stuck fermentation?

[palantier]

I pitched my yeast two days ago in a 1 gallon batch of elderberry mead, after I had left the mead to cool a bit it started to bubble a bit so I mixed a large starter of yeast to see if I could get it to take over from the natural yeast before it went to far, at the time I pitched it the wort was about 1.060 and 32-34C. trouble is now I've got no activity and a thick layer of dead or dormant yeast at the bottom, any help is appreciated?

note: I have found increasing the temperature starts it up again but I get no activity below 25-26C?

 

[bernardsmith]

The temperature when you pitched the yeast was 32 C? That is almost 90 F . My guess is you killed the yeast you pitched. If you had to cool your must then my next guess is that you already killed the wild yeasts in the berries.
What is the current gravity? That will answer your question. The fact that when you raise the temperature above 25C you see "activity" may mean only that any CO2 dissolved in the must is being expelled. Wine ain't beer. You need to use your hydrometer to measure changes in the specific gravity and discount or ignore the activity in your airlock.
My question is whether you measured the pH of this must. My guess is that the honey will have a low pH and the elderberries may drop that pH even further. Honey , as they say, has few if any buffers and so the action of yeast on the diluted honey is to drop the pH to the floor. Yeast don't like that very much, so you need to be on the look-out for very high acid levels during the active fermentation stage. What is the recipe and the method you are using to make this metheglin.

 

[palantier]

thanks,
500g elderberries
1/2 an orange
1/4tsp cinnamon
1/8tsp clove
700g honey

all this goes into a bucket with the mashed elderberries. to this I add 1 tsp of yeast nutrient dissolved in a cup of water and then 4L of boiling water. it's left to cool so everything settle and dissolves evenly before I pitch the yeast, about 6hrs later. I can't test the Ph but the sg is still 1.060, I don't think I killed the yeast at that temp when I pitched because I got a lot of activity, plus I've got a similar recipe going as well and that's fine, the trouble started when the temp dropped to 24-25 over the next hour or so

 

[bernardsmith]

I'm no expert so take what I say with as large a pinch of salt as you like but IF your gravity has not shifted in 72 hours I would say that the lag time is indicating a problem. OK.
IF (large if) IF you are confident that at the temperature you took the first gravity reading is within the range at which your hydrometer is calibrated (hotter liquid is less dense than cold even with the same amount of sugar) and if there really has been no drop in gravity after 72 hours then I would treat this as a stalled fermentation.
To restart this I would a) whip air into the must, b) create a small (1 cup?) yeast starter using say, apple juice and yeast and allow this to get bubbly and frothy. (however long that takes (you might use EC 1118 yeast ) I would then take one cup of your stuck must and add that to the starter. Wait a couple of hours and check to make sure that this is really active. I would then double the volume by adding TWO cups from your stuck must. Wait a couple of hours and if still active I would then take FOUR cups (doubling the volume). After a couple of hours I would combine everything into one carboy. At that point your stuck fermentation has re-started... The yeast will be EC-1118 (if you go that route- Not my favorite yeast to ferment with but this is a killer strain with real muscle to restart a stuck ferment and it takes no prisoners when it comes up against other competing yeasts. Follow instructions regarding rehydration. Good luck.
PS. I think you can get a great deal of "activity" at points just before you kill yeast- for example, if the temperature at which you pitched the yeast was high enough to kill the yeast, it may have taken a few minutes for 99 percent of them to die but they may have lived long enough to convert some of the sugar to CO2 and alcohol. What is the preferred temperature range of the yeast you pitched? At the extremes it is not as if they are going to simply keel over and die instantly but the vast, vast majority are going to be too distressed to do any conversion and are not going to survive very long.. Much beyond those temperatures they are gonners.

 

[TopherM]

FYI, 90F won't kill yeast. They would actually prefer that temp. Yeast start getting debilitated around 125F and start actually dying around 140F.

Now you know, and knowing's half the battle.

 

[bernardsmith]

I don't doubt what you say TopherM, and indeed that rings true for bread yeast- I use water at my body temperature when I bake bread but why do brewers on this and other sites go apoplectic if they cannot bring their wort down to 60 degrees in 15-30 minutes before pitching their ale yeast when all they need is to bring the temperature down to 100- 110 F?

 

[boydster]

I don't doubt what you say TopherM, and indeed that rings true for bread yeast- I use water at my body temperature when I bake bread but why do brewers on this and other sites go apoplectic if they cannot bring their wort down to 60 degrees in 15-30 minutes before pitching their ale yeast when all they need is to bring the temperature down to 100- 110 F?

Hydration temp and fermentation/pitching temp are not the same and shouldn't be confused. If you ferment at 90, your yeast will LOVE it and work insanely fast, but the mead/wine/beer you make will taste awful. We target fermentation temps that make us happy and that the yeast tolerate. We target hydration temps that baby the yeast because it is in a vulnerable state when it is dry.

 

[TopherM]

why do brewers on this and other sites go apoplectic if they cannot bring their wort down to 60 degrees in 15-30 minutes before pitching their ale yeast when all they need is to bring the temperature down to 100- 110 F

Well, the yeast would love it if you pitched at 100-110. Their metabolic rate goes up proportionately with temp, so at 100-110, they would eat sugars faster, reproduce faster, and generally be having a swell time doing the things they love to do most. However, depending on the style of beer, this may be bad for the beer, as they also give off proportionally higher levels of esters and phenolics at those higher temps, which are off flavors in most beer styles.

When you see the optimum temp range on any given yeast packet/vial/pouch, that optimum range is a balance between the yeast fully attenuating and giving off acceptable ester/phenol levels for the given beer style. So, for like most ales, you want to get down to 60ish and pitch there because the yeast are going to fully attenuate and give off minimum off flavors at that temp.

In a standard ale made with a standard Chico strain, like S-05 or 1056, the yeast would give off a sweet, tropical fruit like ester at higher temps. This is somewhat acceptable in low concentrations in some styles, like APAs, IPAs, and Ambers, but you wouldn't want a sweet, tropical fruity Porter or Stout.

For something like a Saison style, the style is actually defined by high levels of esters and phenols, so you purposely heat them up to get that production. It's not uncommon to ferment a saison at 80-90 degrees.

Same thing with something like a Hefewiezen. If you want the Hefeweizen to taste like banana, you ferment it on the high side, where you are purposely upping the yeast's ester production, resulting in the banana flavor. If you want a spicy clove Hefeweizen, you ferment it at a lower temp where the yeast puts off more phenolics that taste like cloves.

So, it's all in what you want the yeast to do per the style. Different strains of yeast have different characteristics and put off different flavors at different temps, and you pitch and ferment at the temps that are appropriate to the style.

 

[palantier]

thanks, before I went ahead and did more or less what Bernard said, on a hunch I stained out the skins and seeds from the must then left it a bit to settle down, when I came back it had developed a nice foamy layer... so it looks like something in the elderberries (skins or seeds i'm not sure) was halting the fermentation, anybody heard of this before?