A fat-soluble pigment, carotene, found in the fat gives the milk a more
or less yellow tinge, which is more pronounced as the fat particles become
more concentrated and form cream. The group of pigments called caroti-
noids, which include carotene, xanthophyll, and related pigments, has been
described in the chapter on fruits and vegetables. The chief pigment of
butter fat is the carotene, but little xanthophyll being found. The depth of
color depends upon the amount of pigment present. The color of carotene in
solution varies from yellow to orange and to a deep red-orange as the
concentration increases. The amount of carotene found in the butter fat
depends upon the extent of carotene in the food of the cow. Green grasses,
hay cured to retain its green color, green corn, and carrots are rich in
carotene. The carotene content of milk fat is less rich during the winter
months, if the food of the cow is poor in carotene during this period. Only
in cow's milk is the fat extensively pigmented. With the exception of
the fat of human milk, which is often pigmented, the fat of the milk of
other animals is either devoid of or contains little pigment.
Salts. Milk contains salts of potassium, sodium, magnesium, calcium,
phosphates, chlorides, and citrates. Traces of sulfates and carbonates are
found. Iron is present in small amount. Iodides are also found in small
amounts, the amount being greater in some localities than in others. Iodides
may be easily transmitted from the feed to the milk. Supplee and Bellis
have found copper to average about 0.52 part per million in freshly drawn
milk. Brickner has reported that milk contains 3.6 to 5.6 parts of zinc per
FAT 295
million parts of milk. Manganese in normal milk averages 0.02^ to 0.06
parts per million. The greater part of the sulfur is found in the milk pro-
teins. Barger and Coyne state that part of the sulfur in milk is found in
the amino acids methionine and cystine of the proteins, but that all of the
sulfur is not accounted for.
The salts of milk are found in milk in solution, in the colloidal state,
and in combination with the proteins. The exact chemical combinations
of the different salts in the milk are not fully determined. For this reason
different authorities report different salt combinations. Thus formulas
imply definite combination, whereas there is a complex salt equilibrium in
milk, which has not been satisfactorily worked out. The citrates, the com-
binations of which may be trisodium and tripotassium citrate, tricalcium
and trimagnesium citrate, are probably entirely in solution. The possible
chlorides of potassium, sodium, and calcium are also in solution. Some
authorities believe that the phosphates are present chiefly as dicalcium
phosphate, CaHP04; others believe that tricalcium phosphate, Ca3(P04)2,
is the principal phosphate combination. The phosphates are partly in solu-
tion, with the greater portion in colloidal dispersion. When the particles
of dicalcium phosphate are heated they become aggregated and partially
precipitated.
Calcium and magnesium are in combination with the casein to form
calcium and magnesium caseinates. Zoller states that there may be traces
of sodium and potassium caseinates.
Lactose. The solubility of lactose and its properties may be found in
the chapter on sugar. It is caramelized by heat at rather low temperatures.
Page 238
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A fat-soluble pigment, carotene, found in the fat gives the milk a more
or less yellow tinge, which is more pronounced as the fat particles become
more concentrated and form cream. The group of pigments called caroti-
noids, which include carotene, xanthophyll, and related pigments, has been
described in the chapter on fruits and vegetables. The chief pigment of
butter fat is the carotene, but little xanthophyll being found. The depth of
color depends upon the amount of pigment present. The color of carotene in
solution varies from yellow to orange and to a deep red-orange as the
concentration increases. The amount of carotene found in the butter fat
depends upon the extent of carotene in the food of the cow. Green grasses,
hay cured to retain its green color, green corn, and carrots are rich in
carotene. The carotene content of milk fat is less rich during the winter
months, if the food of the cow is poor in carotene during this period. Only
in cow's milk is the fat extensively pigmented. With the exception of
the fat of human milk, which is often pigmented, the fat of the milk of
other animals is either devoid of or contains little pigment.
Salts. Milk contains salts of potassium, sodium, magnesium, calcium,
phosphates, chlorides, and citrates. Traces of sulfates and carbonates are
found. Iron is present in small amount. Iodides are also found in small
amounts, the amount being greater in some localities than in others. Iodides
may be easily transmitted from the feed to the milk. Supplee and Bellis
have found copper to average about 0.52 part per million in freshly drawn
milk. Brickner has reported that milk contains 3.6 to 5.6 parts of zinc per
FAT 295
million parts of milk. Manganese in normal milk averages 0.02^ to 0.06
parts per million. The greater part of the sulfur is found in the milk pro-
teins. Barger and Coyne state that part of the sulfur in milk is found in
the amino acids methionine and cystine of the proteins, but that all of the
sulfur is not accounted for.
The salts of milk are found in milk in solution, in the colloidal state,
and in combination with the proteins. The exact chemical combinations
of the different salts in the milk are not fully determined. For this reason
different authorities report different salt combinations. Thus formulas
imply definite combination, whereas there is a complex salt equilibrium in
milk, which has not been satisfactorily worked out. The citrates, the com-
binations of which may be trisodium and tripotassium citrate, tricalcium
and trimagnesium citrate, are probably entirely in solution. The possible
chlorides of potassium, sodium, and calcium are also in solution. Some
authorities believe that the phosphates are present chiefly as dicalcium
phosphate, CaHP04; others believe that tricalcium phosphate, Ca3(P04)2,
is the principal phosphate combination. The phosphates are partly in solu-
tion, with the greater portion in colloidal dispersion. When the particles
of dicalcium phosphate are heated they become aggregated and partially
precipitated.
Calcium and magnesium are in combination with the casein to form
calcium and magnesium caseinates. Zoller states that there may be traces
of sodium and potassium caseinates.
Lactose. The solubility of lactose and its properties may be found in
the chapter on sugar. It is caramelized by heat at rather low temperatures.