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24 Chemistry and Biochemistry of Milk Constituents 461Table 24.4.Typical Concentrations of Vitamins in Milk
and Proportion of Recommended Daily Allowance
(RDA) Supplied by 1 L MilkVitaminAverage Level
in 1 L MilkRDA (%)
in 1 L MilkA 380 rational equivalents 38
B 1 (thiamine) 0.4 mg 33
B 2 (riboflavin) 1.8 mg 139
B 3 (niacin) 9.0 niacin equivalents 53
B 5 (pantothenic acid) 3.5 mg 70
B 6 (pyridoxine) 0.5 mg 39
B 7 (biotin) 30 g 100
B 11 (folic acid) 50 g 13
B 12 (cobalamin) 4 g 167
C15mg 25
D 0.5 g 10
E1mg 10
K35mg 44Source: Adapted from Schaafma 2002.VITAMINS
Milk contains all the vitamins in sufficient quantities to allow
normal growth and maintenance of the neonate. Cow’s milk is
a very significant source of vitamins, especially biotin (B 7 ), ri-
boflavin (B 2 ) and cobalamine (B 12 ), in the human diet. Typical
concentrations of all the vitamins and the percentage of recom-
mended daily allowance supplied by 1 L of milk are shown in
Table 24.4. For specific aspects of vitamins in relation to milk
and dairy products, including stability during processing and
storage, the reader is referred to a set of articles in Roginski
et al. (2002) or Fuquay et al. (2011).
In addition to their nutritional significance, four vitamins are
of significance for other reasons, which have been discussed in
Section ‘Fat-Soluble Vitamins’:
Vitamin A (retinol), and especially carotenoids, are re-
sponsible for the yellow-orange colour of fat-containing
products made from cows’ milk.
Vitamin E (tocopherols) is a potent antioxidant.
Vitamin C (ascorbic acid) may act as an antioxidant or pro-
oxidant, depending on its concentration.
Vitamin B2 (riboflavin), which is greenish-yellow, is re-
sponsible for the colour of whey or UF permeate. It co-
crystallises with lactose and is responsible for its yellow-
ish colour, which may be removed by recrystallisation or
bleached by oxidation. Riboflavin acts as a photocatalyst in
the development of light-oxidised flavour in milk, which is
due to the oxidation of methionine (not to the oxidation of
lipids).SUMMARY
Milk is a very complex fluid. It contains several hundred molecu-
lar species, mostly at trace levels. Most of the micro-constituentsare derived from blood or mammary tissue but most of the macro-
constituents are synthesised in the mammary gland and are milk-
specific. The constituents of milk may be in true aqueous solution
(e.g., lactose and most inorganic salts) or as a colloidal solu-
tion (proteins, which may be present as individual molecules or
as large aggregates of several thousand molecules, called mi-
celles) or as an emulsion (lipids). The macro-constituents can
be fractionated readily and are used as food ingredients. The
natural function of milk is to supply the neonate with its com-
plete nutritional requirements for a period (sometimes, several
months) after birth and with many physiologically important
molecules, including carrier proteins, protective proteins and
hormones.
The properties of milk lipids and proteins may be modified
readily by biological, biochemical, chemical or physical means
and thus converted into a wide range of dairy products. In this
chapter, the chemical and physico-chemical properties of milk
sugar (lactose), lipids, proteins and inorganic salts are discussed.
The technology used to convert milk into a range of food prod-
ucts is described in Chapter 25.REFERENCES
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