Inhibition of recrystallization of ice grains by adsorption of poly(vinyl alcohol) onto ice surfaces

The effect of poly(vinyl alcohol) (PVA) on recrystallization of ice was studied by comparison with the effect of antifreeze protein (AFP) type I. Polycrystalline ice wafers consisting of numerous ice grains, whose initial size was less than 130 mum (i.e., less than the thickness of the ice wafer) were made from solutions containing PVA or AFP type I at various concentrations. The ice wafers were annealed between -2.3 and -2.0 degreesC for 5 h, and then the size of the ice grains was measured using digital microscopy. Even at a PVA concentration as low as about 5 x 10(-7) mol/L, the size of the annealed ice grains made from the PVA solution did not change significantly from the initial size, indicating that PVA is as effective as AFP type I in inhibiting ice recrystallization. The effectiveness of PVA increased (i.e., the grain size decreased) with increasing molar concentration, molecular weight, or degree of hydrolysis of PVA. The function of PVA molecules in the inhibition of recrystallization was analyzed by using the Langmuir adsorption equation.