Milk and dairy products Flashcards
What are the 2 ways epithelial cells in the mammary alveoli produce milk?
Synthesis - of milk fat, protein, lactose
Diffusion - of water, minerals, vitamins
What are the 3 types of milk secretion?
Merocrine
Holocrine
Apocrine
What type of milk secretion do cows do?
Merocrine
What type of milk secretion do goats do?
Holocrine and apocrine
What acid is a natural component of milk?
Citric acid
Which milk has a fat level of 0.1-0.3% and has a lower level of fat-soluble vitamins (particularly vitamin A)?
Skimmed milk
What milk is 1.5-1.8% fat?
Semi-skimmed milk
What milk is 3.5-4.5% fat?
Whole milk
What is milk homogenisation?
Forcing milk through small holes at high pressure to break fat globules
(prevents creamy layer)
What bacteria fermentationt milk to produce yoghurt?
Streptococcus
Lactibacillus
(By forming lactic acid)
What can cause an increased (more alkaline) pH of milk?
Stress
Decreased temperature
What can cause a decreased (more acidic) pH of milk?
Fermentation of lactose
Extensive lipolysis
Increasing temperature
How does a decrease in temperature alter milk pH?
Decrease temperature = increased pH
Inverted relationship
What is the average pH of milk?
6.4-6.8
Salt is added to dairy products for flavour and to increase shelf-life. Why does salt allow dairy products to be kept for longer?
Most bacteria prefer higher water activity
Salt decreases water activity
At what temperature does milk legally have to be kept at on the farm if it is collected daily?
<8 degrees C
At what temperature does milk legally have to be kept at on the farm if it is NOT collected daily?
<6 degrees C
At what temperature does milk legally have to be kept during transport?
<10 degrees C
Milk is not required to be kept refrigerated if it is collected within how long after milking?
2 hours
What is SCC and TVC?
Somatic cell count
TVC = total viable count (number of colonies per 1ml)
Why should pregnant woman avoid non-pasteurised dairy products?
TB
Also leptospirosis
Infectious agents may be found in dairy products due to contamination. At what stages in milk production can contamination occur?
During milking, processing or storage
Give examples of contagious mastitis organisms
Staph aureus, coagulase -ve Staphs
Strep dysgalactiae and agalactiae
Corynebacterium bovis
Mycoplasma spp
Give 3 examples of environmental mastitis pathogens
Streptococcus uberis
E. coli
Klebsiella spp
Spoilage organisms can cause hydrolysis of milk. What physical changes may indicate milk spoilage?
Change in odour, texture, appearance, flavour
What does the phosphatase test of milk assess?
Efficiency of pasteurisation
What does peroxidase test of milk assess?
If hydrogen peroxide present in milk
What does Resazurin test of milk assess?
If contaminated
What does the pH and alcohol tests of milk assess?
If spoilage
What is the Delvotest used to assess in milk?
Presence of antibacterial substances
The Delvotest is used to assess presence of antibacterial substances, based on the inhibition of which bacteria?
Bacillus stearaothermophilus var calidolactis
If wanting to check if milk is spoiled, what test should be used?
pH and alcohol tests
If wanting to check if milk is contaminated, what test should be used?
Resazurin
If wanting to check if there are antibacterial substances present in milk, what test should be used?
Delvotest
If wanting to assess the level of pasteurisation of milk, what test should be used?
Phosphatase test
The Delvotest shows what colour for a positive result, and what for negative?
Positive = purple Negative = yellow
Can raw milk be sold in England?
Yes but not Scotland
Requires annual TB testing and other requirements
