Abstract: The use of raffinose as a glass-forming agent for freeze-dried compositions intended for use in conducting chemical or biochemical reactions such as the PCR. Thus, for instance, there is provided a composition for carrying out a chemical or biochemical reaction, said composition being in a freeze-dried form and comprising (i) a set of reagents comprising at least some of the chemical or biochemical reagents necessary for conducting said chemical or biochemical reaction, and (ii) raffinose. Kits comprising these compositions and methods of using them form a further aspect of the invention.