at 25°/25°C. It means that the weight of the oil at 25° is compared with
the weight of an equal volume of water at 25 °C. Fats and oils are lighter
than water, and if they are poured into water they float on its surface.
Cream has a higher fat content than milk and is lighter than the milk.
The average specific gravity of some edible fats and oils is given below.
Butter not less than 0.905 at 40740°C.
Cottonseed oil about 0.917-0.918 at 25725°.
Corn oil about 0.919-0.921 at 25725°.
Lard about 0.931-0.932 at 15°/15°.
Olive oil about 0.916-0.918.
Distinction between fats and oils. One distinction between fats and
oils is that at ordinary temperatures, 18° to 24°C., the fats are solid
and the oils are liquid. Chemically the fats contain higher percentages
of the saturated glycerides than the oils, and the oils contain more of
the unsaturated glycerides than the fats.
Glycerides. Fats and oils are esters of glycerol and fatty acids, and thus
are often spoken of as glycerides. Glycerol is a trihydric or triatomic
alcohol and as such combines with three fatty acids to form a molecule
of fat or oil. Of the three fatty acids which combine with glycerol to
form the molecule of fat or oil, all may be the same acid. If, for example,
the three are stearic acid, the name of the glyceride is tristearin. Two of
the acids may be the same and the third different. If the molecule con-
tains two stearic and one palmitic acid, it is known as distearo-palmitin.
Each of the three may be a different acid. This gives many possible com-
binations in fats and oils.
The approximate percentage of the unsaturated glycerides in some of
the fats and oils used in cooking is given in Table 59.
TABLE 59
The Approximate Percentage of Unsaturated Glycerides Found in
Some Fats and Oils
Kind of fat
Unsaturated
glycerides
Investigator
Percentage
Coconut oil
6 to 8
Lewkowitsch
Butter
40
Lewkowitsch
Lard
60 to 65
Lewkowitsch
Chicken fat^
77
Kerr
Cottonseed oil
75
Jamieson and Baugham
Peanut oil
From Spanish-type peanuts
75
Jamieson and Baugham
From Virginia-type peanuts
79
Jamieson and Baugham
Corn oil
85
Jamieson and Baugham
^ Personal communication from R. H. Kerr, Bureau of Animal Industry.
544 FATS AND OILS
Since the above figures are approximate, it follows that individual sam-
ples of each oil or fat vary slightly, some having a higher and some a low^er
percentage of unsaturated glycerides. Lard obtained from leaf fat has a
lower percentage of unsaturated glycerides than that obtained from the
back fat of the same animal. In addition, the composition of such fats as
butter, lard, tallow, and chicken fat may be influenced by the diet. Pork
fed soybeans or peanuts in sufficient quantity produces the so-called "soft
pork," because the body fat contains a higher percentage of unsaturated
glycerides, hence is softer at room and refrigerator temperatures.
Page 431
Presented as published in 1932. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
A modernized reading is not available for this page yet. You are seeing the original text.
at 25°/25°C. It means that the weight of the oil at 25° is compared with
the weight of an equal volume of water at 25 °C. Fats and oils are lighter
than water, and if they are poured into water they float on its surface.
Cream has a higher fat content than milk and is lighter than the milk.
The average specific gravity of some edible fats and oils is given below.
Butter not less than 0.905 at 40740°C.
Cottonseed oil about 0.917-0.918 at 25725°.
Corn oil about 0.919-0.921 at 25725°.
Lard about 0.931-0.932 at 15°/15°.
Olive oil about 0.916-0.918.
Distinction between fats and oils. One distinction between fats and
oils is that at ordinary temperatures, 18° to 24°C., the fats are solid
and the oils are liquid. Chemically the fats contain higher percentages
of the saturated glycerides than the oils, and the oils contain more of
the unsaturated glycerides than the fats.
Glycerides. Fats and oils are esters of glycerol and fatty acids, and thus
are often spoken of as glycerides. Glycerol is a trihydric or triatomic
alcohol and as such combines with three fatty acids to form a molecule
of fat or oil. Of the three fatty acids which combine with glycerol to
form the molecule of fat or oil, all may be the same acid. If, for example,
the three are stearic acid, the name of the glyceride is tristearin. Two of
the acids may be the same and the third different. If the molecule con-
tains two stearic and one palmitic acid, it is known as distearo-palmitin.
Each of the three may be a different acid. This gives many possible com-
binations in fats and oils.
The approximate percentage of the unsaturated glycerides in some of
the fats and oils used in cooking is given in Table 59.
TABLE 59
The Approximate Percentage of Unsaturated Glycerides Found in
Some Fats and Oils
Kind of fat
Unsaturated
glycerides
Investigator
Percentage
Coconut oil
6 to 8
Lewkowitsch
Butter
40
Lewkowitsch
Lard
60 to 65
Lewkowitsch
Chicken fat^
77
Kerr
Cottonseed oil
75
Jamieson and Baugham
Peanut oil
From Spanish-type peanuts
75
Jamieson and Baugham
From Virginia-type peanuts
79
Jamieson and Baugham
Corn oil
85
Jamieson and Baugham
^ Personal communication from R. H. Kerr, Bureau of Animal Industry.
544 FATS AND OILS
Since the above figures are approximate, it follows that individual sam-
ples of each oil or fat vary slightly, some having a higher and some a low^er
percentage of unsaturated glycerides. Lard obtained from leaf fat has a
lower percentage of unsaturated glycerides than that obtained from the
back fat of the same animal. In addition, the composition of such fats as
butter, lard, tallow, and chicken fat may be influenced by the diet. Pork
fed soybeans or peanuts in sufficient quantity produces the so-called "soft
pork," because the body fat contains a higher percentage of unsaturated
glycerides, hence is softer at room and refrigerator temperatures.