Food Commodities 29

Sugar

A group of carbhohydrates containing one (Monosaccharide) or two (Disaccharide) sugar units, occurring naturally principally in fruits and honey. It's sweet, soluble and readily absorbed to be used as an energy source. ; Water-soluble crystalline carbohydrate used as a sweetener and preservative for foods. 

History of Sugar

Sugar is made by some plants to store energy that they don't need straight away, rather like animals make fat. People like sugar for its sweetness and its energy so some of these plants are grown commercially to extract the sugar:

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.

An interactive World Map of Sugar production

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 [less a water molecule to make the chemistry work].

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:

12 CO2 + 11 H2 O	=	C12 H22 O11 + 12 O2
carbon dioxide + water	=	sucrose + oxygen

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.

It is thought that cane sugar was first used by man in Polynesia from where it spread to India. In 510 BC the Emperor Darius of what was then Persia invaded India where he found "the reed which gives honey without bees". The secret of cane sugar, as with many other of man's discoveries, was kept a closely guarded secret whilst the finished product was exported for a rich profit.

It was the major expansion of the Arab peoples in the seventh century AD that led to a breaking of the secret. When they invaded Persia in 642 AD they found sugar cane being grown and learnt how sugar was made. As their expansion continued they established sugar production in other lands that they conquered including North Africa and Spain.

Sugar was only discovered by western Europeans as a result of the Crusades in the 11^th Century AD. Crusaders returning home talked of this "new spice" and how pleasant it was. The first sugar was recorded in England in 1099. The subsequent centuries saw a major expansion of western European trade with the East, including the importation of sugar. It is recorded, for instance, that sugar was available in London at "two shillings a pound" in 1319 AD. This equates to about US$100 per kilo at today's prices so it was very much a luxury.

In the 15^th century AD, European sugar was refined in Venice, confirmation that even then when quantities were small, it was difficult to transport sugar as a food grade product. In the same century, Columbus sailed to the Americas, the "New World". It is recorded that in 1493 he took sugar cane plants to grow in the Caribbean. The climate there was so advantageous for the growth of the cane that an industry was quickly established.

By 1750 there were 120 sugar refineries operating in Britain. Their combined output was only 30,000 tons per annum. At this stage sugar was still a luxury and vast profits were made to the extent that sugar was called "white gold". Governments recognised the vast profits to be made from sugar and taxed it highly. In Britain for instance, sugar tax in 1781 totalled £326,000, a figure that had grown by 1815 to £3,000,000. This situation was to stay until 1874 when the British government, under Prime Minister Gladstone, abolished the tax and brought sugar prices within the means of the ordinary citizen.

Sugar beet was first identified as a source of sugar in 1747. No doubt the vested interests in the cane sugar plantations made sure that it stayed as no more than a curiosity, a situation that prevailed until the Napoleonic wars at the start of the 19^th century when Britain blockaded sugar imports to continental Europe. By 1880 sugar beet had replaced sugar cane as the main source of sugar on continental Europe. Those same vested interests probably delayed the introduction of beet sugar to England until the First World War when Britain's sugar imports were threatened.

Today's modern sugar industry is still beset with government interference at many levels and throughout the world. The overall pattern can be seen by investigating the mid 1990s' position in the interactive map on the Introduction page. Annual consumption is now running at about 120 million tons and is expanding at a rate of about 2 million tons per annum. The European Union, Brazil and India are the top three producers and together account for some 40% of the annual production. However most sugar is consumed within the country of production and only approximately 25% is traded internationally.

One of the most important examples of governmental actions is within the European Union where sugar prices are so heavily subsidised that over 5 million tons of white beet sugar have to be exported annually and yet a million tons of raw cane sugar are imported from former colonies. This latter activity is a form of overseas aid which is also practised by the USA. The EU's over-production and subsequent dumping has now been subjected to GATT requirements which should see a substantial cut-back in production over the next few years.

How Sugar is Made 

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 100 tons of cane per hectare or 10 tons of sugar per hectare.

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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 Cane Sugar is Made - the Basic Story Growing the Cane Sugar cane is a sub-tropical and tropical crop that prefers lots of sun and lots of water - provided that its roots are not waterlogged. It typically takes about 12 months to reach maturity although the time varies widely around the world from as short as six months in Louisiana to 24 months in some places. Where it differs from many crops is that it re-grows from the roots so the plant lasts many cycles [or 'ratoons', a word derived from the Spanish to sprout before it is worn out. 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. The cane is taken to the factory: often by truck or rail wagon but sometimes on a cart pulled by a bullock or a donkey! 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. 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, the last stage. In the pan even more water is boiled off until conditions are right for sugar crystals to grow. 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. Once the crystals have grown the resulting mixture of crystals and mother liquor is spun in centrifuges to separate the two, rather like washing is spin dried. The crystals are then given a final dry with hot air before being stored ready for despatch. 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.

How Beet Sugar is Made - the Basic Story White beet sugar is made from the beets in a single process, rather than the two steps involved with cane sugar. Harvesting The beets are harvested in the autumn and early winter by digging them out of the ground. They are usually transported to the factory by large trucks because the transport distances involved are greater than in the cane industry. This is a direct result of sugar beet being a rotational crop which requires nearly 4 times the land area of the equivalent cane crop which is grown in mono-culture. Because the beets have come from the ground they are much dirtier than sugar cane and have to be thoroughly washed and separated from any remaining beet leaves, stones and other trash material before processing. Extraction The processing starts by slicing the beets into thin chips. This process increases the surface area of the beet to make it easier to extract the sugar. The extraction takes place in a diffuser where the beet is kept in contact with hot water for about an hour. Diffusion is the process by which the colour and flavour of tea comes out of the tea leaves in a teapot but a typical diffuser weighs several hundred tons when full of beet and extraction water. The diffuser is a large horizontal or vertical agitated tank in which the beets slices slowly work their way from one end to the other and the water is moved in the opposite direction. This is called counter-current flow and as the water goes it becomes a stronger and stronger sugar solution usually called juice. Of course it also collects a lot of other chemicals from the flesh of the sugar beet. Pressing The exhausted beet slices from the diffuser are still very wet and the water in them still holds some useful sugar. They are therefore pressed in screw presses to squeeze as much juice as possible out of them. This juice is used as part of the water in the diffuser and the pressed beet, by now a pulp, is sent to drying plant where it is turned into pellets which form an important constituent of some animal feeds. Carbonatation The juice must now be cleaned up before it can be used for sugar production. This is done by a process known as carbonatation where small clumps of chalk are grown in the juice. The clumps, as they form, collect a lot of the non-sugars so that by filtering out the chalk one also takes out the non-sugars. Once this is done the sugar liquor is ready for sugar production except that it is very dilute. The next stage of the process is therefore to evaporate the juice in a multi-stage evaporator. This technique is used because it is an efficient way of using steam and it also creates another, lower grade steam which can be used to drive the crystallisation process. Boiling For this last stage, the syrup is placed into a very large pan, typically holding 60 tons or more of sugar syrup. In the pan even more water is boiled off until conditions are right for sugar crystals to grow. 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 add some sugar dust to initiate crystal formation. Once the crystals have grown the resulting mixture of crystals and mother liquor is spun in centrifuges to separate the two, rather like washing is spin dried. The crystals are then given a final dry with hot air before being packed and/or stored ready for despatch. Product The final sugar is white and ready for use, whether in the kitchen or by an industrial user such as a soft drink manufacturer. As for raw sugar production, because one cannot get all the sugar out of the juice, there is a sweet by-product made: beet molasses. This is usually turned into a cattle food or is sent to a fermentation plant such as a distillery where alcohol is made. It does not have the same quality smell and taste as cane molasses so cannot be used for rum production. Power One of the big differences between a beet sugar factory and its cane sugar counterpart is with respect to energy. Both factories need steam and electricity to run and both have co-generation stations where high pressure steam is used to drive turbines which produce the electrical power and create the low pressure steam needed by the process. However the beet factory does not have a suitable by-product to use as fuel for the boilers, it has to burn a fossil fuel such as coal, oil or gas. This is partly because the pulp will not burn properly and partly because the animal feed business has been built from the availability of the pulp.

How Sugar is Refined - the Basic Story Raw sugar is made in tropical countries where sugar cane can be grown profitably. It is then shipped in bulk to a refinery in the country where the sugar is required. It now has to be finally cleaned up, purified and made ready for the consumer. It helps to think of refining as a series of steps from left to right where colour and non-sugars are concentrating to the left and pure sugar is concentrating to the right. However the raw sugar comes into the process to the left of centre, not at one end. In the description that follows the flow of sugar is followed first and then the remainder of the process is reviewed. Affination The first stage of processing the raw sugar is to soften and then remove the layer of mother liquor surrounding the crystals with a process called "affination". The raw sugar is mixed with a warm, concentrated syrup of slightly higher purity than the syrup layer so that it will not dissolve the crystals. The resulting magma is centrifuged to separate the crystals from the syrup thus removing the greater part of the impurities from the input sugar and leaving the crystals ready for dissolving before further treatment. The liquor which results from dissolving the washed crystals still contains some colour, fine particles, gums and resins and other non-sugars. Carbonatation The first stage of processing the liquor is aimed at removing the solids which make the liquor turbid. Coincidentally some of the colour is removed too. One of the two common processing techniques is known as carbonatation where small clumps of chalk are grown in the juice. The clumps, as they form, collect a lot of the non-sugars so that by filtering out the chalk one also takes out the non-sugars. Once this is done, the sugar liquor is now ready for decolourisation. The other technique, phosphatation, is chemically similar but uses phosphate rather than carbonate formation. Decolourisation There are also two common methods of colour removal in refineries, both relying on absorption techniques with the liquor being pumped through columns of medium. One option open to the refiner is to use granular activated carbon [GAC] which removes most colour but little else. The carbon is regenerated in a hot kiln where the colour is burnt off from the carbon. The other option is to use an ion exchange resin which removes less colour than GAC but also removes some of the inorganics present. The resin is regenerated chemically which gives rise to large quantities of unpleasant liquid effluents. The clear, lightly coloured liquor is now ready for crystallisation except that it is a little too dilute for optimum energy consumption in the refinery. It is therefore evaporated prior to going to the crystallisation pan. Boiling In the pan even more water is boiled off until conditions are right for sugar crystals to grow. 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 throw in some sugar dust to initiate crystal formation. Once the crystals have grown the resulting mixture of crystals and mother liquor is spun in centrifuges to separate the two, rather like washing is spin dried. The crystals are then given a final dry with hot air before being packed and/or stored ready for despatch. Recovery The liquor left over from the preparation of white sugar and the washings from the affination stage both contain sugar which it is economic to recover. They are therefore sent to the recovery house which operates rather like a raw sugar factory, aiming to make a sugar with a quality comparable to the washed raws after the affination stage. As with the other sugar processes, one cannot get all of the sugar out of the liquor and therefore there is a sweet by-product made: refiners' molasses. This is usually turned into a cattle food or is sent to a distillery where alcohol is made.

How Sugar is Made - the Different Types There are a bewildering number of sugars and syrups available in the shops while other types are available for the industrial user. Some of the basic differences are discussed below. White sugar is essentially pure sucrose and there is no difference between that derived from cane and that from beet. Different manufacturers produce crystals of different sizes however and this leads to some apparent differences. Smaller crystals dissolve more readily and might therefore appear to be sweeter because none is left at the bottom of the cup and they seem sweeter on the tongue if eaten alone. Similarly smaller crystals have more surfaces per spoonful and appear whiter than larger crystals. [Having said that, some white sugars are less white than others: it depends on how much processing the manufacturer applies. There are several speciality white sugars: caster sugar is just a very small crystal size white sugar icing sugar is ground up white sugar, essentially sugar dust sugar cubes are lumps of sugar crystals "glued" together with a sugar syrup preserving sugar is a special large crystal Brown sugars come in many different styles but are essentially one of two types: sticky browns and free-flowing browns. The sticky browns were originally the sort of mixture that comes out of a cane sugar crystallising pan. The extreme of this, still made in India today, is "juggeri" or "gur" which is essentially such a mixture boiled until dry. In modern refining practice both of these types are made by mixing a refined or at least purified sugar with a suitable syrup. The colour of the sugar and the syrup determines the colour of the final product and the ratio of syrup to sugar plus any drying applied determines whether the product is sticky or free-flowing. Syrups, of which there are again an enormous range, range from pure sucrose solutions as sold to industrial users to heavily treated syrups incorporating flavours and colours. Refiners or "Golden" syrup is a sugar solution which has been carefully treated to invert some of the sucrose. Inversion is a chemical process which breaks down the disaccharide sucrose to its constituent sugars: glucose and fructose. This helps ensure that crystallisation does not occur during storage. Treacle is a similar product made from molasses rather than a pure sugar solution.

How to Cook Sugar

Sugar is widely used in the industrial preparation of foods, including ice creams, yogurts, and presweetened desserts, biscuits, chocolates, and confectionary. In cookery, it's also an important ingredient for enhancing flavour, preserving, etc. as well as for sweetening. 

Sources
@ Webster's New World Dictionary of Culinary Arts by Steven Labensky, Gaye G.Ingram, Sarah R.Labensky
@ Larouss'e Gastronomique by Prosper Montagne
@ http://www.sucrose.com/lhist.html