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PMVPH (round 2) > Milk and dairy production > Flashcards

Flashcards in Milk and dairy production Deck (50):

Define milk

normal mammary secretion of milking animals obtained form one or more milking WITHOUT ADDITION OR EXTRACTION from it, intended for consumption as liquid milk or for further processing (Codex Alimentarius)


Desribe the global reference for food standards

Global reference for for food standards, jointly established in the 60s by WHO and the FAO of the UN. It has contributed to international harmonisation of food standards and as a result to the trade in safe foods of a define quality


Define raw milk

milk which has not been heated beyond 40 degrees or undergone any tx that has an equivalent effect


Define milk product

product obtained by any processing of milk, which may contain food additives, and other ingredients functionally necessary for processing (Codex Alimentarius)


What will dictate world milk consumpton?

Asian markets: by 2050 will be 55% of world population. Dynamic economies, consumption rising.


Why did UK milk production increase by 5.3% compared to previous milk year?

probably related to farmers expanding their herds in response to high milk prices in 2013 and early 2014


What are the biggest world milk producers?

1. USA
2. China
3. India
10. UK


Outline chemical composition of milk

WATER: 87.3%
Whole milk = 3.5%
Semi-skimmed = 1.5%
Skimmed = 0.1-0.3%
SOLIDS (NOT FAT) 8.8% proteins, lactose, minerals, acids, enzymes, vitamins


Outline relationship between dairy consumption and disease

- Increases risk of dz (diabetes, prostate cancer)
- reduces risk of disease (hypertension, breast cancer)
- source of Ca that prevents osteoporosis but as a high protein food increases calcium excretion
* balance important


Outline the UK milk production chain

JUNE 2014:
- 13,815 dairy farms
- av 133 cows/herd
- av. 7,916 l/cow/annum
- milk market of approximately 13.6 billion litres (2013) of which milk for liquid consumption accounted for 6.9 billion litres


T/F: vast majority of milk from dairy farms is delivered to dairies



Outline sale of raw milk and cream in the UK

Allowed in England, Wales and NI but subject to restrictions and requirements. In Scotland, sales of raw milk and cream banned since 2004.


What is the risk of outbreak from raw milk consumption versus pasteurised milk consumption?

150 times greater for raw milk vs. pasteurised milk.


T/F: probably



Primary requirements for raw milk production

- no symptoms of dz communicable to humans through milk
- good general state of health, present no sign of dz that can contaminate milk
- no udder wound likely to affect milk
- no unauthorised substances administered
- withdrawal periods observed
- officially free of brucellosis and bTB


Describe current controls on sale of raw cows' drinking milk hygiene and food labellling - England and Wales

- milk may only be sold direct to consumers by registered milk production holdings or through milk roundsmen
- officially TB free and either brucellosis free or officially brucellosis free
- must comply with hygiene rules
- must bear appropriate health warnings
- compliance monitored by inspections twice a year
- milk is sampled and tested quarterly under the control of the agency to monitor compliance with standards for total bacterial count and coliforms


What can contaminate milk at the pre-harvest level?

- E.coli 0157
- Campylobacter spp
- Listeria monocytogenes
- Salmonella spp
- Yersinia enterocolitica


What is the FSA conclusion on sale of raw milk?

- risk of raw drinking milk consumption, except for vulnerable groups, is acceptable when appropriate hygiene controls are applied- current restriction on sales of raw milk should remain in place as there is uncertainty that consumer protection can be maintained if the market for raw milk is expanded
- risk communication could be improved, particularly fr vulnerable groups, and changes to labelling requirements are proposed to reflect this


Outline inspection of dairy farms for raw milk

- different frequencies in farms across UK
- additional checks are carried out on farms that are members of the Assured Dairy Farmer Scheme
- FSA inspection Autumn 2014 found 25% farms had non-compliances with hygiene standards.


Outline processing of raw milk on arrival at the milk plant

- temperature
- total acidity
- flavour
- odour
- tanker cleanliness
- absence of ABs
- microbiological quality (SCC, aerobic plate count = APC)
- butterfat content and solids-not-fat analysed


How fast does milk need to be processed once arrived on plant?

within 72 hours of receipt


What are the different stages of milk processing?

- FILTRATION: removal of lare particles and FB
- CLARIFICATION: removal of sediment particles
- DECREAMING: milk fat partially or totally reduced through centrifugation
- STANDARDISATION: milk contents adjusted to standards
- HEAT TREATMENT: pasteurisation or sterilisation
- HOMOGENISATION: reduction of size of fat globules


Aim - pastuerisation

- ensure milk safety for human consumption by destroying pathogenic bacteria
- improve shelf life and keep quality by destroying undesirable enzymes and spoilage bacteria


Outline process of pasteurisation

2 different types:
1.) LTLT (low temperature low time) - batch - 63 degrees/30 mins
2.) HTST (high temperature short time) - continuous - 72 degrees/ 15 seconds. recently been extended to 25 seconds by the UK dairy industry to reduce the likelihood of MAP surviving pasteurisation.
- extent of microorganism inactivation = f (temperature, holding time)
- compositional changes occur but are minimal
- taste of pasteurised milk more similar to raw milk than sterilised milk


What is used to test efficiency of pastuerisation?

- alkaline phosphatase test
- milk properly pasteurised is alklaline phosphatase negative


Describe sterilisation of milk

- microbiocidal control measure (complete elimination of microorganisms)
- UHT is 135-150 degrees for 2-5 seconds


Describe UHT method

- UHT is 135-150 degrees for 2-5 seconds
- direct mixing of steam with product
- indirect heating by means of heat exchanging surface
- aseptic packaging


Advantages/ disadvantages of UHT Milk

- changes to milk composition minimal, although certain reduction in vitamin content
- UHT results in change in flavour (flavour of pasteurised milk more similar to that of fresh milk than UHT) and flavour deteriorates over time
- sterility has to be maintained (requires aseptic packaging)
- long shelf life (> 6 months without refrigeration), cheaper storage and transportation


T/F: milk is virtually sterile when synthesised in mammary gland of healthy cow



What types of bacteria are involved in milk contamination?

- spoilage
- pathogenic
- desirable for further processing


Describe spoilage microorganisms and give examples

- deteriorates milk texture, odour, flavour, colour
- degradation of proteins, carbohydrates and fats
- mainly psychotrophic bacteria: Pseudomonas spp, Bacillus, Clostridium, Lactobacillus, micrococcus, streptococcus (all bar Pseudomonas can surviva pasteurisation)


Where is highest risk of pathogenic microorganisms?

- raw milk
- failure in technolgical process (e.g. failure of heat tx) or post-processing contamination


Examples - pathogenic milk microorganisms

- Bacillus cereus
- Listeria monocytogenes
- Yersinia enterocolitica
- Salmonella spp
- E. coli 0157
- Campylobacter jejuni
- MOULDS: aspergillus, penicillium, fusarium spp (mainly as a result of contamination during processing - produce toxins that pose a risk to human health)


What ar ethe most frequent causes of milk-related food poisoning in the EU?

- verocytotoxigenic (VTEC) E. coli
- Salmonella
- Campylobacter


Why are desirable microorganisms used?

- flavour, aroma, alcohol production
- proteolytic and lipolytic activities
- inhibition of undersirable organisms


What is the result of selectively concentrating milk?

cheese production


Outline cheese production

- standardisation of milk = pasteurisation (not always)
- addition of a starter culture and rennet: bacterial fermentation --> lactic acid. Rennet --> coagulation of casein (protein). The combination of lactic acid and casein coagulation --> coagulum (curd).
- Cutting: to facilitate the expulsion of wey. Bacterial growth --> lactic acid. Mechanical tx. Heat tx.
- Ripening (specific requirements if made from unpasteurised milk)


Examples of hazards associated with cheese production



Outline butter production

- av 8.2% fat
- raw material: fresh cream
- add salt: inhibit bacterial growth, enzyme activity
- starter culture: aid preservation, promote flavour
- ripening 3-4h, 3 degrees, followed by churning


Outline hazards associated with butter production



Outline yoghurt production

- clarification, standardisation (desired fat and milk solids-not-fat content), pasteurisation, homogenistion
- addition of starter culture and fermentation (pH 4.2-4.3_
- normally: Streptococcus thermophilus and Lactobacillus delbrueckii
- Other bacteria: Bifidobacterium spp
- Cooling (15-25 degrees), addition of fruits or flavours, packaging and storage


Outline hazards associated with yoghurt production



Describe ice cream production

- Cream (rich in fat) separated from milk
- mixing of base ingredients
- pasteurisation or sterilisation
- homogenisation
- cooling to 7.2 degrees/ 1.5 h
- addition of flavouring and colorants
- freezing
- addition of fruits
- package and hardening


What are the 3 groups of possible hazards at any stage in the food cahin

- chemical
- biological
- physical


Possible sources of contamination at any stage of the production chain - examples

- PRIMARY production: Campylobacter, E. coli in raw milk
- PROCESSING environment: Listeria in environment in cheese plants
- EQUIPMENT/ PEOPLE HANDLING: personnel carreirs of S.aureus
- INGREDIENTS: fruit concentrates in yoghurt
- TRANSPORT: ice cream premix contaminated in truck
- PACKAGING MATERIAL: migration of chemical substances


What is infant botulism?

ingestion of spores by very young
babies, the spores germinate and the bacteria
colonizes the large intestine and produces the toxin. --> honey not suitable for babies (honey can be contaminated by C.botulinum spores)


Is GB free of brucellosis?

Yes - officially brucellosis free (OBF) from 1985
- several reintroductions have occurred since
- decision to suspend/revoke OBF status following outbreak is at discretion of European Commission
- GB's OBF status has been retained however some 3rd countries have sought additional guarantees in respect of trade


Human brucellosis - CS

- weakness associated with fatigue
- undulant (intermittent) fever
- chills
- heavy night sweats
- headaches, body aches
- joint swelling
- other: depression, insomnia, irritability, forgetfulness, other
- COMPLICATIONS: pneumonia, bacterial meningitis, abscesses, arthritis


What are the 3 types of cheese?

- rennet/natural cheese
- fresh cheese/non-ripened cheese
- long-life (processed) cheese


List the stages of outbreak investigation

- ID cases, collect data, describe outbreak
- develop hypothesis, test
- implement control/ prevention methods
- communicate findings