milk quality sdl

Question 1

Write down the main health hazards that you can think of from milk and dairy products – what potential pathogens could be ingested?

Answer 1

bovine tuberculosis (Mycobacterium bovis)

campylobacteriosis (Campylobacter spp.)

listeriosis (Listeria spp.)

zoonotic diphtheria (Corynebacterium ulcerans)

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

What are likely to be consequences of NOT having any form of pre-milking routine?

Answer 6

• Failure to detect clinical mastitis cases – this is very important and if these are missed, will result in:
  o mastitis milk entering the supply (increasing the “Bactoscan”),
  o poor cow welfare (missing painful disease),
  o poor chance of cure (delayed antibiotic treatment)
• Increased bacteria in milk (increased ‘Bactoscan’ or ‘Total Bacterial Count’ – see next section)
• Increased risk of environmental mastitis infections due to inadequate teat disinfection prior to unit attachment
• Bi-phasic milk let-down and inefficient milk harvesting – remember the importance of oxytocin release (LINK ANIMAL HUSBANDRY)
• Increased unit on time and development of teat-end hyperkeratosis (LINK MASTITIS)

Question 7

What would the sites of contamination from scoring dairy cow cleanliness suggest regarding the likely source of contamination?

(legs, tails, flanks, udders)

Answer 7

Question 8

Answer 8

Inadequate teat preparation prior to milking

Question 9

Answer 9

8000

Question 10

Answer 10

140-150

Question 11

Answer 11

14 000 million

Question 12

Answer 12

40%

Question 13

What is ‘High Temperature Short Time’ (HTST) pasteurisation?

Answer 13

HTST pasteurisation was developed from flash pasteurisation and involves heat milk to 71.7ºC for 15 seconds, followed by immediate cooling. This differs from the ‘holding’ method of pasteurisation whereby milk is heated to a lower temperature (around 62 to 66ºC) and ‘held’ there for 30 minutes – this is a common approach if pasteurising colostrum on farm for example.

Question 14

How is the pasteurisation method checked to ensure the correct standard?

Answer 14

The pasteurisation method is checked by testing for alkaline phosphatase (ALP) activity. The pasteurised milk should be ALP negative, as this enzyme is destroyed during the pasteurisation process.

Question 15

What do think the effects of pasteurisation are on the safety of milk…and its nutritional value?

Answer 15

The impact of pasteurisation on nutritional value of milk is of limited, if any, significance. The amount of vitamin C, and some vitamin levels are reduced slightly (thiamine and vitamin B12)

There is a reduced ‘cream line’ due to disaggregation of fat globules

the major significance of pasteurisation is on the milk microbiology

Important pathogens are removed during pasteurisation:
- e.g. Mycobacterium tuberculosis (TB)

However, other pathogens such as Mycobacterium avium paratuberculosis (MAP), the cause of Johnes Disease in cattle that may have a link with Crohn’s Disease in humans, is more of a challenge and there is concern that MAP bacteria could survive the pasteurisation process, although it remains unclear around the risk this may present.

Question 16

What are the key differences between hygiene standards for raw cow’s milk compared to heat-treated milk? What are your thoughts on the risks versus potential benefits of drinking raw milk?

Answer 16

Raw milk:
- the potential health hazards are likely to outweigh the benefits, as the latter are largely based around taste as nutritional effects are minor and other reported beneficial side effects such as reduced risk of asthma are not proven. - Apart from zoonotic infections such as Salmonella spp. and Listeria spp., the main hazard will be TB, particularly if drinking raw milk from herds in endemically affected areas where prevalence in the cattle population is likely to be quite high

Treated milk:
- Hazards with liquid milk that is destined for the processor can be broadly grouped into those relating to the reception and initial storage of the milk, the pasteurisation process, and then the holding and bottling process.

Question 17

Fill in the table with problems/actions that may occur during milk processing

Answer 17