Methods for sterilizing biological materials by irradiation over a temperature gradient

A method for sterilizing a biological material that is sensitive to radiation, said method comprising;

• (a) determining the maximum acceptable temperature (Tmax) for said biological material during irradiation;
• and (b) irradiating said biological material with radiation for a time effective to sterilize said biological material at a rate effective to sterilize said biological material, wherein said irradiating is performed under conditions whereby the temperature of said biological material increases during said irradiating from an initial temperature (Ti) to a final temperature (Tf), wherein said initial temperature (Ti) is no greater than about Tmax−Tobs, wherein Tobs is determined by a process comprising irradiating a sample of said biological material or a suitable substitute therefore with said radiation under the conditions under which said biological material is to be irradiated in step (b) while measuring the increase in temperature of said sample.