and the fat is not so grainy. If in addition to rapid chilling, the fat is also
stirred while it is being cooled it becomes very smooth. If the temperature
to which it is cooled is several degrees below its melting point the fat may
become waxy and so firm that it is rather difficult to cream at ordinary
temperatures. The oil does not separate from the smooth fat as the fat
becomes soft. It is for this reason that only smooth lard or fat is sold in
paper cartons. Grainy lard may be purchased but comes in metal contain-
ers. The commercial smooth lards are not cooled sufficiently to become
waxy.
Fatty acids commonly found in foods. The fatty acids commonly
found combined with the glycerol in food and cooking fats are palmitic,
stearic, and oleic. Chemically the fatty acids of the acetic acid series have
the general formula C/zH2«02. The most important of this series in foods
are the palmitic and stearic, though butyric and caproic, with small amounts
of caprylic and capric, form about 7 per cent of the glycerides of butter.
H H H
Butyric acid
aproic
acid
Caprylic acid
Capric acid
Palmitic acid
Stearic acid
H-
H-
H-
H
H-
C— C— C— C = O
H
H
-i
I
H
H
I
H
H
i
I
H
H
I
-C-
c = o
I
OH
■Hn
I
■HJ4
nH-
I
C
■H-Je OH
■H-|
C — C = 0
I I
i-H-Jg OH
O
H
H
I
H
-H-
I
C
I
■H-
•H-
i
I
l-H-
— C =
I
14 OH
O
— C = 0
6h
HEAT DECOMPOSITION 547
Of the fatty acid series with the general formula CnrL^?i-JD^ oleic acid
is the most important in food fats. The acids of this series contain one
double bond in the chain and are unsaturated.
H rH-
Oleic acid
„4.
i
■H-
— C= C—
■H-n
I
c
■H-
— C = O
I
7 OH
Linolic acid belongs to the fatty acid series with the general formula
CnH2n-402. Linolic and linolenic acids are very important because they
are necessary for proper functioning of the body, and the animal body
does not have the ability to synthesize the unsaturated fatty acids. Linolic
acid contains two double bonds.
Linolenic acid belongs to the series CnH2n-602 and contains three double
bonds.
When oils or fats are hydrogenated, it is generally agreed that the more
highly unsaturated acids are the first to become saturated.
Though present in only small amounts both linolic and linolenic acids
may influence the properties of foods. Their effect, or the effect of their
oxidation products, on gluten quality has been considered. The glycerides
with more than one double bond also oxidize readily. The shortening power
of a fat or oil because of the number of double bonds it contains is still
to be discussed.
Glycerol. Glycerol or glycerin and fatty acids are formed by hydrolysis
of the fats by enzymes during digestion or by saponification, i.e., hydrolysis
by alkalies. Glycerine has the ability to retain moisture to a high degree,
being more hygroscopic than the levulose compounds. It has long been
used by many European bakers to retain the moisture in cakes, cookies, etc.
H
I
H— C— OH H— C— H
„-i-
-OH y C— H + 2 H2O
H— C— OH H— C = O
I
H
glycerol acrolein water
Page 434
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
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and the fat is not so grainy. If in addition to rapid chilling, the fat is also
stirred while it is being cooled it becomes very smooth. If the temperature
to which it is cooled is several degrees below its melting point the fat may
become waxy and so firm that it is rather difficult to cream at ordinary
temperatures. The oil does not separate from the smooth fat as the fat
becomes soft. It is for this reason that only smooth lard or fat is sold in
paper cartons. Grainy lard may be purchased but comes in metal contain-
ers. The commercial smooth lards are not cooled sufficiently to become
waxy.
Fatty acids commonly found in foods. The fatty acids commonly
found combined with the glycerol in food and cooking fats are palmitic,
stearic, and oleic. Chemically the fatty acids of the acetic acid series have
the general formula C/zH2«02. The most important of this series in foods
are the palmitic and stearic, though butyric and caproic, with small amounts
of caprylic and capric, form about 7 per cent of the glycerides of butter.
H H H
Butyric acid
aproic
acid
Caprylic acid
Capric acid
Palmitic acid
Stearic acid
H-
H-
H-
H
H-
C— C— C— C = O
H
H
-i
I
H
H
I
H
H
i
I
H
H
I
-C-
c = o
I
OH
■Hn
I
■HJ4
nH-
I
C
■H-Je OH
■H-|
C — C = 0
I I
i-H-Jg OH
O
H
H
I
H
-H-
I
C
I
■H-
•H-
i
I
l-H-
— C =
I
14 OH
O
— C = 0
6h
HEAT DECOMPOSITION 547
Of the fatty acid series with the general formula CnrL^?i-JD^ oleic acid
is the most important in food fats. The acids of this series contain one
double bond in the chain and are unsaturated.
H rH-
Oleic acid
„4.
i
■H-
— C= C—
■H-n
I
c
■H-
— C = O
I
7 OH
Linolic acid belongs to the fatty acid series with the general formula
CnH2n-402. Linolic and linolenic acids are very important because they
are necessary for proper functioning of the body, and the animal body
does not have the ability to synthesize the unsaturated fatty acids. Linolic
acid contains two double bonds.
Linolenic acid belongs to the series CnH2n-602 and contains three double
bonds.
When oils or fats are hydrogenated, it is generally agreed that the more
highly unsaturated acids are the first to become saturated.
Though present in only small amounts both linolic and linolenic acids
may influence the properties of foods. Their effect, or the effect of their
oxidation products, on gluten quality has been considered. The glycerides
with more than one double bond also oxidize readily. The shortening power
of a fat or oil because of the number of double bonds it contains is still
to be discussed.
Glycerol. Glycerol or glycerin and fatty acids are formed by hydrolysis
of the fats by enzymes during digestion or by saponification, i.e., hydrolysis
by alkalies. Glycerine has the ability to retain moisture to a high degree,
being more hygroscopic than the levulose compounds. It has long been
used by many European bakers to retain the moisture in cakes, cookies, etc.
H
I
H— C— OH H— C— H
„-i-
-OH y C— H + 2 H2O
H— C— OH H— C = O
I
H
glycerol acrolein water