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Functional properties of food

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					Functional properties of food
   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.
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
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 pre-
  gelatinised. 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.
Emulsions
   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
   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
   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
   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
   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.

				
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posted:10/5/2011
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