Milk and Dairy Products Flashcards
What products are made from raw milk?
- Liquid Milk
- Raw bottled
- Pasteurized
- UHT
- Sterilised - Fermented Milk
- Hard Cheese
- Soft Cheese
- Yogurt
- Buttermilk - Butter
- Cream and milk based desserts
- Fresh
- UHT
- Sterilised - Concentrated milk (Dried)
- Ice cream
What is organic milk?
From cows that have been grazed on pasture that had no chemical fertilisers, pesticides or agrochemicals
What is homogenised milk?
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
What is standardised milk?
Milk with the fat content adjusted to a specified value. Ex. Full fat milk
What are the two ways of milk production by the epithelial cells of alveoli?
Synthesis: milk fat, most of the protein components and lactose
Diffusion: water, minerals and vitamins
What are the 4 major components of milk?
Water
Fat
Protein
Lactose
What are the minor components of milk?
Salts, Citric acid, Enzymes, Vitamins, Gases, Phospholipids, Immunoglobulins
What are some foreign components found in milk?
Antibiotics
Herbicides, Insecticides
Non-original water
Cleaning agents
Disinfection agents/residues
Infectious agents?? and enzymes synthetised by these
Describe the main characteristics of skimmed milk
0.1-0.3% fat
- contains slightly more calcium than whole milk and lower levels of fat soluble vitamins (vitamin A)
Describe the main characteristics of 1% fat milk
Contain 40% less total and saturated fat than semi-skimmed milk
Slightly lower levels of vitamin E and A
Higher calcium
What is the fat % of semi-skimmed milk?
1.5-1.8
What of the fat % of whole milk?
3.5-4.5
What is the pH of milk?
6.4-6.8
What causes the pH of milk products to decrease?
Microorganisms if lactose fermenting
Extensive lipolysis
Increasing temperature
What causes the pH of milk products to increase?
Physiological stress
Decreasing temperature
Name 4 systemic infectious agents found in dairy products
TB
Q-fever
Leptospirosis
Salmonellosis
Describe the legal storage temperatures required for milk
<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
Name 4 contagious mastitis pathogens spread during milking
Staphylococcus aureus
Streptococcus dysgalactiae
Mycoplasma spp
Corynebacterium bovis
Name 3 environmental mastitis pathogens
Streptococcus uberis
E.coli
Klebsiella spp
Name 2 mastitis pathogens seen in the summer months
Hydrotaea irritans
Arcanobacterium pyogenes
What is the main reason pregnant women are told to avoid non pasteurised dairy products?
Listeria spp
Which enforcement authority enforces hygiene on farm?
FSA - dairy hygiene inspector
Which enforcement authority enforces hygiene on dairy plants and retailers?
Local authorities
Raw cow’s milk intended for consumption must what standards?
Plate count (TVC) @ 30 °C: ≤ 100 000cfu/ml
Somatic cell count (SCC): ≤ 400 000 cfu/ml
Raw cow’s milk intended for direct human consumption must what standards?
Plate count (TVC) @ 30 °C: cfu/ml ≤ 20 000
Coliforms: <100cfu/ml
What chemical and physical features of milk are assessed following heat treatment
pH
Viscosity: slowest heating part
Acid & anaerobiosis: spores of Clostridium botulinum
Pasteurisation works against which pathogen?
Coxiella burnetti
Describe the 3 pasteurisation methods
- Low Temperature Long Time - LTLT ”holding method”: 63.5°C for 30 min
- High Temperature Short Time (HTST)>72°C minimum 15 sec (recommended by ACMSF: 25 sec)
- 88°C for 1 sec - Flash pasteurization
Describe the features of sterilisation
- 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
Describe UHT
Small milk pots in shops, hotels, planes, etc
- 135 °C for 1 sec
- Plus appropriate holding time to produce ‘commercial sterility’
- Opaque containers
Name the two tests used to assess pasteurisation
Phosphate test - used to assess if pasteurisation has happened
Peroxidase test - to see if it has been over heated – quality control rather than safety
Describe the main features of evaporated milk
- 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
Describe the main features of condensed milk
- 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.
Describe the main features of filtered milk
Microfiltration, ultrafiltration and nanofiltration
Can extend shelf life up to 45 days when stored @ < 7°C and ~7 days once opened.
Describe lactoferrin and an antimicrobial component of milk
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
Describe lactoperoxidase and an antimicrobial component of milk
Bacteriostatic
70% of activity @ 72o C for 15 s,
Destroyed @>78°C for 15 sec
If not detected:»_space;T in pasteurization - qualitative test
UHT effect = inactivated
Describe lysozyme and an antimicrobial component of milk
Bactericidal mainly against Gram + bacteria;
>75% activity retained @ 80oC for 15 s
UHT effect = inactivated
Describe the resazurin test
Oxidation-reduction indicator in cell viability assays for bacteria and mammalian cells
Indicates contamination
The singlepath test is used for which microbe?
Listeria
Which bacteria are involved in the fermentation of yogurt?
Lactobacillus and Streptoccoccus
Describe butter making
Phase inversion: fat-in-water emulsion (milk) into water-in-fat emulsion
Describe the main features of margarine
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
