Why different self-preserved foods don’t preserve each other?


As per the title, if for example butter preserves itself, and strawberry jam preserves itself, why does a blob of butter go mouldy if it’s dropped in the jam jar?

In: Chemistry

It is because the food itself is preserved not the container that holds the said food. For example, butter is not preserved when it is dropped into a jar that contains jam.

Jam is preserved by the ridiculously high sugar content. Butter by the high fat content. A mix of the two has neither the high enough fat content or high enough sugar content to kill mould… and so problem.

In order for a food source to be preserved it has to be a toxic environment for bacteria/mould etc. too high a concentration of something may prevent growth but mixing two substances can dilute the toxic nature of the environment.

Imagine you have two rooms. One has a temperature of 110 degrees Fahrenheit. The other has a temperature of 30 degrees Fahrenheit.

If you are trapped in either room for an extended period of time, you will probably die. Stick them next to each other with a door in between so you can cool off or warm up depending on what you need in the moment, and you’ll last a lot longer. Open the door and let the two rooms mix, and you’ll get a nice, survivable room temperature.

Butter and jam are hostile environments to bacteria, but they are different kinds of hostile environments, and mixing them together compromises that hostility.