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Year 4 Public Health > Milk and Dairy Products > Flashcards

Milk and Dairy Products Flashcards

1
Q
  1. What is organic milk?
  2. What is Jersey and Guernsey milk
  3. What is homogenised milk?
  4. What is standardised milk?
A
  1. Cows that have been grazed on pasture that had no chemical fertilisers, pesticides or agrochemicals
  2. Produced from Jersey or guernsey breeds of cows
  3. Forcing the milk at high pressure through small holes, breaking of fat blobules to spread it evenly and prevent a cream layer
  4. Milk with the fat content adjusted to a specified value- full fat milk
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2
Q

What are animal milk alternatives?

A

Colloidal suspensions or emulsions by milling:
* Cereal-based
* Legum based
* Nut-based
* Pseudocereals

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3
Q

What are natural and foreign components of milk?

A

Natural
* Major- water, fat, protein, lactose
* Minor- salts, citric acid, enzymes, vitamins, gases, phospholipids, immunoglobulins

Foreign
* Antibiotics
* Herbicides
* Insecticides
* Non-original water
* Cleaning agents
* Disinfection

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4
Q

Which milk contains higher calcium and lower levels of fat soluble vitamins?

A

Skimmed milk

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5
Q

What pH range do the following products have?
1. Milk
2. Butter
3. Cheese

A
  1. Milk- 6.4-6.8
  2. Butter 6.1-6.4
  3. Cheese 4.8-7.4
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6
Q

What can cause a decrease or increase in pH?

A

Decrease
* Microorganisms if lactose fermenting
* Extensive lipolysis
* Increasing temperature
Increase
* Physiological stress
* Decreasing temperature

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7
Q

What is the water activity of the following?
1. Whole milk
2. Bacteria
3. Yeast
4. Moulds

A
  1. > 0.9
  2. > 0.9-0.91
  3. > 0.87-0.94
  4. > 0.7-0.8
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8
Q

What are the most important pathogens potentially found in milk, their contamination source and whether they can frow in the bulk tank

A
  • Campylobacter jejuni- environment (faeces)- no
  • Listeria monocytogenes- environment (feeds, faeces)- yes
  • Mycobacterium paratuberculosis- environment- no
  • Salmonella- environment- yes
  • Staphylococcus- interior or teats- yes
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9
Q

What are the most common spoilage organisms in milk, their contamination source, and whether it can grow in the bulk milk tank

What else can be a spoilage source of milk?

A
  • Bacillus sporothermodurans- environment (feeds to faeces)- no
  • Butyric acid bacteria- environment- no
  • Pseudomonas- environment/milking equip- yes
  • Streptococcus thermophilus- environment- yes

Chemical- oxidation of fat

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10
Q

What pathogens potentially found in milk can exitibit a dual role of spoilage and pathogenic?

A
  • Bacillus cereus (spores)- environment/milking equip- can grow in bulk tank
  • E. coli- environment- yes
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11
Q
  1. What systemic infectious agents can be found in milk?
  2. What contagious mastitis pathogens can be found in milk?
  3. What environmental mastitis pathogens can be found in milk?
A
  1. TB, Q-fever, Leptospirosis, Salmonellosis
  2. Staph aureus, strep dysgalac/agalac, mycoplasma, corynebacterium bovis
  3. Strep uberis, E colie, Klebsiella

Arcanobacterium pyogenes- summer mastitis

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12
Q

What can allow the increase of infectious agents in dairy products?

A
  • Milk with high load of bacteria
  • Contamination of product
  • Inadequate storage temperatures
  • Inefficient/deficienct treatments
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13
Q

What should the storage temperature of milk be on farm?

A
  • <8 degrees if collected daily
  • <6 degrees if not daily
  • During transport <10 degrees
  • No refrigeration if collection within 2 hours of milking
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14
Q

Why should pregnant women avoid soft cheeses?

A

Listeria sp

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15
Q
  1. Who enforces milk nationally and locally?
  2. Who checks milk residues
  3. Who is responsbile for eradication programs?
A
  1. FSA- nationally, Local- EHOs
  2. VMD- residues
  3. APHA- eradication programs
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16
Q

What standards do the following types of milk need to meet?
1. Raw intended for consumption
2. Raw milk intended for direct consumption
3. At manufacture of dairy products before processing

A
  1. Plate count <100,000, SCC < 400,000
  2. Plate count <20,000, Coliforms <100
  3. Raw- plate count <300,000, processed <100,000
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17
Q
  1. What is required to sell raw milk from a cow?
  2. What is required to sell raw milk from sheep, goats and buffaloes?
  3. What do both require?
A

Cow
* Herd tuberculosis free
* Health warning
* Inspections twice a year
* Samples and tested quarterly for TVC and coliforms

Sheep goats and buffaloes
* buffalo officially tuberculosis free
* health warning
* Inspections programmed on risk basis

Both
* May only be sold by registered milk production holdings
* Herd brucellosis free or officially brucellosis free
* Comply with hyigene rules
* Health warning

18
Q

Where is raw milk sale banned?

A

Northern Ireland and Scotland

19
Q

What is considered when deciding on a heat treatment?

A

Objective
* Intended shelf life
* To be refrigerated

Later step to reduce hazard
Physical and chemical feature of final product
* pH
* Viscosity
* Acid and anaerobiosis

20
Q

What is the D and Z value of the thermal death curve?

A

D value: heat resistance of organism- time @ given temperature required to reduce population by 1 log

Z value: temperature change required to alter D value by factor of 10

21
Q

What are the different techniques of pasturisation?

A

Low temp long time
* 63.5 degrees for 30 mins

High temperature short time
* >72 minimum of 15 seconds

Flash pasturisation
* 88 degrees for 1 second

22
Q

How is milk ‘sterilised’?

A
  • No legally defined process
  • Efficient against most heat resistant spores
  • Pre-heated to 50 degrees followed by homogenisation
  • FIlled air tight bottles through steam chamber 110-130 degrees for 10-30 minutes
  • Keeps for 6 months without refrigeration- sweeter taste
23
Q

How is UHT milk treated?

A

> 135 degrees for 1 second
* Plus appropriate holding time to produce ‘commercial sterility;
* Opaque containers

24
Q

How is evaporated and condensed milk produced?

A

Evaporated
* Standardising, heat treatment and evaporating the milk under reduced pressure 60-65 degrees
* Homogenised to prevent seprating under storage
* Poured into cans and moved to a steriliser for 10 minutes
* Keeps 1 year without refrigeration

Condensed milk
* Standardised milk 110-115 degrees for 1-2 mins
* Milk homogenised, sugar added and evaporated 55-60 degrees
* Not sterilised, preserved by high surgar content
* Conc upto 3 times of original milk

25
Q

What are the different processes of filtered and dried milk?

A

Filtered
* microfiltration, ultrafiltration and nanofiltration
* Can extend shelf life and can last 1 week when opened

Dried milk
* Spray drying- concentrated milk into a hot air chamber- droplets lose their water and fall to floor as fine powder
* Roller drying- concnetrated milk onto heated rollers, thin film of powder, scraped off

26
Q
  1. What are the antimicrobial properties lactoferrin?
  2. What is the activity following pastuization
  3. What is the activity following UHT?
A
  1. Iron binding protein; deprives Fe, Mg and Ca needed for microbial growth and survival
  2. Similar
  3. Denatured
27
Q
  1. What effect on bacteria does lactoperoxidase have?
  2. What properties does it have after pasturization
  3. What effect does it have after UHT
  4. Why can it be used to qualitate pasturization?
A
  1. Bacteriostatic
  2. 70% activity if not flash pasturised
  3. Inactivated
  4. If not detected temp must have been >78 for 15 seconds
28
Q
  1. What are the antimicrobial properties of lysozyme?
  2. What effect does pasturization have?
  3. What effect does UHT have?
A
  1. Bactericidal mainly against gram + bacteria
  2. > 75% activity retained at 80 degrees for 15 seconds
  3. Inactivated
29
Q
  1. What are the antimicrobial properties of xanthine oxidase?
  2. What activity does it retain after pastrization?
  3. What is the UHT effect?
A
  1. Supplies lactoperoxidase with hydrogen peroxide
  2. Retains activity at 73 degrees for 7 min or 80 for 50 seconds
  3. Inactivated
30
Q
  1. What are the function of bovine immunoglobulins
  2. What is the effect of pasturization
  3. What happens after UHT?
A
  1. Transfers immunity against pathogens to calves
  2. Retains full at 62.7 for 30 min, 59-76^ after HTST
  3. Denatures
31
Q

What are the different Immunoglobulins in cows milk and what are there functions?

A
  • IgG2 most important
  • IgM fixates the complement for opsonisation of pathogens, agglutinates, neutralises toxin
  • IgA agglutination of bacteria and neutralize toxins
  • IgG1 opsonisation of bacteria
32
Q
  1. What are the antimicrobial properties of Nisin and Bacteriocins?
  2. What is there activity after pasturization?
  3. How does UHT affect it?
A
  1. Antimicrobial peptides
  2. Heat stable and retain activity after pasturization
  3. Variable
33
Q
  1. How are oligosaccharides, lipid fragments and protein fragments affected by pasturization and UHT?
  2. What are the anitomicrobial properties of oligosaccharides and lipid fragments?
A
  1. Oligosaccharides- heat stable, lipid fragments/protein- most likely no effect. UHT- no effect
  2. Oligosaccharides- bind to pathogens to prevent adhesion of pathogens to intestinal epithelium
    Lipid- particularly gram + some antiviral activity
34
Q
  1. What is the purpose of the resazurin test?
  2. What is the purpose of a pH and alcohol test?
A
  1. Oxidation-reduction indicator in cell viability assays for bacteria and mammalian cells- indicates contamination
  2. Fermentation leats to alcohol and lactic acid
35
Q

What happens when milk is heated above 85 degrees in cheese processing?

A
  • K-casein reacts with Beta lacto-globulin
  • Micelle becomes coarser and open spongy gel that absorbs liquid
  • Negatively charged K-casein taile sticking out prevents clumping
  • Fat incorpotated into mesh
  • Separation from the water soluble substances (whey)
36
Q
  1. What causes sour or sweet curd formation of cheese?
  2. How is curd processed?
  3. How is cheese ripened?
A
  1. Sour curd- fermentative bacteria (can add acid), Sweet- addition of rennin- 30/40 degrees
  2. Salted, coloured, secondary bacteria, condensing/squeezing
  3. Determines final texture and aroma- hard ripened/soft ripened
37
Q

What is the difference between soft and hard ripened cheese?
Name examples of both

A

Hard- cheddar
* further compression and wrapped in wax/plastic
* Prevent contamination, loss of moisture
* Incubated for bacteria

Soft- camebert
* A microbe on surface
* protein-digesting enzyme: creamier

38
Q
  1. What is cream?
  2. What is yoghurt?
A

Cream is the separation of fat later in milk
* Min 10% fat
* Single cream 18% fat
* Whipping 40% fat
* Double 48% fat

Yoghurt
* Fermentation of milk by lactic acid forming bacteria
* Lactobacillus and streptococcus

39
Q

What is butter and margarine?

A

Phase inversion: fat in water emulsion
Churning:
* ruptures fat membranes
* join and form network with air bubbles
* trapping of liquid
* clumps increase in size
* foam leaks- buttermilk

Margarine
* Hydrogenation of animal or vegetable oils

40
Q

What are the hazards to public health of cheese production?

A
  • Sterility of raw product
  • Hygiene during processing
  • Heat treatment

Year 4 Public Health (13 decks)

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