PROTEINS
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Carbon, oxygen, hydrogen and nitrogen
Protein types- see table on pg 84
Properties of proteins
Denaturation: occur through heat, mechanical agitation, a change in pH or exposure to enzymes
Coagulation: permanent change in the protein from a liquid into a thick mass as a result of heat or
the addition of acids
Functions of eggs
See table on pg 84
Structure
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Egg white is strongest, followed by the whole egg, then egg yolk
Egg works alongside flour to create structure. Many would collapse without the flour to
support
Heat coagulates or sets the egg proteins, giving the product structure
Thickening and setting
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The egg proteins will gradually denature and coagulate when a mixture is heated. They will
thicken to form the structure of the products. Without the coagulated egg, the mixture
would remain runny
Baked custard is cooked in a water bath. The surrounding water prevents the direct heat
coming into contact with the egg, creating a lower baking temperature. This slows down the
process of coagulation and prevents curdling of the cooked mixture.
If an egg custard or sauce is overheated, the mixture is said to have curdled. It is easy to
recognise because tough bits of egg protein float in pools of the squeezed out liquid
Fruit butters or curds are made from the juice of lemons, limes and oranges and are
combined with eggs, sugar and butter to make a spread. The thickening process is a result of
the eggs coagulating when they are combined with the acid from the citrus fruit and heated
Emulsifying
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Egg yolk prevents fat and water from separating
If eggs are too cold or added too quickly to butter and sugar, the emulsion breaks and will
curdle
Aeration
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Eggs trap air as they are beaten, which creates volume and a light texture. This occurs as
they hold the air and the air allows the product to expand when heated
Overbeating egg whites will cause foam to collapse
Improves colour
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They contribute to browning from the maillard reaction
Improve shine when used as a glaze
Yellow-orange carotenoids in the yolk contribute to the yellow colour in cakes etc
Binding
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Helps mix and bind ingredients together. it coagulates upon cooking of a product and forms
part of the products structure
Functions of milk
Adds moisture
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Helps to combine ingredients
Helps to dissolve sugar and hydrate gluten in wheat flour
Colour development
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Glaze
Maillard reaction: breakdown of protein and lactose during baking
Richness
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Full cream milk adds a rich and creamy flavour due to fat content of milk
Soft crusts
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Milk proteins and lactose absorb water so slow down its evaporation from the outside of the
product
Functions of gluten
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Wheat flour
Swells when mixed with water ( gelatinisation )
Denatures and coagulates
Structure building
FATS AND OILS
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Fats and oils have the same make-up as CHO: carbon, hydrogen and oxygen, except it is their
structure that varies, so foods have different properties
Saturated fatty acids: a long carbon chain with all hydrogen atoms attached. They are solid
at room temperature and of animal origin. E.g. milk, butter and meat
Unsaturated fatty acids: a long carbon chain with less than the full number of hydrogen
atoms attached. Present in plant and vegetable oils e.g. peanut, olive, maize and canola
Properties of fats and oils
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Table on page 87
Sensory properties
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A large quantity of fat will provide a moist and oily texture and smooth mouthfeel to a
product
Enhance the flavour of foods i.e. butter adds a rich flavour to products and macadamia and
sesame oils give a distinctive flavour to sauces and dressings
Fried food can give a pleasant aroma as fats and oils breakdown when heat is applied to
them.
High temperatures cause food to form a golden brown appearance on the surface of
products
Improved keeping qualities
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Fats delay products from becoming dry and increase keeping qualities
Aeration
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Fats trap tiny air cells during the beating or creaming process. This trapped air gives a light,
airy texture to baked products
Transferring heat
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Fats and oils can be heated to high temperatures
Food that is deep fried in fat or oil cooks fast and can also absorb some of the fat or oil,
which gives it a strong flavour and a brown crisp texture
Shortening effect
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Fat provides tenderness to cooked food
Fat ( butter ) coats starch grains and separates gluten strands, preventing strong binding and
it provides a crisp shortening effect
Emulsification
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Ability of a fat or oil to be dispersed throughout a liquid
Emulsifiers allow fats and oils to mix with water to form low-fat spreads and salad dressings
Lecithin, a fat found in egg yolk, is a natural emulsifier that is used to make mayonnaise so
the oil and vinegar do not separate on standing
Sealing and protecting
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Fats and oils protect foods from drying out and allowing oxygen coming into contact with
food, causing deterioration.
E.g. bacon contains large amounts of fat to protect the breast of the poultry to stop it drying
out during baking