Recrystallization of ice in ice cream during controlled accelerated storage

Accelerated ice recrystallization in a thin film of vanilla ice cream was studied on a cold stage microscope, housed in a refrigerated glove box. Sample temperature was held constant (within +/-0.01 degrees C) or sinusoidally oscillated for 5 days. Changes in ice crystal size distribution were monitored using an image analysis technique. Several recrystallization mechanisms were observed. Melt-refreeze recrystallization was important for oscillating-temperature conditions, while rounding was particularly apparent at a constant temperature. Accretion was evident for all conditions studied but migratory recrystallization was observed only rarely. Mean ice crystal size increased as a function of approximately time (-0.33). Recrystallization rates increased with mean storage temperature (-20 to -5 degrees C) and amplitude of temperature fluctuations (0.01 to 2 degrees C). However, recrystallization still occurred at very low amplitudes (+/-0.01 degrees C), with a recrystallization rate about half as large as for recrystallization with temperature fluctuations of +/-1 degrees C. Slower temperature fluctuations (2 h cycle) resulted in an initial lag in recrystallization rate that was not observed for more rapid fluctuations (10-min cycle). Copyright (C) 1996 Published by Elsevier Science Limited.