Transcript Functional properties of food pgs 36-38

Functional properties of food
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Food designers need
to understand the
properties of foods
when they are
designing new dishes,
to make sure they
match the product
profile.
Solutions
Examples of a solution are
 Fruit juices
 Sugar and water syrups
 Salt and water brine
A solution is formed when
 A liquid is dissolved in
another liquid, for example
fruit squash in water
 A solid is dissolved in a
liquid like sugar in a cup of
tea.
Solutions will not separate
when left to stand.
Suspensions
A suspension forms when
solid particles are added to
liquid but do not dissolve
 Starch particles such as
flour do not dissolve in a
liquid but they form a
suspension.
 If the suspension is not
agitated the solid particles
fall to the bottom . One
example is when a sauce
pan is not stirred when
heated and lumps form at
the bottom of the pan.
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Gels
A gel is a solid jelly-like
substance. Gels are mostly
liquid but behave like a
solid due to the gelling
agent holding the liquid in
place.
 Gels form when starch is
heated in a liquid and
cooled(gelatinisation).
Examples include
 White sauce
 Lemon meringue pie filling
 Jam
 Flan glaze
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Smart starches
Manufacturers use a large
number of starches which have
been altered to change their
working properties. These are
known a modified starches or
smart starches.
 Some modified starches are pregelatinised. This allows them to
thicken instantly such as cup a
soups or pot noodles
 Some modified starches allow
sauces to be reheated with no
synerisis
 Some modified starches are not
affected by acidity so can be used
to thicken salad dressings.
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Emulsions
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Liquids that will not mix
together are immiscible
such as oils and water.
When shaken together they
form an unstable emulsion
which separates if left
standing.
A mixture only remains
stable if an emulsifier is
used. Lecithin in egg yolk is
an emulsifier.
Egg yolk is used in the
preparation of mayonnaise
where it holds oil and vinegar
together.
It helps the fat in the cake mix
with the egg white.
Foams
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Foams are gas mixed
into a liquid giving a
light texture like in ice
cream.
Meringues are a foam
made by whisking air
(gas) into egg white
(liquid).
When you bake then
the air expands and
the egg white
coagulates to give a
solid structure.
Elasticity
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Wheat contains two
proteins glutenin and
gliadin. When water is
added to wheat flour
they form gluten.
Gluten is very stretchy
or elastic it allows
food made from wheat
flour such as bread and
cakes to rise.
Plasticity
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Plasticity describes how
fats change shape under
pressure such as rubbing in
or spreading
You can easily rub in
Soft margarine
Butter
Lard
Oil cannot be easily
rubbed in
Plasticity allows fat to coat
each flour particle in
rubbed in products like
short crust pastry or
shortbread.
Shortening
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Fats make cakes and biscuits
crumbly and melt in the
mouth by forming a coating
around the starch and protein
molecules in the flour.
This stops the liquid coming
into contact with the flour
and helps stop gluten forming.
Any gluten that does form is
in short lengths not the long
elastic strands found in bread.
These short gluten strands
give us the term shortening.