Milk

Question 1

What are the three ‘phases’ of milk?

Answer 1

Stable- fat globules
Colloidal- casein micelles and why protein
True- soluble minerals (lactose and water)

Question 2

What is casein comprised of?

Answer 2

Alpha, beta and K-caseins in a ratio of 60:40:10

Question 3

Are alpha and beta caseins phosphoproteins or glycoproteins?

Answer 3

Phosphoproteins

Question 4

Are K-caseins phosphoproteins or glycoproteins?

Answer 4

glycoproteins

Question 5

what makes milk white?

Answer 5

calcium phosphate

• caseins self assemble into casein micelles which remain in close association with calcium phosphate which makes milk white

Question 6

outline the importance of casein

Answer 6

it is dispersed in water to carry calcium

it is the dominant protein in bovine milk

Question 7

name the methods by which casein can be separated in milk

Answer 7

skimmed milk powder
acid casein
rennet casein
casein ate
milk protein concentrate
phospchocasein

Question 8

what is skimmed milk powder (SMP)?

Answer 8

• fat is removed via centrifugation
• milk is pasteurised, evaporated and spray dried, which produces a powder that is 35% protein
• can be used for UHT

Question 9

what is acid casein?

Answer 9

• produces yoghurt
• changes pH from 6.7 to 4.6 using HCl, sulphuric acid and lactobacillus which concentrates caseins and eliminates lactose, whey and minerals that are soluble at a low pH
• water washing facilities casein before it is pasteurised and dried

Question 10

what does acid casein produce?

Answer 10

yoghurt

Question 11

what does rennet casein produce?

Answer 11

cheese

Question 12

what is rennet casein?

Answer 12

casein- chymosin- whey and curd

Question 13

what is caseinate?

Answer 13

the neutralisation of acid/ rennet casein through adding alkali
the alkali converts insoluble caseins into casein dispersions which can bind with water, dissolve and rehydrate
sodium hydroxide, calcium hydroxide, ammonium hydroxide and sodium carbonate all increase pH

Question 14

what is milk protein concentrate (MPC)?

Answer 14

concentration of casein using membrane technology

Question 15

what is phosphocasein?

Answer 15

concentration of casein using microfiltration

Question 16

why are milk proteins obtained in powder form?

Answer 16

to prevent spoilage
to store at room temperature
to be used in a range of products

Question 17

outline the uses of casein-based ingredients

Answer 17

acid gels

• caseinate, phospchocasein and skimmed milk powder
• for use in yoghurt and cream cheese

recombined milk proteins

• skimmed milk powder
• for use in UHT milk

food emulsions

• sodium caseinate, skimmed milk powder
• for use in oil-in-water emulsions (ice cream, mayo)
• for use in water-in-oil emulsions (table spreads)

Question 18

what is whey

Answer 18

a by product of the manufacture of dairy products

Question 19

what is beta-lactoglobulin

Answer 19

β-Lactoglobulin is the major whey protein of cow and sheep’s milk- about half the whey in milk

Question 20

what is alpha-lactalbumin

Answer 20

α-Lactalbumin is a protein occurring in the milk of mammals and is especially high in concentration in human milk

Question 21

what is caseinomacropeptide

Answer 21

a casein derived glycopeptide

Question 22

what is immunoglobulin

Answer 22

a globular protein found in blood and mammary glands

Question 23

what is serum albumin

Answer 23

Serum albumin is a large protein present in human and bovine milk and makes up approximately 10%–15% of total whey protein. It is a source of essential amino acids

Question 24

what are lactoferrin and lactoperoxidase

Answer 24

milk proteins with antimicrobial activities

Question 25

name 3 whey protein based ingredients

Answer 25

whey-protein concentrates
whey-protein isolates
whey-protein hydrolysates

Question 26

how are whey-protein concentrates obtained

Answer 26

ultrafiltration

Question 27

how are whey-protein isolates obtained

Answer 27

ion exchange separation

Question 28

how are whey-protein hydrolysates obtained

Answer 28

protein hydrolysis

Question 29

outline the manufacturing considerations for whey

Answer 29

• effects of heat treatment (e.g. denaturation)
• changes during storage of the dry powder (e.g. Maillard)
• flavour change (e.g bitter flavour)

Question 30

what are the uses of whey protein

Answer 30

functional
- solubilisers, gelation, foaming, emulsification

nutritional

• infant formulas
• sport nutriton

Question 31

what are the regulations surrounding whey

Answer 31

ingredients with less than 80% protein are not permitted to be imported to the UK