Milk Proteins

Question 1

What are the three phases of milk and what are they each comprised of?

Answer 1

1. Stable emulsion = microorganisms and fat globules
2. Colloidal suspension = caseins and whey proteins
3. True solution = lactose, water, soluble minerals and non-protein nitrogen

Question 2

What are caseins composed of and in what ratio?

Answer 2

Alpha : beta : kappa

50 : 40 : 10

Question 3

What are alpha and beta caseins?

Answer 3

Phosphoproteins = conjugated proteins containing the amino acids phosphoserine

Question 4

What are kappa caseins?

Answer 4

Glycoproteins = more hydrophilic

Question 5

What do caseins self assemble into?

Answer 5

Micelles = proteins packets

Question 6

How are alpha and beta caseins held together in micelles?

Answer 6

Hydrophobic interactions

Question 7

Where are kappa caseins found in micelles and why?

Answer 7

On the surface to allow for suspension in milk

Question 8

What forces do kappa caseins provide between micelles?

Answer 8

Repulsive steric forces

Question 9

What compound are micelles in close association with and what property does the compound result in milk having?

Answer 9

Calcium phosphate

Results in milk being white

Question 10

What are the importance of caseins?

Answer 10

• Dominant protein in bovine milk
• Carry significant amounts of calcium phosphate
• Can be separated easily to produce functional ingredients

Question 11

How is the separation of casein components from skimmed milk achieved?

Answer 11

By precipitation of membrane processing

Question 12

What does the separation of casein produce and why is it in this form?

Answer 12

Casein based ingredients in powder form so that they do not spoil

Question 13

What are the six main casein based ingredients produced by the separation of caseins?

Answer 13

1. Skimmed milk powder
2. Acid caseins
3. Rennet caseins
4. Caseinates
5. Milk protein concentrates
6. Phosphocaseins

Question 14

Does the production of SMP require major separation processes?

Answer 14

No - except the removal of fat by centrifugation

Question 15

How is SMP produced?

Answer 15

1. Skimmed milk is pasteurized
2. Heat induced denaturation of whey proteins attached to micelles occurs
3. Samples are evaporated and spray dried to produce a powder

Question 16

What percentage of SMP is protein, and of that protein what percentage are caseins?

Answer 16

35% protein

80% caseins

Question 17

Is SMP soluble?

Answer 17

Yes

Question 18

What can SMP be further processed to produce?

Answer 18

UHT milk

Question 19

What are acid caseins produced in preparation for?

Answer 19

Yoghurt production

Question 20

How are acid caseins produced?

Answer 20

1. Caseins self-aggregate as a result of changing the pH of skimmed milk (from 6.7 to 4.6)
2. Caseins remain in the curd
3. Other compounds are eliminated as they are soluble at low pH
4. Water washing
5. Pasteurising
6. Drying

Question 21

What might be used to lower the pH during acid casein production?

Answer 21

Hydrochloric acid
Sulphuric acid
Lactobacillus

Question 22

What are rennet caseins produced in preparation for?

Answer 22

Cheese production

Question 23

How are rennet caseins produced?

Answer 23

1. Caseins self aggregate due to the action of chymosin (rennet)
2. Curd and whey are formed
3. Calcium is recovered
4. Treatment of curd is similar to the production of acid caseins

Question 24

Are dried rennet caseins soluble in water?

Answer 24

No

Question 25

What is the most efficient way of producing high casein ingredients?

Answer 25

Rennet casein production

Question 26

How are caseinates produced?

Answer 26

1. Acid or rennet caseins are neutralised through alkali addition 2. The change in pH converts insoluble acid caseins into casein dispersions = recovering their solubility

Question 27

If pH is increased using sodium hydroxide in caseinate production what type of caseinate is produced?

Answer 27

Sodium caseinate

Question 28

If pH is increased using calcium hydroxide in caseinate production what type of caseinate is produced?

Answer 28

Calcium caseinate

Question 29

How are milk protein concentrates produced?

Answer 29

By the concentration of caseins by membrane technology

Question 30

What do milk protein concentrates contain?

Answer 30

Caseins and whey proteins Low lactose concentration Significant amount of calcium phosphate

Question 31

Why do milk protein concentrates contain an significant amount of calcium phosphate?

Answer 31

Because caseins form micelles

Question 32

What are milk protein concentrates used for?

Answer 32

For fortifying beverages

Question 33

How are phosphocaseins produced?

Answer 33

By microfiltration

Question 34

What do phosphocaseins contain?

Answer 34

Only casein micelles with attached calcium phosphate

Question 35

What percentage of phosphcasein powder is protein?

Answer 35

75-80%

Question 36

When might rehydration of phosphcaseins be possible?

Answer 36

If they are not heated above 50 degrees

Question 37

What are the uses and applications of casein based ingredients?

Answer 37

``` Acid gels Recombined milk Food emulsions Cheese analogue Chocolate Bakery ```

Question 38

What do acid gels do and what casein based ingredients are involved in producing them?

Answer 38

Control gel behaviour during fermentation by bacterial cultures (to produce yoghurt and cream cheese) - Caseinates - Phophocaseins - SMP

Question 39

What casein based ingredient is involved in producing recombined milk and why?

Answer 39

SMP because it is stable at high temperatures

Question 40

What casein based ingredients are used in food emulsions?

Answer 40

Sodium caseinate = protein emulsifier Calcium caseinate and SMP = oil in water emulsions SMP = water in oil emulsions

Question 41

What casein based ingredient is involved in producing cheese analogue?

Answer 41

Rennet Casein

Question 42

What casein based ingredients are involved in producing chocolate?

Answer 42

SMP and whey powders

Question 43

What casein based ingredient is involved in bakery?

Answer 43

SMP

Question 44

What is whey?

Answer 44

A byproduct of the manufacturing of dairy products

Question 45

What is whey comprised of?

Answer 45

1. Beta-lactoglobulins 2. Alpha-lactalbumins 3. Glycomacropeptides 4. Immunoglobulins 5. Serum albumins 6. Lactoferrin and lactoperoxidase

Question 46

What is a property of beta-lactoglobulin?

Answer 46

High proportion of hydrophobic residues

Question 47

What do alpha-lactalbumins form?

Answer 47

Parts of lactose synthase enzymes

Question 48

What are glycomacropeptides?

Answer 48

Glycopeptides derived from caseins

Question 49

What are immunoglobulins?

Answer 49

Heat sensitive globular proteins from blood

Question 50

What do serum albumins contain and how do they affect serum albumins interactions?

Answer 50

A large number of disulphide bridges which react with beta-lactoglobulins

Question 51

Name three whey protein ingredients.

Answer 51

Whey protein concentrates Whey protein isolates Whey hydrolysates

Question 52

How are whey protein concentrates obtained?

Answer 52

By ultrafiltration

Question 53

What might be lost during ultrafiltration of whey?

Answer 53

Alpha-lactalbumins

Question 54

How are whey protein isolates obtained?

Answer 54

By ion exchange separation

Question 55

How are whey hydrolysates obtained?

Answer 55

Protein hydrolysis - incubating proteins with proteolytic enzymes at elevated temperatures

Question 56

What considerations should be taken into account during the manufacturing of whey based ingredients?

Answer 56

Effect of heat treatment Changes during storage Flavour of whey hydrolysates (hydrophobic peptides produce a bitter taste)

Question 57

What are the functional uses of whey proteins?

Answer 57

Solubilizers Gelation Foaming Emulsification

Question 58

What are the non functional uses of whey proteins?

Answer 58

``` Infant formulations Sports nutrition (drinks and bars) ```