Our kits are designed for all the sugar in the kit to be fermented out, with the artificial sweetener used to provide the sweetness (unlike sugar, this cannot be fermented out as it is a chemical that is resistant to fermentation).
Even if additional sugar is added post fermentation, when the sugar in the kit has been fully fermented out, the fermentation will continue unless the cider has been clarified and the yeast completely removed (this is how the bottle conditioning works, with the in-bottle secondary fermentation of the priming sugar). But note that if the cider is clarified it cannot be bottle conditioned / carbonated as this requires live yeast in the bottle.
Unfortunately, the yeast in our Mangrove Jack's Cider kits is a very robust strain of Saccharomyces bayanus, which is the most common species of yeast used for cider making – these strains can ferment comfortably down to 7-10°C (44.6-50°F) and even below this will most likely continue to ferment (as is seen in this case at 5°C (41°F)!)
Here are some alternative methods we would suggest, but we're afraid there is no simple solution:
- Clarifying, back sweetening, and force carbonating in keg – if the cider is clarified with suitable fining agents (such as chitosan or gelatine, ideally used with kieselsol) and then racked off the sediment, this should allow ‘back sweetening’ (i.e. adding sugar after fermenting to dryness) before the cider is force carbonated in kegs. but to be safe this still needs to be combined with #2.
- Add stabilisers / preservatives prior to back sweetening – another way of making a sweet but flat cider, it’s possible to add sodium metabisulphite and potassium sorbate to a fermentation which has completed to dryness before ‘back sweetening’ (ideally the cider would also be clarified to remove the yeast). This method is commonly employed in winemaking to produce sweet, still ciders. However, please note that due to the lower ABV of ciders the cider will oxidise very quickly even in sealed glass bottles; the user would need to store the cider refrigerated and drink within a certain time to avoid the cider going ‘off’ (oxidising, which makes it taste like vinegar).
- Experiment with other artificial or non-nutritive sweeteners – if you don't like the Acesulfame K we include in the kits, you are welcome to experiment with alternatives such as Sucralose or Stevia. They could also consider ‘sugar alcohols’ (known as Polyols); examples of polyols include erythritol, isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol and hydrogenated starch hydrolysates (HSH). It would be on you to ascertain that these ingredients are unfermentable (which we would expect they are), and obviously to establish that you provide an acceptable taste quality. Any such unfermentable sweeteners could potentially be added to dry cider with priming sugar prior to bottling.
- pasteurise or sterile filter the cider before back sweetening. this ensures the yeast are removed or killed so they cannot ferment the sugar added to back sweeten.
IMPORTANT to note that there are always risks around stopping fermentation and/or preventing refermentation, especially if the beverage is to be stored in glass bottles… or even plastic – basically anything that is sealed. The risk is that pressure build up could cause the vessels to explore! So, we don’t really recommend this but advise caution for those wishing to experiment under their own steam.