Flaked Barley and DMS

[bumstigedy]

Hi all,

Need some help determining the source of a vegetal flavor I encountered with a dry stout. The grain bill was as follows:

Maris Otter: 70%
Flaked Barley: 20%
Roasted Barley: 10%

I put this in a few competitions and every judge said it was vegetal; a few cited DMS. I only boiled for 60 minutes and it was a little on the weak side. My theory is that with such a high amount of flaked barley I should have boiled vigorously for 90 minutes. What are your thoughts?

Ruling out the following:
1. infection - since it didn't get worse with time
2. slow cooling - cooled very quickly to temperatures below DMS forming range. Used IWC with wort recirculation and groundwater temperature was cold as this was in February
3. Hops - only a 60 minute bittering addition

The only other thing I will mention is that I ground the roasted barely very fine with a coffee grinder as this is what the recipe called for.

 

[plainbrad]

What kind of yeast did you use. Yeast can do odd things.

 

[bumstigedy]

Wyeast London Ale. Pitched around 65F and fermented around 65F for the growth phase; raised to 68F for the tail end of fermentation.

 

[gratus fermentatio]

What hops did you use? Some hop varieties can get vegetal, even grassy.
Regards, GF.

 

[Bob]

Are you sure it's DMS? I'd be stunned rigid that anyone could detect DMS flavor precursors in Dry Irish Stout; the 10% Roasted Barley should mask it. If it is DMS, it must be present in such fantastic quantities that you've a serious problem.

Which I doubt. Your grist constituents are not remarkable DMS-producers. If you were using Pils malt, I'd not say that, but you're using UK Pale Malt.

It's a mystery. But then again, so much about brewing still is mystery! Science only goes so far.

Recommendations: Try improving the quality and increasing the time of your boil. To reduce DMS, you need a vigorous, rolling boil of at least 90 minutes. It certainly won't hurt anything. If you end up with less wort at the end, just dilute slightly.

Cheers!

Bob

 

[bumstigedy]

I used East Kent Goldings

 

[bumstigedy]

Here are some of the comments from the judges.
I got 3 scoresheets. One was a national judge and the other 2 certified.

Aroma comments: vegetal aroma, cabbage corn aroma/strong dms

Flavor comments: vegetal flavor in aftertaste which is cabbage like, vegetal notes on flavor, vegetal corn/asparagus flavor

 

[devilishprune]

Did you boil with the lid on?

 

[Bob]

Yeah, need more details. How much EKG? Recipe, procedure, everything - we NEED MOAR DATA!

Bob

 

[bumstigedy]

No I didn't boil with the lid on. I'll check my notes, but I think I had about 8 or 9 percent evaporation, so the boil was a bit on the weak side.

 

[bumstigedy]

OK here's the recipe and process info
for 7.5 gallons
OG 1.044
FG 1.012
IBU: 43.1
mash efficiency 75%
Maris Otter 8.2 lbs 70.1%
Flaked Barley 2.3 lbs 19.7%
Roasted Barley 1.2 lbs 10.3%
Mash profile
protein rest 120F 15 minutes
Beta rest 145F 40 minutes
Alpha rest 156F 15 minutes
Mashout 168F
Moved between steps via direct fire with recirculation
1.75 qts/lb
batch sparged
Hops East Kent Goldings 5.8% 2.5 oz at 60 minutes
boiled for 60 minutes
treated water with salts to achieve the following final concentrations
calcium 73 ppm
magnesium 10 ppm
bicarbonate 261 ppm
sodium 93 ppm
chloride 52 ppm
sulfate 46 ppm
whirlflock tablet at 15 min
yeast nutrient at 15 min
cooled very quickly to pitching temperature with immersion wort chiller and wort recirculation. let sit for 25 minutes and racked wort to the carboy leaving the trub behind. cooled to below temperatures where dms forms within a few minutes.
aerated with pure oxygen for about 2 minutes

pitched actively fermenting wyeast london ale yeast from a starter; starter size calculated from mr. malty
fermented around 65F

 

[bumstigedy]

Finally got my other 2 scoresheets in the mail on this one. These 2 judges didn't not any DMS or vegetal flavor as the other 4 did from the other 2 comps, but what they noted was an out of place late addition flavor hop and too much roasted malt. Not sure what caused them to make the flavor hop comment. I think I'm just gonna go start over with a new recipe and brew this one again.