Chemical functions of Carbohydrates Flashcards
Chemical Functions
Caramelisation, dextrinisation, gelatinisation
What is dextrinisation
Starchy foods are clocked by a dry heat that develop a brown colour on the outside.
Examples of dry heat methods
Backing grilling toasting
Example foods of dextrinisation
Bread, cakes, scones, biscuits, pastry.
What is the chemical process of dextrinisation
Starch molecules get broken down into smaller groups of glucose molecules called dextrin
Starch molecules + dry heat = dextrin
Changes when dextrination has been applied
Colour smell texture
What is carbohydrates made up of
Carbon + hydrogen + oxygen
How is burned toast formed
Dry heat drives the oxygen and hydrogen away as the water evaporates. Leaving the black carbon to form.
What is caramelisation
The process of heating sugar (sucrose) that is used in cooking
Changes when caramelisation has been applied
Texture, taste, colour
Chemical reactions of caramelisation
When sugar is heated it melts and forms syrup then boils. The molecules of sucrose break up.
Carbohydrates +heat= water evaporation leaving carbon.
Colour changes order for caramelisation
Clolourless, golden brown, dark brown, black = carbon
Taste/ flavour changes order in caramelisation
Very sweet, toffee, caramel, bitter burned
Texture changes order in caramelisation
Crystals if sugar, syrup , brittle toffee when cool
What can be added to to help avoid sugar burning in caramelisation
Water can help form caramel and flavour development
What not to do when caramelising
Do not stir the syrup - will cause crystallisation and hard lumps.
What is the temperature of caramelisation caramel colour
160-170°C
Example foods of caramelisation
Onions - naturally contain sugars
Process of caramelisation
Sugar sucrose is t melts and forms a syrup and boils. Molecules of sucrose break up, water evaporates as heating continues and syrup turns golden brown, eventually it will burn and turn bitter as water evaporates and carbon is left.
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
Gelatinisation
When starch is heated in a liquid , it gelatinises
Chemical list of the order of gelatinisation
When the starch granules are put into cold water they sink, when starch is heated with water they absorb the water and swell bigger, it will thicken as there is no room for the swollen granules to move. At 80° the starch granules bust and release the starch molecules into the liquid.
What should you always do when gelatinising anything and why
Stir regularly, prevents sticking to bottom and lumpy texture
What happens at 80° with gelatinisation
At 80oC, the starch granules are so swollen
that they start to burst and release the starch molecules into the liquid.
What happens at 100° for gelatinisation
These released starch molecules form a 3D
network that traps water molecules.
At 100oC, the sauce completely thickens.
When something has been gelatinised to 100° what should happen after
Let it cool down to get a solid gel
Examples of gelatinisation
Sauces, pasta , potatoes (same when cooking foods that contain starch)
Summary of 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
