everything you need to know abou carbohydrates including structure, classification, sources, nutritive value and dietec information

1. CARBOHYDRATES

2. Where do they come from?
• Found in plants – manufactured by photosynthesis

3. 1. Elemental composition
• Carbon
• Hydrogen
• oxygen

4. 2. Classification
• Monosaccharide → mono (1) + saccharide [sugar unit]
• Disaccharide → di (2) + saccharide [sugar unit]
• Polysaccharide → poly (many) + saccharide [sugar unit]

5. Monosaccharide
• Chemical formula: C6H12O6
• contains one simple sugar unit (smallest unit of carbs)
Examples Source
Glucose Fruit
Fructose Fruit & honey
Galactose Digested milk

7. Disaccharides (loss of H20)
• Chemical formula: C12H22O11
Examples Source
Maltose (glucose + glucose) Barley
Sucrose (glucose + fructose) Table sugar
Lactose (glucose + galactose) Milk

10. Polysaccharides
• Chemical formula: (C6H1005)n
• N= number of mono joined together
• When 3 or more monosaccharides join together
• Loss of H20 each time
Example Source
Starch Cereals
Pectin Fruit
Cellulose/ fibre Wholegrain foods
Glycogen Meat
Gums Seaweed

12. 3.
properties
of sugar

13. 1) Solubility
• White crystalline compound
• Soluble in water
• Forms a syrup when dissolve
Used as a preservative in canned fruit

14. 2) Sweetness
• All sugars sweet
• Give appetising flavour
• Some much sweeter then others
• Measured on a point scale of sweetness
Cakes

15. 3) Crystallisation
• When a liquid has dissolved as much sugar as it can, it is saturated
• If more sugar is added, crystals of sugar form in the solution and will
solidify when cold
Fudge

16. 4) Caramelisation
• When heated, sugar melts & caramelises
• Happens over 10 gradual stages, between 104 & 177
• Caramelisation occurs @ 160 – attractive brown colour & sweet taste
• Overheating (above 177), caramel will carbonise or burn
Caramel

17. 5) Assists aeration
• Whisking egg whites & sugar – aeration
• Sugar helps to denature protein (extra friction), causing it to unfold and
trap air bubbles
• Whisking creates heat – sets albuim
• will collapse unless heated to set
Meringues

18. 6) Malliard reaction
• Non-enzymic browning of food
• Amino acids + sugars + dry heat = brown colour & crust with
appetising flavour
Toast

19. 7) Hydrolysis
• The reverse of a condensation reaction
• During digestion
• Water and acids or enzymes – split the disaccharides into 2
monosaccharides
No culinary application

20. 8) Inversion
• Water and acids or enzymes – split sucrose (disaccharide) into glucose
& fructose (monosaccharide)
• Known as an invert sugar, sweeter than sucrose
Jam making

21. 4.
Properties
of starch

22. 1) Solubility
• White non-crystalline powder
• Insoluble in cold water
• Soluble in hot water

23. 2) Flavour
• Not sweet

24. 3) Hygroscopic
• Starch is able to absorb moisture from the air
• Causes uncovered foods to become soft and lose their crunch (biscuits)
Prevents cakes from drying out

25. 4) Gelatinisation
• When combined with liquid & heated to 55-70 the starch grains swell,
burst & absorb liquid – increasing thickness
• As temp increases (above 85) it becomes more viscous → viscous
• When the mixture cools, water molecules become trapped → gel
Roux sauce – equal amounts of fat + flour heated with a liquid

26. 5) Hydrolysis
• Reverse of a condensation reaction
• Digestion: water & acids/ enzymes split starch (polysaccharide) into
maltose (disaccharide)
No culinary application because it changes during digestion

27. 6) Dextrinization
• When starch foods are heated, short – chained polysaccharides called
dextrin's change to long-chained polysaccharides called pyrodextrins
• colour change on surface – attractive brown appearance
Toast

28. 5. Properties of
non-starch
polysaccharides

29. Cellulose / fibre
• Insoluble in water
• Cannot be digested by the body but absorbs water as it passes through
the intestinal tract
• Stimulates peristalsis – a muscular wave like movement caused by
muscles of the large intestine contracting and relaxing
• This speeds up the passage of food and waste – preventing bowel
disorder

30. Gums
• Soluble in water
• Have the ability to absorb large amounts of water to form a thick gel with
a firm texture
Ice cream

31. Pectin
• Naturally present in plant cells and cell walls of fruit
• Setting agent – absorb water → gel
• Only in ripe food
• Underripe fruits – in the form of protopectin – cannot absorb water – will not
set
• Overripe fruits – becomes pectic acid – cannot absorb water – will not set
• To be extracted, pectin needs heat & acid
Jam making

32. 6.
Biological
functions

33. Heat and energy
• Keep body temp at 37
• Energy for all activities

34. Fibre helps digestion
• As it moves through the body by peristalsis
• It absorbs water as it passes through the intestinal tract
• This provides bulk to allow the intestine to contract and relax and push
the waste through the digestive system
• This helps to prevent the risk of bowel diorders

35. Spare proteins from being used as energy
• And leaves them to be used for their primary function of growth and
repair

36. Feeling of fullness
• Fibre absorbs water

37. Excess glucose is
• Converted to glycogen, stored in the liver and muscles, is a long term
energy reserve
• Converted to fat, stored as adipose tissue under the skin [insulates the
body and acts as another energy reserve]

38. 7. Effects of heat
Dry heat
• Dextrinisation
• Caramelisation
• Malliard reaction
Moist heat
• Syrup formation
• Gelatinisation
• Cellulose softens
• Pectin extraction

39. 8. Digestion
organ/
gland
Secretion Enzymes Substrate Product
Salivary
gland
Saliva Salivary
amylase
Starch Maltose
Pancreas Pancreatic
juice
Amylase Starch Maltose
Small
intestine
Intestinal
juice
• Maltase
• Sucrase
• Lactase
 Maltose
 Sucrose
 Lactose
o Glucose &
glucose
o Glucose &
fructose
o Glucose &
gelactose

40. 9. Absorption and
utilisation

41. Fructose
• Passes through the wall of the villi →
• Hepatic portal vein transports them to the liver via the bloodstream →
• Converted to glucose

42. Galactose
• Pass through the wall of the villi →
• Hepatic portal vein transports them to the liver via the bloodstream →
• Converted to glucose

43. Glucose
• Pass through the wall of the villi →
• Hepatic portal vein transports them to the liver via the bloodstream →

44. All glucose is then
• Oxidised to produce heat and energy
• Converted to glycogen and stored in the liver and muscles as a long
term energy reserve

45. Excess glucose
• Converted to fat
• Stored as adipose tissue under the skin insulating the body and acting
as an energy reserve