• (a.) Capable of being heated to or somewhat above 55
Ther`mo·sta'ble adjective [ Thermo- + stable fixed.] (Physiol. Chem.) Capable of being heated to or somewhat above 55° C. without loss of special properties; -- said of immune substances, etc. 
thermostable, thermostabile 1. Relatively stable or resistant to heat. 2. Not readily subject to alteration or destruction by heat.