Exploding bottles and wasted alcohol... a brewer's worst nightmare. So what's the culprit? More likely than not, unexpected fermentation caused by sweetening without stabilizing. Luckily for you, avoiding this situation is easier than you think.Â
It happens to everyone - you taste your recent batch of mead that you've spent months working on, but something important is missing. It needs sweetness. You've heard about backsweetening and chemical additives for stabilizing, but you're not sure where to even start. This is a common conundrum for beginner homebrewers, but a vital step in taking your mead to the next level.
Stabilizing Explained
If you're reading this article, you probably already have a general idea how fermentation works, but if you need a quick chemistry lesson, check out this video. I'm going to save you the time and focus on stabilizing.Â
Stabilizing is done after your mead or wine has fully fermented and allows you to add the perfect level of sweetness to a finished product. Although many of my recipes don't require backsweetening, it comes down to personal preference - your mead should taste exactly how you want it to.Â
Stabilizing and sweetening generally involves adding stabilizers, like campden tablets and potassium sorbate, before adding additional honey or other sweeteners.  Without stabilizing, any additional sugars could continue to ferment... and if you bottle prematurely, you could be in for a messy, and potentially dangerous surprise. Because of the importance of stabilizing, I made sure that my mead kits all come standard with stabilizers.Â
Knowing the chemistry of stabilizing can help give you a better understanding of why it works the way it does, and why this method is preferred by brewers worldwide. If you don't care for the details and just want to know what to do, scroll down to How to Stabilize.
The Role of Campden Tablets
Campden tablets are super cheap and easy to use. Depending on where you buy them, they consist of pure sodium metabisulfite or potassium metabisulfite. The key distinction between sodium and potassium metabisulfite lies in the cation associated with the metabisulfite anion, though the differences typically have minimal impact on the final product (I've used both and have noticed zero difference). They're widely used in brewing as the first step of stabilizing, and typically followed by the addition of potassium sorbate... and yes you need both.
Campden tablets serve a dual purpose: inhibit microbial growth and protect against oxidation. When added to a batch that's finished fermenting, hydrolysis occurs, which is a fancy way of saying that water breaks it down into bisulfite ions and sulfur dioxide gas (SO2). Still with me?
SO2 is key here since it inhibits the growth of yeast and other microorganisms. But how exactly does it do this? I'd be lying if I said I knew entirely, but what I do know is that it disrupts crucial cell functions of yeast that impair metabolism and reproduction. More simply put, they help stop yeast from doing what yeast do.Â
As an added bonus, sulfur dioxide reacts with free oxygen to form sulfite and sulfate ions. This helps to remove excess oxygen and inhibit oxidative processes that could potentially change the taste of your brew.
The Role of Potassium Sorbate
So if campden tablets do all of that, what's left for potassium sorbate? And what even is it? Potassium sorbate is actually just a salt derived from sorbic acid, a naturally occurring organic compound found in certain fruits. It's used to complement the actions of sulfur dioxide and further inhibit the growth of yeast so that they don't stand a chance once fully stabilized.Â
When potassium sorbate is added to a beverage, it dissociates into potassium ions (K+) and sorbate ions (C6H7O2-). The sorbate ions are the active component responsible for stopping yeast growth in it’s tracks.
Sorbate ions do not typically kill yeast, but once in attack mode, they begin disrupting cell membrane integrity, inhibiting enzyme activity, and inducing critical DNA damage. Once added, yeast can say goodbye to all hopes of fermentation.
How to Stabilize
So we know what chemicals we need, but how do we actually use them? It's easier than it seems. To stabilize one gallon of mead, just add one crushed campden tablet (or about 0.5 grams), and wait 24 hours before adding 1/2 tsp of potassium sorbate (about 1.5 grams). Wait an additional 24 hours and the batch is stabilized and ready to be sweetened. That's it. Scale those numbers up depending on your batch size.Â
Why not just add everything at the same time? Some people do, but I don't recommend it. The 24-hour waiting period facilitates the occurrence of requisite reactions and permits the dissipation of sulfur dioxide prior to adding potassium sorbate. When added together, sulfur dioxide and sorbate ions can actually react with each other to form sulfonyl derivatives which impart unfavorable flavors or aromas. You've come this far to create great mead, don't ruin it by cutting corners at the end.Â
Why Both Campden Tablets and Potassium Sorbate?
As previously described, both campden tablets and potassium sorbate have their own ways of preventing fermentation and rendering yeast useless... and you shouldn't just pick one or the other. That's why I included both in my new Brewing Ingredient Pack. Individually, they may not do the job as fully or reliably. But together, it's a 1-2 punch. Good cop, bad cop. Peanut butter and jelly. Am I getting carried away?Â
Summary
All in all, stabilizing your mead is the crucial final step to achieving the perfect level of sweetness and ensuring both quality and safety. You know what else you can add besides honey to sweeten once stabilized? Anything you want. Many brewers turn to additional fruit, maple syrup, etc. The world is your oyster, and by employing stabilizers before adding these additional sugars, you'll prevent continued fermentation and avoid potential hazards. Cheers!