Elfmaze - Thanks for the interview link. That was very interesting and helpful.
I dont know about a clone, but you can make a decent farmhouse cider in the same style as a JK Scrumpy by a) starting with unpasteurized fresh pressed juice that is a blend of good apples whatever are the best cider apples in your area, b) keep handling of the juice to a minimum and keep everything scrupulously clean, because wild yeast ferments can easily pick up weird flavors c) let the cider ferment with just the natural yeast at as low a temp as possible and d) stop the fermentation before it gets below 1.020 or so.
The FG of flat, JK Scrumpy at room temp is 1.024. I measured one last year also and it was 1.028. I dont know if that is because they vary from batch to batch, or maybe last year I didnt wait for it to go completely flat and there were some bubbles on the hydrometer.
As JoeSponge pointed out on an earlier exchange (which is why I double checked this eve plus a good excuse to drink another Scrumpy), an FG of 1.024 plus six percent alcohol, means that the SG of their starting juice must be at least 1.072. Thats a lot of sugar, but certainly not impossible. I got a batch of Staymans and Romes this past season that was at 1.064. I have heard of sweating apples to increase the sugar content, so my guess is that it is possible to bump the SG to 1.072 if you have full control over the cold storage process. For the rest of us, it is certainly possible to get a good blend of juice that is in the 1.050 to 1.060 range and end up with a similar end product with a little less punch. Personally, I like it just a tad dryer, so you could let it go to 1.010 to 1.015 and it will still be very nice.
As far as stopping it goes, cold crashing will do the trick. But then you have to either drink it still or force carbonate it in a keg. Id go with the keg. Once you start kegging you wont go back.
So how does Scrumpys stop the fermentation and bottle without cold crashing and forced carbonation?
I think the biggest clue is in the interview where JK said that because they use no fertilizers, they have low levels of nitrogen in their apples. Remember, he said that nitrogen hinders the development of flavor and growth. That is really, really interesting, because nitrogen is also a necessary yeast nutrient. A lot of people ADD nitrogen to prevent stuck fermentations. My guess is that JK has figured out how to induce a stuck fermentation by limiting nitrogen. That is probably more reliable than coming up with a yeast with a low alcohol tolerance.
Nitrogen levels can be measured in wine, but it takes some expensive kit. My guess is that after five generations of cider making, the Koan family has figured out how to tell when the nitrogen is getting low enough that the yeast will starve. If you add some champagne yeast and bottle right before the nitrogen runs completely out, that ought to do the trick!
If you want to test this theory, take a bottle of JK scrumpy and add some DAP. My guess is that it will start fermenting like nobodys business. However, even if I am right I am not sure how helpful that really is, because then trick is how do you tell when nitrogen is so low that you are about to get a stuck fermentation without a lot of expense? If anyone knows the answer to this, then we might have something! Be warned though that one of the signs of a ferment running low on nitrogen is excessive sulfur production, so youd better have a tolerant S.O. while working out whatever kinks there might be in this process.
I was happy to hear that they use Johnathans in their mix, cause those are one of the first good cider apples that will be available next Fall here in Central VA. Cmon September! Ive heard good things about Northern Spys before. There is a place that sells them here but they are expensive. I guess thats because they are outside of their growing range. Staymen, Winesap, York, and Granny Smith are usually plentiful, and Im pretty happy with those so far.