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Y4 - Public Health > Milk and Dairy Products > Flashcards

Milk and Dairy Products Flashcards

1
Q

What products are made from raw milk?

A
  1. Liquid Milk
    - Raw bottled
    - Pasteurized
    - UHT
    - Sterilised
  2. Fermented Milk
    - Hard Cheese
    - Soft Cheese
    - Yogurt
    - Buttermilk
  3. Butter
  4. Cream and milk based desserts
    - Fresh
    - UHT
    - Sterilised
  5. Concentrated milk (Dried)
  6. Ice cream
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2
Q

What is organic milk?

A

From cows that have been grazed on pasture that had no chemical fertilisers, pesticides or agrochemicals

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3
Q

What is homogenised milk?

A

Forcing the milk at high pressure through small holes, breaking of fat globules to spread it evenly and prevent a creamy layer.
Most frequently available

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4
Q

What is standardised milk?

A

Milk with the fat content adjusted to a specified value. Ex. Full fat milk

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5
Q

What are the two ways of milk production by the epithelial cells of alveoli?

A

Synthesis: milk fat, most of the protein components and lactose
Diffusion: water, minerals and vitamins

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6
Q

What are the 4 major components of milk?

A

Water
Fat
Protein
Lactose

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7
Q

What are the minor components of milk?

A

Salts, Citric acid, Enzymes, Vitamins, Gases, Phospholipids, Immunoglobulins

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8
Q

What are some foreign components found in milk?

A

Antibiotics
Herbicides, Insecticides
Non-original water
Cleaning agents
Disinfection agents/residues
Infectious agents?? and enzymes synthetised by these

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9
Q

Describe the main characteristics of skimmed milk

A

0.1-0.3% fat
- contains slightly more calcium than whole milk and lower levels of fat soluble vitamins (vitamin A)

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10
Q

Describe the main characteristics of 1% fat milk

A

Contain 40% less total and saturated fat than semi-skimmed milk
Slightly lower levels of vitamin E and A
Higher calcium

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11
Q

What is the fat % of semi-skimmed milk?

A

1.5-1.8

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12
Q

What of the fat % of whole milk?

A

3.5-4.5

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13
Q

What is the pH of milk?

A

6.4-6.8

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14
Q

What causes the pH of milk products to decrease?

A

Microorganisms if lactose fermenting
Extensive lipolysis
Increasing temperature

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15
Q

What causes the pH of milk products to increase?

A

Physiological stress
Decreasing temperature

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16
Q

Name 4 systemic infectious agents found in dairy products

A

TB
Q-fever
Leptospirosis
Salmonellosis

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17
Q

Describe the legal storage temperatures required for milk

A

<8°C if collected daily
<6°C if not daily collection
During transport- <10°C
No refrigeration if collection within 2 hrs of milking
At home ideally: 3C to 5 C

18
Q

Name 4 contagious mastitis pathogens spread during milking

A

Staphylococcus aureus
Streptococcus dysgalactiae
Mycoplasma spp
Corynebacterium bovis

19
Q

Name 3 environmental mastitis pathogens

A

Streptococcus uberis
E.coli
Klebsiella spp

20
Q

Name 2 mastitis pathogens seen in the summer months

A

Hydrotaea irritans
Arcanobacterium pyogenes

21
Q

What is the main reason pregnant women are told to avoid non pasteurised dairy products?

A

Listeria spp

22
Q

Which enforcement authority enforces hygiene on farm?

A

FSA - dairy hygiene inspector

23
Q

Which enforcement authority enforces hygiene on dairy plants and retailers?

A

Local authorities

24
Q

Raw cow’s milk intended for consumption must what standards?

A

Plate count (TVC) @ 30 °C: ≤ 100 000cfu/ml
Somatic cell count (SCC): ≤ 400 000 cfu/ml

25
Q

Raw cow’s milk intended for direct human consumption must what standards?

A

Plate count (TVC) @ 30 °C: cfu/ml ≤ 20 000
Coliforms: <100cfu/ml

26
Q

What chemical and physical features of milk are assessed following heat treatment

A

pH
Viscosity: slowest heating part
Acid & anaerobiosis: spores of Clostridium botulinum

27
Q

Pasteurisation works against which pathogen?

A

Coxiella burnetti

28
Q

Describe the 3 pasteurisation methods

A
  1. Low Temperature Long Time - LTLT ”holding method”: 63.5°C for 30 min
  2. High Temperature Short Time (HTST)>72°C minimum 15 sec (recommended by ACMSF: 25 sec)
  3. 88°C for 1 sec - Flash pasteurization
29
Q

Describe the features of sterilisation

A
  • No legally defined process
  • Efficient against most heat resistant spores
  • Pre-heated ~ 50oC followed by homogenisation
  • Filled airtight bottles through steam chamber at 110-130ºC for 10-30 minutes.
  • Keeps for ~ 6 months without refrigeration. If opened ~ 5 days
  • Sweeter taste
30
Q

Describe UHT

A

Small milk pots in shops, hotels, planes, etc
- 135 °C for 1 sec
- Plus appropriate holding time to produce ‘commercial sterility’
- Opaque containers

31
Q

Name the two tests used to assess pasteurisation

A

Phosphate test - used to assess if pasteurisation has happened
Peroxidase test - to see if it has been over heated – quality control rather than safety

32
Q

Describe the main features of evaporated milk

A
  • Standardising, heat treatment and evaporating the milk under reduced pressure (60°C - 65°C)
  • Homogenised to prevent it separating under storage
  • Poured into cans and moved to a steriliser for 10 minutes
  • Keep ~ 1 year without refrigeration
33
Q

Describe the main features of condensed milk

A
  • Standardised milk @ 110-115°C for 1-2 min
  • Milk homogenised, sugar added and evaporated (55-60ºC).
  • Not sterilised, preserved by the high sugar content
  • Concentration up to 3 times that of the original milk.
34
Q

Describe the main features of filtered milk

A

Microfiltration, ultrafiltration and nanofiltration
Can extend shelf life up to 45 days when stored @ < 7°C and ~7 days once opened.

35
Q

Describe lactoferrin and an antimicrobial component of milk

A

Iron-binding protein; deprives Fe, Mg and Ca needed for microbial growth and survival, having bacteriostatic effects
Similar activity pre and post pasteurization
UHT effect = denatured

36
Q

Describe lactoperoxidase and an antimicrobial component of milk

A

Bacteriostatic
70% of activity @ 72o C for 15 s,
Destroyed @>78°C for 15 sec
If not detected:&raquo_space;T in pasteurization - qualitative test
UHT effect = inactivated

37
Q

Describe lysozyme and an antimicrobial component of milk

A

Bactericidal mainly against Gram + bacteria;
>75% activity retained @ 80oC for 15 s
UHT effect = inactivated

38
Q

Describe the resazurin test

A

Oxidation-reduction indicator in cell viability assays for bacteria and mammalian cells
Indicates contamination

39
Q

The singlepath test is used for which microbe?

A

Listeria

40
Q

Which bacteria are involved in the fermentation of yogurt?

A

Lactobacillus and Streptoccoccus

41
Q

Describe butter making

A

Phase inversion: fat-in-water emulsion (milk) into water-in-fat emulsion

42
Q

Describe the main features of margarine

A

Not a dairy product
Hydrogenation of animal or vegetable oils to give the desired texture
Bubbling hydrogen through the oil at high temperature in the presence of a metal catalyst
Saturation of carbon-carbon bonds in previously unsaturated fats

Y4 - Public Health (12 decks)

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