The present invention relates to methods for preventing or inhibiting ice recrystallisation in substances (e.g. biological materials and food products) which are susceptible to ice crystal growth upon cryopreservation and/or thawing therefrom. The methods relate to the use of compositions comprising poly(proline) or a variant or derivative thereof. Also provided are kits and compositions comprising poly(proline) which can be used in the methods of the invention.