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Carbohydrates

TermDefinition
Photosynthesis The process by which a plant uses the energy from the sunlight to produce
Classification of Carbohydrates 1. Monosaccharides 2. Disaccharides 3. Polysaccharides
Elemental composition •Carbon •Hydrogen •Oxygen
Monosaccharides • A Monosaccharide contains one sugar unit • C6 H12 O6 is the chemical formula of a monosaccharide • Examples of monosaccharides are: Glucose, Galactose and Fructose
Disaccharides • Are formed when two monosaccharides join together with the loss of water (condensation) • The chemical formula is C12 H22 O11 • Examples of disaccharides are: Sucrose, Maltose and Lactose
Polysaccharides • These are formed when three or more monosaccharides join together with a loss of a water molecule each time. • Formula: (C6 H10 O5)n • They may be straight or branched • Examples of polysaccharides: Cellulose, Starch, Gums and Pectin
Properties of Sugar: Solubility • Sugars are white crystalline compounds that are soluble in water • Solubility is increased by heating the water • A syrup is formed when sugar is heated • Used to preserve tinned fruit
Properties of Sugar: Assists Aeration •Sugar helps to denature egg protein, causing it to unfold & entrap air bubbles •This enables aeration to occur •A temporary foam is formed •E.g. meringues
Properties of Sugar: Crystallisation •This occurs if more sugar is added than can be absorbed by a liquid •Crystal particles are formed when the mixture cools •Crystallisation is used in the confectionery and sweet industry
Properties of Sugar: Caramelisation • When sugars are heated, they produce a range of brown substances know as a caramel • the range occur between 104°C & 177°C • Eventually, the heat will cause carbonisation (burning) • E.g. crème brulee, caramel squares, banoffi pie
Properties of sugar: Maillard Reaction •Sugar (Carbohydrate) + Amino Acid + Dry Heat = Browning of foods, e.g. roast potatoes
Properties of sugar: Sweetness •Sugar has varying degrees of sweetness Fructose is the sweetest.Lactose is the least sweet •Fructose has a relative sweetness of 170 •Lactose has a relative sweetness of 15
Properties of sugar: Hydrolysis • Hydrolysis is the chemical breakdown of a molecule by adding water to produce smaller molecules • This occurs when water is added to a disaccharide to produce two monosaccharides •Hydrolysis is the reverse of the condensation reaction
Properties of sugar: 8.Inversion •Known as ‘invert sugar’ • Inversion may be brought about by either: - Heating sucrose with an acid -Adding an enzyme: invertase in yeast baking or sucrase in digestion • Invert sugar is used in jam, it reduces crystallisation
Properties of Starch: Flavour •Starch (a white powder) is not sweet in flavour
Properties of Starch: Insoluble •Starch is insoluble in cold water
Properties of Starch: Hygroscopic •This property relates to how starch absorbs moisture from the air e.g. biscuits soften if they are not kept air tight • This keeps cakes moist
Properties of Starch: Dextrinisation •Dextrins are shorter chains of starch •In dry heat, starch chains shorten to form dextrins •This causes a brown colour to form in food. E.g. toasting bread
Properties of Starch: Gelatinisation •When starch is heated in the presence of water, starch grains swell, burst & absorb the liquid, resulting in the thickening of the liquid •Complete gelatinisation happen at 100°C • e.g flour to thicken soups and sauces
Properties of Non-Starch Polysaccharides: Cellulose •Can absorb large amounts of water • Cannot be digested, however adds bulk to the diet (gives a feeling of fullness) • Aids the removal of waste from the body • Is insoluble in water
Properties of Non-Starch Polysaccharides: Gel Formation • When pectin is heated in the presence of acid and sugar, water becomes trapped • The long chains of polysaccharides cool to form a gel • An example of this is in making jam
Properties of Non-Starch Polysaccharides: Pectin extraction The following shows the pectin change in the ripening of fruit: Under-Ripe to ripe to Over-Ripe protopectin to Pectin to Pectic Acid. Protopectin cannot form a gel to set jam. Heat needs to be added to the fruit .lemon juice changes protopectin to pectin
Effects of Heat on Carbohydrates: Dry Heat ▪ Carbohydrate foods browns due to the presence of dextrins, e.g.Toast ▪ Sugar caramelises, e.g. Caramel slices▪ Maillard reaction occurs because of the interaction between sugar & amino acids, e.g. roast potatoes
Effects of Heat on Carbohydrates: Moist Heat ▪ Cellulose softens, e.g. cooked vegetables ▪ Gelatinisation: e.g. flour used to thicken sauces ▪ Pectin is extracted by heating fruit in water with sugar & acid, e.g. jam making ▪ Sugar dissolves in warm liquid, e.g. making syrups
Culinary uses of sugar • Sweetener - desserts • Preservative - jam • Caramelisation – caramel custard • Fermentation – yeast bread • Gel formation – sugar combines with pectin to form gel – jam making. • Colour – a sugar solution prevents discolouration of cut fruit.
Culinary uses of starch • Thickener – sauces, soups, stews. • Hygroscopic – absorbs moisture to increase shelf life of cakes, keeps baking powder dry. • Dextrinisation – browning e.g.toast
Culinary uses of non-starch polysaccharides • Gel formation – jam pectin forms gel with acid and sugar. • Cellulose absorbs moisture and gives feeling of fullness. • Cellulose adds texture e.g. breakfast cereals
Biological Functions of Carbohydrates • Carbohydrates are used for heat and energy for the body. • They spare protein so it can be used for growth and repair. • Cellulose moves food through intestine preventing constipation.
Digestion of Carbohydrates: Mouth Mouth: Physically broken by teeth. Salivary Amylase breaks Starch into Maltose. .
Digestion of Carbohydrates: Intestine: •Pancreatic juice: -Amylase breaks Starch into Maltose. •Intestinal Juice: -Maltase breaks Maltose into Glucose. -Sucrase breaks Sucrose into Glucose & Fructose. -Lactase breaks Lactose into Glucose and Galactose
Created by: Caoimhek
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