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Milk and Dairy Flashcards

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1
Q

What countries are the top 3 milk producers?

A
  1. USA
  2. India
  3. China
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2
Q

The top 2 producers of milk among Canadian provinces are:

A

Ontario, Quebec

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3
Q

Milk is defined as:

A

fluid from mammary glands of mammals, produced for the purpose of feeding their young

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4
Q

The most produced type of milk is ___, followed by ___, ___, and ____.

A

Cow; buffalo, goat, sheep

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5
Q

What hormone plays a major role in milk production and release?
What hormone supplement may be given to lactating cows to increase production?

A

oxytocin

bovine somatotropin

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6
Q

List the main components of (whole) bovine milk in increasing proportion:

A

vit&minerals < protein (whey < casein) < fat < sugar

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7
Q

the 3 major dairy companies in Quebec:

A

Saputo
Parmalait
Agropur

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8
Q

Describe the general process of milk production in the mammal: (6)

A
  1. oxytocin bind to secretory cells of ALVEOLUS
  2. fluid enters lumen of alveolus
  3. fat globules, proteins, lactose synthesized and secreted by SC -> added to milk
  4. albumin and immunoglobulins transported from blood and added
  5. electrolytes brought in from pumps or channels
  6. milk flows into CISTERN -> ready to exit through teat
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9
Q

What is the major sugar in milk? Describe its synthesis process.

A

Lactose

  1. Glucose taken into secretory cell
  2. some will freely diffuse into golgi
  3. Some convert into galactose in lumen (glu -> Glu-P -> UDP-Glu -> UDP-Galactose)
  4. UDP-galactose moved into golgi (ACTIVE TRANSPORT)
  5. Combined by LACTOSE SYNTHETASE
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10
Q

In the production of milk in the mammary gland, what do the secretory cells synthesize and contribute?
What is not synthesized by those cells?

A

Proteins (most)
Fat globules
Sugar (lactose)

Not made by SC:
albumin
immunoglobins
electrolytes

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11
Q

The secretion of lactose into milk will be accompanied by ____, due to _____.

A

water

osmotic draw

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12
Q

The proteins synthesized by alveolar cells are made in the ____ of the cells.

A

ribosomes

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13
Q

the fat globules of milk are produced in the ___ of the ____ cells.

A

ER

secretory alveolar

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14
Q

What is the top dairy breed in Canada?

What are some other types?

A

Holstein (93%)

Jersey, Ayrshire, Brown swiss

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15
Q

What is the average lactation length and amount for cows?

A

305 days

7000 - 20 000 kg

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16
Q

What is bST, and what is it used for? How is it produced?

A

bovine somatotropin, permitted in some countries to stimulate milk production

produced by transferring gene for hormone production from cow to e. coli -> ferment -> harvest and purify protein hormone

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17
Q

How is the secretion by SC of fat globules into milk different from other components such as lactose?

A

Most components exocytosed: vesicles bud off from golgi, travel to surface and fuse with cell membrane, contents released

Fat globules: brought to cell surface, bud outside, encased in membrane (becomes membrane bound lipid globule)

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18
Q

Are milk fat globules high in cholesterol?

A

No, smallest constituent (2%)

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19
Q

True/False: milk fat contains a high level of MAGs.

A

False: least constituent (0.02-0.04%)

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20
Q

The 4 main lipids types in milk fat are: (list in decreasing order)

A

TAG, DAG, PL, keto-acid glycerides

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21
Q

The biggest constituent of a milk fat globule is ____, followed by ______.

A

protein (41%)

phospho and glyco lipids (30%)

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22
Q

What fatty acid is the highest in milk?

A

palmitic (C16), about 24%

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23
Q

What is greater in milk, the amount of short chain FAs or the amount of PUFAs ?

A

short chain FAs

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24
Q

The 3 highest SFAs in milk are:

A

C16, C14, C18

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25
Q

What are the proportions of SFAs, MUFAs, and PUFAs in milk fat?

A

SFA: 55% (C4 - C18 most common)
MUFA: 19.7%
PUFA: 3.5%

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26
Q

The second most common fatty acid in milk is:

A

oleic acid (C18:1)

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27
Q 
What are the shorthand chem notations for:
lauric acid
myristic acid
palmitic acid
stearic acid
A

C12
C14
C16
C18

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28
Q

The 3 types of PUFAs in milk:

A

omega 6, omega 3, CLA (conj. linoleic acid)

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29
Q

The phospholipids in milk fat globules are associated with:

Why would this be problematic, and what is done to rectify it?

A

LIPOPROTEIN LIPASE (enzyme)

during homogenization, membrane is disrupted and enzyme comes into contact with FA -> will hydrolyze and oxidize, make off-flavors (rancidity)
so: need pasteurization (heat treatment) to denature enzyme

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30
Q

C18:1 and C16:1 are known as:

A

oleic acid; palmitoleic acid

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31
Q

In WHOLE milk that is not processed, what will eventually happen due to the fat globules? Is this desirable or not, and what process is used to prevent it?

A

coalesce into bigger globules -> rise to surface
PHASE SEPARATION
good for when want to take out milk fat (make butter, cream)
bad for drinking milk (want smooth even product)
can HOMOGENIZE: break up fat molecules mechanically

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32
Q

Which should occur first: homogenization, or pasteurization?

A

pasteurization: deactivate LPL (otherwise milk will become rancid within minutes after homogenization)

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33
Q

milk has a (small/wide) range of FA types. How does this affect its physical properties?

A

wide
many different melting points -> very gradual melting along range of temperatures
(spreadability)

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34
Q

which would go rancid faster: raw or homogenized milk (both are unpasteurized)?

A

homogenized (membranes are disrupted)

raw milk globules are still intact, less lipid oxidation occurs

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35
Q

describe the two methods of milk/fat separation.

A

gravitational: allow to separate naturally
put in shallow pans -> skim off top
or: put in narrow tank -> spout at bottom collect liquid

centrifugal: spin at high speed to quickly separate (much more efficient, better recovery)

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36
Q

Milk protein may be classified as ____ or ____. How are they distinguished?

A

Casein; Whey

caseins have similar isoelectric point of pH 4.5 - will precipitate out; also are high in P and thus have Ca binding ability
several very hydrophobic AA regions -> easily aggregate

Whey have various isoelectric points (leftoever in liquid after removal of casein); does not have P, cannot bind Ca

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37
Q

What causes caseins to precipitate out?

A

at isoelectric point protein is net neutral -> lowest point of solubility
also: Ca will associate with P groups, decrease solubility

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38
Q

the casein proteins are: (5)

A 
as1
as2
B
gamma
kappa
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39
Q

The whey proteins are: (5)

A 
a-lactalbumin
B-lactoglobulin
serum albumin
immunoglobulins
minor proteins
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40
Q

What is the proportion of caseins to whey?

A

83:`17

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41
Q

What are the major and minor caseins?

A

major: alpha and beta (23kDa)
minor: gamma and kappa, also lambda (derived from degradation of alpha or beta)

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42
Q

The major whey protein is:

A

beta-lactoglobulin (10% of total)

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43
Q

Caseins generally have high content of ______, but the major caseins lack what amino acid?

A

essential AA

cysteine

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44
Q

How is kappa casein different from other caseins, and what important role does it play?

A

smaller than alpha or beta, with large CARBOHYDRATE MOIETY
less P, so less Ca binding
ESSENTIAL FOR MAINTAINING MICELLE STRUCTURE
protects other caseins (once hydrolyzed, other caseins will precipitate out)

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45
Q

Although overall, caseins act _____, they have some polar regions that are high in what?

A

non-polar

phosphate, glutamate, aspartate

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46
Q

Caseins precipitate readily in high concentrations of ___, as _____. What is the exception?

A

Ca
Ca-caseinates
k-casein

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47
Q

What bond in k-casein, once hydrolyzed, will cause the degradation of the micelle?

A

Phe105 - Met106

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48
Q

Where do gamma and lambda caseins come from specifically?

A

gamma: from breakdown of as1 casein
lambda: from breakdown of B casein

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49
Q

What changes will cause milk micelles to revert to casein complexes, and eventually to soluble caseins?

A

lower pH, temperature, Ca

higher P, citrate

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50
Q

k-casein usually forms a ____, due to ___ bonds between ___ residues.

A

trimer
disulfide
cysteine

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51
Q

How can you favor the creation of larger micelles?

A

high Ca , high temp

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52
Q

What factors will promote micelle formation?

A

raising temp, pH, Ca

lower P, citrate

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53
Q

Casein micelles are associated with a lot of ____, and are held together by what bonds?

A

water (highly solvated)

Hydrophobic interactions
H bonds
electrostatic interaction (Ca -P bridges between P-Ser, P-Thr, Glutamic acid)
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54
Q

What are the products of chymosin (rennet) on kappa-casein? what are the fates of each?

A

cleaves between Phe105 and Met106 -> PARA-KAPPA-CASEIN, and a glycomacropeptide

para-k-casein will precipitate with Ca ions
glycomacropeptide stays in solution

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55
Q

What genetic modifications further increases cleavage rate of chymosin on kappa casein?

A

replace Met106 with Phe106 (increase by 80%!)

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56
Q

What acts as a bridge that allows binding between Serine, Threonine, and Glutamic acid residues in milk micelles?

A

Ca, Ca-phosphate

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57
Q

What is the second most abundant whey protein, and what is its function?

A

a-lactalbumin

activates GALACTOSYL TRANSFERASE - enzyme for moving galactose from UDP galactose in golgi for LACTOSE SYNTHESIS

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58
Q

Where are immunoglobulins and serum albumin produced, and how are they added to milk?

A

Produced in liver

added via bloodstream

59
Q

Over half of the whey protein in cow milk is:

A

B-lactoglobulin (18kDa)

60
Q

The whey protein ____ has a high MWt of 69kDa, and functions as _____.

A

BSA (bovine serum albumin)

FFA carrier

61
Q

The milk carbohydrates are:

A 
lactose
lactose oligosaccharides (minor)
62
Q

The types of immunoglobulins are:______.

What is their general structure and purpose?

A

IgG1, IgG2, IgA, IgM
2 light chains, 2 heavy chains
provide calf with passive immunity

63
Q

After heating milk at 95C for 20 min, and acidifying to pH 4.7, what remains in solution is known as:______. What are they?

A

proteose-peptones

glycolytic enzymes, small proteins, etc

64
Q

Free fatty acids in milk are bound to ____

A

BSA

65
Q

lactose is about ____% of milk by weight

A

4-6%

66
Q

The galactose in lactose is always in ____form

A

b-pyranose

67
Q

What types of lactose are in milk? What are their differences?

A

alpha and beta

alpha: more stable, monohydrate form, glucose in a-pyranose form
beta: anhydrate form, higher solubility, more sweet, higher proportion at high processing temp, glucose in b-pyranose form

68
Q

lactose is broken down by lactase, also known as _____. What are the products, and how does this affect taste?

A

beta-galactosidase
glucose and galactose
becomes sweeter

69
Q

What vitamins are added to milk and why?

A

A: to make up for amount removed with fat (enrich)
D: to prevent deficiency (fortify)

70
Q

Milk contains many helpful minerals, but:

A

also contains small amounts of harmful ones like Pb and As

71
Q

What are some minor components in milk?

A

Vitamins
Minerals
Organic acids (lactic, orotic, citric, acetic)
hormones and GF
enzymes (catalase, lysozyme, aldolase, carbonic anhydrase)

72
Q

How are caseins usually separated out?

A

acidification with acetic acid

73
Q

What vitamins are highest in milk (soluble, and fat soluble)?

A

C and E

74
Q

density is an important measure for milk because (2):

What factors affect it?

A
  • relate mass to volume (convert)
  • estimate solids content

depends on composition (fat!) and temperature

75
Q

What are some hormones found in milk?

A 
Prolactin
thyroxine
estradiol
insulin
progesterone
growth hormone
76
Q

What determines the value of milk?

A

fat content

77
Q

Why is lactose useful for the pharmaceutical industry?

A

less sweet, used as a filler

78
Q

What are some growth factors in milk?

A

IGF1, IGF2, transforming GF-a, transformin GF-b

79
Q

Why must milk be processed to be sold?

A

risk of pathogens: M. bovis, Salmonella, E. coli

80
Q

Describe the collection of milk for processing:

A

milk collected on farm -> cooled to 4.4C
delivered in insulated tank
mix with other milk within 2 days, or directly to processing plant
*maintain at 4.4C or below!

81
Q

True/False: it is illegal to sell raw milk in Canada.

A

True

82
Q

____ content in milk tends to stay constant, while ___ and ___ can vary.

A

protein; fat and lactose

83
Q

What QC tests are necessary prior to processing? (5)

A

determine fat and total solids ($$$)
estimate sediment
microbiological tests (total, coliform, yeast, mold)
determine freeze point (see if any extra water)
assess flavor

84
Q

What process is used to remove impurities? What impurities specifically?

A

clarification

sediment, animal cells, some bacteria

85
Q

What could produce off-flavors in milk?

A

fat oxidation
fat lipolysis
animal feed used
absorption of odors

86
Q

What types of heat treatment can be done on milk?

Which is not applicable for milk to be drunk?

A

pasteurization (HTST or batch)
Thermization
UHT
Sterilization

Thermization is a sub-pasteurization process, meant for milk to be further processed into cheese

87
Q

How does a clarifier work for milk?

A

centrifuge at high speed to separate out sediments. can use with hot or cold milk.

88
Q

Heat is applied by _____ (3) for UHT processes.

A

heating coils, heating plates, or steam injection (then aseptic packaging)

89
Q

Order the heat treatment methods for milk in increasing temperature.
Also order them in increasing time.

A

temp: thermization < HTST < sterilization < UHT
time: UHT < HTST < thermization < sterilization

90
Q

Sterilization of milk is accomplished by heating in an ______.

A

autoclave

91
Q

List the basic milk products in terms of increasing fat:

A

skim milk (fortify or unfortified) < partly skim < whole milk < half and half < light cream < heavy cream < butter

92
Q

How does homogenization work?

A

milk forced through small opening, turbulence and shear force causes globules to break up into tiny globules < 1micrometer in diameter

creates a more stable emulsion

93
Q

The two methods for gravitational fat removal from milk are:

A

shallow pan

deep setting

94
Q

What is the removal of fat from milk known as? What purpose does it serve?

A

Creaming
make low fat milk products
or use fat to make cream, butter

95
Q

What are some further processed milk types?

A

filled milk (with added non-milk fat)
toned milk (added water or skim milk)
reconstituted milk (rehydrated milk powder)
lactose free (with lactase)
low sodium
flavored
canned (evaporated, condensed) - remove moisture, add sugar

96
Q

Why is milk powder made?

A

as ingredient for further processing (formula, milk chocolate, etc)

for long shelf life, for countries with no dairy farming/refrigeration

97
Q

What is the most common drying method for milk, and what are two alternatives?

A

spray drying

drum drying (normal or vacuum)
fluidized bed drying (using CO2 or N as foaming gas)
98
Q

Once cream is removed from milk, what other products can be derived?

A

churn cream -> obtain butter and buttermilk

can heat butter and clarify (remove milk solids) -> ghee

99
Q

Does the drying process of milk affect the enzymes and proteins? What are the implications of this?

A

No; usually happens below 70C. Whey is not denatured, and enzymes are still active
so: enzymes can still cause oxidation and browning during storage

100
Q

Once the cream is removed from unpasteurized milk, what other steps can be taken to produce other products? (3)

A

heat treatment

obtain pasteurized milk for drinking

or: acidify -> curd separation -> cheese and whey
or: add bacteria -> yogurt

101
Q

What are some fermented dairy products? (4)

A

yogurt
buttermilk
sour milk
sour cream

102
Q

Milk fat is used to produce: (3)

A

butter
cream
ice cream

103
Q

Butter is a ______ emulsion, which is made possible by

A 
water in oil
hydrophilic emulsifiers (lauroyl glutamate)
104
Q

What are the 3 types of butter?

A

Sweet cream (from non-soured cream)
Cultured (from soured cream)
Soured (from non-sour cream, but fermented later)

105
Q

Whipping cream should contain at least ___% fat. good quality cream should show volume increase of ___%, and not ____.

A

35%
80%
separate

106
Q

Describe the butter making process:

A

churning: agitate milk/cream vigorously at 12-18C (so milk fat part solid, part liquid)
incorporates air -> whipped cream
continue agitation -> becomes more coarse, eventually semi-solid fat granules will separate from liquid phase
(butter and buttermilk)

107
Q

What is a typical ice cream formulation?

A

66% water, 14% sucrose, 11% non-fat milk solids, 10% milk fat, 2% glucose syrup, and small amounts of stabilizers(emulsifiers) and thickeners (polysaccharides)

also: flavorings and colors

108
Q

What is overrun, and how is it calculated? What is the usual amount?

A

increase in volume of ice cream due to whipping in air

100x (final volume - initial volume)/initial volume = % overrun

usually 70-100% (volume about doubles)

109
Q

At what stage in ice cream making are the other add-ins (fruits, nuts, etc) added?

A

soft ice cream stage (before hardening)

110
Q

Describe the steps of ice cream production: (6)

A
  1. components mixed
  2. ice cream mix pasteurized (batch or HTST)
  3. high pressure homogenization
  4. cooled to increase viscosity (4.4C)
  5. cooled while mixing in air (-5.5C)
  6. semi-solid ice cream put in package, cooled to -34C (hardening)
111
Q

What causes the sour taste of fermented milk products?

A

lactic acid from lactic acid bacteria metabolic activity

112
Q

What are some common LABs?

A

lactobacillus, lactococcus, leuconostoc, pediococcus, streptococcus

113
Q

What are the 2 types of fermentation that occur, and what determines what type will take place?

A

homofermentative: only produce lactic acid
heterofermentative: produces other byproducts as well (acetic acid, ethanol, CO2)

depends on bacteria type - different enzymes and pathways. homo uses glycolytic only, while hetero use pentose phosphate pathway
(both act on carbohydrates)

114
Q

the lactic acid produced in milk can be either _____ or ______. Which one should be limited in the diet and why?

A

L enantiomer, D enantiomer

limit D: not normally produced in humans so not metabolized well

115
Q

How is soured buttermilk made?

A

add S. lactis to skim or part skim milk -> thick, sour, bubbly product

116
Q

Why does thickening and curdling occur in fermented milk products?

A

increased acidity will cause coagulation of caseins

117
Q

What non-bacteria microbe is used to produce kefir, and what is the result?

A

yeast (torula)

some alcohol content, contains “grains” made of clotted milk and yeast bodies

118
Q

After the production process for fermented milk products is complete, what should take place?

A

heat to kill microbes

or keep at cool temperatures to slow growth (active culture)

119
Q

How is the casein separated from whey for cheese making?

A

acid/rennet used to cleave kappa casein -> will precipitate with Ca, allows other caseins to coagulate with Ca and heat -> forms curd

120
Q

The 3 basic steps of cheese production:

A

curdle milk
remove whey
ripening of curd (add microflora)

121
Q

What steps take place before the actual curdling of cheese? (2)

A 
standardize protein and fat content
additives added (lysozyme, nitrates, Ca)
122
Q

what are some classification methods for cheese? (4)

A

source of milk (cow, goat, etc)
moisture/hardness (soft, semi-soft)
fat content
curdling method (acid vs rennet)

123
Q

How do enzyme coagulation and acid coagulation of milk differ?

A

enzyme: use rennet/chymosin
acid: require combination with heat. use starter culture or add acid directly.

Acid method has higher protein recovery

124
Q

After the curd has formed, what steps are taken?

A

cut and heated gently, cubes will shrink and expel whey

then removed from whey

125
Q

What will determine the final pH of the cheese?

A

the final moisture in the curd (determines the amount of FERMENTABLE LACTOSE)

126
Q

What happens during cheese ripening?

A

bacteria, mold, yeast, and milk enzymes will degrade proteins, fat, and lactose -> produce flavor and texture changes

127
Q

What causes the shrinking of curd when heated? What other effect happens?

A

increased hydrophobic interactions -> shrinks protein matrix -> syneresis

also: more lactic acid produced (fermentation rate increased)

128
Q

the qualities of the final cheese will depend on what factors for ripening conditions? (4)

A

microbial content
humidity
temperature
biochemical composition of curd

129
Q

Why would removing citrate help to increase coagulation of caseins?

A

Normally citrate has a chelating effect; removing it allows caseins to coalesce together

130
Q

Where are enzymes for cheese making sourced? (4)

A

Chymosin/Pepsin: from animal stomachs
plant enzymes
proteinases from microbes
or genetically modify microbes to produce rennet

131
Q

added ___ and ___ will increase the firmness of the curd.

A

Ca; P

132
Q

What are the 2 types of starter cultures, and what are the 3 important characteristics they should have?

A

mesophilic (20-40C) or thermophilic (up to 45C)

  1. produce lactic acid
  2. break down protein (ripening)
  3. make CO2 (for some cheeses, holes)
133
Q

Why is lactic acid production important for cheese? (3)

A
  • initial curdling
  • contraction of curd -> squeeze out whey
  • LAB suppresses other undesirable microbes
134
Q

proteolysis during the ___ stage is caused by proteases from ____(3), and produces:

A

ripening
milk, bacteria culture, added enzymes
flavor and aroma compounds

135
Q

Lactic acid production will stop when:

A

heat is applied (kill bacteria)

or all lactose used up

136
Q

What bacteria is used to make holes in swiss cheese? How does this work?
What is sometimes done as an alternative?

A

propionic acid bacteria
convert lactic acid -> propionic acid, acetic acid, CO2
CO2 is dissolved, but once becomes saturated will produce bubbles -> forms holes in ripening curd

can also directly inject CO2 (faster, lower pH)

137
Q

What additive is included in small quantities to prevent clostridium?
When is it not needed?

A

saltpeter (NaNO3 or KNO3) - nitrates

if milk is microfiltered, then this is not necessary (or less is needed)

138
Q

Aside from nitrates, what other additives are included in cheese sometimes, and what are their purposes? (2)

A

CaCl2 - increase firmness of curd

Na2PO4 - add before CaCl2, to increase elasticity (esp in low fat cheese)

139
Q

How is salt applied to cheese? (2)

A

dry salting

brining

140
Q

Salt will affect: (3)

A

consistency
taste
bacterial processes

141
Q

addition of salt to cheese will cause______ due to ______(2).

A

expelling more moisture

osmotic pressure, precipitate out whey proteins (salting out)

142
Q

What is the final treatment for curd after whey is removed? (2)

A
  1. moulding (either put in mould directly, or first press into blocks and cut to size)
  2. pressed (pneumatic/hydraulic presser) - expel more whey, develop texture
143
Q

Why would color agents be added to cheese, and what are some common examples? (3)

A

for appearance, and to correct for seasonal variations in color of milk fat

carotene, orleana (seasonal variations)
green chlorophyll (make paler blue cheeses)

food commodities (5 decks)

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