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Public Health and Food Safety > Milk Grading, Processing, & Hygiene > Flashcards

Milk Grading, Processing, & Hygiene Flashcards

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1
Q

What are the top 3 producers of milk in the world?

A
  1. India
  2. EU
  3. US
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2
Q

What are the 2 layers of cells in the mammary gland?

A
  1. LACTOCYTES (mammary epithelium) - milk-producing cells located on the surface inside the gland
  2. BASAL MYOEPITHELIUM - smooth muscle cells surrounding lactocytes
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3
Q

What surrounds each alveolus of mammary glands?

A

blood capillaries to provide nutrients for the synthesis and expression of milk

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4
Q

What hormone is necessary for milk secretion? Where is it secreted from?

A

oxytocin - causes myoepithelial cells to squeeze each alveolus to discharge the milk into the lumen of ductules

pituitary gland —> bloodstream

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5
Q

What are the 2 storage spaces for milk in the mammary gland?

A
  1. alveoli - 60-80%
  2. cistern - 20-40%
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6
Q

How many mammary glands do cows have?

A

4 quarters that are able to work independently from one another

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7
Q

What is the timeline for dairy cow mating and colostrum/milk production?

A
  • heifers mate at 15 months
  • give offspring by 2 y/o
  • continues to give birth each year up to 9 y/o
  • produces colostrum for 3-5 days
  • produces milk for about 305 days (10 months) and is dry for 2 months
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8
Q

How does colostrum compare to milk?

A
  • 2x more dry matter
  • 3x more minerals
  • 5x more proteins
  • more fat-soluble vitamins
  • viscous, thick, waxy, yellow
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9
Q

Why is colostrum not shipped to milk processing factories? Why must milk be properly processed?

A

not suitable for processing

milk has a nearly complete diet, but it is naturally in the pH and moisture danger zone —> conditions favored by bacteria

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10
Q

What are the 5 molecular components of milk? Why do dairy industries separate it into these components?

A
  1. water (87%)
  2. carbohydrates (4.9%)
  3. fat (3.7%)
  4. protein (3.3%)
  5. vitamins (1.4%)

allows for the production of diverse dairy products, like cheese, fat-rich butter, fat-free products, lactose-free products

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11
Q

How can adulteration of milk be observed molecularly?

A

proportion of milk composition will deviate from normal proportions

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12
Q

What are the 3 categories milk fats? Which ones produce essential fatty acids not made by the body?

A
  1. saturated fats (65%) - all single bonds
  2. mono-unsaturated fats (29%)
  3. poly-unsaturated fats (6%)

poly-unsaturated (omega) fatty acids —> linoleic, linolenic, and trans fatty acids

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13
Q

What 4 products are milk fats the raw material for?

A
  1. cream
  2. butter
  3. ghee
  4. fat-standardized liquid milk - fat-free, 1%, 2%, whole
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14
Q

What are the 2 categories of milk proteins? What are they based on?

A
  1. whey - soluble in water
  2. casein - insoluble in water
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15
Q

What is casein the major raw material for?

A

cheese

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16
Q

What are the 4 major vitamins and minerals found in milk?

A
  1. vitamin B12 - cobalamin, found only in food of animal origin
  2. vitamin B2 - riboflavin
  3. calcium - best dietary source
  4. phosphorus
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17
Q

What are the 3 major characteristics of milk used to distinguish contaminated from clean?

A
  1. aroma - no off-odors (ensure milk is not too hot)
  2. pH - 6.5-6.8
  3. titratable acidity - 0.13-0.17 (total concentration of free protons and undissociated acids in a solution that can react with a strong base and be neutralized)
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18
Q

What 7 major parameters are routinely checked by regulatory agencies for quality raw milk production?

A
  1. somatic cell counts - 750000 cells/mL
  2. bacterial counts - 100000 cfu/mL
  3. organoleptic quality - color, odor, taste, consistency
  4. chemical composition - water, fat, protein, mineral
  5. adulteration/residues
  6. pH - 6.5-6.8
  7. temperature - < 4 C
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19
Q

What 3 nutritional constituents are used to identify adulterated milk? What is the proper proportion of each?

A
  1. water (87%)
  2. fat (3.25%)
  3. non-fat solids (8.25%)
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20
Q

What are high somatic cell counts related to? Where in the process is this tested? What is the federal cutoff for Grade A milk?

A

mastitis —> udder health monitoring

storage of milk in bulk tanks

> 750000 cells/mL

21
Q

What are bacteria counts related to? How is this tested? What is the federal cutoff for Grade A milk?

A

sanitary practices

standard plate count

> 100000 cfu/mL

22
Q

What are the 4 methods of raw milk bacterial count? How are they done? What do each target?

A
  1. standard plate count/total aerobic colony count - serially diluted milk samples are plated on agar and incubated for 48 hr at 32 C —> general aerobic bacterial present in milk at pickup
  2. preliminary incubation count - hold milk at 12.8 C for 18 hours prior to plating —> subgroups of bacteria that grow well at refrigerator temps (psychrotrophic)
  3. lab pasteurization count - hold milk at 63.8 C for 30 minutes prior to plating —> subgroups of bacteria that survive heat treatment (thermoduric)
  4. coliform bacteria counts - plating on selective media that inhibits other bacteria (MacConkey) —> subgroups of bacteria that are associated with manure or environmental contamination
23
Q

What is the most common cause of high bacteria counts? What are some other causes?

A

poor cleaning of milking systems allows milk residues to remain on the surface and provide nutrients for the growth and multiplication of bacteria that contaminate subsequent milking

  • mastitis (Staph. aureus, Strep., coliforms)
  • soiled cows
  • unsanitary milking practices
  • failure to cool milk rapidly to < 4 C
  • failure of water heater
24
Q

What 4 aspects of milk are observed to calculate organoleptic quality?

A
  1. COLOR - white
  2. ODOR - no off-odor
  3. TASTE - pleasantly sweet
  4. CONSISTENCY - liquid, but not watery
25
Q

What are 3 causes of milk flavor changes? What part of this milk is responsible for taste change?

A
  1. environmental contamination - feed, barn, cow, weed, lacks freshness, stale
  2. bacterial/microbial - acidic, bitter, malty, fruity, fermented, putrid, rancid
  3. chemical/enzymatic/processing - ketotic, salty, rancid, bitter, oxidized, astringent, medicinal, flat

milk fat

26
Q

What tends to cause acidic (sour), barn-like, bitter (beer), paper, and cooked flavor changes in milk?

A
  • ACIDIC = sour lemon taste due to lactic acid produced by microbes due to poor refrigeration
  • BARN = feces odor/taste due to poor ventilation, unclean condition, or ketosis
  • BITTER = hops taste due to break down of milk proteins by microbial enzymes
  • PAPER = milk absorbed odor of carton pack
  • COOKED = boiled by improper pasteurization
27
Q

What tends to cause cow-like, feed-like, flat, garlic/onion, rancid, and salty flavor changes in milk?

A
  • COW = cow breath or fecal odor due to acetone during ketosis or acetonemia
  • FEED = silage, hay, grassy flavor due to feeding before milking
  • FLAT = watery, adulteration by water addition
  • G/O = consumption of garlic weed
  • RANCID = soapy, putrified fat due to the release of FFA by microbial destruction of milk fat
  • SALTY = late lactation, mastitis
28
Q

When are pH, temperature, and drug residues measured in milk? How?

A

rapid on-site milk test —> avoids contamination before shipment

  • pH = measure to be 6.5-6.8
  • temperature = measured to be < 4 C
  • residues = tests negative by lateral flow assay
29
Q

What are 3 advantages to milk grading?

A
  1. standardized milk prices
  2. determines type of milk sold on liquid form
  3. determines the types of milk that require further processing (for cheese) before consumption
30
Q

What 4 criteria used to grade milk?

A
  1. chemical constituents
  2. load of bacteria
  3. bulk tank SCC
  4. organoleptic features
31
Q

What are the 3 milk grades?

A
  1. certified - < 10000 cfu/mL bacteria
  2. grade A - < 100000 cfu/mL bacteria
  3. grade B - < 500000 cfu/mL bacteria
32
Q

What is grade B milk used for?

A

not sold as liquid milk due to poor quality —> processed for other products, like cheese, before consumption

33
Q

Milk grading criteria:

A
34
Q

How is milk processed?

A

milk composition is manipulated to form another dairy product by pasteurization and cooling followed by separation, standardization, or fermentation

35
Q

What is the point of pasteurization? Cooling?

A

PASTEURIZATION - > 63 C kills microbes

COOLING - < 4 C (except cheese and yogurt) prevents the growth of microorganisms using cold water, ice water, brine solution, or alcohol solution (glycol)

36
Q

What are the 4 types of milk pasteurization?

A
  1. ultra-high temperature - 120-140 C for 2-4 sec (long shelf life)
  2. canned - 115-120 C for 15-20 mins using autoclave or treatment chamber
  3. high temperature, short time (flash) - 72-74 C for 20 secs (widely used)
  4. low temperature, long time (batch) - 63 C for 30 mins

(higher temperatures are even able to kill vegetative bacteria, like Coxiella burnetii)

37
Q

How are yogurt and cheese pasteurized?

A

YOGURT - 40-45 C for 15 mins, then cool to needed temp for fermentation

CHEESE - 30-35 C for 15 mins, then cool to need temp for fermentation

38
Q

What is the most common cooling step in the dairy industry?

A

keep dairy products at < 4 C at all steps of the process by refrigeration cold-holding

39
Q

What is thermization?

A

type of pasteurization at 57-68 C for 15 mins that targets pathogenic bacteria and leaves good bacteria in the product —> low temp will not alter structure and taste of milk

40
Q

How are milk components sorted?

A

nono-pore membrane technology —> micro, ultra, nanopore membranes

41
Q

What are the 5 general steps for milk processing?

A
  1. COLLECTION - collected from dairies and stored in tanks that cool it to < 4 C and transferred to plant
  2. SEPARATION - sedimentation, debris, and bacteria removed from milk (heavier and lighter milk are also separated to form cream and skim milk)
  3. PASTEURIZATION - milk is heated and cooled
  4. STANDARDIZE - fat homogenizing through atomizer to stop fat from floating to the top
  5. PACKAGING - packed in cartons for retail or further manufactured for other material
42
Q

Cheese production:

A
43
Q

What 4 products of milk are based on water/moisture content?

A
  1. whole milk - 87% water, 13% solid
  2. evaporated canned milk - 60% of water removed
  3. sweetened condensed milk - 60% of water removed and replaced by sugar
  4. dry/powdered milk - water entirely removed
44
Q

What is whey?

A

liquid part of milk without any solids

45
Q

What is yogurt? Cheese?

A

YOGURT = cultured milk with starter Lactobacillus bacteria

CHEESE = cultured milk with starter Lactobacillus bacteria and rennet enzyme, solid part is removed from liquid part

46
Q

What 3 milk products are based on fat content?

A
  1. ghee - butter clarified to remove its milk solids and water content, leaving 99-100% pure fat
  2. butter - fat and protein components of churned cream
  3. cream - higher fat layer skimmed from the top of milk before homogenization
47
Q

What cattle breeds produce premium milk? Why

A

Golden Guernsey or All-Jersey

higher milk fat content and creamier taste

48
Q

What are the top 5 biological hazards associated with milk and its products?

A
  1. Listeria monocytogenes
  2. E. coli
  3. Salmonella
  4. molds and yeast
  5. Staph

Public Health and Food Safety (23 decks)

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