Food Chemistry

10.1 Milk 501

Table 10.3.Consumption of milk and dairy products in
FR Germany (in kg/capita and year)

1996 2003 2005

Consumer milk 66.7 66 67
Fresh milk products 9.9 12.2 12
(without yoghurt)
Yoghurt 13.1 15.3 16.8
Cream and cream products 7.6 7.4 7.4
Butter 7.3 6.6 6.5

The measurement of redox potentials of milk
and its products can also be of value. The redox
potential is+ 0 .30 V for raw and+ 0 .10 V for
pasteurized milk,+ 0 .05 V for processed cheese,
− 0 .15 V for yoghurt and− 0 .30 V for Emmental
cheese.

10.1.2 Composition

The composition of dairy cattle milk varies to
a fairly significant extent. Table 10.5 provides
some data. In all cases water is the main ingredi-
ent of milk at 63–87%. In the following sections,
only cow’s milk will be dealt with in detail since
it is the main source of our dairy foods.

10.1.2.1 Proteins

In 1877 O. Hammarsten distinguished three
proteins in milk: casein, lactalbumin and lac-
toglobulin. He also outlined a procedure for their
separation: skim milk is diluted then acidified
with acetic acid. Casein flocculates, while the

Table 10.4.Main structural elements of milk

Name Type of Percentage Number Diameter Surface Specific
dispersion ( 1 −^1 ) (mm) (m^2 /l densitya
milk) (g/ml)

Fat globules Emulsion 3. 81013 100–10,000 70 0. 92
Casein micelles Suspension 2. 81017 10–300 4000 1. 11
Globular proteins Colloidal 0. 61020 3–6 5000 1. 34
(whey proteins) solution
Lipoprotein Colloidal
particles suspension 0. 01 1017 10 10 1. 10
a 20 ◦C.

Table 10.5.Composition of human milk and milk of

various mammals (%)

Milk Protein Casein Whey Sugar Fat Ash

protein

Human 0. 9 a 0. 40. 57. 14. 50. 2

Cow (bovine) 3. 22. 60. 64. 63. 90. 7

Donkey 2. 01. 01. 07. 41. 40. 5

Horse 2. 51. 31. 26. 21. 90. 5

Camel 3. 62. 70. 95. 04. 00. 8

Zebu 3. 22. 60. 64. 74. 70. 7

Yak 5. 84. 66. 50. 9

Buffalo 3. 83. 20. 64. 87. 40. 8

Goat 3. 22. 60. 64. 34. 50. 8

Sheep 4. 63. 90. 74. 87. 20. 9

Reindeer 10. 18. 61. 52. 818. 01. 5

Cat 7. 03. 83. 24. 84. 80. 6

Dog 7. 44. 82. 6

Rabbit 10. 4

aAfter the 15-th day of the breast feeding period the

protein content is increased to 1.6%.

whey proteins stay in solution. This established

a specific property of casein: it is insoluble in

weakly acidic media. It was later revealed that

the milk protein system is much more complex.

In 1936Pedersen used ultra-centrifugation to

demonstrate the nonhomogeneity of casein, while

in 1939Mellanderused electrophoresis to prove

that casein consists of three fractions, i. e.α-,β-

andγ-casein. The most important proteins of milk

are listed in Table 10.7. The casein fraction forms

the main portion. Major constituents of whey

proteins,β-lactoglobulin A and B andα-lactal-

bumin, can be differentiated genetically. Other

protein constituents, e. g., enzymes, are present

in much lower quantities; they are not listed in

Table 10.7.