reoccurring over attenuation issues

I'm an all grain brewer with just 10 batches under my belt. I'm trying to figure out what part of my brewing process needs refinement and or adjustment. I brew 5 gal batches utelizing a 10 gal igloo cooler as my mash/lauter tun. All my batches over attenuate to some varying degree. My beers finish good but always under the anticipated FG. I always use proven published recipes from books and mags(brewing better beer, modern homebrew recipes, brew your own etc). All recipes are inputed into beersmith to scale for my equipment.

I always make an appropriate starter with intentions to pitch commercial yeast pitching rates(pro brewer 1.0 ale). I'm pretty spot on with locking into my mash temp for the required mash time. I always sanitise everything with star san. I don't think I could be anymore maticulous with my processes.

I always use a single infusion mash schedule and batch sparge. After mashing I vorlauf then drain 1st runnings into my 10 gal kettle. I then sparge with my entire sparge volume of 168F water. Stirr, rest for 10-15min vorlauf then drain 2nd runnings into my kettle. I usually boil for 90 and cool to pitching temps(65F to 68F) with an immersion cooler. I aerate my wort with a wine degassing whip loaded into my cordless drill. I let it rip into the wort from top to bottom creating a frothy krausen-like foamball on top of the wort, then pitch my yeast. I usually see activity within 2-4hrs of pitching and use a water bath to maintain somewhat consistent fermentation temps. I usually reach FG within 5 days.

That's pretty much my process every time I brew. I just can't seem to figure out why my beer always finishes up at a lower than anticipated FG. For example, I brewed a Pliny recipe last week from brewing classic styles. The recipe's OG 1.080 and FG 1.013 matched beersmith, but my FG was 1.008. The recipe before was a smoked pumpkin Saison with an OG1.058 and FG1.012 and I finished at 1.006. If anybody has any ideas as to what may be the cause of this issue, I am all ears and appreciatee your suggestions. Could a mashout step possibly help with this issue?

 

Does your hydrometer read 1.000 for room temperature water?

 

I have been having similar problems. The problem for me, I'm 90% sure, is the thermometer being out during the mash. I use cheap digital thermometers with a probe in the mash. I think the probes get damaged from the mash temps or start leaking and the temps are all over the place. Latest batch, I raised the mash temps a few degrees and brewed an amber with 15% crystal, that finished at 1.021 lol.

I also found my efficiency dropping recently, I think this is another symptom of mashing too low.

 

What yeasts do you use?
Have you checked your hydrometer?
Have you checked your mash thermometer?

My guess is that you are using a highly attenuative yeast such as US-05 and you might be mashing too low for too long. If you find your mash temperature is like 148 F or lower and you are mashing for longer than 60 minutes, this will increase attenuation slightly.

Also the mashout is making matters even worse.

Try 152 F for just 40 minutes and skip the mashout, and just get the wort to a boil as fast as possible. That might fix 'er. FWIW, I've been mashing almost every batch (about 100 batches) at 150 F for 40 minutes for the past 10 years. Try it; you might like it.

 

Yes my hydrometer is reading at 1.000 at room temp. I also use a refractometer with atc during the brewing process before yeast.

 

I'm sure you are super dialed into your system and produce consistantly good results. I'm just trying to brew a recipe and have my FG jive with the recipe's intended FG. So far I can't seem to accomplish that. Little frustrating, not knowing what my issue is. Do you think if I incorporate a mashout step at 170 I may be able to denature the the grains and lock into a saccharification profile? Seems as if mash out is generally skipped by many homebrewers.

 

I see now that you are batch sparging with 168 F water, then recirculating for up to 15 minutes. You should measure the temperature during this time as I bet it's only about 160 F, which is insufficient to kill off the alpha amylase and thus essentially having the exact opposite of the intended effect -- instead of killing the enzymes to prevent further conversion, you are instead actually speeding up the conversion by the alpha amylase for those 15 minutes. This extra conversion makes your wort more fermentable than average. Hence if you either sparge with like 195 F water to actually mash out, or skip the mashout step, you'll be mashing for less time and will reduce conversion and thus increase FG.

Like I said, mash for just 40 minutes, and also use much hotter water for the batch sparge. Then you will see the attenuation that you expect.

Another thing is choice of yeast. In looking at the reviews on WLP568 for example I can see that that yeast averages 86% attenuation, which is pretty typical for a saison. So if you saw like 90% attenuation with yours, it wouldn't be unheard of. The other yeasts, I wouldn't have expected the ~90% attenuation that you were seeing, thus my pointers above should help more with those.

Hope this helps.

 

That makes sence! Thank you for the advice. I'm brewing wed and I will employ these methods into my brew schedule and let you know how the beer finishes up. Thanks again.

 

To further dmtaylor's statement, I use the formula in How to Brew, for how much boiling liquor to add to get up to 170*, and fire up the boil at 1 inch in the kettle. If your mashing at a 1.5 ratio it takes quite a bit of liquor.

 

I think dmtaylor is pretty spot on. The one thing you didn't mention in your OP is your mash temp. There is a huge difference in attenuation based on temps. A possible solution instead of doing a 40 minute mash is to adjust your mash temps. Higher temps will produce less fermentables

 

I theorize that mash time may have a greater effect on fermentability than mash temperature. More experiments are needed. In any event, if you want to really limit fermentability, then try mashing for just 30 minutes at 156 F or something like that -- this would take both variables to an extreme.

 

Possibly. I stated it because I had the exact same problem the OP is having. So going from a mash temp of 152 to 156 made a big difference for me.

 

Sorry, I thought I had mentioned that I'm brewing Gordon Strong's recipes and mashing at the recipe's indicated temp. I always take corrective measures when more than a degree off at dough in. Brewing his American Dubbel Brown this afternoon. The recipe calls to mash belgian 2 row, munich and dark munich at 150F for 60, then choc malt, special B, caramunich and caravienne malts are added at vorlauf.

I am planning to take half of my sparge water(2.2gal) and mash out at 68-70 for 15 minutes. Then add the remaining 2.2gal sparge water at 195F, and the steeping grains to begin vorlauf. Any objections or tweaks I should make to the process? Thanks
Demetrios

 

Yes... Any extension of temperatures below 168 F is going to result in high attenuation because alpha amylase is still plenty active below that point. The 15 minutes you're talking about -- be sure to measure the temperature, and if it's not 168 F or higher than don't wait 15 minutes but immediately add the rest of your sparge water to get up there. Even boiling water might not get you to mashout temperature. If you want to try the process above then consider boiling the second half of the sparge water instead of just 195 F.

 

OK, so that brew session didn't go so well. The mash temp was fine, but when I attempted to mash out with half of my sparge water (2.35gal) at 197F, it only brought the mash temp up to 164. I then added 1.5gal of boiling sparge water which brought the temp up to 168F. The combined volume maxed out my 10gal igloo MLT. I vorlaufed then drained into my kettle and had only about a gallon of water left for sparge. So ultimately this turned into a no sparge method. I did hit my pre boil SG of 1.046, surprisingly. I had to boil for 120 min to achieve the target OG of 1.056. Actually came in at 1.058.

For next brew session would it be feasible to mash, vorlauf, run off 1st runnings into the kettle then add my sparge water at boiling to hit 168-170F? It does make sense to mash for 45min, add steeping grains at vorlauf,(15min or so) run off 1st runnings then sparge with water hot enough to achieve mash out temp of 168F. I now don't really see the need to mash out when the sparge water could reach mashout temp.

Another issue was draining the kettle into the fermenter with 2oz whole leaf hops in the wort. .5oz FWH, .5oz @10 and 1oz @ flame out. What a nightmare trying to drain that mess. Perhaps some kind of hop bag next time? Thanks for your advice.

 

So I might have missed it, but I didn't notice you address your thermometer. If it is off by a few degrees, you will obviously not get an accurate measurement of your mash temperature, and so a mash that appears to be spot on may in fact be several degrees different.

This happened to me about a year ago. My dial thermometer got knocked off its calibration at some point, and was reading about 6 degrees high. 4 batches of beer that I thought I was mashing in the 152F area were actually down around 146, and it definitely produced a noticeable difference in the FG.

 

Go ahead and use all boiling water for your sparge next time and see if you can hit 168 F. It won't hurt anything assuming the mash pH is where it needs to be about 5.2 to 5.5.

When using whole hops, a hop bag is a must.

I think we're getting closer to perfection now.

 

He's checked his thermometers, two different ones and they match.

 

Ah, I missed that. That's what I get for offering my opinion before I've had my coffee!

 

Just checked FG on this beer and confirmed 3 consecutive readings of 1.012 over the course of a week. The method of batch sparging to achieve mashout temp of 170F has worked for me! Intended FG 1.014. That's a step in the right direction. I used this method for 3 preceding beers, so I'll have a better indication of the consistency of this method. The one thing I have noticed in utilizing this method is a change in fermentation behavior. Beers using this method fermented less vigorously and much longer. The Dubbel Brown fermented slow and steady for 3 weeks! I have never had a beer ferment this way until using this method. Usually vigorous fermentation for 3 days then complete in 7. Interesting. Thanks for all the help with this matter.
Demetrios

 

Glad it's working well for you. I think you will get similar results with the other batches you've brewed with this method.

Belgian yeasts are notoriously finicky and slow to ferment. I think that's likely more the problem than the change in process. Have you used any English yeasts recently? Those often finish fermenting within 2-3 days. Depending on the exact strain, I would be surprised if non-Belgian ale yeast strains take very much longer than about a week to finish fermentation under normal conditions (moderate gravity, reasonable temperatures, etc.).