Abstract
A water solution placed in a freezer changes into a polycrystalline state of ice in keeping with the exclusion of the solute. This exclusion is attributed to growth of the ice crystals, as the growth only consumes water molecules, leading to concentration of the excluded solute into a lastly frozen area. This phenomenon was named "progressive freeze-concentration (PFC)", which is sometimes the problem for quality preservation of water-containing materials, such as foods and tissues. Here we examined whether antifreeze protein (AFP) works to prevent PFC, since AFP can bind specifically to ice crystals to inhibit their growth. For this purpose, we froze the AFP solution containing red-colored ink in a house-made PFC device consisting of a glass vessel sandwiched by heat insulating materials. The ink was concentrated near the bottom of a placoid ice prepared in the PFC device without AFP, while it was dispersed with AFP. A level of dispersion was dependent on the AFP concentration and ice crystal shape. These results suggest that AFP possesses inhibitory effect on PFC, which was presumably correlated with the known abilities of AFP, such as ice-shaping, thermal hysteresis, and ice recrystallization inhibition.
