This weekend we bottled our second test batch of the season: a blend of mid-season Pender apples, harvested in early October and pressed in a friend's backyard in Vancouver. No sulfites added, and left to ferment with wild natural yeasts. The ferment had a slow and steady start, and an even slower finish, which resulted in a 1.010 specific gravity (medium-dry), clearing to a beautiful amber-golden hue.
Rather than waiting an additional couple months for the temperatures to rise and bring down the residual (remaining) sugars we seized the chance to bottle this delicious batch while it had enough sweetness to balance its strong acidity and surprisingly tannic finish.
With a last minute blend of some drier cider, it was kegged, carbonated, and bottled. The other option to achieve a medium or semi-dry sugar level would be to let the cider finish fermenting to dryness and then ‘back-sweeten’ with a desired amount of sugar, honey, syrup or juice.
Without sterile filtration--a very expensive process--there are inevitably yeast cells in every bottle, which, if left to their own device, would one day wake up, ferment all the remaining sugar into a little more booze, and off-gas more and more carbon dioxide until the bottle exploded into spectacular shrapnel.
So, because we don't have a 50,000 dollar cross-flow filtration system, we need to kill that remaining yeast--with heat.
Hence the widely-practiced process of bath pasteurization. For the home-scale hobbyist that basically means using a big canning pot and heating the cider for a designated time and temperature--taking all appropriate safety precautions of course: heat-proof gloves, face-protection and toe-covered footwear (as you can see I have very good advice but I seldom follow it myself).
For the cider, the big danger is literally cooking the cider during this process: imparting a jammy, cooked apple aroma. Done well, it simply rounds the flavor and aroma, and according to some can even emulate the delicate "aging" process.
We'll crack open a bottle soon and find out.