Abstract
Ice crystal structure size in frozen food is inversely proportional to the advance rate of ice front, reflecting
the important role of the molecular diffusion of water in the process of ice crystal growth. In the freezing
preservation of living cells, the water permeability in the plasma membrane seriously affects freezing
tolerance of cells. Plant cells, in general, have much lower water permeability in the membrane compared
with animal and microbial cells so that the membrane structure of plant cells is easily destroyed by
intracellular ice crystal formation. By controlling the ice crystal structure size very large, the progressive
freeze-concentration becomes possible. This method is very effective to make the freeze concentration
system much simpler compared with the conventional method of suspension crystallization to reduce the cost
of freeze concentration substantially. Thermal unfolding of proteins was analyzed in terms of water activity
in aqueous solutions. The protein unfolding ratio was correlated well to the water activity of the system,
which was described well by the modified Wyman-Tanford equation. From this analysis, the free energy
difference (ΔΔG) for protein stability in a solution and in pure water could be obtained.
