1. C ARBOHYDRATES Provide the main source of energy for the body Made up of the elements Carbon, Hydrogen and Oxygen Carbohydrates are made by plants during photosynthesis Overview Carbohydrates can be split up into: 1. Sugars (simple) divided into intrinsic (within the cellular structure of the food, e.g. in whole fruit or vegetables) and extrinsic (not bound within the cellular structure of the food, e.g. the lactose in dairy products. Honey and table sugar are also examples. These are referred to as non-milk extrinsic sugars (NMES). 1.1 Monosaccharides: Glucose (fruit, onions, potatoes) Fructose (fruit, honey) Galactose (milk) 1.2 Disaccharides: Lactose = glucose + galactose (milk) Maltose = glucose + glucose (barley) Sucrose = glucose + fructose (sugar beet or sugar cane) 2. Starch (complex) 2.1 Polysaccharides: Starch (rice, potatoes, cereals, root vegetables, seeds, unripe fruit) 2.2 Non-Starch Polysaccharides: Insoluble = Fibre (NSP) (skins of fruit and vegetables, bran, wholegrain cereal) Soluble = Pectin (orchard and citrus fruits, berries used in jams gels and jellies) Gums ( seaweed, carrageenan and stems of plants and fruit used as thickeners stabilisers and emulsifiers)

2. 1.1 M ONOSACCHARIDES These sugars contain 2 to 7 carbon atoms (most commonly 6, ‘hexoses’ and occasionally 5 carbon atoms, ‘pentoses’). The formula is C 6 H 12 O 6 This formula applies to any monosaccharide with 6 carbon atoms, not just to glucose. The monosaccharides are glucose, galactose and fructose. The nutritional content of monosaccharides is sugar in its simplest form, which is used for quick energy release. It can be converted to glycogen for storage. 1. Glucose (Dextrose) is found in large amounts in grapes and in smaller quantities in other fruit and vegetable juices, also in the blood of living animals. Most carbohydrates are converted to glucose during digestion. 2. Fructose (Laevulose) is chemically similar to glucose except that the arrangement of the atoms within the molecule is different slightly. Fructose is found in many fruits and in honey. It is the sweetest sugar known. 3. Galactose is also similar to glucose chemically. It is not found naturally in foods, but is produced when milk sugar (lactose – a disaccharide) is broken down.

3. G LUCOSE Found in large amounts in grapes and smaller amounts in carrots and peas. Glucose syrup which is used in commercial manufacture is not pure glucose, but a mixture of other carbohydrates, glucose and water. There are two forms of glucose alpha and beta. It’s important to remember that the only difference in the two is that in alpha glucose, the hydroxyl group (OH), is at the bottom of the structure and in Beta glucose, the OH is at the top. Fructose is one and a half times sweeter than glucose. An equal mixture of fructose and sucrose is called invert sugar – found in honey, made when making jam. The structure of fructose changes depending on if it is found in its own or whether it is joined with other sugars. This doesn’t occur in foods but it is formed when lactose if broken down during digestion F RUCTOSE G ALACTOSE

4. C HEMICAL STRUCTURE OF MONOSACCHARIDES

5. Disaccharides have the formula C 12 H 22 O 11 These sugars are formed when two monosaccharides join together during a condensation reaction (when water is eliminated). Made up of one molecule of glucose and one molecule of fructose. It occurs naturally in sugar beet and sugar cane. It is also found in fruit and vegetables Sucrose is not a reducing sugar. Ordinary sugar is almost pure sucrose (caster sugar/ sugar in tea etc). Is formed when two glucose units join together. When the two units join, water is eliminated and the remaining O2 atom forms a bridge between the two glucoses. This bridge is called a glycosidic link. Maltose forms when grain is germinated for the production of beer, and malt liquors. Maltose is a reducing sugar. During digestion starch is broken down by the enzyme amylase (this enzyme is present in our saliva). Is a molecule of glucose and a molecule of galactose. It is the sugar present in milk. (Cow’s milk = 4 to 5% Human milk = 6 to 8%) 1.2 D ISACCHARIDES S UCROSE M ALTOSE L ACTOSE

6. 2.1 P OLYSACCHARIDES Simple polysaccharides are long chains of one type of monosaccharide joined together. They are thus big molecules and are insoluble in water. Occasionally there are branches formed by 1- 6 glycosidic links. The general formula is (C 6 H 10 O 5 )n where n can be many thousands of monosaccharide units. Starch is the energy reserve of plants. It can be recognised under microscope by its shape that is granular. It exists in two forms: amylose (straight chain of alpha glucose units) and amylopectin (many shorter, branched chains of alpha glucose). The main sources of starch in the diet come from plants such as potatoes, wheat, rice, corn and other cereal crops. Nutritionally starch is important because it provides the body with a slow release form of energy from the carbohydrate which the starch provides. Unlike the monosaccharides however, starchy foods can provide other essential nutrients to the diet, including protein, fat, the B-group of vitamins, vitamin C in the case of potatoes, potassium, copper, calcium, selenium, magnesium, manganese, iron and non-starch polysaccharide.

7. Types of starch: Amylose The simplest form of starch. It is a straight chain of a-glucose units. Consists of between 50 – 500 glucose units joined in a straight chain. The a-glucose units are joined by a, 1-4 glycosidic links to make a chain. The glucose units tend to spiral. There are six glucose units per turn of the spiral. Starch

8. Amylopectin Amylopectin is more complex in structure and is much larger than amylose. It often has many thousand glucose unit components. Composed of many shorter chains of α -glucose with many branches May contain up to 2,000,000 glucose units joined in a branched-chain structure. The glucose units are linked to form short branching chains which gives amylopectin a 'tree-like' appearance. The branches in the chain are produced by a, 1- 6 glycosidic links. A glycosidic link is when the two glucoses condense together and water is eliminated. The remaining oxygen atoms form a bridge between the two glucoses. This bridge is called a glycosidic link. o-o-o-o o-o-o-o-o-o-o-o-o o-o-o-o-o-o o-o-o-o

9. In terms of nutrients, NSP does not contribute anything to the diet, but it does increase the feeling of fullness, speeds the passage of stools, helps reduce bowel disorders and aids the process of digestion and absorption of minerals generally. Humans do not have the necessary enzymes to digest NSP. Too little soluble and insoluble fibre in your diet can lead to digestive problems such as constipation, diverticular disease (distortion and inflammation of the digestive tract), appendicitis and haemorrhoids (piles) Soluble: Found in the flesh of fruit and vegetables, oats beans and lentils The soluble sources of NSP are as follows: pectin, (found in citrus fruits, soft fruits and apples) beta-glucans (found in oats, barley and rye) and arabinose (found in pulses). Digestion partially breaks it down to form a gel like substance that can coat the digestive tract. This helps to speed up digestion Soluble NSP is thought to reduce LDL blood cholesterol levels and control blood sugar levels by slowing the absorption of sugar and cancer or other digestive problems 2.2 Non Starch Polysaccharides (NSP)

10. Insoluble: Cellulose is insoluble; the body cannot digest insoluble fibre It acts as a bulking agent absorbing the end-products of digestion to allow waste products to be removed from the body Heating may soften the cellulose, but it does not gelatinise as starch does, thus remaining undigested in the digestive system, aiding peristalsis. Found mainly in the outer skin plants such as grains, rice, fruit, vegetables and pulses. They have the ability to hold water and thus aid peristalsis. Cellulose gives plants structure in the form of long fibres. It is a very large molecule, often made up of several thousands of monosaccharide units: beta glucose (as opposed to alpha glucose in starch). These units are joined together by 1- 4 glycosidic links.

11. C OMPARING AMYLOSE AND CELLULOSE

12. Pectin Complex mixture of polysaccharides found in many fruits and some root vegetables. Apples and the peel of citrus fruits are particularly rich in pectin. Main importance: Gelling Agent (e.g. jam making) Pectin is broken down in fruit as fruit ripens – jam will not gel well if made from over ripe fruit. For pectin to form a really good gel, 65% of it needs to be sugar. pH affects gel strengths (pH 3.0-3.5). Lemon juice lowers this setting. Gums Tragacanth, arabic and guar – Produced by plants and are used in food manufacturing as thickeners, stabilizers and gelling agents in foods. E.g. Ice cream, salad dressing and fruit pie fillings. Certain seaweed extracts are used in a similar manner. These include carrageenan (Irish Moss), alginates e.g. sodium alginate and agar (agar-agar). Agar is also used in the preparation of microbiological media. http://www.everbum.com/food-additives/food-additives-thickeners-stabilizers-emulsifiers/ Glycogen Carbohydrate only found in animals Animals store glycogen in muscles and liver and when required, it converts it to glucose which is broken down to provide energy. Glycogen, like Amylopectin, is composed of branched chains of glucose units. E XTRA INFORMATION