434 Chapter 17
Reduced lactose products. To improve
heat shock resistance and the sandiness defect
of frozen desserts, reduced lactose concen-
trated milk can be used as a source of serum
solids. The lactose - reduced ingredient is
manufactured by holding the product at room
temperature to effect lactose crystallization
(subsequent to the condensing step in a
vacuum pan). Crystallized lactose is centri-
fuged out to obtain the reduced lactose
product. It has been used in high - solids ice
cream mixes. Approximately 25% of serum
solids can be replaced with low - lactose skim
milk. Another approach for lactose reduction
is to use food - grade lactase to effect hydro-
lysis of lactose prior to the condensing step.
In some cases, ultrafi ltration of skim milk
to obtain retentate of reduced lactose content
has been employed. Removal of lactose from
skim milk increases the protein content,
which in turn increases the acidity and vis-
cosity of the mix. However, the texture and
storage quality of the frozen dessert is mark-
edly improved. Ice cream mix containing
lactose - hydrolyzed serum solids freezes at a
lower temperature and does not become too
hard in storage. Because of conversion of
disaccharide lactose to the monosaccharides
glucose and galactose, a noticeable depres-
sion in freezing point is affected. Accordingly,
at draw and storage temperature, the ice
cream displays a noticeably softer texture
which is an interesting consumer feature.
Lactose hydrolysis, therefore, provides a tool
to favorably alter the melting properties of
ice cream. Use of reduced lactose serum
solids, on the other hand, leads to no differ-
ence in melting characteristics of the frozen
dessert.
Lactose hydrolysis also affects the sweet-
ener level. Because lactose is only 16% as
sweet as sucrose, lactose hydrolysis products
are much sweeter (53% as sweet as sucrose).
Thus, the sweetener content of the mix can
be reduced a little when lactose hydrolyzed
skim milk is used. From the standpoint of
formulation, various grades (or lines) of icelight color, and be free from scorched parti-
cles and easily dispersible. NFDM should be
bought only in such quantity as can be used
before the product develops off fl avors and
kept in cold storage. This slows the develop-
ment of a stale fl avor that can impart an old
or storage fl avor defect to ice cream. It can
be stored up to one year without loss in
quality. For use in ice cream mix, extra - grade
low - or medium - heat NFDM is recom-
mended. There is no great advantage in using
more expensive agglomerated or instant
NFDM for frozen desserts. Incorporation of
dry milk into ice cream mix is facilitated by
the use of a powder funnel and blender pump
or special blending equipment.
Dry sweet whey. Dry sweet whey is com-
monly used at a 25% replacement level of
serum solids in ice cream. Because it con-
tains 72% lactose as compared to 52% lactose
in nonfat dry milk, its incorporation beyond
the suggested level may result in crystallized
lactose, the cause of the sandiness defect in
ice cream. Delactosed whey, demineralized
whey, and whey protein concentrates are not
frequently used due to cost constraints, but
they have been investigated for their texture -
modifying properties.
Sodium and calcium caseinates. Sodium
and calcium caseinates improve the whipping
properties of the mix, heat - shock resistance,
body, and texture of ice cream. Sodium
caseinate at about the 0.5% level in the mix
accords a slow - melt character to ice cream.
However, these ingredients are relatively
expensive and used very rarely.
Hydrolyzed milk proteins. Hydrolyzed
milk proteins may be derived from casein or
whey fractions of milk. They act as func-
tional stabilizers in frozen desserts and can
replace gelatin, gums, celluloses, alginates,
and other hydrocolloids. Although they are
expensive ingredients, they may be preferred
for their consumer - friendly appearance on
the label. Hydrolyzed whey proteins are
subject to a limitation of 25% serum solids
replacement.