Milk

Question 1

How much milk is needed for 1kg of cheese?

Answer 1

8.5kg

Question 2

How much milk is required to make 1kg of whole milk powder?

Answer 2

7.81kg

Question 3

How much milk is required to make 1kg skimmed milk powder?

Answer 3

10.72kg

Question 4

How much milk is needed to make 1kg of condensed milk?

Answer 4

2kg

Question 5

How much milk is needed to make 1kg of yoghurt/buttermilk?

Answer 5

1.1kg

Question 6

What are the milk quality tests?

Answer 6

Organoleptic- visual and odour
Protein content- Kjeldahl process
Milk fat content- Gerber method
NIR (near infrared) can be used to measure fat, protein and lactose

Question 7

How much milk solids are in condensed milk?

Answer 7

50-60%

Question 8

Sweetened condensed milk contains how much milk solids?

Answer 8

70%

Question 9

How is milk powder made?

Answer 9

Drum drying or spray drying

Question 10

Homogenisation of milk

Answer 10

Fat globules obtain a surface rich in casein proteins therefore they can behave as large casein micelles which forms a stable and uniform suspension of fat

Question 11

Why are small milk fat globules easier to digest than large milk fat globules?

Answer 11

Due to the larger surface area to volume ratio of smaller droplets

Question 12

Name the 4 ways to heat treat milk

Answer 12

Thermization, low pasteurization, high pasteurization and sterilization

Question 13

Thermization

Answer 13

65°C for a few seconds

Question 14

Low pasteurization

Answer 14

63°C for 30 mins or 72°C for 15 seconds

Question 15

High pasteurization

Answer 15

85°C for 20 seconds

Question 16

Sterilization

Answer 16

110°C for 30 mins, 130°C for 30 seconds or 145°C for 1 second (UHT)

Question 17

How does heating change milk?

Answer 17

• Colour (more brown)
• Flavour (Maillard reaction)
• Texture (whey protein associating with casein micelles)
• Nutritional value (ketone formation)

Question 18

Why do reaction rates vary?

Answer 18

Water activity (Aw)

Question 19

Concentrated milk products

Answer 19

Deteriorate at intermediate Aw values

Question 20

When does water activity of milk increase?

Answer 20

When heated therefore reactions decrease when temperature increases

Question 21

Milk definition

Answer 21

An aqueous solution of protein, fat, vitamins and minerals that carries emulsified fat globules and a dispersion of casein micelles

Question 22

What is milk made from?

Answer 22

• 87.5% water
• 3.9% fat (TAG)
• 3.4% protein
• 5.2% vitamins and minerals

Question 23

What are the 2 proteins of milk?

Answer 23

• 80% casein
• 20% whey

Question 24

What is the structure of casein?

Answer 24

• Short lengths of alpha-helix and beta-sheet
• Hydrophilic and hydrophobic regions