Here's one of my old posts about Acetobacter sp.
Ok,
I went through my old microbiology lab books and found a group of chemoheterotrophic bacteria that some of us may find familiar. It is possible that these bacteria could use sorbate to proliferate, and taint mead.
These are acetic acid bacteria which are used in Mother of Vinegar for making vinegar; and they oxidize primary and secondary sugars in fermenting liquids. In our case we are talking about conversion to keto-sugars: sobital to sorbase, mannitol to fructose, and erythritol to erythulose.
The good news is that these little beasties need O2 in order to carry out their conversion and oxidation reactions (Gluconobacter sp. and acetobacter sp. are the two Genus of the bacteria I'm talking about). They are markedly acidophilic growing in pH as low as 4, with an optimal pH in the range of 5 to 6.
For me that means that I will keep my pH range in the low threes, and rack my meads to corny kegs that have been evacuated of 02 and infiltrated with C02. In this case the sorbate should be sufficient to stabilize and prevent refermentation. The low pH and anaerobic enviornment will prevent the acetic acid bacteria from oxidizing the ethanol and other available substrates into acetic acid.
I'll follow this post with an extended excerpt from my reference source along with a bibliography.
Cheers,
Oskaar
Hope that helps.