PH23-23: Milk Hygiene Flashcards
Define spoilage.
Deterioration in foodstuff
Psychrotrophic organisms
Usually destroyed by pasteurisation
What are the potential pathogenic micro-organisms in milk?
- TB
- Brucellosis
- Typhoid fever
- Bacillus cereus
- Listeriosis
- Yersinia
- Salmonella
- E. coli
- Campylobacter
Define Pasteurisation
The heating of every particle of milk (or milk product) to a specific temperature for a specified period of time, without allowing recontamination of that milk or milk product during the heat treatment process
What is the temp and time for vat pasteurisation? High temperature short time?
Vat: 63C for not less than 30 min
HTST: 72C for not less than 15 sec
Describe the batch method (vat pasteurisation).
The batch method uses a vat pasteurizer, which consists of a jacketed vat surrounded by either circulating water, steam or heating coils of water or steam. In the vat, the milk is heated and held throughout the holding period while being agitated.
Describe the continuous method (HTST).
Cold raw milk at 4C is drawn into the pasteurizer, where it is warmed to approx 60C by heat given up by host pasteurized milk flowing in a countercurrent direction on the opposite side of the heat exchanger. The raw milk is then forced through the heater section, where hot water on opposite sides of the plates heats the milk to a temp of at least 72C. The milk then passes onto the holding section, where it is kept at 72C for at least 16 sec.
What are the methods for checking milk following pasteurisation?
- Containing the enzyme alkaline phosphatase is bad
- Plate counts and coliform numbers
- Extraneous water in the milk
- Chemical composition
- Taints
- Bitty cream
Pasteurized milk must be phosphatase negative, peroxidase positive, with a low plate count test and low coliform test
At what temp must milk be kept refrigerated?
4C
What criteria are the basis of payment of milk prdoucers?
Milk quality
Hygienic quality
Pattern of supply
Volume per collection
What is Ultra High Temperature sterilisation of milk?
Complete elimination of all micro-organisms
Use of temps over 135C for 2-5 seconds
What are the advantages and disadvantages of UHT treatment?
Advantages
- High quality
- Long shelf life
- Packaging size
- Cheaper packaging
Disadvantages
- Sterility - complex equipment
- Keeping quality - heat resistant enzymes
- Cooking of milk - abnormal flavours
What is milk composed of?
What is the benefit of using start cultures for cheese and yoghurt?
Natural micro-organisms destroyed in pasteurisation
Efficient
Controllable
Predictable
Improve flavour and aroma
Inhibit undesirable organisms
What are the reasons for antibiotic test failures?
Human error
- Incorrect milk withholding time
- Incorrect cow ID
Equipment fault
- Mechanical failure
- Contamination of equipment
Off-label use of antimicrobial products
- Change of duration of treatment
- Change of frequency of administration
- Change of dose
