Acetyl Production, Oxygenation, and Minerals

[sma117ime]

Gents,

I usually add more yeast after 2 weeks in the primary to clean up acetyl, which has worked wonderfully. I've also read some interesting scientific articles that show the conversion relationships between acetyl, diacetyl, and ethanol, but I was wondering, can minerals specifically affect this relationship (such as Zinc or Magnesium).

 

[Hermit]

The yeast you already have should be sufficient. Are you having problems if you don't add extra yeast after two weeks?

 

[sma117ime]

Not all the time. I had real problems with acetyl compounds during my first few brews, and ANYTIME I have used liquid yeast. Its a long story, but this past batch was going great until I added some yeast nutrient to the primary to speed things up (I know a stupid thing to do). The taste beforehand was ok, no acetyl compounds at all, it was just a little cloudy due to using some oats as an adjunct. I'd really began to hone my process well before this incident producing great tasting beers within a month. Since I posted, I added a zinc vitamin to 1 ounce bottled water (boiled), and then to the beer, and there has been a noticeable difference in acetyl in just 24 hours, but I am curious about "fixing" brews when they go off track. As I mentioned, well, adding another packet of wine or bottle conditioning yeast near the end of primary fermentation usually erases ALL traces of acetyl compounds, but it didn't work with this one at all. Of course, I usually don't use yeast nutrient either.

 

[Hermit]

I picked up some zinc supplements thinking about using it for beer. Nasty tasting stuff. I wouldn't add a whole one to a 5 gallon batch. I used one for a three gallon batch of canned wort for starters. I decant the liquid from those though so it doesn't end up in the beer.

 

[Pie_Man]

By acetyl compounds, what flavor compounds are you referring to? Ccontrolling fermentation temperatures in the beginning of fermentation (first 1-3 days) should limit many unwanted flavors compounds if pitched in the correct amount. That seems easier than trying to clean up the off flavor later in the process by adding more yeast.

Perhaps you are attempting this intentionally, I am not sure.

 

[ajdelange]

I'm not sure I understand the emphasis on acetyl compounds as they are at the heart of life on this planet. Acetaldyhyde is the simplest acyl compound CH3COH and the product of decarboxylation of pyruvic acid (CH3COCOOH) but add a couple of protons and electrons and you have ethanol (CH3CH2OH). Diacetyl, which as the name suggests, is two acyl groups (CH3COCOCH3), gets those acyl groups from alpha acetolactic acid which got them from pyruvate originally. Acetyl Coenzyme A is the "Hub of Metabolism". Its function is to move acyl groups around to all the various places they are needed in the normal operation of essential biochemical reactions.

There is no problem with acyl groups but rather being sure that they combine in the correct ways to produce the acetyl compounds we want (ethanol) and not the ones we don't (diacetyl). We emphasize that another we don't (acetaldehyde) is the precursor to ethanol which we do.

 

[sma117ime]

Right,

Acetaldyhyde is part of the process, and that process can definitely take a wrong turn with the addition of oxygen and other compounds. I had my process down pat, and messed up the clock with the addition of yeast nutrient which had other minerals and compounds. I should have been happy with leaving it a little longer to clarify. I will let you guys know if the zinc addition is the cure all or not. Give me another day or two (hopefully it won't take too long).

 

[ajdelange]

Assuming that diacetyl and acetaldehyde are the bete noirs it isn't so much that the process takes a wrong turn as it is that the yeast aren't given enough time to do their jobs. Properly managed they will clean up both diacetyl and acetaldehyde to acceptable levels.

The other possibility is that there is an infection by organisms which produce these compounds at levels beyond which the yeast can process.

 

[zwiller]

Took a hydro sample yesterday of a saison brewed last weekend that has a touch of acetyldehyde. Been a long time since I had this happen. I am seeing some conflicting info about removing it. The conventional thought is that give the yeast time to clean it up. The opposing thought is that it basically just needs time to evaporate (68F boiling point). Maybe a combination of the 2?

Plan to give it a week at 68F (basement ambient) and see if this helps. Does a week seem reasonably long enough?

 

[sma117ime]

Gents,
I'm going to throw in the flag and call this one infected at this point. Not sure if I should add brett now, or fruit, or maybe pour it out. The only thing I can figure is that there was some bacteria residing on the yeast nutrient that survived being dissolved in boiling water for a couple of minutes. The acetyl levels are coming back now.

 

[sma117ime]

Zwiller,

As I mentioned before, up until now I've been able to clean up acetyl (like within 24 to 48 hours) by adding another batch of yeast (1122 produces no acetyl). You could try that, also, with this possibly infected batch I have right now, adding a dissolved zinc tablet seemed to work also (for a while). About the heat, this could be valid also since I regularly put mine in a hot room also. Actually, I'm going to try this with this batch, the experiment continues!

 

[sma117ime]

Took a sample yesterday, acetyl levels are fading, getting nice caramel and toasty flavors, still haven't poured it out yet. This after being reminded to try and leave it in a "hot room".

 

[zwiller]

Sorry I missed your post. Glad to read yours improved and hope it continues. Mine did and I cannot detect any off flavors this point.

 

[ajdelange]

Took a sample yesterday, acetyl levels are fading, ....

Since we don't want all acetyls to fade can we call these 'bad-acetyls'?

 

[sma117ime]

Checked on it today,
Ehh, Ruby Red Grapefruit Juice.

Not sure where the infection originated from.

 

[sma117ime]

I brewed another batch in between these threads and paid the utmost attention to sanitation. This batch at bottling last night had that distinctive sour taste developing, so here I am stuck with approximately 10 gallons total of sour beer. The batch which started this thread is becoming lambic sour at this point. So, reluctant to pour it out, still reluctant, I elected to do more research. In fact, I've bottled the second batch and added about 1/16 tsp of egg shells to each bottle (sounds stupid but this is an experiment), and about 2oz of crushed egg shells to the original batch which is still in the secondary container. So hopefully I can glean some knowledge, and maybe even still have some consumable beer. Not sure If I should go ahead and buy new plastic fermenter and bottling bucket for the next batch. I am also tempted depending on how this goes of adding some (cold steeping) some dark grains on the original batch to make a lactic/sour type stout (although I am sure this is not a lactic infection because there is no film on top). So, again to the bottled batch, since I krausen to bottle, I'll open one at the end of this week to let you guys know if the powdered egg shells improved the taste.

 

[sma117ime]

Powdered egg shells do lower the acid levels. But I'm definitely in sour beer (infected beer) territory now, so thus not much more to say on this thread. I still think the infection came from the wyeast nutrient somehow. The last time I used it, was in one of my first brews (using roselare yeast). Not sure how that yeast got in there, but the smells and tastes are definitely reminiscent.

 

[sma117ime]

It's Pedio judging by the ropelike formations in the dregs. The eggshells worked for a little while but it soured again.