As the fat particles clump at the liquid/air interface, or within the
liquid, the increased rigidity they give the foam permits inclusion of more
air bubbles and extension of the films with the result that the dryness of
the foam is increased. See Fig. 31. Larger fat particles clump more readily
and thus form the structural support offered by the fat more easily. This
offers an explanation of why cream from milk containing larger fat parti-
cles, milk from Jersey and Guernsey breeds, whips more quickly than
cream containing smaller fat particles, milk from other breeds.
Aging improves the whipping qualities of cream. The viscosity increases
with aging. As a general rule, treatment that increases the viscosity increases
the whipping properties. Pasteurization tends to reduce the whipping
quality of cream.
Babcock has found that the best whipping is obtained at a temperature
of 45 °F. or lower. At this temperature agitation favors the clumping
together of the fat particles. At high temperatures, both the higher tem-
perature and the agitation increase the dispersion of the fat. Above 50°F.
the decrease in stiffness of whipped cream is in direct ratio to increase in
temperature, so that 30-per cent cream will not whip at 72°F.
300
MILK AND CHEESE
Babcock found acidity up to 0.3 per cent, at which sour taste is evident,
had no effect on whipping quality. If acid was added in excess of 0.3 per
cent, whipping quality improved, whether added to fresh or aged cream,
when the amount added began to curdle the cream.
The addition of sugar to cream either before or after whipping was
found by Babcock to decrease the stiffness of the cream. For each 2 tea-
spoons added to 100 cc. (about ]/\ cup) the stiffness decreased four points
on the stiffness scale. Adding the sugar before whipping the cream
decreased the volume obtained and increased the whipping time.
The denaturation or coagulation of the protein film at the air/cream
interface, increases the stiffness of the whipped cream. Since colloidal
Fig, 31. — Diagram of a cross section through whipped cream. Fat globules of
the cream are shown as small black spots. Magnification about 180 (Rahn).
reactions require time, it is a better practise to add sugar to whipped cream
after, rather than before or during the whipping process. By this procedure
denaturation is more complete, which offers an explanation of why the
volume of the cream is less affected by the addition of the sugar last. The
addition of sugar lessens the stiffness and decreases the volume of the
whipped cream because it either prevents denaturation and/or peptizes
the protein film.
Reaction of Milk
Freshly secreted milk is nearly neutral to litmus. The reaction varies
slightly but has an approximate pYi of 6.6. The freshly secreted milk con-
tains carbon dioxide. The amount of this gas in the milk decreases during
milking and the subsequent handling of the milk, while the percentage of
oxygen and nitrogen increase. For this reason the titratable acidity decreases
for a time in milk exposed to the air. Confined milk does not show as great
RENNET COAGULATION 301
a decrease in titratable acidity as the exposed milk, for the percentage of
carbon dioxide lost is smaller.
Page 243
Presented as published in 1932. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
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As the fat particles clump at the liquid/air interface, or within the
liquid, the increased rigidity they give the foam permits inclusion of more
air bubbles and extension of the films with the result that the dryness of
the foam is increased. See Fig. 31. Larger fat particles clump more readily
and thus form the structural support offered by the fat more easily. This
offers an explanation of why cream from milk containing larger fat parti-
cles, milk from Jersey and Guernsey breeds, whips more quickly than
cream containing smaller fat particles, milk from other breeds.
Aging improves the whipping qualities of cream. The viscosity increases
with aging. As a general rule, treatment that increases the viscosity increases
the whipping properties. Pasteurization tends to reduce the whipping
quality of cream.
Babcock has found that the best whipping is obtained at a temperature
of 45 °F. or lower. At this temperature agitation favors the clumping
together of the fat particles. At high temperatures, both the higher tem-
perature and the agitation increase the dispersion of the fat. Above 50°F.
the decrease in stiffness of whipped cream is in direct ratio to increase in
temperature, so that 30-per cent cream will not whip at 72°F.
300
MILK AND CHEESE
Babcock found acidity up to 0.3 per cent, at which sour taste is evident,
had no effect on whipping quality. If acid was added in excess of 0.3 per
cent, whipping quality improved, whether added to fresh or aged cream,
when the amount added began to curdle the cream.
The addition of sugar to cream either before or after whipping was
found by Babcock to decrease the stiffness of the cream. For each 2 tea-
spoons added to 100 cc. (about ]/\ cup) the stiffness decreased four points
on the stiffness scale. Adding the sugar before whipping the cream
decreased the volume obtained and increased the whipping time.
The denaturation or coagulation of the protein film at the air/cream
interface, increases the stiffness of the whipped cream. Since colloidal
Fig, 31. — Diagram of a cross section through whipped cream. Fat globules of
the cream are shown as small black spots. Magnification about 180 (Rahn).
reactions require time, it is a better practise to add sugar to whipped cream
after, rather than before or during the whipping process. By this procedure
denaturation is more complete, which offers an explanation of why the
volume of the cream is less affected by the addition of the sugar last. The
addition of sugar lessens the stiffness and decreases the volume of the
whipped cream because it either prevents denaturation and/or peptizes
the protein film.
Reaction of Milk
Freshly secreted milk is nearly neutral to litmus. The reaction varies
slightly but has an approximate pYi of 6.6. The freshly secreted milk con-
tains carbon dioxide. The amount of this gas in the milk decreases during
milking and the subsequent handling of the milk, while the percentage of
oxygen and nitrogen increase. For this reason the titratable acidity decreases
for a time in milk exposed to the air. Confined milk does not show as great
RENNET COAGULATION 301
a decrease in titratable acidity as the exposed milk, for the percentage of
carbon dioxide lost is smaller.