how come some laboratory media required to be sterilized at lower than 15PSI in the autoclave for lesser time?

Question

how come some laboratory media required to be sterilized at lower than 15PSI in the autoclave for lesser time? and What is the rationale behind the removal of inside the autoclave before allowing it to go up to 15 PSI

Answer 1

Some components found in some media are not as stable in heat. So, heating to 15 PSI raises the temperature of the medium to the point where these components (I think certain vitamins and certain amino acids, but I'm not sure which) decompose.