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Milk Composition & Synthesis
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Milk Composition
Minerals


Calcium and phosphorous are the major minerals found in milk. These minerals are required in large quantities by the rapidly growing neonate for bone growth and development of soft tissues. Calcium and phosphorous mostly are associated with the casein micelle structure. Milk also contains most other minerals found in the body.


Some minerals, such as Zn, Mg, Fe, Cu, Mn, and Mo, are required by enzymes as cofactors.

Fe is low in milk of many species relative to the needs of the neonate. Fe is essential for the neonate as part of hemoglobin. In many species the neonate is born with some liver stores of Fe; however, the piglet does not and needs an Fe supplement (injection) soon after birth. Fe in milk is bound to lactoferrin, transferrin, xanthine oxidase, and some to caseins.

Zn in cow's milk is mostly bound to casein, but some is bound to lactoferrin.

Cu is bound to the caseins, to ß-lactoglobulin, to lactoferrin, and some to the milk fat membranes.

Mo is bound to xanthine oxidase, an enzyme associated with the cell membrane and on the inner surface of the milk fat globule membranes.

Mn is associated with the milk fat membranes.

Co is an essential part of vitamin B12.

Minerals contribute to the buffering capacity of milk, the maintenance of milk pH, the ionic strength of milk, and milk's osmotic pressure.

Trace elements may enter the milk during milk synthesis or by contamination after the milk is removed from the cow; for example from metal containers, etc. Cows raised near industrial plants can have higher milk Cd and Pb. Cows raised near highways can have higher milk Pb. 

Mineral Secretion in Milk

Mineral

% Total

% in Soluble Form

Ca

0.12

25 (rest of Ca is in the casein micelle form)

P

0.10

44 (rest of P is in the casein micelle form)

Mg

0.01

20

K

0.15

100

Na

0.05

100

Cl

0.11

100


The Ca and P are either in the casein micelles and in citrate and phosphate complexes.

Average values for milk salt constituents in whole milk

Constituent

mg/100ml milk

Calcium (Ca)

123

Phosphorous (P)

95

Magnesium (Mg)

12

Potassium (K)

141

Sodium (Na)

58

Chlorine (Cl)

119

Sulfur (S)

30

Citric acid

160

Trace Elements in Cow Milk

The milk concentration of some elements can be increased by increasing the amount in the diet. These particularly include I, B, Br, Co, Mn, Mo, Se, and Zn. The table below shows examples of the concentrations of various elements in milk when fed a normal diet vs. a diet where that particular element was supplemented.

Trace elements in cow milk (micrograms per liter)

Cow Receiving
Element

Normal Ration

Supplement
of Element

Aluminum

460

810

Arsenic

50

450

Boron

270

660

Bromine

600

Increases

Bromine (costal areas)

2800

-

Cadmium

26

No increase

Chromium

15

-

Cobalt

0.6

2.4

Copper

130

No increase

Fluorine

150

Increases

Iodine

43

Up to 2700

Iron

450

No increase

Lead

40

Increases

Manganese

22

64

Molybdenum

73

371

Nickel

27

No increase

Selenium (low Se area)

40

Increases

Selenium (high Se area)

Up to 1270

-

Silicon

1430

No increase

Silver

47

-

Strontium

171

-

Vanadium

0.092

-

Zinc

3900

5100

Study Question

How much of the calcium and phosphorous found in milk would you expect to find in the serum phase of milk?

 


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