The Functions and Properties of Food Flashcards
(29 cards)
What are the two types of carbohydrates?
Starches and sugars
In what foods are starches found?
Flour, potatoes, pasta, rice and bread
In what foods are sugars found?
Fruits, drinks and sweet baked products
What can starch be used for?
Bulking agent
Thickening agent
Gelling agent
What is gelatinisation?
When heated, starch granules absorb liquid and swell and then burst to thicken a liquid
What is suspension?
A solid held in a liquid e.g. starch granules do not dissolve in a liquid and so if they are not stirred they sink to the bottom and form lumps
Give an example of gelatinisation
Wheat flour is used with fat and milk to make a white sauce
What is a gel?
A small amount of a solid mixed in a large amount of liquid that then sets
What are modified starches?
Starches that have been modified to perform additional functions e.g. used to thicken food when boiled water is added in cup-a-soup
What are the functions of sugar?
Preserves food Sweetens Bulking agent Improves or changes flavour Aerates food products Keeps food products moist Stabilises whisked mixtures Adds colour Speeds up fermentation
How does sugar help to preserve foods?
In large quantities it creates unsuitable conditions for microorganisms to grow e.g. in jams and chutney
How does sugar help to aerate food products?
When sugar is beaten with butter or egg it helps trap air to make cakes light
How does sugar help to speed up fermentation?
Increases the rate at which yeast releases carbon dioxide in bread making
How does sugar help to add colour?
When sugar is heated it turns golden brown. This is called caramelisation
What are protein foods made up of?
Small units called amino acids that are linked together in a chain. When proteins are heated the links in the chain change and this alters the structure of the food
What is aeration?
When air is trapped in a mixture
What is coagulation?
When eggs are heated, they change from a liquid to a solid, change colour and set. Full coagulation happens at 70°C
What is an emulsion?
A mixture of two liquids - unless an emulsifier is added eventually they will separate
What is the emulsifier in mayonnaise?
Egg yolk contains a substance called Lecithin, which is also found in soya beans. When egg yolk is mixed with oil and vinegar it stops the liquid separating.
What happens in shortening?
The fat coats the flour particles, preventing the absorption of water. This prevents gluten from developing resulting in a crumbly texture
What are the functions of fats and oils?
Shortening ability Prevent lumps of flour forming in a sauce Add colour Can form part of an emulsion Act as cooking medium Adds distinct flavour
How do fats help to aerate foods?
When fat is creamed with sugar it helps trap air
How do fats help to add a flaky texture to pastry?
The fats help to separate layers by creating steam
How do fats help to extend the shelf life of foods?
The fat helps the products retain its moisture for longer
