Questions
& Answers
from
"On Ice Cream" featured in Dairy Foods magazine
and sourced from "On Ice Cream" technical short courses.
Antifreeze
Proteins in Ice Cream:
Question:
What are antifreeze proteins and how can they be used in ice cream?
Answer:
The term "antifreeze proteins" was first used to describe
specialized proteins that allow arctic fish to survive in water at temperatures
below the freezing point of their body fluids. These proteins have also
been found in other biological systems that survive sub-freezing temperatures,
such as winter wheat, rye and canola, as well as several insect species.
The proteins function by inhibiting ice crystallization and minimizing
ice crystal growth.
Recently, the term "ice structuring proteins" (ISP) has been
used to refer to these compounds.
The capability to limit ice crystal size presents an interesting ice
cream application opportunity for ISP. Most of the published research
has been reported in patents covering frozen desserts made using ISP
from a variety of sources. The patents show that low levels of ISP in
ice cream can reduce ice crystal growth rate substantially and control
the shape of ice crystals in ways that provide unique textural and structural
characteristics.
Of the various sources, ISP derived from plants seems to be the most
likely form to achieve consumer and regulatory acceptance. It also is
the most easily recovered source. As a result, commercial application
research tends to focus on plant-derived ISP.
A recent report of initial results from research investigating the functionality
of ISP extracted from winter wheat is encouraging. It indicates that
the addition of ISP to ice cream yields a product with considerable
less ice crystal growth during heat shock as compared to ice crystal
growth in a control (no added ISP).
ISP is a potentially valuable tool for improving shelflife by limiting
ice crystal growth. Addition of ISP to ice cream could support significant
changes in composition and handling. For example, one of the ISP patents
includes a claim that the small ice crystals in ISP ice cream makes
it possible to take packaged ice cream directly to the hardening room,
and bypass the conventional rapid hardening step.
ISP, however, cannot completely replace the functionality of other ice
crystal-control ingredients, such as stabilizers. Stabilizer systems
affect properties not influenced by ISP, such as handling properties
at the freezer, melting behavior and perception of cold-ness, creaminess
and richness.
Therefore, the initial use of ISP alone is likely to occur in products
in which stabilizers are not used, or in new products designed around
ISP functionality. To take advantage of ISP functionality in existing
products without changing their established properties, it will be necessary
to use ISP in addition to the conventional stabilizer system. It is
likely that suppliers will develop specialized stabilizer blends designed
to be used with ISP.
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