LEMON FOAM

1
LEMON FOAM

• If you are interested in making a light foamy
  dessert - great for those unexpected visitors -
  get ready to learn the Lemon Foam recipe.
• Its quick, easy and has a very interesting
  chemistry to it.
• RECIPE
• - Briskly beat the contents of a can of
  evaporated milk and a can of condensed milk until
  the mixture is thick and creamy.
• In the meantime, squeeze the juice from 3 lemons.
• When the foam mixture is ready, add the lemon
  juice.
• Place the mixture in the fridge and, if you like,
  sprinkle it with some powdered cinnamon, roasted
  ground almonds or crushed biscuit.
• - What do you think? Its cool and delicious with
  a very sticky consistency, right?
• What has happened in this very simple mixture?
• The characteristics of the milk

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ESPUMA DE LIMÃO (cont.)
Lemon juice in the foam When you pour the lemon
juice into the foam, you will notice that it
immediately becomes thicker and stickier. In
order to understand how this happens, we need to
talk about a certain part of the milk protein
casein which makes up more than 80 of the
total protein content of milk. Lets take a
look at the average composition of cows
milk. We often say you cant judge a
book by the cover when were talking about
people. The same is true for many substances. In
the case of milk, the smooth white appearance
hides a very complex composition and organisation
of its component parts. It contains an emulsion
(a mixture which appears homogenous), composed of
fat globules, proteins (casein) and a solution,
composed of sugars (lactose), proteins, vitamins
and minerals salts.   Casein is composed of
negatively-charged units which because of this
negative charge repel each other and move freely
around the milk.   When you add an acid, such as
lemon juice, the pH of the milk will fall
(acidity increases) and this environment causes
the milk proteins the casein to attract each
other and bond that is, to join together,
making a lump (or curd) which sinks to the bottom
giving the final mixture a thick sticky texture.
Maria Margarida Guerreiro
Water 87
Protein 4
Fat 3,5
Lactose 5
Mineral salts  1-2