Orientation in lubricants. Wilson and Barnard, with other investi-
gators, find the "animal and vegetable oils to be superior in oiliness to
straight mineral oils." They conclude that the property of oiliness is due
to selective adsorption of parts of the oil by the metal surface so that they
adhere closely and are not squeezed out from between the metals, or in
other words the polar groups of the animal and vegetable oils are attracted
by the polar metal, and the fat or oil is less readily squeezed out from
between the metal surfaces than oils or fats containing no polar groups.
Thus they make better lubricants.
Theory o£ shortening power applied to cookery. If the results
of Langmuir and Harkins can be applied to lubricants they should be
equally applicable to the use of fats and oils in cookery. The glycerol part
of the fat is attracted by water. If it adheres closely to the water, one
can conceive that the water might cement the flour particles less firmly
together. Fats and oils with double bonds in their fatty acid chains, or
those containing unsaturated glycerides, can be spread over a greater sur-
face area than the saturated fats and would thus adhere to a larger water
surface, or compete with the gluten for the water. Also, since the double
bond of the fat adheres closely to the metal surface, it may be that it will
SURFACE AREA COVERED 565
adhere to the amino groups of the flour proteins, as well as to the water.
This would make it more difficult to squeeze out from between the flour
particles. Fats and oils containing unsaturated glycerides would have more
shortening power because they cover a greater surface area per molecule
and because they adhere more firmly to the water surface. If this is true,
the fats and oils having the highest percentage of unsaturated acids and
covering the greatest surface area should give the tenderest baked products.
However, the area covered by a given amount of fat or oil in a dough or
batter may vary. A sphere gives the least surface area for a definite weight
or volume of a substance. If the oil or fat is emulsified and distributed in
the batter in small spheres the total area covered may be less than if the
same weight were distributed in very thin films or sheets. Even in oil-in-
water emulsions the surface area covered for a definite weight of oil will
vary with the degree of dispersion of the oil, for the greater the dispersion
the greater the surface area covered.
The surface area covered determines the shortening power of
a fat or oil in baked products. The degree of shortening produced
by a fat or oil in a given product depends primarily upon the surface area
of the flour particles covered by the fat or oil. To a lesser degree shorten-
ing power may also depend upon the extent of separation of the egg and
milk proteins and the sugar from the flour particles by the fat. The fats
and oils are insoluble in the other ingredients of baked products. Thus they
may to a greater or less degree mechanically separate the ingredients of
the batter but they never entirely lose their identity or change their char-
acteristics. If flour and water are mixed together and baked, the resulting
product is very hard, firm, and tough. When the water is added to the
flour the protein particles become hydrated and form a continuous phase,
somewhat similar to a gel, throughout the mass.
Page 450
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.
Orientation in lubricants. Wilson and Barnard, with other investi-
gators, find the "animal and vegetable oils to be superior in oiliness to
straight mineral oils." They conclude that the property of oiliness is due
to selective adsorption of parts of the oil by the metal surface so that they
adhere closely and are not squeezed out from between the metals, or in
other words the polar groups of the animal and vegetable oils are attracted
by the polar metal, and the fat or oil is less readily squeezed out from
between the metal surfaces than oils or fats containing no polar groups.
Thus they make better lubricants.
Theory o£ shortening power applied to cookery. If the results
of Langmuir and Harkins can be applied to lubricants they should be
equally applicable to the use of fats and oils in cookery. The glycerol part
of the fat is attracted by water. If it adheres closely to the water, one
can conceive that the water might cement the flour particles less firmly
together. Fats and oils with double bonds in their fatty acid chains, or
those containing unsaturated glycerides, can be spread over a greater sur-
face area than the saturated fats and would thus adhere to a larger water
surface, or compete with the gluten for the water. Also, since the double
bond of the fat adheres closely to the metal surface, it may be that it will
SURFACE AREA COVERED 565
adhere to the amino groups of the flour proteins, as well as to the water.
This would make it more difficult to squeeze out from between the flour
particles. Fats and oils containing unsaturated glycerides would have more
shortening power because they cover a greater surface area per molecule
and because they adhere more firmly to the water surface. If this is true,
the fats and oils having the highest percentage of unsaturated acids and
covering the greatest surface area should give the tenderest baked products.
However, the area covered by a given amount of fat or oil in a dough or
batter may vary. A sphere gives the least surface area for a definite weight
or volume of a substance. If the oil or fat is emulsified and distributed in
the batter in small spheres the total area covered may be less than if the
same weight were distributed in very thin films or sheets. Even in oil-in-
water emulsions the surface area covered for a definite weight of oil will
vary with the degree of dispersion of the oil, for the greater the dispersion
the greater the surface area covered.
The surface area covered determines the shortening power of
a fat or oil in baked products. The degree of shortening produced
by a fat or oil in a given product depends primarily upon the surface area
of the flour particles covered by the fat or oil. To a lesser degree shorten-
ing power may also depend upon the extent of separation of the egg and
milk proteins and the sugar from the flour particles by the fat. The fats
and oils are insoluble in the other ingredients of baked products. Thus they
may to a greater or less degree mechanically separate the ingredients of
the batter but they never entirely lose their identity or change their char-
acteristics. If flour and water are mixed together and baked, the resulting
product is very hard, firm, and tough. When the water is added to the
flour the protein particles become hydrated and form a continuous phase,
somewhat similar to a gel, throughout the mass.