Fruity Kolsch - Starter Issue?

I just tasted a Kolsch I made about a 6 weeks ago. There is an intense fruity flavor, in addition to a fruity aroma, much stronger than I've ever had for a Kolsch. I'm wondering the cause of this.... I don't think it's an infection, as I've tasted that before, this flavor/aroma is very different. Below is my process and what I think might be the cause of this flavor/aroma. Please let me know if you've experienced this or have any ideas to it's cause... Thanks!!!

Size: 6.0 gal
Efficiency: 84.21%
Attenuation: 75.5%

Original Gravity: 1.049 (1.044 - 1.050)
Terminal Gravity: 1.012 (1.007 - 1.011)
Color: 4.77 (3.5 - 5.0)
Alcohol: 4.84% (4.4% - 5.2%)
Bitterness: 25.8 (20.0 - 30.0)

Ingredients:
0.5 lb Vienna Malt
6.5 lb Pilsner Malt
0.5 lb Rice Hulls
2.0 oz Hallertau(4.1%) - (45.0 min)
3.0 lb Global Kolsch Malt
2.0 ea WYeast 2565 Kolsch

Mash Temp: 150 F Duration: 90 min.

Fermentation:
I prepared a starter of ~ 2L with 2 packs of the Wyeast Kolsch Strain, using #s according to the Mr. Malty pitch rate calculator. I allowed the starter to do it's thing on a stir plate for 18 hours at 70 F. I cooled the starter to 58 F then pitched the entire thing into my 6G of wort. I fermented at 58 F for 2 weeks, and then let the carboy sit in a fridge at 38 F for 3-1/2 weeks.


2 things I that have come to mind are:

1) I did not oxygenate/aerate the wort, and I've read that not doing this can lead to an intense fruity aroma.... though I've never observed this.

2) I pitched almost 2L of starter which was sitting at 70 F for 18 hours. I'm wondering if fruity flavors may have been produced here, which I'm now tasting in the final beer?


Again, any discussion is welcome!

Did you decant the starter?

I have never used the Wyeast kölsch yeast, only White Labs, so I can't speak to that specific strain. But in my experience with kölsch (which I do brew quite alot of and have experimented with almost every variable therein), you actually tend to get more fruity esters at the much lower temps like you fermented at (i ferment at 60-62), and surprisingly very little when fermented above 70. Actually, the above 70 experiments were tragically lacking- seems to strip almost all character out, but some folks loved it.

I usually ferment 2 weeks or so at the low temp and then let it raise to room temp for a week for the yeast to finish its cleanup before cold crashing and racking to a keg- this seems to be the optimum method at this point. Age may help, but in re-reading your post- I wouldn't have left the beer on the yeast in a cold-crash for that long. No autolysis paranoia, just seems unnecessary. The 'lagering' can be done after packaging.

And FWIW, if you do a starter there is no need to use 2 packs of yeast.

joety said:

Did you decant the starter?

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I did not decant the starter... which is why I think some of that mixture may have contributed to this flavor/aroma to the final beer.

fartingdog said:

I have never used the Wyeast kölsch yeast, only White Labs, so I can't speak to that specific strain. But in my experience with kölsch (which I do brew quite alot of and have experimented with almost every variable therein), you actually tend to get more fruity esters at the much lower temps like you fermented at (i ferment at 60-62), and surprisingly very little when fermented above 70.

And FWIW, if you do a starter there is no need to use 2 packs of yeast.

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Thanks for the suggestions. These are all things I should have done


Interesting that the high temps lead to less fruit with the White Labs strain. On the Wyeast page they claim lower temps give less fruitiness. I will have to try a higher fermentation temp to see what happens.

With the yeast starter, I only have a 2L flask, so wanted to make a starter no greater than that volume. The Mr Malty calculator, for the style, O.G. and volume suggested a 3L starter with using one wyeast pack, but only around 1.5L with 2 packs. I am relatively new to making starters, so as just going with that calculator for generating pitching amounts.

Thanks again!

kxx said:

Interesting that the high temps lead to less fruit with the White Labs strain. On the Wyeast page they claim lower temps give less fruitiness. I will have to try a higher fermentation temp to see what happens.

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Yeah, kind of took me aback- it was a split batch to see what would happen. It came across alot dryer as well The results also surprised the hell out of a few grand-master judges as it seems to go against conventional wisdom. On your next batch, give it a shot and split the fermentation and see what happens. There is nothing like a good kölsch!

I have a friend whose kölsch keeps beating mine- his method is to ferment cool (60º) for the first few days of heavy fermentation, then lets it rise up to room temp for the remainder of the ferment. He gets very low esters w/ that method.