Milk Quality and Grades

Question 1

What does the growth of microorganisms in the milk depend on?

Answer 1

1. Microbial inhibitors.
2. Moisture availability.
3. Nutritional requirements.
4. Osmotic pressure.
5. Oxygen requirements.
6. pH or acidity.
7. Temperature.

Question 2

What 2 families of bacteria produce lactic acid?

Answer 2

1. Lactobacilleaceae.
2. Streptococcaceae.

Question 3

What are homofermenters?

Answer 3

Bacteria that produce only lactic acid.

Question 4

What are heterofermenters?

Answer 4

Bacteria that produce acetic acid, carbon dioxide, diacyl, ethanol, lactic acid.

Question 5

What 2 genera of microorganisms are probiotic?

Answer 5

1. Bifidobacterium.
2. Lactobacillus.

Question 6

What 3 types of microorganisms are lipolytic and proteolytic?

Answer 6

1. Bacteria.
2. Mold.
3. Yeast.

Question 7

What 4 specific bacteria are classified as enteric bacteria?

Answer 7

1. C. perfringens.
2. E.coli.
3. Salmonellae.
4. Shigellae.

Question 8

What are coliforms?

Answer 8

Bacteria with a fecal origin. Often indicate fecal contamination.

Question 9

What do the presence of coliforms indicate as it pertains to milk?

Answer 9

Low hygienic milking practices.

Question 10

What 2 genera of microorganisms are psychrophilic?

Answer 10

1. Bacillus.
2. Pseudomonas.

Question 11

What 7 microorganisms are associated with foodborne illness?

Answer 11

1. Campylobacter spp.
2. Clostridium botulinum.
3. L. monocytogenes.
4. Mycobacterium avium spp.
5. Paratuberculosis.
6. Salmonella spp.
7. S. aureus.

Question 12

What are somatic cells?

Answer 12

Leukocytes and a small number of epithelial cells present in the milk.

Question 13

What are the 3 types of leukocytes?

Answer 13

1. Lymphocytes.
2. Monocytes.
3. Polymorphonuclear (PMN) cells.

Question 14

What are PMN cells?

Answer 14

1. Basophils.
2. Eosinophils.
3. Neutrophils.

Question 15

When does the proportion of PMN relative to other somatic cells in the milk during mastitis?

Answer 15

It increases.

Question 16

What happens to the SCC overall during mastitis?

Answer 16

Bacterial growth.

Question 17

What 2 enzymes increase in activity as a result of increased SCC activity?

Answer 17

1. Lipase.
2. Protease.

Question 18

What 3 characteristics of milk are influenced by the SCC?

Answer 18

1. Chemical.
2. Organoleptic.
3. Physical.

Question 19

What is the FAO definition of good-quality raw milk?

Answer 19

1. Free of abnormal colors, odor, and off-flavors.
   2.Free of chemicals (antibiotics, detergents).
2. Free of debris and sediment.
3. Low in bacterial count.
4. Normal composition and acidity.

Question 20

How is milk quality tested?

Answer 20

By measuring volume and/or weight.

Question 21

How are the organoleptic characteristics of milk tested?

Answer 21

1. Appearance.
2. Smell.
3. Taste.

Question 22

What are the compositional characteristics of milk?

Answer 22

1. Fat.
2. Protein.
3. Solids (likely non-fat).

Question 23

How is milk hygiene tested?

Answer 23

1. Cleanliness.
2. Hygienic conditions.
3. Quality.

Question 24

What are 3 adulterants that can be placed in milk?

Answer 24

1. Added solids.
2. Preservatives.
3. Water.

Question 25

What is all milk tested for that the dairy industry has zero tolerance for?

Answer 25

Drug/chemical residue.

Question 26

What are the 3 methods used to measure somatic cells/do a SCC?

Answer 26

1. Direct microscopy. 2. Somatic cell counter. 3. California Mastitis Test.

Question 27

What is the downside to using direct microscopy?

Answer 27

It is time consuming. *Was the standard for years.

Question 28

What precisely does the somatic cell counter measure?

Answer 28

Total somatic cells/mL. *Objective method.

Question 29

How is a California Mastitis Test (CMT) conducted?

Answer 29

Milk from each quarter is placed into the corresponding quarter of the paddle, a reagent is added that will rupture the walls of somatic cells and react with the nuclear material to cause a color change and coagulate the milk.

Question 30

What are the 4 microbiological/chemical tests that are used to evaluate milk quality?

Answer 30

1. Differential culture. 2. Molecular techniques. 3. Plate count. 4. Titratable acidity.

Question 31

What is done in a differential culture?

Answer 31

The milk is cultured on a plate that selects for certain kinds of bacteria and against other types. *Likely done after or in conjunction with a plate count.

Question 32

What is done in molecular techniques?

Answer 32

The genetic material of the microorganisms is analyzed.

Question 33

What is done in a plate count?

Answer 33

The milk is cultured and the number of colonies formed is counted. Used for aerobic bacteria.

Question 34

What is done in titratable acidity?

Answer 34

Measures lactic acid produced by bacterial fermentation using an indicator.

Question 35

What are common causes of a high plate count?

Answer 35

1. Dirty milk equipment. 2. Mastitis. 3. Poor cooling. 4. Poor udder prep.

Question 36

What is done in a preliminary incubation count?

Answer 36

Milk samples held at 55 F for 18 hours are plated, allowing bacteria that prefer cooler temperatures to dominate the plate, if they are present. *Monitors cleaning and sanitizing efficiency of milking equipment.

Question 37

How are the 3 ways antibiotics and inhibitors are detected in milk?

Answer 37

1. Culture Geobacillus stearothermophilus with paper disks impregnated with the milk sample and see if a zone of inhibition appears. 2. A snap test. 3. High-performance liquid chromatography (HPLC).

Question 38

What 2 devices are used to detect added water in milk?

Answer 38

1. Cryoscope. 2. Hygrometer.

Question 39

How does the cryoscope detect added water?

Answer 39

By measuring the freezing point of milk.

Question 40

How does the hydrometer detect added water?

Answer 40

Measures the specific gravity/density of milk.

Question 41

What is the other name for Grade "A" Milk?

Answer 41

Fluid grade milk.

Question 42

What is fluid grade milk?

Answer 42

Milk with sufficiently sanitary conditions.

Question 43

What % of the milk produced in the U.S. is Grade A?

Answer 43

>90%.

Question 44

What are the pasteurized milk ordinance (PMO) requirements?

Answer 44

1. Freedom from adulterants and from diseased animals. 2. Proper construction and cleanliness of milking barn and milking room. 3. Adequate and safe water supply. 4. Milk utensils and equipment properly constructed, cleaned, and sanitized. 5. Sanitary waste disposal and adequate treatment of human waste. 6. Milking accomplished with minimum risk of contamination. 7. Cooling within a prescribed time to a satisfactory temperature. 8. Control of insects and rodents. 9. Satisfactory conditions of the milk.

Question 45

What temperature does Grade A milk need to be cooled to?

Answer 45

45 F or less w/in 2 hours after the completion of milking.

Question 46

What is the acceptable level of colony forming units (cfu)/mL in Grade A milk from individual producers? In comingled milk?

Answer 46

a. <100,000. b. <300,000.

Question 47

What is the acceptable level of somatic cells/mL in Grade A milk?

Answer 47

<750,000.

Question 48

What is the policy for drugs or inhibitors in Grade A milk?

Answer 48

There should not be any.

Question 49

When is a dairy's license revoked?

Answer 49

After they have failed to meet the Grade A milk regulatory standards 3 out of the past 5 times. *Suspended at 2 failures.

Question 50

What is the alternate name for Grade "B" milk?

Answer 50

Manufacturing milk.

Question 51

What is manufacturing milk used for?

Answer 51

Dairy products.

Question 52

What temperature does Grade "B" milk need to be cooled to?

Answer 52

40 F or less w/in 2 hours of the end of milking.

Question 53

What is the acceptable cfu/mL level in Grade B milk?

Answer 53

<1,000,000

Question 54

What is the acceptable somatic cells/mL in Grade B milk?

Answer 54

<750,000.

Question 55

What is the policy concerning drug residue and inhibitors in Grade B milk?

Answer 55

Zero tolerance.