If you're like me and want sweetened mead, there are several ways to do it, but most have drawbacks or risks. I've been brewing meads and ciders for a couple years now and still haven't found a foolproof way to completely deactivate the yeast for safe backsweetening.
1. You can cold crash and/or let sit for a long time after primary fermentation. MOST (emphasis on "most") of the yeast will drop to the bottom. Carefully racking off the lees will give you product that doesn't have much yeast left in it. But if there's even one live yeast cell left, it can start eating the new sugar and eventually multiply and grow exponentially. Cold crashing and racking is not 100% effective at removing all of the yeast.
2. You can ferment until the yeast can't ferment any more. Most yeasts have an alcohol tolerance from about 12% to 18% ABV. If your ABV is above that, the yeast may still be there but they can't do anything because they're essentially too drunk to eat more sugar. The strategy here is to add enough honey/sugar in primary fermentation so there's still some left when it's done. Then you can add more sugar and not have a risk of fermentation restarting. The problem is that yeast can't read. So even if the manufacturer like Lalvin says a particular yeast has a tolerance of 14%, they might stop below or above this number. And this won't work if you want a finished brew below the yeast's ABV tolerance.
3. You can add potassium sorbate and potassium metabisulfite (Campden tablets are a specific format of this chemical) after racking and before back sweetening. Sorbate doesn't kill yeast but will prevent it from multiplying. Couple this with cold crashing or sitting (to get rid of most of the yeast) and the sorbate should prevent any significant refermentation after back sweetening. Eventually the few yeast cells remaining after racking will die on their own without reproducing. This is a very common method to sweeten ciders and other brews with a desired ABV well below the yeast tolerance. But even this isn't foolproof. I've had brews restart even after the use of sorbate, and I don't know why. There is some information I've found that says potassium sorbate has a shelf life of a year or less, so old sorbate may not be effective.
4. You can pasteurize. Heat kills yeast. There are LOTS of different suggestions on the forums and YouTube for how to pasteurize. Some heat and hold, perhaps using a sous vide immersion circulator in a large water batch. Some suggest boiling water in a pot, removing from the heat, and adding bottles of brew to the hot water. In any case, you need at least 140F IN THE BOTTLE, not just in the pot. Higher temperatures require less time to kill the yeast. At 140F, you might want 15 minutes. At 165F it's more like 2 minutes. At 180F it's more like 10 seconds. Pasteurization of open bottles risks boiling off some of the alcohol, especially at higher temperatures. Pasteurization of sealed bottles carries some risk of exploding bottles because the pressure in the bottle will jump up during the heating, especially with carbonated beverages. All pasteurization risks changing flavors of your brews, with higher temperatures more likely to do so. And pasteurization of a product with pectin (like ciders or other fruit beverages) can create a gelatinous substance in what was once perfectly clear product.
5. You can filter to remove the yeast cells. But this takes a fine filter, which risks filtering out some flavor components. Certainly you wouldn't want to filter a hazy brew or your filter will clog immediately.
On another note, try adding some dried cherries to your cherry melomel once you have stabilized it using one of the above methods. I use about a half to full pound per gallon and let sit for 2 weeks. It will add a little bit of sweetness, though you'll likely still need some honey. But it really boosts the cherry flavor and provides more mouthfeel.
Brian
