first homebrew competition - stout sour flavor?

I entered my oatmeal stout in a home brew competition and just got back the score sheets. Overall I am very happy with the results - especially for my second brew ever, my first partial mash, and the first recipe I crafted myself (with the help of BeerSmith). There were two judges - one scored it a 34/50 and the other, a 31/50. To quote one - "A nice drinkable stout. Good roast character and nice complexity with fruit and hops"

However, they both commented on a tartness or sour flavor - "slight grainy sourness", "slightly fruity ester leading to some tartness in the finish...detracts from style".

I'm not sure I taste it - I'll have to taste one again to see if I can find it - but what could cause this? My recipe is here - https://www.homebrewtalk.com/f68/jims-oatmeal-stout-1-a-117352/

Thanks for any input

Maybe the molasses in the Turbinado?

talkingmonkey said:

Maybe the molasses in the Turbinado?

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There is no molasses in the turbinado. It is "unrefined" and not like brown sugar which has added molasses. I wouldn't think the bottling sugar would would produce a sour flavor, but then again, I'm still really new to all this.

what temperature did you ferment at? what yeast did you use

JLem said:

However, they both commented on a tartness or sour flavor - "slight grainy sourness", "slightly fruity ester leading to some tartness in the finish...detracts from style".

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Nice job on your second batch!!

One explanation could be the lack of a starter... that could have caused some of the fruity esters... Fermentation temps could have a lot to do with it as well.

I used Irish Ale yeast (White Labs #WLP004) and fermented at about 67 F (I only heat my house to an ambient 65 F during the winter). I did not use a starter on this batch and it stalled out at 1.020, so that might account for it. Though would the esters result in sourness?

BTW I tasted one last night - I think what the judges are calling sour is something I was calling a bit of an astringent aftertaste - something I attributed to the roasted barley

could be, but i woudln't think so unless it was over roasted, was it a 350 or 450l roast? how much did you use?

sometimes this astringency is a result of mashing your grains at too high a temp. i have always had a hard time controlling the mash temp on a partial mash brew. that's one reason i switched to all grain.

99blackgt said:

could be, but i woudln't think so unless it was over roasted, was it a 350 or 450l roast? how much did you use?

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I used 1 lb - I'm not sure about the L rating

android said:

sometimes this astringency is a result of mashing your grains at too high a temp. i have always had a hard time controlling the mash temp on a partial mash brew. that's one reason i switched to all grain.

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My temp control is pretty good - I use a digital probe thermometer to monitor it. I stick the mash in a pre-heated oven (and then turn the heat off) so the temp is steady the entire time - maybe moves only 1 degree F or so. I think I mashed this one at 154-155 F.

Did you roast it yourself or buy it already roasted?

MacBruver said:

Did you roast it yourself or buy it already roasted?

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Already roasted.

Well, I emailed the judges, just to get more feedback on this sour taste. I didn't expect them to remember my beer, but simply asked what they thought would cause the tartness.

One email bounced - from the judge (an apprentice - what's that?) that gave me the lower score. I haven't heard back from the other. Doubt I will at this point. What's the point of including an email if a) it's not right or 2) you don't reply? Sorry...just venting a bit