432 Chapter 17
packaging because crystallization of the fat
is fairly slow. It can be frozen if it is not to
be used immediately.
Butter oil and anhydrous milk fat are
rarely used as fat sources in frozen desserts
in the United States, but they are popular
choices in other parts of the world. Dry cream
and dry whole milk also are not widely used
in the formulation of ice cream mix because
they are prone to oxidative fl avor issues.Milk - Solids - Not - Fat
Milk - solids - not - fat include milk protein,
sugar (lactose), and minerals. Depending on
the ingredient, the ratio of components varies
greatly, which can affect the frozen product ’ s
fl avor and texture. Fluid whole and skim milk
are excellent sources of solids and fat because
of their clean fl avor. The fl avor and texture
can be adversely affected as milk products
are further processed by condensing, drying,
and separation processes (see below). The
lactose and mineral portions of the milk
solids affect the freezing point of the continu-
ous phase, just as added sweeteners do.
Lactose in ice cream can crystallize, causing
a fl avor defect known as sandiness. This can
occur at high concentrations of milk solids or
when adding ingredients with high concen-
trations of lactose such as acid or sweet whey.
Fluctuations in the storage temperature of ice
cream also contribute to the formation of
lactose crystals. The proteins contributed by
the milk solids help with emulsifi cation, aer-
ation, and foaming, and they contribute to the
stabilization of air bubbles, and water holding
(which contributes to viscosity in the con-
tinuous phase).Sources of Milk - Solids - Not - Fat
Fluid whole and skim milk. Both fl uid
whole and skim milk are excellent sources of
MSNF and should be used in the mix when-
ever they are available at a reasonable cost.it is necessary to prevent off fl avors from
developing. Only the best cream should be
processed for storage, and it should contain
no developed acidity. Off fl avors that are
likely to develop in frozen cream are oxi-
dized, rancid, fi shy, oily, and tallowy. A fi shy
fl avor in dairy products occurs when trimeth-
ylamines are formed by the hydrolysis and
oxidation of lecithin, a naturally occurring
phospholipid in milk. Factors which promote
development of this fl avor are high acidity
and the presence of pro - oxidants such as iron
or copper salts. Heat - treating cream helps
it to resist oxidation (Ewbank and Gould,
1943 ). Following heat processing, cream
intended for frozen storage should be frozen
quickly. Proper packaging and handling of
frozen cream is also important; stainless steel
or plastic containers are preferred. Quick -
frozen cream is held at − 23.4 ° C ( − 10 ° F) or
lower. Disadvantage of frozen cream are the
necessity of thawing it prior to use, and han-
dling issues.
Butter. Fresh sweet - cream unsalted butter
is often used for ice cream, as it is often
the least expensive source of fat. Sweet
cream butter has been found to whip more
slowly due to loss of natural emulsifi ers
(the phospholipids) in the buttermilk frac-
tion. However, this is easily overcome with
commercial emulsifi ers and homogenization.
Butter can be stored frozen for an extended
shelf life; however, it can suffer the same
oxidative defects as frozen cream and it can
absorb odors from the environment. Storage
in proper packaging is crucial.
Plastic cream. Separating sweet cream
(28% to 35% fat) a second time in a special
separator bowl at relatively high temperature
60 ° C (140 ° F) provides cream with a fat
content of 79% to 81%. Because of this high
fat content, the product solidifi es to a plastic
or solid mass upon cooling, and is therefore
known as plastic cream. If the product is
cooled quickly to 4.4 ° C (40 ° F), it remains in
a liquid state which allows for immediate