Recrystallization inhibitor

A method of preventing or inhibiting ice recrystallization in a substance which is susceptible to ice crystal growth upon cryopreservation and/or warming or thawing therefrom, the method comprising the step:

• (i) treating the substance with a composition comprising poly(proline) or a variant or derivative thereof,
• wherein the poly(proline) or a variant or derivative thereof is a homogeneous or heterogeneous mixture of polymers which consist substantially or exclusively of linear chains of proline residues, the polymers having the general structure:
• wherein n=3-200 (SEQ ID NO:
• 1);
• or 3-150 (SEQ ID NO:
• 2) or 5-100 (SEQ ID NO:
• 3);
• or 10-100 (SEQ ID NO:
• 4), 10-50 (SEQ ID NO:
• 5) or 10-25 (SEQ ID NO:
• 6);
• or 10-20 (SEQ ID NO:
• 7) or 11-15 (SEQ ID NO:
• 8).