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Flashcards in Properties of Proteins Deck (32)
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1

List the properties of proteins
(6)

Denaturation
Elasticity
Maillard reaction
Solubility
Gel Formation
Foam Formation

2

What is denaturation?
(3)

A change in the nature of a protein chain
It involves the unfolding of a protein chain which results in an irreversible change in shape
One this happens the protein often coagulates (sets or becomes hard)

3

How does denaturation result in coagulation?

Denaturation involves the unfolding of a protein chain which results in an irreversible change in shape which often results in coagulation

4

What means bring about denaturation?
(4)

Heat
Chemicals
Mechanical action
Enzymes

5

How does heat bring about denaturation?

Heat causes protein chains to unfold and bond together which causes food to coagulate

6

How do chemicals bring about denaturation?

By lowering or raising pH levels by the addition of acids or alkalis a protein's structure can be denatured

7

How does mechanical action bring about denaturation?

Mechanical action such as whipping or beating causes protein chains to unfold and brings about partial coagulation

8

How do enzymes bring about denaturation?

Enzymes cause a change to the nature of a protein's structure

9

Give a culinary use of denaturation brought about by heat

Egg whites coagulate and change from translucent to opaque at 60 degrees Celsius and egg yolks coagulate at 68 degrees Celsius

10

Give a culinary use of denaturation brought about by chemicals

A vinegar-based marinade tenderises meat by denaturising proteins

11

Give a culinary use of denaturation brought about by mechanical action

Whipping of eggs when making a sponge cake

12

Give a culinary use of denaturation brought about by enzymes

The enzyme rennin in rennet causes caseinogen in milk to coagulate during the making of cheese

13

Describe the elastic property of proteins

Some fibrous proteins such as gluten in wheat are quite elastic

14

Give a culinary use of the elastic property of proteins

Gluten makes yeast dough elastic enough to trap the carbon dioxide gas produced by yeast which helps it rise

15

Describe the Maillard reaction in proteins

This is the non-enzymic browning of food.
It occurs when an amino acid reacts with a carbohydrate (sugar) under dry heat

16

What does the Maillard reaction occur between?

An amino acid and a carbohydrate (sugar)

17

Under what condition does the Maillard reaction occur?

Under dry-heat

18

Give a culinary application of the Maillard reaction of proteins

It gives an attractive brown colour to foods such as shortbread biscuits and roast potatoes

19

Describe the solubility property of the Maillard reaction

Most proteins are insoluble in water, apart from collagen in meat (soluble in hot water) and egg albumin (soluble in cold water)

20

Give a culinary use of the solubility property of the Maillard reaction

Moist heat tenderises meat by converting collagen to gelatine

21

Describe the gel formation property of a protein
(3)

When collagen (protein present in the bones and skin of meat) is heated it is converted to gelatine
Gelatine can absorb large amounts of water when heated as protein chains uncoil and water becomes trapped
This forms a sol and on cooling it forms a gel which is a semi-solid viscous solution with a three dimensional protein matrix in which water molecules become trapped

22

What happens to collagen when it is heated?

It is converted into gelatine

23

What protein is converted to gelatine when it is heated?

Collagen

24

What property does gelatine have that is used in the setting of jam?

Gelatine can absorb large amounts of water when it is heated

25

How does gelatine absorb large amounts of water?

When gelatine is heated it's protein chains uncoil and water becomes trapped

26

What is formed when gelatine absorbs a large quantity is absorbed

A sol is formed

27

What is formed when a sol is cooled?

A gel

28

What is a gel?

A semi-solid viscous solution

29

How is a gel formed?

When gelatine is heated it absorbs water to form a sol which when cooled forms a gel which is a semi-solid viscous solution

30

Give a culinary use of the gel formation property of a protein

Its setting power is useful in making cheesecakes and jellies