Functional properties of food

Year 11: ObjectivesWhatUnderstand functional properties of foods

HowResearch into functional properties and their uses

WhyTo be able to apply them to your own learning and when preparing food for others

Bronze

Identify the functional properties of protein, starch, sugar, fats and oils

Silver

Be able to explain the functional properties of different food groups and what happens when heat is applied

GoldPredict what happens to the properties of different foods at key temperatures, being able to describe in detail the terms gelatinisation, gel, suspension and modified starch

Outcomes

Carbohydrates - Starch

• 2 main types of carbohydrates– Starch, found in flour, potatoes, pasta,

rice and bread– Sugars, found in fruits, drinks and sweet

baked products

– Modified starch is used in commercial production

Types of starch

• Obtained from cereals such as wheat and maize

– Wheat flour– Cornflour– Arrowroot

Uses of starch

• Bulking – forms the main structure of a product e.g. In biscuits, cakes and pastry.

• Thickening agent– Raw starch tastes floury– Needs to be cooked

Gelatinisation1. Starch particles do not dissolve in cold liquid, they

form a suspension.2. If the liquid isn’t stirred, the starch granules sink

to the bottom, stick together and form lumps.3. At 60˚C, the starch granules begin to absorb the

liquid and swell.4. At 80˚C, the granules will have absorbed 5x their

volume until they burst open, releasing starch into the liquid.

5. Gelatinisation is complete when the liquid reaches 100˚C.

6. When the sauce cools, it gets even thicker, setting into a gel.

Heat starch granules in liquid

Starch granules become swollen at 60˚C

Starch granules burst at 80˚C

The liquid thickens and gelatinizes at 100˚C

Starch gelatinizes when heated in a liquid, producing a thickened liquid

Effects of Heat

Egg

• White starts to coagulate until it turns from a liquid to a solid.• Egg yolk continues to cook until it

becomes dry and hard.• Over cooking – green and black ring

[iron sulphur] forms around the yolk.

Cheese

• Fat in the cheese melts and separates.

• Protein coagulates and shrinks.• Over cooking makes cheese tough

and stringy.• Makes the cheese hard to digest.

Meat• Kills bacteria.• Makes it tender.• Improves flavour.• As the heat increases the structure of

the meat tightens and it becomes firmer.

• Meat shrinks in size.• Colour changes• Fat melts.

Pasta - carbohydrate• Starch grains start to soften.• The pasta absorbs water and swells

in size.• Change of colour.• As the temperature increases the

starch escapes.

Vegetables

• Makes the food more digestible.• Reduces the bulk.• Vitamins can be lost in water –

leached out. (water soluble vitamins B and C)

• Heat destroys vitamins.• Over cooking softens the structure.

Sugar• Dry heat converts the Starch into a simple sugar DEXTRIN.• Further cooking cause

caramelisation.

• Sugar is heated to very high temperature, turns brown and thickens adding flavour.

• Over cooking blackens the mixture.

Bread

• Flour forms the structure.

• When the bread is cooked dextrinisation occurs.

• Starch from the flour is converted into sugar, which is caramelised giving the bread colour.

Why cook foods?

• Destroys bacteria.• Short term preservation.• Makes food easier to digest.• More appealing and attractive.• Warm meal.• Enhance flavours.