Milk and Dairy Production

Question 0

What is raw milk?

Answer 0

Milk which has not been heated beyond 40C or undergone any treatment that has an equivalent effect

Question 1

Define milk

Answer 1

Normal mammary secretion of milking animals obtained from one or more milking without either addition to it or extraction from it, intended for consumption as liquid milk or for further processing

Question 2

What is a milk product?

Answer 2

A product obtained by any processing of milk, which may contain food additives, and other ingredients functionally necessary for the processing

Question 3

How has milk consumption changed in recent years in the UK?

Answer 3

Liquid milk consumption has decreased but yogurt consumption has increased

Question 4

How will milk consumption change globally in the next few years?

Answer 4

Will be affected by major market trends such as those in the Asian market which is rapidly increasing
Rapid growth of the global population over 65 will define consumption habits of dairy products

Question 5

Who is the largest milk producer in the world? How much do they produce? Where is the UK in terms of production?

Answer 5

USA producing 85 billion litres of milk

UK is 10th producing about 15 billion litres of milk

Question 6

What is the chemical composition of milk?

Answer 6

87. 3% water
88. 9% fat
89. 8% solids (not fat) - protein 3.25%, lactose 4.6%, minerals 0.65%, acids 0.18%, enzymes and vitamins

Question 7

How does cheese composition differ from that of milk?

Answer 7

More saturated fat

Question 8

How does yogurt composition differ from milk?

Answer 8

May contain probiotics

Question 9

What are the current debates around milk consumption and health?

Answer 9

Increases risk of diabetes and prostate cancer vs reduced risk of hypertension and breast cancer
Source of calcium that prevents osteoporosis vs high protein food that increases calcium excretion

Question 10

In which countries in the UK is raw milk sales allowed?

Answer 10

England, Wales and N. Ireland subject to certain restrictions and requirements
Banned in Scotland since 2004

Question 11

What are the requirements for raw milk production?

Answer 11

Do not show any symptoms of infectious diseases communicable to humans through milk
Cows in good general state of health, present no sign of disease that might result in the contamination of milk
Do not have any udder wound likely to affect the milk
No unauthorised products or substances have been administered/withdrawal periods have been observed
Herd is free from TB and brucellosis

Question 12

What are the current controls on the sale of raw cow’s milk in hygiene and food labelling regulations in England and Wales?

Answer 12

May only be sold directly to consumers by registered milk production holdings at the farm gate/in a farmhouse catering operation or through milk roundsmen
Supplying herd must be TB and brucellosis free
Production holding, milking premises and dairy must comply with hygiene rules
Must bear the appropriate health warning

Question 13

How is raw milk production monitored?

Answer 13

Inspections twice a year
Milk is sampled and tested quarterly under the control of the Agency to monitor compliance with standards for total bacteria count and coliforms

Question 14

What is raw milk checked for on arrival at processing plant?

Answer 14

Temperature, total acidity, flavour, odour, tanker cleanliness, absence of ABs, microbiological quality (SCC, APC)

Question 15

How is milk processed?

Answer 15

Filtration (removal of large particles and FBs), Clarification (removal of sediment particles), Decreaming (milk fat removed), Standardisation (milk contents adjusted to standards), Heat treatment (pasteurisation/sterilisation), Homogenisation (reduction of size of fat globules), Cooling, Filing and storage

Question 16

Why pasteurise milk?

Answer 16

Ensure safety of milk for human consumption by destroying pathogenic bacteria
Improve shelf-life and keep quality by destroying undesirable enzymes and spoilage bacteria

Question 17

How is the extent of micro-organism inactivation varied during pasteurisation? What are the two different types?

Answer 17

Temperature and holding time is altered
LTLT (low temp long time) at 63C for 30 mins
HTST (high temp short time) at 72C for 15 secs (extended to 25secs for UK dairy industry to reduce likelihood of Mycobacterim avium paratuberculosis surviving pasteurisation)

Question 18

What test is used to test the efficiency of pasteurisation? What result of the test is good?

Answer 18

Alkaline phosphatase

If the test is negative then the milk is properly pasteurised

Question 19

How does sterilisation differ from pasteurisation?

Answer 19

Microbiocidal control measure so all micro-organisms are eliminated

Question 20

What is the process of sterilising milk?

Answer 20

Held at 135-150C for 2-5 seconds by either direct mixing of steam with the product or indirect heating by means of heat exchanging surface
Packaged and filled aseptically

Question 21

What are the advantages of UHT (sterilised) milk?

Answer 21

Changes to milk composition are minimum

Long shelf life

Question 22

What are the disadvantages of UHT (sterilised) milk?

Answer 22

Results in a flavour change that deteriorates over time

Sterility has to be maintained

Question 23

How do bacteria get into milk?

Answer 23

Sterile in the udder so contamination occurs during or after milking

Question 24

What are the different categories of bacteria that contaminate milk?

Answer 24

Spoilage
Pathogenic
Desirable for further processing

Question 25

What do spoilage bacteria do to the milk?

Answer 25

Deteriorate the milk’s texture, odour, flavour and colour

Degradation of proteins, carbohydrates and fats

Question 26

Which bacteria are classified as spoilage bacteria?

Answer 26

Pseudomonas spp
Bacillus
Clostridium
Lactobacillus
Micrococcs
Streptococcus

Question 27

Which of the bacteria involved in spoilage survive pasteurisation?

Answer 27

Bacillus
Clostridium
Lactobacillus
Micrococcs
Streptococcus

Question 28

What are the most common pathogenic bacteria?

Answer 28

Bacillus cereus, Listeria monocytogenes, Yersinia enterocolitica, Salmonella spp, E. coli O157, Campylobacter jejuni

Question 29

What are the most common pathogenic moulds in milk?

Answer 29

Aspergillus, Penicillium, Fusarium spp,

Question 30

What are the most frequent causes of milk-related food poisoning in the EU?

Answer 30

Verocytotoxigenic (VTEC) E. coli
Salmonella
Campylobacter

Question 31

Why are desirable micro-organisms important?

Answer 31

Flavour, aroma and alcohol production
Proteolytic and lipolytic activities
Inhibition of undesirable organisms

Question 32

Define cheese production

Answer 32

Traditional way of preserving the nutritional qualities of milk
Result of selectively concentrating the milk

Question 33

How is cheese produced?

Answer 33

Standardisation of milk, sometimes pasteurisation
Addition of started culture and rennet (bacterial fermentation -> lactic acid, Rennet -> coagulation of casein)
Cutting to facilitate the expulsion of whey (bacterial growth -> lactic acid, mechanical treatment, heat treatment)
Ripening (specific requirements if made from unpasteurised milk

Question 34

How is butter made?

Answer 34

Raw material is fresh cream
Salt is added to inhibit bacterial growth and enzyme activity
Started culture aids preservation and promotes flavour
Ripening for 3-4 hours at 3C

Question 35

What is the process of yogurt production?

Answer 35

Clarification, standardisation, pasteurisation, homogenisation
Addition of starter culture (normally Strep thermophilus and Lactobacillus delbrueckii) and fermentation at pH 4.2-4.3
Cooling at 15-25C with addition of fruits and flavours, packaging and storage

Question 36

How is ice cream made?

Answer 36

Mixing of base ingredients, pasteurisation or sterilisation, homogenisation, cooling to 7.2C/1.5hrs, addition of flavouring annd colourants, freezing, addition of fruits, package and hardening