Once fermented, I am considering kegging three gallons of cider and putting the keg away for about six months. Is that a good amount of time for a brett cider?
Take notes and report back in six months
I honestly have no good information.
Brett works and changes over time because it has a several different metabolic pathways. Beer has a lot of different size sugar chains (starch, dextrines, sucrose, maltoise, etc), and brett breaks them down (several outside of the cell itself) into manageable pieces, then comes back later to eat them. I think of it like butchering a cow - brett knows how to do that; brett breaks down starches, dextrines, simple sugars, and even dead yeast. Beer yeasts (sacch) know how to cut a steak, but that's about it; they can metabolize simpler sugars, but cannot handle starch or dextrines (most strains). Wine yeasts are like children, picky eaters who like only simple sugars like sucrose, dextrose, fructose, and glucose.
Apple juice is mainly fructose and glucose, which is why it ferments so dry. It lacks the complex sugars and starches which feed brett over the long term, allowing it to give its unique flavors over a long fermentation schedule. I don't know what brett is going to do with the other compounds in apple juice. My farmhouse cider was a nice success, but I didn't notice a huge change over about five months. It was also a mild strain of brett, so YMMV. Good luck regardless.
