Pacman/ester

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ejbru

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Last weekend I brewed what I am calling an english bitter, exept I used Pacman that I had bottle harvested.

I have used this yeast before, but it was in a stout, so I didn't get a great sense of the yeast flavor. Today when I racked to secondary I took a sample. I was shocked at the esters! Its like drinking banana bread. I have never had it this bad, and I thought that this yeast wouldn't produce many esters. The thing that really surprises me is that I also fermented this beer a little cooler than I normally would, I was down to 60 F rather than my normal 65.

So my question is, has anyone used this yeast, and did you have a similar problem, or what am I missing here? I was also wondering if I can expect the banana flavor to tame at all during secondary, my only experience with high esters was in a wheat, I skipped the secondary and was happy to have the esters.

I did this primarily to grow up a cake that I will pitch a Russian Imperial on today, so I'm not terribly heartbroken that the beer wasn't a certain way. But I would still prefer the beer to be a little more malty if I can get it that way.
 
According to one of my teachers, ester formation is almost completely unaffected by temperature. More important is the strain of yeast, and length of fermentation time.

Banana flavour is caused by iso-amyl-acetate, and is usually most noticeable in Bavarian wheat beer yeasts.

It is unusual that you would have these flavours in your beer, when using a relatively neutral American ale yeast.

Secondary fermentation, and indeed any continued contact with the yeast will cause more ester production, until the yeast is no longer able to produce esters. This is one advantage of filtration, as bottle conditioned beers will continue to develop esters as they mature on the yeast.

More information about the way this beer was fermented would help to find your problem. It is possible there is something wrong with your yeast(contamination or mutation). It is also possible that you under-pitched, and the longer fermentation process caused higher ester production.
 
Pulled the yeast out of a bottle of Rogue Shakespear oatmeal stout about 2 weeks before fermentation. I poured the dregs into a starter .5 cup of DME and 2 cups water. I stepped this up to fill a half gallon jug and replaced the solution a couple times until I pitched it in the wort which was about 68 degrees. Once it was in I aerated for about 5 minutes (shaking) and put it in the fermentation chamber which was set at 60 degrees and stayed there until I pulled it out today. We got krausen by the next morning and it held on for about 3 days before dropping. Everything looked normal, and like I said no other off smells or flavors.

At this point I think I am going to run to the LHBS and pick up whatever american ale yeast they have 2 packs of and go with that.

So I suppose the thought is that another yeast got in there during the starter?
 
It is possible, although there are other reasons you may have this flavour.

Trying again with a store bought American ale is a good idea. Follow your original process as closely as possible.

Also I don't know if you have saved the pacman yeast, but it would be a good idea. Pitch some into a small amount of wort, and look to see if the same flavour develops.

When it is all done, compare this beer, the original banana tasting beer, and the HBS yeast beer. I believe this will help you to ascertain whether the off flavour was caused by your fermentation methods, or an issue with the yeast culture itself.

If all three have this flavour it is your method of fermentation.
If both the Pacman yeast ones do, it is likely a contamination or mutation of the culture.
If only the original Pacman does, you know there is an unforeseen variable during that specific fermentation that increased ester production.

Good luck!
 
According to one of my teachers, ester formation is almost completely unaffected by temperature. More important is the strain of yeast, and length of fermentation time.

.

Huh? Esters are almost always a side effect of temperature. Your teacher is wrong on that one. Sure, some strains are more estery than others, but almost every strain will throw more esters at 75 degrees than 65 degrees. I agree that the strain of yeast contributes, as some strains are bigger ester producers than others, but even a very estery strain fermented at low temperatures will have far less banana than the same strain fermented at high temperatures.

Pacman is notoriously "clean" with very little in the way of esters, so something obviously happened. If it's not temperature related, it could very well be stressed yeast.
 
I was able to get a couple packs of 1056 on short notice, I will just pitch that and be safe.
 
Huh? Esters are almost always a side effect of temperature. Your teacher is wrong on that one. Sure, some strains are more estery than others, but almost every strain will throw more esters at 75 degrees than 65 degrees. I agree that the strain of yeast contributes, as some strains are bigger ester producers than others, but even a very estery strain fermented at low temperatures will have far less banana than the same strain fermented at high temperatures.

Pacman is notoriously "clean" with very little in the way of esters, so something obviously happened. If it's not temperature related, it could very well be stressed yeast.

My teacher was the head brewer at a major German brewery for several years. I believe he also has a PHD in related sciences.

If you don't believe me I can attempt to contact him regarding this issue. I'm sure he can explain much better than I can.

According to him ester production is not affected by temperature, and esters are often confused with other compounds that do form at higher temperatures.

I was extremely surprised when he told me this, as I was under the opposite impression as well.
 
I would be interested in seeing some literature on this as well. Its kind of counter to everything I have seen before.
 
I think you need to go back to your teacher on this question. Your statements are contradicting everything I have ever seen written on this subject and contrary to my experience (and it seems like the experience of many other's here too)
 
Sent a message to my teacher regarding this.

Hope I didn't misunderstand what he was teaching.

If not I will hopefully get something In writing that will verify my claim.
 
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