I have recently been asked by my local health department to stop using Ganache pending an assessment on microbial stability… it’s very frustrating! It’s not from a complaint, issue or such; my new inspector just doesn’t believe it can last more than 4 hours at room temp so I have to prove to them that it can! (They are happy with all my other fillings due to the high sugar content).

I’ve been struggling to find a citable reference for ganache stability/shelf life; would anybody be able to help me?

Typically I use (used!!) white ganache at 3:1 ratio, I prefer it whipped although I know that shortens its life due to the incorporation air/moisture. I would fill and cover between 3-5 days before decorating and it lives in the fridge until covered in fondant which usually happens the day of/day after covering. If I allow a max of 3 days for the customer to eat their cake I am essentially offering a max shelf life of 8 days at room temperature (fondant covered); does that seem excessive?

I used to use fresh cream heated in a pan but since I started preparing further in advance I switched to high fat cream substitute because of its 3 month shelf life which I figured (but can’t prove!) would transfer to the finished ganache; I do use the gradual microwave melting method though so the ‘cream’ never comes close to a control point temperature…

…Can you tell this is stressing me out slightly!

I would just wait for the study results. While ganache ratios may be the same, methodology for its preparation would vary from person to person based on the very examples you mentioned, what type of cream, how long is the cream heated, air vs no air incorporated. Sometimes the potential problem with ganache (especially molding) is even more significantly related to how the ganache is handled after it has been made, so even properly made ganache stored and/or thawed inappropriately could become hazardous.

I was going to come in here and tell you to have your specific recipe tested for stuff like pH and aW but if they're already doing a study, just hold off for the results. I don't think citing literature would convince them as much as scientific results specific to your recipe and methods.