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Wheat proteins improve ice cream quality.

Ice-modifying proteins extracted from winter wheat may help ice cream stay smooth and creamy during long periods in the freezer, scientists at the University of Guelph tell us. Ice cream gets its creamy texture from the way that fat molecules, air bubbles and ice crystals assemble within a highly concentrated mixture of sugar water. Getting this assemblage right can be difficult.

Microscopy images of ice cream reveal a matrix of tiny fat globules surrounding air bubbles and ice crystals. Ice cream is an emulsion, so the matrix of fat particles must be stabilized by milk proteins to prevent the fat from clumping together. The other component of the emulsion is a solution of sugar water, from which the ice crystals form during freezing. The solution never freezes completely, allowing ice cream to be scooped and chewed at freezer temperatures.

Guelph scientists examined ways to improve ice cream quality by introducing new ingredients and manipulating its structure. They've discovered a possible use for certain proteins found in winter wheat, which help the plant survive winter by modifying the growth of cell-damaging ice crystals. Their research was done in collaboration with Ice Biotech Inc., which developed the proteins. Using these proteins in ice cream has made for some really smooth batches of ice cream, according to the scientists.

In the past, Guelph scientists studied the effect of stabilizers on the recrystallization of ice cream that experienced constant and fluctuating temperatures during storage. They had determined that polysaccharide stabilizers did not affect the initial ice crystal size distribution of model solutions or ice cream frozen in a batch process.

Investigators found that a constant storage temperature of -30 C did not affect the overall ice crystal size. This was probably because of the proximity of this temperature to the glass transition temperature of the unfrozen phase. Stabilizers did not affect the size distributions of the ice crystals because they did not affect the glass transition temperature.

Recrystallization caused by fluctuations in temperature seemed to be dictated by migratory recrystallization. The overall increase in storage temperature most likely induced smaller crystals to melt, probably diffuse and to accrete, which overwhelmed the amplitude of the fluctuation. The melt-refreeze process was most likely the predominant mechanism of recrystallization, and in this case, stabilizers had a measurable effect in controlling ice crystal size.

Further information. Doug Goff, Department of Food Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada; phone: 519-824-4120; fax: 519-824-6631; email:
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Publication:Emerging Food R&D Report
Date:Nov 1, 2003
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