The freezing process. If the ice-cream mix has not been cooled
before it is put in the freezer it is better to turn the freezer slowly until
the mix is cooled. If the freezer is turned rapidly while the mix is at a
temperature above 4.5°C. or 40°F. the butter fat is clumped together and
a buttery product results. If carried far enough, butter may even be
churned in the mix. The mix does not hold the air incorporated in it until
its temperature is cooled to about 1°C. or 34°F., so that rapid turning is
of no advantage from this standpoint until the mix is cooled. With a
freezer turned by hand, if the freezer is turned rapidly all the time, one's
energy is often expended before the freezing is finished, and it is during
the latter part of the freezing period that the turning should be rapid. The
size of the crystals formed during freezing depends upon the rate of turn-
ing of the freezer and the length of time of the freezing process. Stirring
the solution during crystallization increases the number of nuclei formed,
and the resulting crystals are smaller than if the mixture is not stirred.
If the ice cream is not stirred during freezing, few nuclei are formed, the
water crystals join onto each other, and a product with very coarse, large,
spiny crystals is the result. On the other hand, if the ice cream is stirred
the size of the crystals depends upon the rate of turning. Very slow turn-
ing while freezing is in progress results in larger crystals; rapid turning
results in smaller crystals. If the freezer is turned very slowly the crystals
build onto the crystals already formed ; with rapid turning many new
crystals are developed. The time of the freezing process also affects the
size of the crystals. If the crystals are formed very rapidly, too little air is
mixed with the cream, which produces an ice cream without a velvety
texture. Since rapid freezing occurs with low temperatures it is better not
to have the temperature of the brine too low, thus 1 part of salt to 8 parts
of ice produces good results.
Overrun. The addition of air to the ice cream during freezing causes
it to swell so that the ice cream increases in bulk. This increase is known
as the swell or overrun.
This swell or overrun due to the incorporation of air particles gives a
smoother, more velvety texture to the ice cream. Mortensen states that it is
preferable to have the air cells in the finished cream small, for the strength
of the film of a small air cell is stronger than that of a large one. To
obtain small air cells in the ice cream the mix should be viscid. A viscid
PERCENTAGE OVERRUN
93
substance resists incorporation of air, and it will be worked in in finer
divided portions. With increased viscosity the air is held in the mix better
after it is incorporated. Mortensen includes homogenization as an impor-
tant factor in increasing the viscosity of the ice-cream mix.
Page 74
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The freezing process. If the ice-cream mix has not been cooled
before it is put in the freezer it is better to turn the freezer slowly until
the mix is cooled. If the freezer is turned rapidly while the mix is at a
temperature above 4.5°C. or 40°F. the butter fat is clumped together and
a buttery product results. If carried far enough, butter may even be
churned in the mix. The mix does not hold the air incorporated in it until
its temperature is cooled to about 1°C. or 34°F., so that rapid turning is
of no advantage from this standpoint until the mix is cooled. With a
freezer turned by hand, if the freezer is turned rapidly all the time, one's
energy is often expended before the freezing is finished, and it is during
the latter part of the freezing period that the turning should be rapid. The
size of the crystals formed during freezing depends upon the rate of turn-
ing of the freezer and the length of time of the freezing process. Stirring
the solution during crystallization increases the number of nuclei formed,
and the resulting crystals are smaller than if the mixture is not stirred.
If the ice cream is not stirred during freezing, few nuclei are formed, the
water crystals join onto each other, and a product with very coarse, large,
spiny crystals is the result. On the other hand, if the ice cream is stirred
the size of the crystals depends upon the rate of turning. Very slow turn-
ing while freezing is in progress results in larger crystals; rapid turning
results in smaller crystals. If the freezer is turned very slowly the crystals
build onto the crystals already formed ; with rapid turning many new
crystals are developed. The time of the freezing process also affects the
size of the crystals. If the crystals are formed very rapidly, too little air is
mixed with the cream, which produces an ice cream without a velvety
texture. Since rapid freezing occurs with low temperatures it is better not
to have the temperature of the brine too low, thus 1 part of salt to 8 parts
of ice produces good results.
Overrun. The addition of air to the ice cream during freezing causes
it to swell so that the ice cream increases in bulk. This increase is known
as the swell or overrun.
This swell or overrun due to the incorporation of air particles gives a
smoother, more velvety texture to the ice cream. Mortensen states that it is
preferable to have the air cells in the finished cream small, for the strength
of the film of a small air cell is stronger than that of a large one. To
obtain small air cells in the ice cream the mix should be viscid. A viscid
PERCENTAGE OVERRUN
93
substance resists incorporation of air, and it will be worked in in finer
divided portions. With increased viscosity the air is held in the mix better
after it is incorporated. Mortensen includes homogenization as an impor-
tant factor in increasing the viscosity of the ice-cream mix.