Unexpected overattenuation - Patersbier

[Jayjay1976]

This batch has been fermenting for about a month, I'm bottling it tomorrow so I checked the gravity this morning, instead of the anticipated 1.011 it is at 1.004! Infection? Diastaticus? Or was it my step mash routine?? I've had batches finish a few points lower than expected, but 7 points?

The gravity sample tasted great, it's light bodied but still retains pretty decent mouthfeel, and despite the low FG it doesn't taste nearly as dry as saisons I've bought or brewed.

The grain bill was thrown together to use up a bunch of odds and ends I had in my specialty grain bin, and the yeast I used is 3787 Trappist High Gravity, 4oz slurry saved from a previous batch (maybe 2 months old), propagated on a stir plate into a 2L starter 48 hours before brew day.

The brew day proceeded normally, and I hit my target OG exactly..

The deets:
Title: Patersbier #1
Author: Meeee
Brew Method: All Grain
Style Name: Trappist Single
Boil Time: 75 min
Batch Size: 6 gallons (fermenter volume)
Boil Size: 7.5 gallons
Boil Gravity: 1.038
Efficiency: 70% (brew house)

STATS:
Original Gravity: 1.048
Final Gravity Expected/Actual: 1.011/1.004
ABV Expected/Actual: 4.85%/5.78%
IBU (tinseth): 24.41
SRM (morey): 6.19

FERMENTABLES:
8.5 lb - German - Pilsner (77.1%)
1 lb - Torrified Wheat (9.1%)
0.33 lb - Flaked Wheat (3%)
5 oz - German - Acidulated Malt (2.8%)
4 oz - German - CaraFoam (2.3%)
2 oz - American - Caramel / Crystal 10L (1.1%)
2 oz - American - Caramel / Crystal 20L (1.1%)
3 oz - Belgian - Special B (1.7%)
3 oz - German - Melanoidin (1.7%)

HOPS:
0.75 oz - Tettnanger US, Type: Pellet, AA: 5.5, Use: Boil for 75 min, IBU: 15.17
0.75 oz - Tettnanger US, Type: Pellet, AA: 5.5, Use: Boil for 10 min, IBU: 5.26
1 oz - Hallertau Blanc, Type: Pellet, AA: 9.9, Use: Boil for 1 min, IBU: 1.5
1 oz - Hallertau Blanc, Type: Pellet, AA: 9.9, Use: Whirlpool for 10 min at 150 °F, IBU: 2.47

MASH GUIDELINES:
1) Temp: 138 F, Time: 30 min
2) Temp: 152 F, Time: 20 min
3) Temp: 168 F, Time: 10 min Mashout
Starting Mash Thickness: 3.15 qt/lb

OTHER INGREDIENTS:
0.75 tsp - Calcium Chloride, Time: 0 min, Type: Water Agt, Use: Mash
YEAST:
Wyeast - Trappist HG 3787
Starter: Yes
Form: Liquid
Attenuation (avg): 76%
Flocculation: Med-High
Optimum Temp: 64 - 78 F
Water: 100% RO

 

[ba-brewer]

They do say a protein rest can cause troubles with modern malts so it could of been your mash schedule.

Or maybe your initial slurry was healthier than expected and you over pitched which can give a higher attenuation. What kind of attenuation did you get in the previous use?

If the fermentor was still bubbling after a month maybe an infection. You dont have too much gravity left to feed a wild yeast if that was the case you should be fairly safe to bottle. If you are nervous check a bottle in a week or two and if the carbonation seem good chill them all to stop the yeast.

My diastaticus contamination was easy to find in a cream ale due to the unexpected clove and banana aromas. It also left a film on the surface of the beer but that is not always the case. Mine also happen after yeast sat a while between pitches and that yeast was reused several times before that. Most likely it was there earlier just at a level I could not tell, I keg when gravities are close to expected FG not a fixed time so I could of ranched it for a while without knowing.

 

[Yooper]

That's a pretty typical FG for a patersbier in my experience, and not a problem.

But 138F is a very unusual rest- too high for a protein rest, and a bit low for a beta amylase rest. What made you choose that temperature?

 

[Jayjay1976]

That's a pretty typical FG for a patersbier in my experience, and not a problem.

But 138F is a very unusual rest- too high for a protein rest, and a bit low for a beta amylase rest. What made you choose that temperature?

After reading your comment I looked back through my notes from brew day, seems I mashed in at 138 and then ramped up slowly using only one element until it reached the next temperature, then resting for the time specified before ramping up to mashout. I can't recall off the top of my head where I read about this mashing technique but I'll report back when I find it. I guess it resulted in an extremely fermentable wort. I fermented it at room temp to let the Belgian yeast shine; it was an extremely vigorous fermentation early on, starting a couple of hours after pitching but I haven't seen any sign of activity in the airlock in at least 10 days. Somehow it still has definite body, not nearly as thin as I expected when I saw the FG. Either way I have no problem with the result so long as it is truly finished so bottling tomorrow won't result in gushers.

 

[Yooper]

After reading your comment I looked back through my notes from brew day, seems I mashed in at 138 and then ramped up slowly using only one element until it reached the next temperature, then resting for the time specified before ramping up to mashout. I can't recall off the top of my head where I read about this mashing technique but I'll report back when I find it. I guess it resulted in an extremely fermentable wort. I fermented it at room temp to let the Belgian yeast shine; it was an extremely vigorous fermentation early on, starting a couple of hours after pitching but I haven't seen any sign of activity in the airlock in at least 10 days. Somehow it still has definite body, not nearly as thin as I expected when I saw the FG. Either way I have no problem with the result so long as it is truly finished so bottling tomorrow won't result in gushers.

Yes, I strongly suspect your mashing schedule was responsible for the high attenuation. I’ve never rested above 133 for a protein rest, and never did a saccarification rest below 147, so that’s my guess but I think it’d be a decent guess anyway.

 

[Jayjay1976]

I bottled this batch yesterday, primed to 2.5 volumes with raw sugar. I'll report back with first impressions this weekend once they've had a chance to carb up a bit.

I have had a couple of batches that over-carbed lately including a few gushers, and beers turning out a bit too dry post-bottling in general; so being presently paranoid about vectors for infection I took a super close look at my bottling gear this morning. While scrutinizing my bottling wand I noticed that the entire assembly had a bit of buildup so I went over each piece meticulously and discovered a tiny o-ring I had never noticed before on the tip valve which had collected crud. I also swabbed out the rigid tubing and the other parts with a bit of cotton and noticed it was accumulating some brown goop. I gave all the little parts a good scrubbing with an old toothbrush including the valve on the bottling bucket and all threaded parts, then a short soak in hot star san. I suspect a bit of diastaticus was making its way into my batches from a few saisons I brewed a while back. That or some other hot filth is eating up residual sugars, unless maybe I need to re-think my approach to mashing temps in general.

 

[ScrewyBrewer]

@Jayjay1976 looking at your hydrometer sample the meniscus reading looks to be 1.010 to me.

 

[ba-brewer]

Here are a couple link to a podcast about diastaticus

http://masterbrewerspodcast.com/068-diastaticus-part-1
http://masterbrewerspodcast.com/069-diastaticus-part-2

 

[Jayjay1976]

@Jayjay1976 looking at your hydrometer sample the meniscus reading looks to be 1.010 to me.

Sorry, here is a better shot.

 

[Jayjay1976]

Here are a couple link to a podcast about diastaticus

http://masterbrewerspodcast.com/068-diastaticus-part-1
http://masterbrewerspodcast.com/069-diastaticus-part-2

Hey thanks! I'm always looking for homebrewing podcasts, hadn't heard of this one yet.

 

[ba-brewer]

Made me feel better when you hear the professionals have troubles too.

Easy for things to go undetected unless you really look. The more you repitch the better the chance of it growing to a easily detected level.

If you find that carbonation levels are too high you can chill the beer to stop further attenuation/carbonation. If you are really worried you could also do a test bottle in a soda bottle to see if pressure continues to build.

 

[Jayjay1976]

Today marks 2 weeks since bottling day, and this batch turned out pretty good! Crisp and pretty dry but still a nice bit of malty sweetness, just enough to match the mild flavors of the noble hops. I credit the CaCl addition for rounding out the flavor; let's see how it matures after a few weeks at 40. Pic of the pour coming soon.