carbohydrates science

what are they made up of

what are they made up of

CHO

what does cho stand for

carbon, hydrogen, oxygen

another name for dietary fibre

non-starch polysaccharide

dietary energy

sugar: gives sweetness

starch: doesn’t taste like anything

dietary fibre: another type of carbohydrate

where can glucose be found

• ripe fruits and some vegetables

• powdered liquids or tablet form to provide a fast source of energy

(- converted into glucose during digestion)

fructose

found in fruit, juices + honey

galactose

found in the milk of mammals

form part of the milk sugar lactose

sucrose

glucose + fructose

use for sucrose

commonly used in cookery

is the type of sugar that can be added to tea or used in cake

maltose

glucose + glucose

alternative name for maltose

malt sugar

where is maltose found

cereals such as barley (where it is formed during germination)

lactose

glucose + glucose

where is lactose found

found in milk (is not as sweet as sucrose)

polysaccharids

made up of many monosaccharide molecules (typically glucose) joined together

they are insoluble in water and normally tasteless

what do polysaccharides include

starch, pectin, dextrin, cellulose, glycogen

dextrinisation

can only happen when there is starch and dry heat.

is the breaking up of starch molecules to smaller groups of glucose molecules

when foods containing starch are heated (without the presence of water), they can also produce water compounds known as dextrin

when does dextrinisation occur

when the heat breaks the large polysacchardies known as dextrin

these dextrins can also product a brown colour

example of dextrinisation

toast

gelatinisation

when mixed with water, starch granules swell and eventually rupture, absorbing liquid which will thicken the mixture

when cooled, if enough starch is used, a gel with form

this process is used in the production of blancmange

key temperatures for starch molecules

60ºC: when the starch molecules swell from absorbing the liquid

62º-80º: when the starch molecules burst from being so swollen and the starch properly combines with the water/liquid used

100º: when the sauce becomes completely thickened

what happens when a sauce isn’t constantly stirred

a sauce has to be constantly stirred, if it isn’t, the starch will fall to the bottom and won’t combine properly with the liquid, the sauce will also end up burning

caramelisation

when sucrose (table sugar) is heated above its melting point and undergoes physical and chemical changes to produce caramel

this process can happen to natural products since they have glucose in it

can caramelisation happen without water

yes, the process can happen more readily without water

the syrup will caramelise with rapid heating

this process is used extensively in the production of confectionery

what happens if the caramel is overheated

overheating will cause the substance to become bitter, dark and burnt

why is caramel added to foods

to enhance a either bitter or sweet taste

what will happen is caramel is mixed too quickly when being formed

sugar crystals will begin to form