Properties of Carbohydrates PDF

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Summary

Properties of Carbohydrates...

Description

DEXTRINISATION OF STARCH

GELATINISATION OF STARCH

CRYSTALLISATION OF DISACCHARIDES

CARAMELISATION

DEFINITION Starch breaks down into dextrins Polysaccharide starch can undergo a partial chemical breakdown into shorter glucose chains called dextrins Dextrins = half-way stage in the breakdown of starch to glucose Process of starch absorbing water in the presence of heat Large swollen granules bump against each other and eventually the granules burst and the starch molecules spread through the liquid to start thickening When temp reaches 90°C liquid has thickened to a paste Formation of solid crystals that occurs when a very concentrated sugar solution cools Sugar is dissolved in a liquid and heatedliquid evaporates concentrating (supersaturating) the sugar solution Movement + slow cooling = large crystals Process of monosaccharides and disaccharides turning brown with heat Caramelisation of sugar= sweet and brown colour Sucrose will melt at 186°C above this acid will form and molten sugar will turn a light brown colour = caramelise

FACTORS AFFECTING Exposure of the starch granules to dry heat The action of acids The action of certain enzyymes

EXAMPLES Heat: bread turning brown during toasting Toasted brekky cereals = sweeter taste

EXPERIMENT

Change in temp Change in pH (lemon juice is meant to reduce the thickness of the curd) Agitation Presence of sugar- results in a sofer less stable gel

Custard (custard powder) White sauce Gravy Jam Lemon meringue flling

Lemon meringue

Temp: hoter the water = greater amount of sucrose that can dissolve in it Acidity: prevents crystallisationn product stays runny Agitation: stirring the sugar solution encourages crystals to develop Fat: will surround small sugar crystals Honey: will prevent formation of large crystals

Confectionery: Toffee Britle Fudge Caramel

Toffees

Crème caramel Caramel sauce Barley sugar Honeycomb

Honeycomb...