I am making my third batch of cider using juice from a local farm, so far its worked out well other than a persistent haze in one batch. I want to try and simplify / improve by process by removing a racking and priming step if possible. I would like to rack my bucket fermentation early at an SG that will ensure i generate sufficent additional CO2 in keg for the finished product. What calculation should I be using assuming I will run to total dryness? eg. If I rack at 1.020 and after the secondary ferm end at just below 1 what volumes of CO2 will be in the cider assuming I keep the keg sealed or an appropiate top pressure? Could I use this to produce fully sparkling cider for bottling? If any one has any insight, guidance or advise I would be most greatful. Kind Regards Arend
Wow, that's a tricky one. I'm of the opinion you wont make the same quality cider with this method. Fermentation is the most important part of the process, and the hardest to keep consistent. Towards the end of fermentation the yeast are cleaning up their byproducts, they are battling alcohol levels and fatigue as it is. Fermenting under pressure will not only stop fermentation stank from blowing off, it will make the clean-up job even more difficult.
If you want to try, I would base my calculations on your experience in previous batches. I will attempt to get this right:D, please check my work and let me know what I missed.
Say you want 2 volumes of pressure, and your storing at 65 F. I will assume you've got a 5 gallon batch. Mr Palmer's handy nomograph located here, tells us you need to add 2.4 oz of priming (cane) sugar to 5 gallons.
So what we need to understand, is how many gravity pts 2.4 oz of sugar adds to your 5 gallon batch. 16 oz of (cane) sugar in 1 gallon yields 1.046, so in 5 gallons you'll get 1.0092 (46/5). That means that 1 oz of cane sugar in 5 gallons will give you 1.000575 (9.2/16). If Palmers chart says we need 2.4 oz, that's the equivalent of adding .00138 (.575*2.4) of specific gravity pts.
You need to bottle when your cider is .00138 higher than the expected F.G, which you can really only know from experience with this cider must.
Say these apples always ferment out to 1.000 (for simplicity), you need to bottle at 1.00138 and then store at 65 F.
Good Luck, and please let me know if this works out.
If you want to do everything in one vessel, consider an entirely pressurized fermenter setup.
The key piece to this is the Spunding valve, which will control the release of pressure to keep your fermenter at a specific pressure level.
Now, downsides. The first 2 that come to mind are: 1. You'll have to seal with Trub in the bottom where the Dip tube for that keg is, which means blowing out a lot of trub before you get good cider 2. Autolysis: If you don;t rack, you'll be staying on the yeast cake forever which may cause autolysis. Autolysis is when the yeast cells decay and rupture, spilling their fetid insides into your carefully produced cider.
Personally, I would definitely stick with fermenting in a dedicated vessel and then rack out to a keg or secondary for further clearing/maturation. Force carbonation is a great way of not having to worry about priming and being able to get exactly the carbonation profile you're looking for.