Woodruff and Blunt have reported the changes in fats absorbed by
potato chips and a dough mixture. They state that the iodine number is
lowered, and the percentage of free fatty acids increased. These changes
are not great, but the fat absorbed by the food undergoes greater changes
than the fat in which the food is cooked. Long cooking or use of the fat
increases the amount of decomposition of the fat. The higher the tempera-
ture to which the fat is heated, the greater the decomposition products
formed. Thus during cooking the fat should not be heated higher than the
temperature needed for cooking the food.
Morgan and Cozens found that fats used for frying a standard dough
showed consistent decreases in iodine number, lowering of the melting
point and increases in acidity and refractive index. They state that in
general the increase in acidity is greater in those fats showing the larger
amounts of absorption.
King et al. used 9 fats, including 3 kettle-rendered lards from animals
fed on rations consisting largely of (1) peanut, (2) corn, and (3) brewer's
rice, a standard prime steam lard, a hydrogenated lard, a hydrogenated
cottonseed oil, and three highly refined oils from corn, cottonseed, and
peanuts, respectively, for studying frying of potato chips. The fat absorbed
by the chips was about the same for all the fats used. Chemical tests
showed deterioration of all fats. After 10 fryings the fitness of the fats,
particularly the lards on account of their high peroxide value, for further
use was questionable. They found no relation between chemical changes
and the flavor of the chips. The percentage of free fatty acids in the fat
COMPOSITION AND NATURE OF FOOD 555
extracted from the chips was greater than in the frying fat. Based largely
upon desirability of flavor the palatability tests indicated oils were preferable
to lards for frying potato chips, those fried in peanut oil ranking highest
with cottonseed oil second. Of the lards, the hydrogenated and that from
animals whose rations consisted largely of peanuts were considered best.
Potato chips fried in oils and in most cases those stored in the refrigerator
kept fresh longest.
The Amount of Fat Absorbed by Fried Foods
The chief factors governing the amount of fat which will be absorbed by
a food during frying are (1) the time of cooking, (2) the temperature of
the cooking fat, (3) the total surface area of the food, and (4) the com-
position and nature of the food.
Time of cooking. In general, it can be stated that the longer the food
is cooked the greater the fat absorption. There will be some exceptions
to this. For instance, with some foods cooked at high temperatures, coagu-
lated material or a hardened crust may prevent greater fat absorption
with longer cooking. Other foods which contain a high percentage of fat
like breaded pork chops may lose fat during cooking. This is also true of
fried chicken, if the chicken has a high fat content.
Temperature of cooking fat. Usually there is less fat absorption at
higher cooking temperatures. This is probably due to the quick formation
of a crust or coagulated material at the high temperature. However, slight
differences in cooking temperature, 30° to 40°C., cause little variation in
fat absorption. Ordinarily food is cooked at moderate temperatures to
thoroughly cook the food without excessive browning.
Page 441
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Woodruff and Blunt have reported the changes in fats absorbed by
potato chips and a dough mixture. They state that the iodine number is
lowered, and the percentage of free fatty acids increased. These changes
are not great, but the fat absorbed by the food undergoes greater changes
than the fat in which the food is cooked. Long cooking or use of the fat
increases the amount of decomposition of the fat. The higher the tempera-
ture to which the fat is heated, the greater the decomposition products
formed. Thus during cooking the fat should not be heated higher than the
temperature needed for cooking the food.
Morgan and Cozens found that fats used for frying a standard dough
showed consistent decreases in iodine number, lowering of the melting
point and increases in acidity and refractive index. They state that in
general the increase in acidity is greater in those fats showing the larger
amounts of absorption.
King et al. used 9 fats, including 3 kettle-rendered lards from animals
fed on rations consisting largely of (1) peanut, (2) corn, and (3) brewer's
rice, a standard prime steam lard, a hydrogenated lard, a hydrogenated
cottonseed oil, and three highly refined oils from corn, cottonseed, and
peanuts, respectively, for studying frying of potato chips. The fat absorbed
by the chips was about the same for all the fats used. Chemical tests
showed deterioration of all fats. After 10 fryings the fitness of the fats,
particularly the lards on account of their high peroxide value, for further
use was questionable. They found no relation between chemical changes
and the flavor of the chips. The percentage of free fatty acids in the fat
COMPOSITION AND NATURE OF FOOD 555
extracted from the chips was greater than in the frying fat. Based largely
upon desirability of flavor the palatability tests indicated oils were preferable
to lards for frying potato chips, those fried in peanut oil ranking highest
with cottonseed oil second. Of the lards, the hydrogenated and that from
animals whose rations consisted largely of peanuts were considered best.
Potato chips fried in oils and in most cases those stored in the refrigerator
kept fresh longest.
The Amount of Fat Absorbed by Fried Foods
The chief factors governing the amount of fat which will be absorbed by
a food during frying are (1) the time of cooking, (2) the temperature of
the cooking fat, (3) the total surface area of the food, and (4) the com-
position and nature of the food.
Time of cooking. In general, it can be stated that the longer the food
is cooked the greater the fat absorption. There will be some exceptions
to this. For instance, with some foods cooked at high temperatures, coagu-
lated material or a hardened crust may prevent greater fat absorption
with longer cooking. Other foods which contain a high percentage of fat
like breaded pork chops may lose fat during cooking. This is also true of
fried chicken, if the chicken has a high fat content.
Temperature of cooking fat. Usually there is less fat absorption at
higher cooking temperatures. This is probably due to the quick formation
of a crust or coagulated material at the high temperature. However, slight
differences in cooking temperature, 30° to 40°C., cause little variation in
fat absorption. Ordinarily food is cooked at moderate temperatures to
thoroughly cook the food without excessive browning.