Milk Quality and Grades Flashcards
What does the growth of microorganisms in the milk depend on?
- Microbial inhibitors.
- Moisture availability.
- Nutritional requirements.
- Osmotic pressure.
- Oxygen requirements.
- pH or acidity.
- Temperature.
What 2 families of bacteria produce lactic acid?
- Lactobacilleaceae.
- Streptococcaceae.
What are homofermenters?
Bacteria that produce only lactic acid.
What are heterofermenters?
Bacteria that produce acetic acid, carbon dioxide, diacyl, ethanol, lactic acid.
What 2 genera of microorganisms are probiotic?
- Bifidobacterium.
- Lactobacillus.
What 3 types of microorganisms are lipolytic and proteolytic?
- Bacteria.
- Mold.
- Yeast.
What 4 specific bacteria are classified as enteric bacteria?
- C. perfringens.
- E.coli.
- Salmonellae.
- Shigellae.
What are coliforms?
Bacteria with a fecal origin. Often indicate fecal contamination.
What do the presence of coliforms indicate as it pertains to milk?
Low hygienic milking practices.
What 2 genera of microorganisms are psychrophilic?
- Bacillus.
- Pseudomonas.
What 7 microorganisms are associated with foodborne illness?
- Campylobacter spp.
- Clostridium botulinum.
- L. monocytogenes.
- Mycobacterium avium spp.
- Paratuberculosis.
- Salmonella spp.
- S. aureus.
What are somatic cells?
Leukocytes and a small number of epithelial cells present in the milk.
What are the 3 types of leukocytes?
- Lymphocytes.
- Monocytes.
- Polymorphonuclear (PMN) cells.
What are PMN cells?
- Basophils.
- Eosinophils.
- Neutrophils.
When does the proportion of PMN relative to other somatic cells in the milk during mastitis?
It increases.
What happens to the SCC overall during mastitis?
Bacterial growth.
What 2 enzymes increase in activity as a result of increased SCC activity?
- Lipase.
- Protease.
What 3 characteristics of milk are influenced by the SCC?
- Chemical.
- Organoleptic.
- Physical.
What is the FAO definition of good-quality raw milk?
- Free of abnormal colors, odor, and off-flavors.
2.Free of chemicals (antibiotics, detergents). - Free of debris and sediment.
- Low in bacterial count.
- Normal composition and acidity.
How is milk quality tested?
By measuring volume and/or weight.
How are the organoleptic characteristics of milk tested?
- Appearance.
- Smell.
- Taste.
What are the compositional characteristics of milk?
- Fat.
- Protein.
- Solids (likely non-fat).
How is milk hygiene tested?
- Cleanliness.
- Hygienic conditions.
- Quality.
What are 3 adulterants that can be placed in milk?
- Added solids.
- Preservatives.
- Water.
What is all milk tested for that the dairy industry has zero tolerance for?
Drug/chemical residue.
What are the 3 methods used to measure somatic cells/do a SCC?
- Direct microscopy.
- Somatic cell counter.
- California Mastitis Test.
What is the downside to using direct microscopy?
It is time consuming.
*Was the standard for years.
What precisely does the somatic cell counter measure?
Total somatic cells/mL.
*Objective method.
How is a California Mastitis Test (CMT) conducted?
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.
What are the 4 microbiological/chemical tests that are used to evaluate milk quality?
- Differential culture.
- Molecular techniques.
- Plate count.
- Titratable acidity.
What is done in a differential culture?
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.
What is done in molecular techniques?
The genetic material of the microorganisms is analyzed.
What is done in a plate count?
The milk is cultured and the number of colonies formed is counted. Used for aerobic bacteria.
What is done in titratable acidity?
Measures lactic acid produced by bacterial fermentation using an indicator.
What are common causes of a high plate count?
- Dirty milk equipment.
- Mastitis.
- Poor cooling.
- Poor udder prep.
What is done in a preliminary incubation count?
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.
How are the 3 ways antibiotics and inhibitors are detected in milk?
- Culture Geobacillus stearothermophilus with paper disks impregnated with the milk sample and see if a zone of inhibition appears.
- A snap test.
- High-performance liquid chromatography (HPLC).
What 2 devices are used to detect added water in milk?
- Cryoscope.
- Hygrometer.
How does the cryoscope detect added water?
By measuring the freezing point of milk.
How does the hydrometer detect added water?
Measures the specific gravity/density of milk.
What is the other name for Grade “A” Milk?
Fluid grade milk.
What is fluid grade milk?
Milk with sufficiently sanitary conditions.
What % of the milk produced in the U.S. is Grade A?
> 90%.
What are the pasteurized milk ordinance (PMO) requirements?
- Freedom from adulterants and from diseased animals.
- Proper construction and cleanliness of milking barn and milking room.
- Adequate and safe water supply.
- Milk utensils and equipment properly constructed, cleaned, and sanitized.
- Sanitary waste disposal and adequate treatment of human waste.
- Milking accomplished with minimum risk of contamination.
- Cooling within a prescribed time to a satisfactory temperature.
- Control of insects and rodents.
- Satisfactory conditions of the milk.
What temperature does Grade A milk need to be cooled to?
45 F or less w/in 2 hours after the completion of milking.
What is the acceptable level of colony forming units (cfu)/mL in Grade A milk from individual producers? In comingled milk?
a. <100,000.
b. <300,000.
What is the acceptable level of somatic cells/mL in Grade A milk?
<750,000.
What is the policy for drugs or inhibitors in Grade A milk?
There should not be any.
When is a dairy’s license revoked?
After they have failed to meet the Grade A milk regulatory standards 3 out of the past 5 times.
*Suspended at 2 failures.
What is the alternate name for Grade “B” milk?
Manufacturing milk.
What is manufacturing milk used for?
Dairy products.
What temperature does Grade “B” milk need to be cooled to?
40 F or less w/in 2 hours of the end of milking.
What is the acceptable cfu/mL level in Grade B milk?
<1,000,000
What is the acceptable somatic cells/mL in Grade B milk?
<750,000.
What is the policy concerning drug residue and inhibitors in Grade B milk?
Zero tolerance.
