The Science of Cooking Food

Question 1

Give 4 reasons why we cook food:

Answer 1

-To make food safe to eat as heat kills pathogenic bacteria
-To soften the food, making it easier to chew, swallow and digest
-To make it look appetising and improve the flavour
-To warm us up - hot food in cold weather

Question 2

What are 3 methods of heat transference to food?

Answer 2

-Conduction
-Convection
-Radiation

Question 3

What 3 factors affect the size/density and appearance of all protein, fat and carbohydrate foods permanently?

Answer 3

-When it is beaten
-When it is eaten
-When pH value is changed

Question 4

What 4 reasons cause proteins to denature and coagulate?

Answer 4

-When they are heated
-When they come into contact with acidic/alkaline ingredients
-When they are whisked, beaten or kneaded (foams and gluten develops)
-When the proteins unravel becoming firm when heated

Question 5

What 3 reasons cause changes to fats?

Answer 5

-At room temperature fats can be easily spread and mixed with other ingredients. This property is called plasticity
-Fats melt and become liquid when heated. They add flavour and texture to cooked food, and some fat can ‘melt out’ from the ingredient
-Fats ‘shorten’ gluten strands in shortcrust pastry and biscuits creating a crumbly texture

Question 6

What happens when starchy carbohydrates, such as flour, mix with a liquid and are heated?

Answer 6

They gelatinise.

Question 7

What is plasticity?

Answer 7

At room temperature fats can be easily spread and mixed with other ingredients.

Question 8

What is gelatinisation?

Answer 8

The thickening of a mixture, in the presence of heat, due to the swelling of starch grains.

Question 9

What happens to sugary carbohydrates, such as the natural sugar in fried onion, when heated?

Answer 9

They will caramelise (become golden brown)

Question 10

What happens to starchy carbohydrates when exposed to dry heat?

Answer 10

They create dextrins.

Question 11

What is dextrin?

Answer 11

A fibre in wheat that slows down digestion.

Question 12

Name 3 acidic ingredients:

Answer 12

-Tomatoes
-Vinegar
-Lemon/lime juice

Question 13

What happens when fruit/vegetables are exposed to oxygen?

Answer 13

They go brown due to oxidising of enzymes.

Question 14

What happens when meat is exposed to oxygen?

Answer 14

The red surface becomes brown/grey due to oxygen affecting myoglobin.

Question 15

What is myoglobin?

Answer 15

A protein that stores oxygen in the muscle cells of animals.

Question 16

What happens when fish is exposed to oxygen?

Answer 16

Oxygen works with fish enzymes making it spoil rapidly and smell fishy.

Question 17

What happens when fats and oils are exposed to oxygen?

Answer 17

Oxygen turns fats and oils rancid.

Question 18

What is an emulsion?

Answer 18

When oil and water join together in suspension (so they don’t separate out)

Question 19

Give 3 examples of emulsifications:

Answer 19

-Creamed cake mixtures
-Milk
-Butter
-Vegetable fat spread

Question 20

How do you make mayonnaise?

Answer 20

Combine sunflower oil, vinegar and egg yolk.

Question 21

Give 3 uses of enzymes in food:

Answer 21

They are needed to soften, flavour and ripen many foods.

Question 22

Name 4 raising agents:

Answer 22

-Aeration
-Steam
-Chemical raising agents
-Yeast