Rogers states that the factors affecting clumping are ''temperature,
the acidity, the fat content and its degree of dispersion, the degree of
agitation, and the fluidity of the system. The fat content, the degree of
agitation and the fluidity of the system determine the probability of col-
lisions of the globules." The tendency of the fat globules to clump is
greatest when the milk is cooled rapidly to 7° to 8°C., but if the fat
globules become solid at the low temperature before creaming is allowed to
take place the rate of creaming is retarded. The temperature that favors
clumping is also best for whipping the cream. Most cream is separated
from the milk by mechanical means. The fat particles left in the milk
after separating the cream are those less than 1/x and those between 1 and
2/A in diameter.
Butter. The fat globules in cow's milk are suspended in the milk and
thus do not form a permanent emulsion, though they may be so reduced
in size by homogenization that they form a permanent emulsion. Of the
dififerent theories formulated for explaining the manner in which emulsions
are stabilized the adsorption film theory is usually connected with milk.
Substances that lower surface tension tend to collect at the interface be-
tween two non-miscible systems. Proteins tend to lower the surface tension,
FAT 297
hence tend to collect at the interface. The layer or film around the fat
globules probably consists of adsorbed calcium caseinate, with some lactal-
bumin, globulin, and calcium phosphate. This membrane may be weakened
or broken in various ways. When milk is heated slowly, the membrane
surrounding some of the fat globules may be broken and a number of
globules may coalesce. Sometimes milk that has been heated and then
cooled has a more oily appearance due to this coalescing of the fat globules.
The membrane surrounding the fat particles may be broken by mechanical
agitation. Formation of butter in churning is brought about in this manner.
There are two theories regarding butter formation. One is that the
emulsion is reversed from the type found in the milk and that the butter
is a water-in-fat emulsion. The other view is that butter is formed by
packing the fat globules into a compact mass, and that water and air
are enmeshed during this process. Temperature and the formation of a
foam are both important in churning. At a temperature above 65 °C. there
is no aggregation of fat particles. Below 65° the tendency to clump in-
creases and is at a maximum at 7° to 8°C. A favorable temperature for
butter formation is below 24° and above 10°C. At temperatures below
4°C. the fat globules do not adhere to each other and aggregation does
not take place. At temperatures above the melting point of butter, no
butter is formed.
The fat particles tend to clump at the liquid/air interface, so that air
beaten in during the churning process accelerates clumping of the fat.
Butter may be churned from sweet or sour cream. The flavor of butter
from the sweet cream is milder and different from that of the sour-cream
butter. Many housekeepers prefer the sweet-cream butter for table use and
the sour-cream butter for cooking.
Page 240
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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Rogers states that the factors affecting clumping are ''temperature,
the acidity, the fat content and its degree of dispersion, the degree of
agitation, and the fluidity of the system. The fat content, the degree of
agitation and the fluidity of the system determine the probability of col-
lisions of the globules." The tendency of the fat globules to clump is
greatest when the milk is cooled rapidly to 7° to 8°C., but if the fat
globules become solid at the low temperature before creaming is allowed to
take place the rate of creaming is retarded. The temperature that favors
clumping is also best for whipping the cream. Most cream is separated
from the milk by mechanical means. The fat particles left in the milk
after separating the cream are those less than 1/x and those between 1 and
2/A in diameter.
Butter. The fat globules in cow's milk are suspended in the milk and
thus do not form a permanent emulsion, though they may be so reduced
in size by homogenization that they form a permanent emulsion. Of the
dififerent theories formulated for explaining the manner in which emulsions
are stabilized the adsorption film theory is usually connected with milk.
Substances that lower surface tension tend to collect at the interface be-
tween two non-miscible systems. Proteins tend to lower the surface tension,
FAT 297
hence tend to collect at the interface. The layer or film around the fat
globules probably consists of adsorbed calcium caseinate, with some lactal-
bumin, globulin, and calcium phosphate. This membrane may be weakened
or broken in various ways. When milk is heated slowly, the membrane
surrounding some of the fat globules may be broken and a number of
globules may coalesce. Sometimes milk that has been heated and then
cooled has a more oily appearance due to this coalescing of the fat globules.
The membrane surrounding the fat particles may be broken by mechanical
agitation. Formation of butter in churning is brought about in this manner.
There are two theories regarding butter formation. One is that the
emulsion is reversed from the type found in the milk and that the butter
is a water-in-fat emulsion. The other view is that butter is formed by
packing the fat globules into a compact mass, and that water and air
are enmeshed during this process. Temperature and the formation of a
foam are both important in churning. At a temperature above 65 °C. there
is no aggregation of fat particles. Below 65° the tendency to clump in-
creases and is at a maximum at 7° to 8°C. A favorable temperature for
butter formation is below 24° and above 10°C. At temperatures below
4°C. the fat globules do not adhere to each other and aggregation does
not take place. At temperatures above the melting point of butter, no
butter is formed.
The fat particles tend to clump at the liquid/air interface, so that air
beaten in during the churning process accelerates clumping of the fat.
Butter may be churned from sweet or sour cream. The flavor of butter
from the sweet cream is milder and different from that of the sour-cream
butter. Many housekeepers prefer the sweet-cream butter for table use and
the sour-cream butter for cooking.