Melting point o£ fats. Because of the mixture of glycerides the
melting points of fats are not constant but vary. The melting points of fats
are not only affected by the percentage of their component unsaturated fatty
acids but also by the length of the saturated acid chains. The shorter
saturated fatty acids have lower melting points than the longer ones, and, in
general, the fats composed of glycerides containing a high percentage of
the higher or longer chained saturated fatty acids have the highest melting
points; those with a high percentage of the shorter saturated fatty acids
have intermediate melting points; and those with a high percentage of
unsaturated acids have the lowest melting point. As the percentage of the
shorter fatty acids or the unsaturated fatty acids is increased the melting
point of the fat is lowered. Butter produced in summer has a lower melting
point than butter produced in the winter months because the percentage
of unsaturated fatty acids is higher in the summer. The oils have a higher
percentage of oleic acid and consequently have a low melting point. Hard
fats like mutton tallow contain high percentages of palmitic and stearic
acids and little oleic and have a high melting point. Soft fats like lard con-
tain more oleic acid than tallow but not so much as the oils.
Congealing point. The solidifying point of a glyceride or a mixture
of glycerides is lower than the melting point, the difference in the two
often being great. For example, Bloor cites the melting point of a sample
of tristearin as 71.5°C., whereas the solidifying point was 52.5°C. A sample
of butter melted at 34.5° but congealed at 22.7°C. This wide spread in
melting and congealing points has some advantages and some disadvantages.
When melted fats are added to a batter or other product they do not
solidify as rapidly as they would if the melting and congealing points were
the same. On the other hand, butter once melted requires a lower tempera-
ture to congeal.
Iodine number (or value). The iodine number is defined as the
number of grams of iodine absorbed by 100 grams of fat or other substance.
The iodine is absorbed by the unsaturated carbons or at the double bonds.
The class to which an oil belongs is indicated by its iodine number. The
non-drying oils, such as peanut and coconut, have iodine values less than
100. Cacao butter and the fats such as lard, beef, and mutton tallows, and
butter also, have iodine values below 100. The semi-drying oils, which
include corn, cottonseed, sesame, wheat, oat, rice, rye, Brazilnut, raisin
seed, peach, cherry, and apricot kernels, and many others, have iodine
TEXTURE AND CONSISTENCY OF FATS 545
values between 100 and 130. Drying oils, which include linseed and soy-
bean, have iodine values above 130.
Acid value. Acid value is defined as the number of milligrams of
KOH required to neutralize the free fatty acids in one gram of substance.
It is a measure of the quantity of free fatty acids or those not combined in
glycerides and is usually reported as "free fatty acids as oleic."
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Melting point o£ fats. Because of the mixture of glycerides the
melting points of fats are not constant but vary. The melting points of fats
are not only affected by the percentage of their component unsaturated fatty
acids but also by the length of the saturated acid chains. The shorter
saturated fatty acids have lower melting points than the longer ones, and, in
general, the fats composed of glycerides containing a high percentage of
the higher or longer chained saturated fatty acids have the highest melting
points; those with a high percentage of the shorter saturated fatty acids
have intermediate melting points; and those with a high percentage of
unsaturated acids have the lowest melting point. As the percentage of the
shorter fatty acids or the unsaturated fatty acids is increased the melting
point of the fat is lowered. Butter produced in summer has a lower melting
point than butter produced in the winter months because the percentage
of unsaturated fatty acids is higher in the summer. The oils have a higher
percentage of oleic acid and consequently have a low melting point. Hard
fats like mutton tallow contain high percentages of palmitic and stearic
acids and little oleic and have a high melting point. Soft fats like lard con-
tain more oleic acid than tallow but not so much as the oils.
Congealing point. The solidifying point of a glyceride or a mixture
of glycerides is lower than the melting point, the difference in the two
often being great. For example, Bloor cites the melting point of a sample
of tristearin as 71.5°C., whereas the solidifying point was 52.5°C. A sample
of butter melted at 34.5° but congealed at 22.7°C. This wide spread in
melting and congealing points has some advantages and some disadvantages.
When melted fats are added to a batter or other product they do not
solidify as rapidly as they would if the melting and congealing points were
the same. On the other hand, butter once melted requires a lower tempera-
ture to congeal.
Iodine number (or value). The iodine number is defined as the
number of grams of iodine absorbed by 100 grams of fat or other substance.
The iodine is absorbed by the unsaturated carbons or at the double bonds.
The class to which an oil belongs is indicated by its iodine number. The
non-drying oils, such as peanut and coconut, have iodine values less than
100. Cacao butter and the fats such as lard, beef, and mutton tallows, and
butter also, have iodine values below 100. The semi-drying oils, which
include corn, cottonseed, sesame, wheat, oat, rice, rye, Brazilnut, raisin
seed, peach, cherry, and apricot kernels, and many others, have iodine
TEXTURE AND CONSISTENCY OF FATS 545
values between 100 and 130. Drying oils, which include linseed and soy-
bean, have iodine values above 130.
Acid value. Acid value is defined as the number of milligrams of
KOH required to neutralize the free fatty acids in one gram of substance.
It is a measure of the quantity of free fatty acids or those not combined in
glycerides and is usually reported as "free fatty acids as oleic."