Chemical Functions of Carbohydrates PDF

Chemical Functions of Carbohydrates Chemical Functions of Macronutrients Proteins Fats Coagulation Shortening Denaturation Plasticity Emulsification Aeration Chemical Functions of Carbohydrates Carbohydrates...

Chemical Functions of Carbohydrates Chemical Functions of Macronutrients Proteins Fats Coagulation Shortening Denaturation Plasticity Emulsification Aeration Chemical Functions of Carbohydrates Carbohydrates Caramelisation Dextrinisation Gelatinisation Dextrinisation Dextrin Dextrinisation When foods containing starch such as bread, cakes, scones, biscuits and pastry are cooked by dry heat, they develop a brown colour on the outside. Dry heat methods: Baking Grilling Toasting Dextrinisation Starch molecules get broken down into smaller groups of glucose molecules called dextrin. Dextrinisation Dextrinisation Sensory changes: Colour Smell Texture Dextrinisation Burnt toast = carbon Carbohydrates = carbon + hydrogen + oxygen Dry heat drives away the hydrogen and oxygen (as water/evaporation) Chemical Functions of Carbohydrates Carbohydrates Caramelisation Dextrinisation Gelatinisation Caramelisation https://www.youtube.com/watch?v=8OonKbQo3Z4&t=12s Caramelisation is the process of heating sugar (sucrose) that is used in cooking. When a sugar has caramelised, we see changes to the texture, taste and colour. Carbon + Sucrose is a hydrogen + disaccharide. oxygen = carbohydrate Caramelisation When sugar is heated, it melts, then forms a syrup, then boils. As this happens, the molecules of sucrose start to break up. Caramelisation Carbon + hydrogen + oxygen + = (carbohydrate) Caramelisation h20 Carbon + hydrogen + oxygen + = (carbohydrate) Water evaporation Caramelisation Colour changes Colourless Golden Dark Black + clear Brown Brown Caramelisation Colour changes Colourless Golden Dark Black = + clear Brown Brown carbon Caramelisation Taste/Flavour profile changes Very Bitter + Toffee Caramel sweet burnt Caramelisation Texture profile changes Brittle Crystals Syrup toffee of sugar when cool Caramelisation When making caramel, it is usual to add water to the sugar in a pan and heat it gently on the hob until the water evaporates and the caramel forms. This avoids burning the sugar at the beginning of the process and helps with flavour development. Caramelisation You must not When you make caramel, and stir the syrup pour it out of the pan, it makes as it long ‘strings’ of sugar that go caramelises. If brittle when they cool. you do - it will crystallise into The temperature of large, hard caramelising sugar lumps. is 160-170oC. Caramelisation Some foods, such as onions, naturally contain sugar in their cells. This sugar will come out of the cells and caramelise if the food is sauteed or roasted with some fat or oil.  Caramelisation When sugar (sucrose) is heated, it melts, then forms a syrup, then boils. Molecules of sucrose start to break up. As heating continues, water evaporates and syrup changes from colourless to golden brown. Ideal temperature for caramel = 160-170oC. Still no stirring otherwise large lumps will form. Eventually it will burn and become bitter as all of the water is evaporated. Left with carbon. Foods that contain natural (intrinsic) sugar will caramelise. Sautéing softens and breaks down = sugars release. The heat changes the sugars and caramelises them, so that they turn a golden brown colour and develop a characteristic flavour. Caramelisation The breaking up of sucrose (sugar) molecules when heated = a change in colour, flavour + texture of the sugar as it turns into a caramel. Chemical Functions of Carbohydrates Carbohydrates Caramelisation Dextrinisation Gelatinisation  https://www.youtube.com/watch?v=zjyhMzjDaVI&list=PLXVl8Mt9AJ_qlI4FVE41vterGuB87YZT1&index=3& Gelatinisation t=6s = gelatinised liquid = starch/solid gel When starch is heated in a liquid, it gelatinises. This is useful when making sauces. Gelatinisation When starch granules are put into cold water, they sink to the bottom of the pan. Gelatinisation 60C When starch granules are put into water and heated, they start to absorb the water which causes them to swell and get bigg er.  Gelatinisation 60oC When making a sauce, it will begin to thicken, because there is less room for the swollen granules to move around. Gelatinisation 60C Stir the sauce regularly: - prevent starch molecules from staying at the bottom = swell up, stick together - avoid lumpy texture Gelatinisation 80-85C At 80-85C, the starch granules are so swollen that they start to burst and release the starch molecules into the liquid. Gelatinisation 100C These released starch molecules form a 3D network that traps water molecules. At 100oC, the sauce completely thickens. Gelatinisation 100C Cools down = solid gel Gelatinisation  Gelatinisation Starch is released in the same way when cooking foods containing starch. Water changes to a opaque colour = the starch being released. Gelatinisation 60oC Starch granules are heated in liquid Starch granules become swollen 80oC Starch granules burst 100oC The liquid thickens and gelatinises Forms a gel when cooled