Food Science- Proteins

Question 1

What are proteins made from?

Answer 1

Amino Acids

Question 2

What does ‘denature’ mean?

Answer 2

It is when a protein molecule changes shape by the use of heat, acid or mechanical action (like whisking).

Question 3

How can proteins be denatured?

Answer 3

Acids, heat or mechanical action

Question 4

What does the term ‘marinading’ mean?

Answer 4

It is the process of soaking meat or vegetables in a strongly flavoured liquid before cooking- to give it flavour, or help breakdown the muscle fibres.

Question 5

What types of foods can be used as marinades?

Answer 5

Strongly flavoured liquids (pineapple juice), lemon juice, acids- vinegars

Question 6

What does the term ‘curdled’ mean?

Answer 6

When an acid is added to milk, the proteins denature and start clumping together, this is called curdling.

Question 7

How does mechanical action denature proteins?

Answer 7

The protein is stretched into strands and forms a structure that allows air to be captured, the air bubbles are held together by a mesh of protein.

Question 8

How does kneading affect the protein in bread?

Answer 8

The protein in bread (gluten) is denatured via mechanical action, this makes it stretchier and more elastic.

Question 9

What is the term used for proteins that are first denatured by heat and then set?

Answer 9

Coagulation, this change is irreversible.

Question 10

Explain what happens to the following proteins when they are heated:
Meat and poultry (birds)
Fish
Eggs
Wheat
Milk
Cheese

Answer 10

Meat and poultry (birds)- meat shrinks, overheating can make it chewy, collagen will turn to gelatine.
Fish- shrink, overcooking will make it tough.
Eggs- white becomes solid at 60C, yolk becomes solid at 70C.
Wheat- Gluten sets and gives baked products a firm texture.
Milk- Proteins coagulate for form a skin on milk.
Cheese- fat melts in cheese, proteins denature then coagulate, and will become rubbery if overheated