Sugar Technology

1. Sugar Technology Food Technology 2010

2. Where is sugar cane and beet grown? • How Sugar is Made - an Introduction • 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.

3. Sucrose • 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].

4. 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.

5. 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.

6. Production of sugar from cane • Harvesting, handling and storage • Cleansing • Juicing extraction • Evaporation • Purification • Crystallisation

7. Production of sugar from cane • Harvesting, handling and storage • Canes are gathered manually and hand cut and tied in bundles. Cane deteriorates rapidly so it has to be processed immediately • Cleansing • Stalks are washed and cut at the sugar mill. Rotating knives shred the can into pieces and multiple sets of three roller mills grind

8. Production of sugar from cane • Juicing/Extraction • The shredded sugarcane travels on a conveyor belt through a series of heavy duty roller which extract juice from the pulp • Pulp that remains is called Bagasse, it is dried and used as fuel • The raw juice moves on to be clarified • The last juice to be extracted is of low quality less than 60% sucrose • Evaporation • The filtered juice is evaporated under vacuum, concentrated at low temperature and the sugar crystallised in vacuum pans

9. Production of sugar from cane • Purification • Clarification is carried out to remove suspended solids and some soluble material and production of a clear neutralized juice for crystallization • Treatment involves the addition of lime (Ca OH2), which neutralises acids and prevents possible inversion, and then it is heated and settled • Carbon dioxide is bubbled through, which removes excess lime • pH 6.5 gives a lighter colour and more turbid juice • pH 7.5 gives a darker colour and higher clarity • Good clarification may require the addition of phosphate if the level in the juice is too low • Sterilisation of juice by heating is part of the process, but some thermophillic bacteria can survive

10. Production of sugar from cane • Crystallisation • The liquid is concentrated until it crystallises into impure brown sugar and the remaining liquid is molasses or treacle • Brown sugar is refined by dissolving in water, filtering through charcoal and bleaching with S02 • Inside a sterilized vacuum pan, pulverized sugar is fed into the pan as the liquid evaporates, causing the formation of a thick mass of crystals • The crystals are spun-dry in a centrifuges, producing raw white sugar • The remaining liquid is golden syrup

11. Properties of sucrose 1. Sweetening agent 2. Preservative at high levels 3. Texturising agent • Soft drinks: diet vs. non diet, rigidity of pectin gels increases as sugar is increased 4. Flavour enhancer • Mayonnaise, soups- at sub threshold levels (i.e. not detectable as sweet), blends and enhances flavours 5. Flavour modifier • At threshold levels can modify flavour e.g. acidity of fruit, soft drinks etc. 6. Dispersing agent • Added to dry blends because of its crystalline structure, which on mixing will break up agglomerations of other ingredients to give an even mix e.g. cake mixes, custard, dry soft drink blends 7. Caramelisation Sucrose melts at approx 176oC, it changes colour from yellow to brown

12. Terms in sugar technology Dextrose Equivalent D.E • Number of grams of reducing sugar considered as dextrose per 100g of solids of the product Glucose Syrup • A purified aqueous concentrated solution of nutritive saccharides obtained from starch and having a D.E of 20 or more Corn Syrup • A glucose syrup obtained from corn starch Dextrose • Term applied to the product obtained by the complete hydrolysis of starch namely D-glucose High Fructose Corn Syrup • Are derived from glucose syrup where part of the dextrose has been isomerised to fructose (can contain up to 55% fructose) Maltodextrins • Are those purified concentrated solutions obtained from starch having a DE of less than 20 • As well as defining DE value of glucose syrup it may be necessary to include a complete sugar or carbohydrate profile

13. Syrups • Glucose syrup is made by hydrolysing starch with acid, it is mostly maize starch, potato starch or wheat starch • It is possible to take the process to completion to produce pure dextrose with a DE of 100 • However the commonest type of glucose syrup in sugar confectionary is 42DE • The glucose industry then started to use enzymes to produce other syrups such as high maltose glucose syrups • The application of enzymes to glucose syrups was further extended to include the conversion of dextrose to fructose by glucose isomers, the resulting syrups were known as High Fructose Corn syrup

14. Invert Sugar • Invert sugar is related to sucrose • Sucrose can be hydrolyzed by acids or enzymes into two monosaccharides, glucose and fructose according to this equation • C12H22O11 + H20 C6H1206 + C6H1206 Sucrose water Glucose Fructose • Confectionary trade refers to glucose as dextrose, and fructose as levulose • The hydrolyzed mixture of dextrose and levulose is called invert sugar • Invert sugar can prevent or help control the degree of sucrose crystallisation

15. Sweetness • Sugar Sweetness • Sucrose (10% soln) 100 • Glucose Syrup 62 DE 59 • Glucose Syrup 42 DE 41 • HFCS (42% fructose) 100 • Glucose is generally added to a food because it has certain functional properties and the sweetness is then adjusted using alternative sweeteners

16. Humectancy and Hydroscopicity • The ease or difficulty that foods have in either gaining (or losing) moisture when placed in an atmosphere that is different from their equilibrium humidity’s can be described by: • Humectancy: the ability of a food to resist changes in moisture. Low DE syrups are described as being humectants • Hygroscopic: the ability of a food to absorb moisture from the atmosphere. The higher the DE value the more moisture will be absorbed

17. Control of Crystallization • Generally the more complexthe mix the slower will be the tendency for crystallization to occur • Therefore low DE sugars, because of their more complex structures will decay the onset of crystallization • At room temperature, about two parts sucrose can be dissolved in one part of water, giving a concentrated solution of approx 67% • If the solution is cooled without agitation, it becomes supersaturated- clear hard boiled sweets • Upon further cooling, especially with agitation, the sucrose crystallises- fudges

18. Crystallisation and fudges • Crystallisation can be speeded enormously if even a single minute sucrose crystal is added to the supersaturated solution • A seed crystal is a surface that sucrose molecules can begin to attach themselves to—it could be a few sucrose molecules stuck together, a piece of dust, or even a little air bubble. • Once a seed crystal forms, it grows bigger and bigger as the fudge cools. A lot of big crystals in fudge makes it grainy

19. Colligative Properties • Boiling Points • Colligative properties are defined as those properties that depend upon the number of particles rather than the nature of the particles • In most confectionery the most important of these is the elevation of boiling point • As sugars are very soluble, very large boiling point elevations are produced e.g. as large as 50oC • Remembering that elevation of the boiling point is proportional to the concentration of the solute it is not surprising that the boiling point is used as a measure of concentration

20. Colligative Properties • The boiling point of a liquid is the temperature at which the vapour pressure is equal to the atmospheric pressure • If the pressure is increased the boiling point will also increase whereas reducing the pressure will reduce the boiling point • Most sugar confectionery is made by boiling up a mixture of sugars in order to concentrate them • The use of a vacuum has advantages as energy consumption is reduced, browning is reduced and whole process is speeded up

21. Browning • During manufacture it is advantageous to minimize boiling point elevation (by using low DE) • The lower the boiling point the lower the chance of undesirable browning reactions (Caramelisation) taking place • Immediately after production glucose syrups are clear, On storage brown discolouration may occur. Maillard reaction • Reducing sugars, notably glucose and fructose, react with amino acids (present as impurities) to give brown pigments Acidic conditions • May cause glucose to undergo a Caramelisation reaction. (Spray-dried syrups with low water activity, can be stored for a long time without brown discolouration)

22. Flavour Enhancer • Flavour of spices may be enhanced by use of high DE glucose syrups. • Low DE glucose syrups contain larger molecules, which may leave taste buds with insipid sensation and makes other flavour sensations