Abstract: Disclosed is a sterilizing composition including (i) at least one mono or dialdehyde; (ii) at least one glycol or polyol or derivative thereof; (iii) a non-ionic first surfactant; and (iv) a second surfactant having a cloud point in the range of about 30° C. to 50° C. Also disclosed is a sterilizing composition including (i) at least one mono or dialdehyde; (ii) at least one glycol or polyol or derivative thereof; (iii) a non-ionic first surfactant; and (iv) a second surfactant, wherein the second surfactant is a quaternary ammonium compound. A process for preparing the compositions of the invention is also disclosed. The compositions of the invention are low or substantially non-foaming under high pressure, high temperature conditions, thus allowing maximum benefit from the new, more reliable, generation of automated endoscope reprocessing machines.