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Flashcards in Milk and Dairy Production Deck (37):

Define milk

Normal mammary secretion of milking animals obtained from one or more milking without either addition to it or extraction from it, intended for consumption as liquid milk or for further processing


What is raw milk?

Milk which has not been heated beyond 40C or undergone any treatment that has an equivalent effect


What is a milk product?

A product obtained by any processing of milk, which may contain food additives, and other ingredients functionally necessary for the processing


How has milk consumption changed in recent years in the UK?

Liquid milk consumption has decreased but yogurt consumption has increased


How will milk consumption change globally in the next few years?

Will be affected by major market trends such as those in the Asian market which is rapidly increasing
Rapid growth of the global population over 65 will define consumption habits of dairy products


Who is the largest milk producer in the world? How much do they produce? Where is the UK in terms of production?

USA producing 85 billion litres of milk
UK is 10th producing about 15 billion litres of milk


What is the chemical composition of milk?

87.3% water
3.9% fat
8.8% solids (not fat) - protein 3.25%, lactose 4.6%, minerals 0.65%, acids 0.18%, enzymes and vitamins


How does cheese composition differ from that of milk?

More saturated fat


How does yogurt composition differ from milk?

May contain probiotics


What are the current debates around milk consumption and health?

Increases risk of diabetes and prostate cancer vs reduced risk of hypertension and breast cancer
Source of calcium that prevents osteoporosis vs high protein food that increases calcium excretion


In which countries in the UK is raw milk sales allowed?

England, Wales and N. Ireland subject to certain restrictions and requirements
Banned in Scotland since 2004


What are the requirements for raw milk production?

Do not show any symptoms of infectious diseases communicable to humans through milk
Cows in good general state of health, present no sign of disease that might result in the contamination of milk
Do not have any udder wound likely to affect the milk
No unauthorised products or substances have been administered/withdrawal periods have been observed
Herd is free from TB and brucellosis


What are the current controls on the sale of raw cow's milk in hygiene and food labelling regulations in England and Wales?

May only be sold directly to consumers by registered milk production holdings at the farm gate/in a farmhouse catering operation or through milk roundsmen
Supplying herd must be TB and brucellosis free
Production holding, milking premises and dairy must comply with hygiene rules
Must bear the appropriate health warning


How is raw milk production monitored?

Inspections twice a year
Milk is sampled and tested quarterly under the control of the Agency to monitor compliance with standards for total bacteria count and coliforms


What is raw milk checked for on arrival at processing plant?

Temperature, total acidity, flavour, odour, tanker cleanliness, absence of ABs, microbiological quality (SCC, APC)


How is milk processed?

Filtration (removal of large particles and FBs), Clarification (removal of sediment particles), Decreaming (milk fat removed), Standardisation (milk contents adjusted to standards), Heat treatment (pasteurisation/sterilisation), Homogenisation (reduction of size of fat globules), Cooling, Filing and storage


Why pasteurise milk?

Ensure safety of milk for human consumption by destroying pathogenic bacteria
Improve shelf-life and keep quality by destroying undesirable enzymes and spoilage bacteria


How is the extent of micro-organism inactivation varied during pasteurisation? What are the two different types?

Temperature and holding time is altered
LTLT (low temp long time) at 63C for 30 mins
HTST (high temp short time) at 72C for 15 secs (extended to 25secs for UK dairy industry to reduce likelihood of Mycobacterim avium paratuberculosis surviving pasteurisation)


What test is used to test the efficiency of pasteurisation? What result of the test is good?

Alkaline phosphatase
If the test is negative then the milk is properly pasteurised


How does sterilisation differ from pasteurisation?

Microbiocidal control measure so all micro-organisms are eliminated


What is the process of sterilising milk?

Held at 135-150C for 2-5 seconds by either direct mixing of steam with the product or indirect heating by means of heat exchanging surface
Packaged and filled aseptically


What are the advantages of UHT (sterilised) milk?

Changes to milk composition are minimum
Long shelf life


What are the disadvantages of UHT (sterilised) milk?

Results in a flavour change that deteriorates over time
Sterility has to be maintained


How do bacteria get into milk?

Sterile in the udder so contamination occurs during or after milking


What are the different categories of bacteria that contaminate milk?

Desirable for further processing


What do spoilage bacteria do to the milk?

Deteriorate the milk's texture, odour, flavour and colour
Degradation of proteins, carbohydrates and fats


Which bacteria are classified as spoilage bacteria?

Pseudomonas spp


Which of the bacteria involved in spoilage survive pasteurisation?



What are the most common pathogenic bacteria?

Bacillus cereus, Listeria monocytogenes, Yersinia enterocolitica, Salmonella spp, E. coli O157, Campylobacter jejuni


What are the most common pathogenic moulds in milk?

Aspergillus, Penicillium, Fusarium spp,


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

Verocytotoxigenic (VTEC) E. coli


Why are desirable micro-organisms important?

Flavour, aroma and alcohol production
Proteolytic and lipolytic activities
Inhibition of undesirable organisms


Define cheese production

Traditional way of preserving the nutritional qualities of milk
Result of selectively concentrating the milk


How is cheese produced?

Standardisation of milk, sometimes pasteurisation
Addition of started culture and rennet (bacterial fermentation -> lactic acid, Rennet -> coagulation of casein)
Cutting to facilitate the expulsion of whey (bacterial growth -> lactic acid, mechanical treatment, heat treatment)
Ripening (specific requirements if made from unpasteurised milk


How is butter made?

Raw material is fresh cream
Salt is added to inhibit bacterial growth and enzyme activity
Started culture aids preservation and promotes flavour
Ripening for 3-4 hours at 3C


What is the process of yogurt production?

Clarification, standardisation, pasteurisation, homogenisation
Addition of starter culture (normally Strep thermophilus and Lactobacillus delbrueckii) and fermentation at pH 4.2-4.3
Cooling at 15-25C with addition of fruits and flavours, packaging and storage


How is ice cream made?

Mixing of base ingredients, pasteurisation or sterilisation, homogenisation, cooling to 7.2C/1.5hrs, addition of flavouring annd colourants, freezing, addition of fruits, package and hardening