugar cane grows and white sugar is made from the raw sugar in the country where it is needed. Beet sugar is easier to purify and most is grown where it is needed so white sugar is made in only one stage.

Sugar Production

Sugar is produced in 121 Countries and global production now exceeds 120 Million tons a year. Approximately 70% is produced from sugar cane, a very tall grass with big stems which is largely grown in the tropical countries. The remaining 30% is produced from sugar beet, a root crop resembling a large parsnip grown mostly in the temperate zones of the north.

Sugar Cane

Sugar cane is a genus of tropical grasses which requires strong sunlight and abundant water for satisfactory growth. The Latin names of the species include Saccharum officinarum, S. spontaneum, S. barberi and S. sinense. As with most commercial crops, there are many cultivars available to the cane farmer, usually hybrids of several species. Some varieties grow up to 5 metres tall.

The cane itself looks rather like bamboo cane and it is here that the sucrose is stored. In the right climate the cane will grow in 12 months and, when cut, will re-grow in another 12 months provided the roots are undisturbed.

A typical sugar content for mature cane would be 10% by weight but the figure depends on the variety and varies from season to season and location to location. Equally, the yield of cane from the field varies considerably but a rough and ready overall value to use in estimating sugar production is 10 tons per hectare.

Sugar Beet

Sugar beet is a temperate climate biennial root crop. It produces sugar during the first year of growth in order to see it over the winter and then flowers and seeds in the second year. It is therefore sown in spring and harvested in the first autumn/early winter. As for sugar cane, there are many cultivars available to the beet farmer. The beet stores the sucrose in the bulbous root which bears a strong resemblance to a fat parsnip. A typical sugar content for mature beets is 17% by weight but the value depends on the variety and it does vary from year to year and location to location. This is substantially more than the sucrose content of mature cane but the yields of beet per hectare are much lower than for cane so that the expected sugar production is only about 7 tons per hectare.

How is sugar processed?

The initial stage involves sampling, weighing and washing the sugarcane. From there the material passes to can crushers and then into the mill. The bagasse, which results from the milling, is used in the boilers for steam production that is used to power the process. The surplus bagasse from this stage is used in industry.

Juice obtained from the mill is weighed in order to continue with the heating, clarifying and filtering process whereby those materials found in the juice, different to sucrose, are separated. Once the juice evaporates concentrated cane syrup is obtained which is taken to pans, where crystallization takes place. Subsequently the cooked mass is obtained, that then goes to a centrifuge, where the sugar is separated from the syrup.

Finally, the sugar is dried, cooled and packaged in its different forms, ready for sale.

	Harvesting Sugar cane is harvested by chopping down the stems but leaving the roots so that it re-grows in time for the next crop. Harvest times tend to be during the dry season and the length of the harvest ranges from as little as 2 ½ months up to 11 months.
	Extraction The first stage of processing is the extraction of the cane juice. In many factories the cane is crushed in a series of large roller mills: similar to a mangle [wringer] which was used to squeeze the water out of clean washing a century ago. The sweet juice comes gushing out and the cane fibre is carried away for use in the boilers. In other factories a diffuser is used as is described for beet sugar manufacture. Either way the juice is pretty dirty: the soil from the fields, some small fibres and the green extracts from the plant are all mixed in with the sugar.
	Clarification The extracted cane juice is pH tested and adjusted with lime before it is heated and sent to large clarifying tanks. These tanks allow for the settling of solids to the bottom leaving only clear juice to continue through the process.
	Evaporation The factory can clean up the juice quite easily with slaked lime (a relative of chalk) which settles out a lot of the dirt so that it can be sent back to the fields. Once this is done, the juice is thickened up into a syrup by boiling off the water using steam in a process called evaporation. Sometimes the syrup is cleaned up again but more often it just goes on to the crystal-making step without any more cleaning. The evaporation is undertaken in order to improve the energy efficiency of the factory.
	Boiling The syrup is placed into a very large pan for boiling. In the pan even more water is boiled off until conditions are right for sugar crystals to grow.
	Crystallisation The heated syrup begins to crystallize and separates into sugar crystals and molasses called "massecuite." The crystallizers cool the mixture of sugar crystals and molasses which causes the crystals to grow in size.You may have done something like this at school but probably not with sugar because it is difficult to get the crystals to grow well. In the factory the workers usually have to throw in some sugar dust to initiate crystal formation.
	Centrifugation To remove the sugar crystals from the molasses, high-speed rotating centrifugals spin off the molasses leaving only the raw sugar crystals on the centrifugal screens. The remaining product is blackstrap molasses which is then stored in tanks and later sold as cattle feed. After all of the commercially recoverable raw sugar is produced it is transferred into huge warehouses for storage until It is ready to be transported to refineries. Sugar processing is a highly specialized, computer-controlled, technical process that requires a combination of sensitive machinery and experienced individuals to succeed. Approximately one ton of sugarcane is required to produce 220 pounds of raw sugar. We at Sugar Cane Growers Cooperative of Florida are proud of our facilities and the people who run them.
	Storage The final raw sugar forms a sticky brown mountain in the store and looks rather like the soft brown sugar found in domestic kitchens. It could be used like that but usually it gets dirty in storage and has a distinctive taste which most people don't want. That is why it is refined when it gets to the country where it will be used. Additionally, because one cannot get all the sugar out of the juice, there is a sweet by-product made: molasses. This is usually turned into a cattle food or is sent to a distillery where alcohol is made.
	Power So what happened to all that fibre from crushing the sugar cane? It is called "bagasse" in the industry. The factory needs electricity and steam to run, both of which are generated using this fibre. The bagasse is burnt in large furnaces where a lot of heat is given out which can be used in turn to boil water and make high pressure steam. The steam is then used to drive a turbine in order to make electricity and create low pressure steam for the sugar making process. This is the same process that makes most of our electricity but there are several important differences. When a large power station produces electricity it burns a fossil fuel [once used, a fuel that cannot be replaced] which contaminates the atmosphere and the station has to dump a lot of low grade heat. All this contributes to global warming. In the cane sugar factory the bagasse fuel is renewable and the gases it produces, essentially CO2, are more than used up by the new cane growing. Add to that the factory use of low grade heat [a system called co-generation] and one can see that a well run cane sugar estate is environmentally friendly.

Uses of Sugar

Sugar is used for many purposes in the food industry. It is vital in maintaining the safety and availability of our food.

• Ice cream is made thicker and smoother with sugar. More than 20% of ice cream is sugar.
• Sugar helps cakes to be moist and soft, and to stay fresh longer.
• Soft drinks and fruit juice are often 10% or 12% sugar. As well as adding flavour, the sugar makes the drinks heavier and more pleasant to drink.
• The sugar in jams helps them to keep for a longer time, by stopping mould and germs from growing.
• Natural sugar in canned fruit also acts as a preservative in the same way.
• Condensed milk relies on up to 55% sugar content.
• Cane sugar is used in making many lollies.
• Sugar is used to bring out the flavours of other foods such as preserved meats, tomato sauce and canned soup.
• Custard is made smooth and creamy as well as sweet by sugar.
• Many medicines have sugar added to hide their bitter taste. Some cough syrups have sugar to make them more soothing