I'm in a disagreement with an acquaintance over this question. I contend that so long as every part of whatever is placed inside an autoclave reaches 251 degrees F and stays at 251 deg F for half an hour, it will be sterile, including things like sealed bottles of olive oil.
He says that unless the hot steam reaches every part of the item, it won't be sterile, regardless of how hot the thing gets or how long it stays hot. In his own words: "I have an autoclave at work. I have sealed autoclave test strips within vials of water and oil and autoclaved for 15-20mins: water test strip turned purple which showed it WAS successful at sterilising and the oil test strip stayed yellow, showing that it WASN'T successful for the oil. I tried another test strip with new oil sealed in a new vial and autoclaved for 2+hrs and this still was UNSUCCESSFULL, test strip was still yellow. OIL CAN NOT BE STERILISED IN AN AUTOCLAVE!"
Oil can be sterilized in using dry heat only. Water in the steam does not penetrate the substance of the oil since oil is not water soluble. This can cause an explosion hazard. Mineral oil or other machine lubrication is somtimes sterilized by dry heat for use in the operating room in the sterile field. The dry method requires that no more than 30cc (1 ounce) be placed in a container not to exceed 1/4 inch in depth. The time depends on the type of dry heat sterilizer. It can take as much as 1 to 6 hours. Some teperatures must be as high as 400 degrees. Not a good Idea to steam autoclave closed bottles of oil. 251 degrees for 30 minutes will not do it. Don't forget that autoclaves operate on the principle of steam under pressure. The pressure goes up to 30lbs.
