Dairy pt 2 Flashcards
where do the proteins, fats, minerals, and lactose from milk go when they’re initially produced?
lumen of the mammary gland
describe the percentage composition of a fat globule
- proteins (41%)
- fats (46%)
- moisture (13%)
what types of lipids are present in milk? what are their percentage compositions?
- phospho and glycolipids (30%)
- neutral glycerides (14%)
- cholesterol (2%)
what function do the phospho and glycolipids serve in a lipid globule
essential components of membranes as well as emulsifiers
why is there such a large percentage of phospho and glycolipids in fat globules?
fat globules are surrounded by lipid bilayers
what kind of neutral glycerides are there in a fat globule?
- triglycerides (95%)
- diacylglycerides (1.5-1.6%)
- keto acid glycerides (0.9-1.3%)
- phospholipids (0.8-1%)
what plant sterols are present in milk? where are they made?
B-sitosterol, sitosterol; in plants, obtained through diet
do phospholipids prefer hydrophobic or hydrophilic interactions? why?
hydrophobic, because the polar portion (phosphate) is smaller
describe the fatty acid profile of milk
- saturated (55%)
- monounsaturated (18-20%)
- polyunsaturated (3-5%)
what is the significance of having a high saturated fat content?
- increases susceptibility to oxidation and rancidity
- serves as a greater source of energy
what significant PUFAs are there in milk?
- linoleic acid
is linoleic acid conjugated or nah?
nah
expand CLA
conjugated linoleic acid
what is CLA?
linoleic acid but the double bond is shifted from position 12 to 11
where do CLAs exist?
in animal tissues: emat, milk, eggs
how are CLAs able to have different properties amongst themselves
cis/trans forms
supposed health benefits of CLA?
intervention strategies, body composition, cardio-vascular health, immunity, asthma, cancer and diabetes
are the claimed health benefits of CLA founded?
not really - results haven’t been consistent; not many human studies; studies not long enough
describe how phase separation happens
if you let raw milk sit undisturbed for some time, the fat globules will coalesce and float to the top
when is phase separation desirable and undesirable?
desirable: butter, cheese, ice cream
undesirable: liquid milk
what is cream?
fat phase
what is buttermilk?
aqueous phase
what is whey?
further separation of buttermilk
what are the 2 methods of purposely separating milk phases?
1) plop in trays, wait
2) centrifusion
which method of milk is the most efficient?
centrifusion
how do you keep milk from separating?
homogenization
describe the process of homogenization
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
how does homogenization affect milk’s capacity to go rancid? what kind of rancidity are we talking about?
increases susceptibility because lipid bilayer is disrupted, permitting lipases access to fatty acids
hydrolytic rancidity
how do you prevent hydrolytic rancidity?
pasteurize milk prior to homogenization
what are the 2 types of milk proteins?
caseins, whey
what’s the difference between caseins and wheys?
caseins have a high phosphate content
why are caseins able to have more phosphates?
caseins have a high amount of serine and threonine which have OH groups for phosphate groups to bind to
what’s it called when serine and threonine are phosphorylated?
phosphoserine, phosphothreonine
how is calcium caseinate formed
phosphorylated groups of amino acids bind to calcium, making calcium caseinate
describe the solubility of calcium caseinate
less soluble at acidic pH
what kinds of caseins are there?
- 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
list the whey proteins
- beta-lactoglobulin
- alpha-lactalbumin
- bovine serum albumin
- minor proteins
- immunoglobulins
describe beta-lactoglobulins
function not clearly understood; cause allergic response in some people
describe alpha lactalbumins
regulate action of enzyme transfer of galactose from DUP-galactose to glucose by the enzyme galactosyltransferase
describe BSA
synthed in the liver and transported to the lumen of mammary glands; serves as an energy source and transport for free fatty acids
describe the minor whey proteins
enzymes, lactoferrin, transferrin
describe immunoglobulins
associated with impartin immunity to young
