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Product Design
Food Products
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Learning objectives
Learning objectives
To understand that food products require the right
proportions of ingredients.
To learn about the physical and chemical
properties of starch, sugar, protein and fat.
To understand about the role of raising agents in
food production.
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Food groups
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Food groups
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Which foods are high in protein?
Which foods are
high in protein?
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Properties of proteins
The main property of proteins is that they coagulate on heating –
they become solid.
The protein in the white and the yolk of an egg both set when
cooked (the yolk takes longer to set than the white as it contains
less protein).
The protein in meat and fish coagulates too.
Acid sets protein. If acid is added to milk, it curdles. These curds
make cheese.
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Eggs
Eggs can be used in a number of useful ways since they
coagulate. They can be used for:
binding – the egg coagulates and sticks the dry ingredients
together as they are cooked (used for burgers and cakes)
coating – egg and breadcrumbs coat fish before frying; the egg
coagulates and provides a barrier to stop oil seeping in
glazing – the egg sets during baking and turns golden brown as
it reacts with the starch (Maillard reaction)
thickening – egg can be used instead of starch to thicken
custard and soup. It also sets the sauce in a quiche
foaming – the protein in the white of the egg unravels when
beaten and holds lots of air; it can increase to eight times its
original volume.
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Using eggs
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Meat and fish
The muscle tissues of meat and fish mainly contain protein which
coagulates during cooking. The length of the muscle fibres and
how they are grouped together determines how much cooking
time is needed for the meat or fish to become tender.
Fish needs a shorter cooking time than meat because it is
made up of short muscle fibres held together in bundles with a
small amount of collagen (which dissolves when heated). Fish
can easily become overcooked with the liquid in the muscle
being evaporated away, leaving the fish dry and chewy.
Meat has longer muscle fibres than those of fish, which are
bundled together with collagen and elastin. Elastin is tough and
yellow in colour and binds the muscle fibres to the bone in
addition to binding the muscle fibres together.
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Why does meat vary in tenderness?
Which is the
toughest meat
out of these
examples?
The tenderness of meat is dependent on the
length and size of the muscle fibres.
The length of the fibre and amount of
connective tissue varies according to which part
of the animal the muscle tissue comes from.
The more the muscle works, the longer the
fibres are and the more connective tissue there
is, meaning that the meat is tougher and needs
more cooking time.
fillet steak?
breast?
thigh?
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leg joint?
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How can meat be tenderized?
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Which foods are high in carbohydrates?
Which foods are
high in
carbohydrates?
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Which foods are high in carbohydrates?
Carbohydrates are divided into three groups – starch, sugar and
non-starch polysaccharides (NSP), more commonly known as
fibre. They all have different functions.
starch
sugar
fibre
Fibre can affect the way starch works. It absorbs more
water and creates a heavy texture. Compare
wholemeal bread with white bread!
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Properties of starch
Starch has the property of being a filling ingredient. Flour is used
as a bulk ingredient in all baked products and creates the
structure of a product.
When starch is wet and heated, it
gelatinizes – it absorbs liquid and
swells to give a good open texture,
especially if a raising agent is used.
When starch is dry
and heated it
dextrinizes – it goes
golden brown.
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Flour
Flour can be made from starchy foods other than wheat –
cornflour (from maize), rice flour, potato flour and rye flour are
some examples. The higher protein content of wheat flour,
however, makes it an important ingredient in baked products as
it mixes with liquid to form gluten. Making bread is an example:
The flour is mixed with liquid to produce
gluten. By kneading the dough, the
protein strands are untangled and more
gluten is produced. The gluten is not only
strong and elastic, holding the bread
together, but also traps the gases that
form in bread when you cook it.
Strong flour contains more protein than ordinary flour and is
therefore better for making bread. The varying amounts of protein
in different wheats makes them suitable for different
food
products.
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Different wheats
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Properties of sugar
Sugar makes foods sweet and is also an
important bulking agent.
When sugar is caramelized – heated to a
temperature above its melting point – it adds
colour, flavour and texture.
Sugar can preserve a product if used in large
amounts.
Sugar helps food products stay moist because it
is hydroscopic – attracted to water.
When sugar is heated in the presence of proteins,
non-enzymic browning takes place – it turns a
product brown.
Most importantly, sugar aerates a mixture –
increases its size.
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Aeration
When sugar is beaten with fat, air gets incorporated into the
mixture and sticks to the sugar crystals. The fat surrounds the air
bubbles and traps them in the mixture, making the mixture lighter
and more aerated. In a sponge cake, the butter and sugar should
be beaten for eight minutes!
Caster sugar is the best sugar to use because it has a large
number of fine crystals, which means more air bubbles and
better aeration.
Granulated sugar has fewer and bigger crystals.
The crystals in icing sugar are
too small for aeration to work.
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Which foods are high in fat?
Which foods are high in fat?
Sunflower oil has very
little flavour but a very
high smoking point; it is
a polyunsaturated fat
which is better for the
heart.
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Olive oil has lots
of flavour, quite a
high smoking
point and is a
monounsaturate
which is best for
the heart.
Butter has a low
smoking point with
lots of flavour; it is
a saturated fat.
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Properties of fats
Fats can be animal or vegetable and solid or liquid. They have
different properties and other functions in addition to adding
flavour and being used in cooking. They are used for spreading
(on bread), aerating (they help sugar to trap the air on account of
their plasticity – they are mouldable and pliable) and shortening
(they make baked products crumbly).
Shortening creates the crumbly soft texture of cakes, rather than
the chewy texture which is desired in bread. A high fat content
stops the protein in flour from absorbing liquid by surrounding the
flour particles and forming a waterproof coating. This prevents
gluten from forming which would make the mixture elastic and
stretchy and creates a crumbly and ‘short’ mixture instead.
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Enzymic browning
Enzymic browning occurs in fruit and vegetables when they are
cut open and their cut surface is exposed to the air. The
enzymes in the fruit and vegetables react with the oxygen in the
air, gradually turning the surface brown.
To stop enzymic browning taking place, vegetables can be
coated in a dressing and fruit can be covered in an acid such as
lemon juice.
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What are raising agents?
All sorts of ingredients are used for their sensory or nutritional
function, such as herbs in a sauce or peppers on a pizza. There
is one other group of ingredients, however, which has an
important physical function in food products – these are raising
agents.
Raising agents are used to make baked products rise. They are
gases which expand on heating and push up the surrounding
mixture. Three different gases can be used:
air – added mechanically by whisking, creaming or sieving
steam – requires a lot of liquid being present, such as in
batters and choux pastry, or a very high temperature, such as
in cooking bread
carbon dioxide – added chemically or biologically.
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Carbon dioxide
Carbon dioxide is produced chemically or biologically.
Baking powder is the chemical raising agent most commonly
used to produce carbon dioxide; liquid and heat are also
needed. Baking powder is a commercial mix of bicarbonate of
soda, acid and flour (to add bulk). Bicarbonate of soda can be
used on its own but leaves an aftertaste and yellow colour – in
gingerbread this does not matter!
Yeast is a biological raising
agent. Yeast needs food,
warmth, liquid and time to
ferment and produce carbon
dioxide. It is used in most
breads, getting its own food
from the sugar in the flour.
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The properties of bread
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Properties of food quiz
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Key points
Key points
Successful food products are made by using the
right proportions of ingredients.
Starch, sugar, protein and fat all have important
functions in food production.
Raising agents are used in food production to
make baked products rise.
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