Influence of temperature on crystallization of lactose in ice-cream

Sandiness in ice-cream due to lactose crystallization can still be a problem in many circumstances. Lactose crystallization occurs in ice-cream as the unfrozen phase becomes supersaturated. However, the effects of storage temperature and temperature fluctuations on lactose crystallization have not been very well quantified. In this work, an accelerated storage apparatus was used to determine the effects of thermal fluctuations (from ±0.01°C to ±2.0°C), at several mean storage temperatures (from −5.0 to −20.0°C), on the onset of lactose nucleation and subsequent crystal growth in a standard vanilla ice-cream. the induction time for nucleation initially decreased as temperature was lowered (for temperature oscillations of ±1.0°C), until a minimum induction time of 3 h was found between −10.0 and −12.0°C. Further decreases in storage temperature caused the induction time to increase. the induction time for nucleation increased as the extent of temperature fluctuations increased, from 0.01 to 2.0°C, while initial lactose crystal growth rate showed the opposite trend. the initial growth rate increased as temperature decreased between −5.0 and −10.0°C, but then decreased for temperatures below −10.0°C. At −20.0°C lactose crystals grew very slowly. At −10.0°C the rate of growth decreased with increasing amplitude of temperature oscillations.