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.
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 coldness, 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.