Transcript Pectin - manorhousehomeeconomics

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The process by which green plants use energy from the
sun to change carbon dioxide and water into glucose and
oxygen.
Carbon dioxide + Water → Glucose + Oxygen.
6CO2
+ 6H2O → C6H12O6 + 6O2
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There are 3 types of carbohydrates
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2.
3.
Monosaccharides
Disaccharides
Polysaccharides
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CH2OH
C
O
H
H
H
C
OH
C
OH
H
C
C
H
OH
OH
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A Monosaccharide contains one sugar unit
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C6H12O6 is the chemical formula of a monosaccharide
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Glucose, fructose and galactose are the 3
monosaccharides
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Are formed when two mono saccharides join together
with the elimination of water (condensation)
There are three disaccharides: maltose, sucrose &
lactose
The chemical formula is C12H22O11
C6H12O6
+C6H12O6
C12H24O12
- H2O
C12H22O11
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These are formed when three or more
monosaccharides join together with a loss of a water
molecule each time.
 They may be straight or branched
 Examples: Starch, pectin, cellulose, gums & glycogen
 Pectin, cellulose & gums are also known as Non-Starch
Polysaccharides
 Starch is made up of glucose units arranged as
follows:
1. Straight chains are known as amylose or
2. Branched chains are known as amylopectin
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Formula: (C6H10O5)n
C6H12O6
- H2O
(C6H10O5)n n=the number of times a bond is formed
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Chemical structure of a polysaccharide
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Class
Chemical
Formula
Example
Source
Monosaccharides C6H12O6
Glucose
Fructose
Galactose
Fruit
Honey
Digested
milk
Disaccharides
C12H22O11
Maltose=Glucose+Glucose
Sucrose=Glucose+Fructose
Lactose=Glucose+Galactose
Barley
Table sugar
Milk
Polysaccharides
(Complex Carbs)
(C6H10O5)n Starch
Cellulose
Pectin
Glycogen
non-starch
polysaccharides
Bread, pasta
Whole
cereals
Fruit cell wall
Liver and
muscle cells
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These are also known as NSPs, dietary fibre and
roughage
NSPs cannot be digested in the body and absorb
large amounts of water
They aid the removal of waste from the body by a
process known as peristalsis
Peristalsis is the muscular movement of food along
the gut
Sources of NSPs include wholemeal bread, brown rice
& wholemeal pasta
Refined foods contain few if any NSPs
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1.
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3.
Sugar
Starch
Non-Starch Polysaccharides
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1.Solubility
 Sugars are white crystalline
compounds that are soluble in
water
 Solubility is increased by
heating the water
 A syrup is formed when sugar
is heated
2. Assists Aeration
 Sugar denatures egg
protein, enabling
aeration to occur, e.g. in
the making of sponge
cakes – the egg when
whisked with sugar
becomes aerated
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3. Crystallisation
 This occurs if more sugar is
added than can be absorbed
by a liquid
 Crystal particles are formed
when the mixture cools
 Crystallisation is used in the
confectionery and sweet
industry
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4. Caramelisation
 When sugars are heated, they produce a range of
brown substances know as a caramel
 There are ten gradual changes in sugar between
melting and caramelisation
 These stages occur between 104°C & 177°C
 Eventually, the heat will cause carbonisation (burning)
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5. Maillard Reaction
 Sugar (Carbohydrate) + Amino Acid + Dry
Heat = Browning of foods, e.g. roast potatoes
6. Sweetness
 Sugar has varying degrees of sweetness based
on a point scale using the tasting method
 Sucrose has a relative sweetness of 100
 Fructose has a relative sweetness of 170
 Lactose has a relative sweetness of 15
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7. Hydrolysis
 Hydrolysis is the chemical breakdown of a molecule
by adding water to produce smaller molecules
 This occurs when water is added to a disaccharide to
produce two monosaccharides
 Hydrolysis is the reverse of the condensation
reaction
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8.Inversion
 The hydrolysis of sucrose is also known as the
inversion of sucrose (mixture of glucose & fructose),
known as ‘invert sugar’
 Inversion may be brought about by either: (a) heating
sucrose with an acid; or (b) adding the enzyme
invertase, or sucrase
 Invert sugar is used in production of jam
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1.
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Flavour
Starch (a white powder) is not sweet in flavour
2.Solubility
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Starch is insoluble in cold water
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Hygroscopic
This property relates to how starch absorbs moisture
from the air e.g. biscuits soften if they are not kept
air tight
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4. Dextrinisation
 Dextrins are shorter chains of starch
 On heating, dextrins form longer chains & become
brown-coloured substances called pyrodextrins
 An example of dextrinisation is toasting bread
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5. Gelatinisation is based on the principal that when
starch is heated in the presence of water, starch
grains swell, burst & absorb the liquid, resulting in the
thickening of the liquid
 As the temperature rises, this mixture becomes even
more viscous, forming a sol (A sol contains particles
that do not fully dissolve but are evenly dispersed
throughout the liquid)
 On cooling, this becomes a gel
 An example of this is using flour to thicken soups and
sauces
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6. Hydrolysis
 Hydrolysis is a chemical
breakdown of a molecule
by adding water to
produce smaller
molecules
 Disaccharides become
monosaccharides partly
due to hydrolysis
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Cellulose
Can absorb large amounts of water
Cannot be digested, however adds bulk to
the diet (gives a feeling of fullness)
Aids the removal of waste from the body
Is insoluble in water
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2.
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Pectin
Pectin is a polysaccharide found in fruit and vegetables
It is involved in setting jams & jellies
The following shows the pectin change in the ripening of fruit:
Under-Ripe to ripe to Over-Ripe
Protopectin to Pectin to Pectic Acid
(pectose)
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For pectin extraction :
1. Use fruit rich in pectin, e.g. Blackcurrants & Apples
2. Heat needs to be applied to the fruit
3. Add an acid, e.g. Lemon juice changes protopectin to pectin
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3. Gel Formation
When pectin is heated in the presence of acid and
sugar, water becomes trapped
 The long chains of polysaccharides cool to form a gel
 An example of this is in making jam
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Dry Heat
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Carbohydrate foods
browns due to the
presence of dextrins,
e.g.Toast
Sugar caramelises, e.g.
Caramel slices
Maillard reaction
occurs because of the
interaction between
sugar & amino acids,
e.g. roast potatoes
Moist Heat
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Cellulose softens, e.g.
cooked vegetables
Starch grains swell,
burst & absorb liquid,
e.g. flour used to
thicken sauces
Pectin is extracted by
heating fruit in water
with sugar & acid, e.g.
jam making
Sugar dissolves in warm
liquid, e.g. making syrups
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Sweetener - desserts
Preservative - jam
Caramelisation – caramel
custard
Fermentation – yeast bread
Gel formation – sugar
combines with pectin to
form gel – jam making.
Colour – a sugar solution
prevents discolouration of
cut fruit.
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Thickener – sauces, soups,
stews.
Hygroscopic – absorbs
moisture to increase shelf
life of cakes, keeps baking
powder dry.
Dextrinisation – browning
e.g.toast.
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Gel formation – jam pectin
forms gel with acid and
sugar.
Cellulose absorbs moisture
and gives feeling of
fullness.
Cellulose adds texture e.g.
breakfast cereals
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Carbohydrates are used for heat and energy for the
body.
They spare protein so it can be used for growth and
repair.
Excess carbohydrate is changed to glycogen and stored
in liver and muscle as an energy reserve or it is changed
to body fat (adipose tissue) which insulates the body.
Cellulose moves food through intestine preventing
constipation.
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Mouth:
Physically broken by teeth.
Salivary Amylase breaks Starch into Maltose.
Stomach:
Physically churned up.
Intestine: Pancreatic juice
(Pancreas)
Amylase breaks
Starch into Maltose.
Intestinal Juice:
(Ileum)
Maltase breaks
Maltose into Glucose.
Sucrase breaks
Sucrose into Glucose & Fructose.
Lactase breaks
Lactose into Glucose and Galactose.
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Absorption:
Monosaccharides are
absorbed through the villi
of the small intestine into
the blood stream and are
carried to the liver in the
portal vein.
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Monosaccharides can be oxidised to produce energy
(cellular respiration).
 Some monosaccharides are changed to glycogen and
stored in liver and muscle as an energy reserve.
 Excess carbohydrate is changed to body fat and stored
in the adipose tissue under the skin.
 Vitamin B1, B2 and Pyrodoxine are needed to metabolise
carbohydrates.
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