17B-1 |
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A. REGAND, H. D. Goff, and M. Schroeder. Dept. of Food Science, Univ. of Guelph, Ontario Agricultural College, Guelph, ON N1G 2W1, Canada Ice structuring proteins (ISPs) are of utmost importance in the freezing tolerance of over-wintering cereal crops. Extracellular ice nucleation and ice recrystallization inhibition are promoted in the apoplast of the plant by these proteins. Such functionalities suggest possibilities for their use as natural ice modulators in the cold storage of frozen foods. Our objective was to determine the effect that the addition of an extract from cold-acclimated winter wheat grass (AWWE) has on the ice recrystallization behaviour of quiescently frozen ice cream model solutions. Differences in the activity of the protein in retarding ice crystal growth (ICG) with the addition of common ice cream ingredients to sucrose solutions or after pasteurization were evaluated. Samples were frozen and temperature-cycled in a cold stage of a light microscope. Recrystallization rates were calculated from image analysis of images acquired by bright field microscopy. ISP activity was defined as the % ICG inhibition compared to 0% AWWE. Ice recrystallization in sucrose solutions was significantly reduced when more than 0.125% protein from AWWE was added. At concentrations above this, a plateau was observed, which constituted a 70% reduction in ICG. The addition of other ingredients to sucrose solutions significantly reduced ICG. However, the activity of the ISPs was reduced up to 43% with the presence of other ingredients. Pasteurization eliminated ISP activity in complex mixes and reduced it significantly in sucrose solutions. A combined effect of the interaction of ISPs with other components rather than only protein denaturation is suggested. The increase in viscosity and total solids with added ice cream ingredients will reduce the kinetics of diffusion mediated processes, such as the adsorption to the ice-water interface that has been proposed as the main mechanism of action for ISPs. ISPs may prove to be valuable food ingredients with appropriate formulation testing and product development.
Session 17B, Dairy Foods: General
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