Over attenuation and alcohol taste - what did I do wrong?

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cheesebach

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Just put together my all grain homebrew setup this past summer and recently had a problem with a Leffe Brune clone recipe that I purchased from AHS. The Leffe Brune is SWMBO's favorite beer, so it was a bit unfortunate that this was the only batch of the 4 I've done that hasn't turned out. I'm feeling a need to redeem myself this weekend and giving this recipe another shot, but I wanted to get some advice from the experts here for things I could try to improve the outcome this time. I'm willing to tweak the recipe a bit or try an entirely different one if someone here is familiar with the beer and has tried brewing anything similar to it.

Basically, the finished beer came out close to 1% higher ABV than expected from the recipe and had a very thin, dry mouth feel with no hint of sweetness - much different from the slightly sweet, malty, medium-full bodied character of the actual beer. The color was also lighter than I was expecting (Leffe Brune is a dark brown/mahogony). There was also a hot/alcohol taste.

Below are the basics of the recipe with my mash and fermentation details:

Grains:
11.5 lb Belgian Pilsner Malt
0.5 lb Aromatic Malt
0.25 lb Biscuit Malt
0.25 lb Munich Malt
0.25 lb Chocolate Malt
2 oz Honey Malt

Mash: 1.25 qt/lb, 60 minutes, started at 151F, ended at 150F after 60min.

Boil Additions:
0.5 lb Dark Candy Sugar
4 oz Malto Dextrin
1 oz Brewer's Gold (60 min)
0.5 oz Styrian Golding (15 min)

2 vials WLP 530 Belgian Abbey Ale

Target OG: 1.067
Actual OG: 1.065 (Think i was a couple points shy due to not tipping my mash tun to fully drain it)
Volume into fermenter: 5.25 gallons

Target FG: 1.017
Actual FG: 1.011

Pitched @69F, controlled temps to 72F for first 3 days, let rise to 75F for the remainder of primary fermentation (18 days).

Secondary fermentation: 4 weeks at 74F in glass carboy. I had more headspace than I was expecting (probably about a half gallon). I know this isn't ideal, but it was my first brew doing a secondary and I didn't realize that the carboy I had was 5.5 gallons to the top until later.

I'm pretty confident in my mash temps, since my digital and glass thermometer were matching at the start of the mash. This was my first time trying to use Bru'n water and RO water to build my water though. With this grain bill, I added about 0.5g/gallon of gypsum and 0.5g/gallon of CaCl2 and the grains should have put me at around 5.3 pH without the addition of any acid. I didn't have a pH meter to check this at the time though.

Some ideas I had were the following:
1) Reduce fermentation temps - The temps I used don't seem unusually high for the strain based on what I've read, but this might help to lower the attenuation?
2) Increase mash temp to 154F to decrease the fermentability of the wort. It seems like this shouldn't be necessary with the 4oz of malto dextrin that the recipe calls for though?
3) Skip secondary in carboy and condition at 70F in keg instead to prevent any oxidation due to the headspace.

Do these changes make sense? Or can anybody spot something else that may have gone wrong in my process that would cause this? Thanks in advance for any feedback :mug:
 
I'd say that those fermentation temps are too high. With that yeast, despite some recommendation to the contrary, going up over 68 F for the first 3 days often lends a harsh alcohol flavor. I start that one at 65 and slowly go up to 68 over 5 days then finish out at 72.
 
I do tend to pitch that yeast a little cooler as well and let it slow rise. I don't think dropping it a few degrees is going to help with attenuation though, and I don't think fermenting it too cold is a good strategy. 530 acts like a beast for me, always up over 85% apparent attenuation. The 4 oz of maltodextrin is only going to add 2 pts to your FG so not surprised that didn't really get you up to 1.017. I would try mashing high next time and maybe up the dextrin. Did you try letting this one age a bit?
 
Thanks for the input guys - it sounds like keeping the fermentation temps lower especially during the peak should help a bit. As far as increasing the mash temps, would 154F (up from 151F) likely be enough to have a noticeable affect on fermentability? Or should I shoot even higher? Also, is there a way to roughly estimate how much the final ABV is affected by increasing the mash temp?
 
I find that you need to change the mash temp pretty significantly to get a big difference in FG. Like going from under 150 to 156 or so. This is general experience though, I don't typically brew Belgians targeted to finish that high.
 
The hot alcohol taste would be fermentation temps.

To darken it up more you might add more Munich.

Are you mashing out? Not doing so would allow conversion to continue making a more fermentable wort.
 
The hot alcohol taste would be fermentation temps.

To darken it up more you might add more Munich.

Are you mashing out? Not doing so would allow conversion to continue making a more fermentable wort.

Thanks for the input - I did do a mash out on this one, but I undershot my mash out temp by a bit. I think it only got up to around 160F. I'll definitely try bumping up my sparge water temp this time.

As far as the color goes - is it likely that increasing my mash temp this time (sounds like maybe 156F is a good target) will affect the color noticeably? Would adding another 0.25 lbs of Munich be a good starting point?
 
Based on the information provided I would guess it was a result of fermentation temp schedule.

Although you didn't mention in OP, this sounds like over oxygenation if you're using pure O2, too
 
Although you didn't mention in OP, this sounds like over oxygenation if you're using pure O2, too

Do you mean over oxygenation as in before fermentation? I usually get a good inch or more of foam on top of the wort before I pitch by whipping it with a whisk. Is it possible to over- aerate at that point in the process? I'm not using any pure O2.
 
It is not over oxygenation. You cannot reach those levls without using pure O2

Pitched @69F, controlled temps to 72F for first 3 days, let rise to 75F for the remainder of primary fermentation (18 days).

Fermentation temp is your problem. You mention 72. Is that ambient temp or measured wort tremp? If it was ambient, then definitely too hot. That yeast can heat up to as much as 10 degrees over ambient when at the temp is that high. So you could have easily been in the high 70's to even low 80's. If it was measured wort temp then it is still slightly too hot for the beginning of fermentation.

It is often repeated here that , "Belgian yeasts like it hot" This is not good advice. Sure they do like to be warmed up to finish out, but starting lower at the beginning of fermentation will produce a much better brew. Starting too hot at the beginning will produce fusels. Fusels do not age out. One of the first Belgians I made I took that bad advice and pitched in the low 70's and fermented in a room where the ambient temp was 75. Pure Fusel bomb. I still have some around over five years later and it still is a fusel bomb. The only redeeming thing is that brew ended up being great for cooking.
 
Once again, thanks for all the advice in this thread. I brewed this recipe again yesterday and am feeling confident that I'll have a better result this time.

Fermentation temp is your problem. You mention 72. Is that ambient temp or measured wort tremp? If it was ambient, then definitely too hot.

The temps I mentioned in the OP were based on attaching my probe to the side of my fermentation bucket using some plumbers putty. This was an idea I borrowed from someone else on the forum. I'd assume this pretty closely matches the wort temps near the outside of the bucket, probably within 1-2 degrees. I'm hesitant to add a thermowell and control using internal temperature, since I'd be worried about larger temperature swings and overshooting the target temp. However, I've been trying to think of a convenient way to get a thermometer down to the wort through the lid just as a sanity check during active fermentation.

For this batch, I chilled the wort down to 65F before pitching and I'll probably try to hold it there until fermentation starts slowing down. From what I've read, Westmalle pitches at 64 and lets it rise to 68F. When is typically the best time to allow temps to start rising?

As far as the other measurements go, I was right on the mark with my starting mash temp at 156.2F, but I forgot to account for more heat loss than usual due to opening the lid of the cooler take a pH reading. The temps had dropped to about 152F by the end of the mash. Mash pH was a little above target at 5.56 (targeting 5.4). After 60 minutes, I sparged and got the grain bed up to 165F. The OG came in at 1.068 - right in line with what I was expecting with the extra 2oz of malto dextrin that I added this time. I pitched last night around 8pm and the airlock was bubbling away when I checked before work this morning. Hopefully I should have a pretty tasty brew in 2 months time :)
 
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