Dairy pt 2

Question 1

where do the proteins, fats, minerals, and lactose from milk go when they’re initially produced?

Answer 1

lumen of the mammary gland

Question 2

describe the percentage composition of a fat globule

Answer 2

• proteins (41%)
• fats (46%)
• moisture (13%)

Question 3

what types of lipids are present in milk? what are their percentage compositions?

Answer 3

• phospho and glycolipids (30%)
• neutral glycerides (14%)
• cholesterol (2%)

Question 4

what function do the phospho and glycolipids serve in a lipid globule

Answer 4

essential components of membranes as well as emulsifiers

Question 5

why is there such a large percentage of phospho and glycolipids in fat globules?

Answer 5

fat globules are surrounded by lipid bilayers

Question 6

what kind of neutral glycerides are there in a fat globule?

Answer 6

• triglycerides (95%)
• diacylglycerides (1.5-1.6%)
• keto acid glycerides (0.9-1.3%)
• phospholipids (0.8-1%)

Question 7

what plant sterols are present in milk? where are they made?

Answer 7

B-sitosterol, sitosterol; in plants, obtained through diet

Question 8

do phospholipids prefer hydrophobic or hydrophilic interactions? why?

Answer 8

hydrophobic, because the polar portion (phosphate) is smaller

Question 9

describe the fatty acid profile of milk

Answer 9

• saturated (55%)
• monounsaturated (18-20%)
• polyunsaturated (3-5%)

Question 10

what is the significance of having a high saturated fat content?

Answer 10

• increases susceptibility to oxidation and rancidity

- serves as a greater source of energy

Question 11

what significant PUFAs are there in milk?

Answer 11

• linoleic acid

Question 12

is linoleic acid conjugated or nah?

Answer 12

nah

Question 13

expand CLA

Answer 13

conjugated linoleic acid

Question 14

what is CLA?

Answer 14

linoleic acid but the double bond is shifted from position 12 to 11

Question 15

where do CLAs exist?

Answer 15

in animal tissues: emat, milk, eggs

Question 16

how are CLAs able to have different properties amongst themselves

Answer 16

cis/trans forms

Question 17

supposed health benefits of CLA?

Answer 17

intervention strategies, body composition, cardio-vascular health, immunity, asthma, cancer and diabetes

Question 18

are the claimed health benefits of CLA founded?

Answer 18

not really - results haven’t been consistent; not many human studies; studies not long enough

Question 19

describe how phase separation happens

Answer 19

if you let raw milk sit undisturbed for some time, the fat globules will coalesce and float to the top

Question 20

when is phase separation desirable and undesirable?

Answer 20

desirable: butter, cheese, ice cream
undesirable: liquid milk

Question 21

what is cream?

Answer 21

fat phase

Question 22

what is buttermilk?

Answer 22

aqueous phase

Question 23

what is whey?

Answer 23

further separation of buttermilk

Question 24

what are the 2 methods of purposely separating milk phases?

Answer 24

1) plop in trays, wait

2) centrifusion

Question 25

which method of milk is the most efficient?

Answer 25

centrifusion

Question 26

how do you keep milk from separating?

Answer 26

homogenization

Question 27

describe the process of homogenization

Answer 27

feed milk through a small orifice under pressure to break fat globules into very small particles that are easier to be kept suspended uniformly throughout the aqueous phase

Question 28

how does homogenization affect milk’s capacity to go rancid? what kind of rancidity are we talking about?

Answer 28

increases susceptibility because lipid bilayer is disrupted, permitting lipases access to fatty acids

hydrolytic rancidity

Question 29

how do you prevent hydrolytic rancidity?

Answer 29

pasteurize milk prior to homogenization

Question 30

what are the 2 types of milk proteins?

Answer 30

caseins, whey

Question 31

what’s the difference between caseins and wheys?

Answer 31

caseins have a high phosphate content

Question 32

why are caseins able to have more phosphates?

Answer 32

caseins have a high amount of serine and threonine which have OH groups for phosphate groups to bind to

Question 33

what’s it called when serine and threonine are phosphorylated?

Answer 33

phosphoserine, phosphothreonine

Question 34

how is calcium caseinate formed

Answer 34

phosphorylated groups of amino acids bind to calcium, making calcium caseinate

Question 35

describe the solubility of calcium caseinate

Answer 35

less soluble at acidic pH

Question 36

what kinds of caseins are there?

Answer 36

• alpha and beta: (larger and have more phosphate groups)
• kappa: have a large non-protein (mostly CHO) portion; prevent coagulation when intact
• gamma: smaller than kappa; formed as a breakdown product in the hydrolysis of caseins

Question 37

list the whey proteins

Answer 37

• beta-lactoglobulin
• alpha-lactalbumin
• bovine serum albumin
• minor proteins
• immunoglobulins

Question 38

describe beta-lactoglobulins

Answer 38

function not clearly understood; cause allergic response in some people

Question 39

describe alpha lactalbumins

Answer 39

regulate action of enzyme transfer of galactose from DUP-galactose to glucose by the enzyme galactosyltransferase

Question 40

describe BSA

Answer 40

synthed in the liver and transported to the lumen of mammary glands; serves as an energy source and transport for free fatty acids

Question 41

describe the minor whey proteins

Answer 41

enzymes, lactoferrin, transferrin

Question 42

describe immunoglobulins

Answer 42

associated with impartin immunity to young