Stuck Fermentation

What is it about mead and stuck fermentation? If you google search "mead stuck fermentation", you find that this is a widespread problem for home mead makers. I recently had to deal with it in my most recent attempt at mead.

Back in August, secondary fermentation of this mead had more or less stopped. Things had been going pretty well, and I assumed that most of the sugar must have been used up by the yeast. As I noted in an earlier post, I broke my hydrometer and therefore had no quick way to measure the specific gravity. (Actually, I could have measured out a volume of mead and measured the mass, from which you can easily calculate density. I have a cute little jeweller's electronic balance that measures to 0.01 g.) So, without knowing the completeness of the fermentation, I racked the mead with the intention to let it age and clarify.

As the mead was "aging", I noticed that there was a constant, very slow rate of gas production in the carboy. In the meantime, the batch of peach melomel was getting to the end stage of secondary fermentation, and it was time to rack it. Last week, I decided to rack the melomel and the mead, checking the specific gravity of each using my new hydrometer. Here's what I found:

Peach Melomel s.g. = 0.990 (Conclusion: fermentation is complete, and it's time to let it age)

Mead s.g. = 1.038 (Conclusion: oh crap, fermentation is stuck)

So, I had to intervene. I added two Campden tablets (crushed and pre-dissolved), 1 tsp of yeast nutrient, and a packet of Lalvin EC-1118 yeast. Bubble formation seemed to pick up within a few hours. The next day, gas production still wasn't as fast I would like, so I raised the temperature in the room using an oil heater, and also added 2 tsp of yeast energizer. Yeast energizer has a slightly different nutrient mix as yeast nutrient. Three days later, the fermentation in the mead was chugging along nicely, and continues:

Gas production after kick-starting the fermentation

with yeast nutrients and higher temperature.

Did fermentation resume because of added nutrients for the yeast, the higher room temperature (from 17 up to 22 degrees C), or both? I don't really know, but I suspect it was mostly the nutrients. After all, the peach melomel, which presumably had more nutrients from the peach juice, seemed to work out fine in the relatively cool room in which I keep this stuff. Lesson for next time: add more nutrient, with the proviso that "yeast energizer" is likely the more effective.

Mead v.2

My first attempt at mead left me unsatisfied. Looking back, there were three things that I did incorrectly:

1. Failed to add yeast nutrient. Honey does not have the range of minerals and other nutrients that yeast require. Fermentation only really started once I added the yeast nutrient. Further, all of my  fussing around to get fermentation started would have introduced unwanted oxygen, which would have led to undesirable compounds that affect taste.
2. Starting specific gravity was too high at the beginning (1.120) and the end (1.019) of fermentation.This gave a mead that was sweet, heavy, and very alcoholic. The balance of taste wasn't right (and still isn't!).
3. Honey quality. A friend from my undergraduate days at university now runs a honey business, and she pointed out that Costco honey is rubbish - if I want to make good mead, I need to start with quality honey. ("Okay. Point taken.")

So, it is now over two years after my first attempt at mead, and I finally got around to my second attempt. This time, I'm not making any of the mistakes I made the first time.

We have a great farmers market in St. Albert, and there are always three or four honey producers there. My wife and I went shopping one Saturday morning and obtained 7 kg of unpasteurized, local honey for $50. The vendor was Good Morning Honey Ltd.

Mead recipe:

3 Campden tablets
2 tsp yeast nutrient
10 L distilled water
Honey
1 packet of Lalvin EC-1118 yeast

Campden tablets and yeast nutrient were added to the water in the sterilized primary (bucket). Honey was added, with stirring, until s.g. = 1.088. After 24 hours, the yeast was hydrated and added to the must. Fermentation bubbles were observed within one hour of pitching the yeast.

After four days in the primary, s.g. = 1.065. I decided to rack the mead to a carboy. Fermentation has continued since then (6 days ago).

Mead, after racking to carboy.

I think most chemists will know what I'm talking about when I describe this fermentation as "clean". What I mean is this: when chemists conduct a chemical reaction the lab, especially when they are trying to synthesize a compound, they strive for a "clean" reaction. A clean reaction is something we recognize easily from the absence of unwanted precipitates, the absence of guck on the sides of reaction flasks, the relative transparency of solutions, and colours that you want to see (e.g. you don't want to see your mixture turn brown when the product you want is colourless). These are simply physical clues that a reaction is going right.

This mead has been "clean" from the beginning: the colour hasn't changed, the liquid is as transparent as you could expect if there were only little bits of yeast and bubbles that were scattering light. You can tell that clarification is going to be a snap. And, there was hardly any foaming, which suggests a very pure honey (i.e. no surfactants of any kind - natural or artificial).

The plan is to let this mead ferment all the way to dryness and then I will rack it and let it bulk age in a carboy for a couple of months. I'm looking forward to enjoying some of this mead over the Christmas holidays.