Attenuation

Ok, here is the deal. I've been brewing for 17 years. I have always had attenuation problems.

I've used pure 02. I've used an aquarium pump. I've underpitched, I've overpitched. I'm always about 3-5 points short of where I want to be.

Not a huge deal in my most recent beer, but a problem nonetheless, since the problem is so consistent.

I made a dry stout. 10G batch. Used 2 smackpacks of Wyeast 1084 Irish Ale yeast. Oxygenated with pure O2 inline in my chill wizard. Pitched a little warmer than I would have liked, at about 78 because I couldn't get it to chill any further with the ground water at 78. I pitched right away, and put fermenters in my basement at 69. Fermented 17 days at 69. Went to secondary today, and am short on my FG. OG was 1.043-1.044. FG is 1.013-1.014 giving me a finished beer of 3.8% alcohol. Now, I was only shooting for 4.2%, but I still came up short. Not the end of the world, but annoying as hell! BTW, I mashed for an hour at 149 degrees.

Any tips? There has got to be SOMETHING I'm doing wrong here. I can't figure out what it is. It doesn't even seem to matter if I pitch on top of an old yeast cake immediately.

what yeast strain?

edit: sorry I see it now

Have you double checked your thermometer you use for mashing? It might be a good idea to invest in a good thermometer and calibrate it often.

You should make a starter. 2 pack is only half what would be required for that beer.

Check your thermometer. It could be off.

Mash thinner 1.5 quarts per lb

Mash longer 90 mins at 149F

check your mash pH

The first thing I'd do is double check the accuracy of the thermometer. If you mashed a beer, even a stout, at 149, it should be pretty fermentable wort.

The next thing I'd look at is the choice of yeast strains. Some yeast strains attenuate to 67%, some 80%. If you want greater attenuation, choosing a more attenuative strain will help.

By the way, a FG of 1.013 seems about right for a stout. I probably wouldn't want it any lower than that. If you want a higher ABV, the easiest fix would be to increase the fermentables next time- a higher OG will be an easy way to work around this issue.

As was mentioned, even with a low OG, two packages of yeast for a 10 gallon batch is underpitching. I'm not sure it's the issue, but it certainly didn't help.

I hear ya guys. I use a Brewmagic system, so I'm pretty certain the thermometer is right. Also, this time I used Wyeast 1084, which means I should have gotten about 73%. IIRC. So, I think my attenuation this time was about 70%. It doesn't seem to matter what strain I use, and I've batch sparged with a cooler prior to the last 3 batches. No differnence.

Mash PH I assume is 5.2. Or, I use the 5.2 powder anyway. I don't have any ph testing equip.

From reading the first post, it sounds like you're considering the gravity when transferring from primary to secondary as your FG. I've noticed that while I drop the majority of gravity in the primary (after a few weeks), I still drop less than a handful of points while in the secondary. That is, gravity into primary could be 1.040, gravity after a week or two into secondary could be like 1.015, and gravity after another few weeks at bottling time could be like 1.011.

What's your gravity at bottling? Does it drop down into your desired FG range?

On second thought, I don't think I've ever dropped 4 points in secondary. Maybe just 1 or 2 or so.

Yeah, I've never dropped in secondary more than like 2 points. I don't bottle though, I keg. Also... I've almost ALWAYS use starters. This last time, i didn't because I was short on time, so I just bought another smack pack. I figured 2 smack packs in such a low gravity wort would be fine. I was only 1.043 or so to start.

Killervector said:

I use a Brewmagic system, so I'm pretty certain the thermometer is right.

Mash PH I assume is 5.2.

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You know the old saying about assuming things?


Best thing is to know what you've got, don't assume anything.

Could fool around with a little acid malt I guess....

Killervector said:

I hear ya guys. I use a Brewmagic system, so I'm pretty certain the thermometer is right. Also, this time I used Wyeast 1084, which means I should have gotten about 73%. IIRC. So, I think my attenuation this time was about 70%. It doesn't seem to matter what strain I use, and I've batch sparged with a cooler prior to the last 3 batches. No differnence.

Mash PH I assume is 5.2. Or, I use the 5.2 powder anyway. I don't have any ph testing equip.

Click to expand...

I don't know much about the Brewmagic system, but why would the thermometer be right? Is it a Thermapen, or auto calibrating?

The calibrate them all at the factory by hand before the system ships. Its only seen 2 brews so far, so I can't imagine its wrong. Also, its on a thermocouple that is digitally monitored. The heat exchanger then keeps the temp at the right spot. There is also a therm attatched to the actual brew kettle. It reads the same as the thermocouple. Also, I had the same issues before with my old setup despite constantly recalibrating thermometers, and such.

Killervector said:

The calibrate them all at the factory by hand before the system ships. Its only seen 2 brews so far, so I can't imagine its wrong. Also, its on a thermocouple that is digitally monitored. The heat exchanger then keeps the temp at the right spot. There is also a therm attatched to the actual brew kettle. It reads the same as the thermocouple. Also, I had the same issues before with my old setup despite constantly recalibrating thermometers, and such.

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Gotcha. I just use a plain ol' thermometer so I check it every so often. The first thing I think of with under (or over) attenuation is temperature. That's usually the cause.

The next cause is usually yeast health and underpitching. Along with that goes lack of aeration, also.

Since you've covered all of those, I'm unsure of what to consider next. Mash pH might play a part, but if you're getting conversion shown by iodine testing, I'm not sure what else to consider.

When you measure OG and FG, do you apply any of the temperature correction factors? If not, should you? If you try it, does it get you closer to your FG?

Maybe your hydrometer is broken or mis-reading?

meh.... temperature correction isn't an issue. I use a refractometer with ATC for my OG. I use a hydrometer to test FG at 70 degrees.

it's all about mash temperature. also, you can add sugar to boost ABV without adding to the FG.

OMG... a Blago sighting! LOL

I would guess that it is PH. Test it and find out.

1.044 to 1.014 is 68.18% attenuation. That yeast, according to Wyeast is only supposed to attenuate at 71-75% so you are close. If you made a big starter (5000ml for 10 gallons, decanted), you would have hit your FG. If you don't want to make starters, I would suggest using 3 packets of something like safale -04 for 10 gallons of that beer. That will get you closer to your intended FG.

JonK331 said:

1.044 to 1.014 is 68.18% attenuation. That yeast, according to Wyeast is only supposed to attenuate at 71-75% so you are close. If you made a big starter (5000ml for 10 gallons, decanted), you would have hit your FG. If you don't want to make starters, I would suggest using 3 packets of something like safale -04 for 10 gallons of that beer. That will get you closer to your intended FG.

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Fermentation temp is also important. I like to start ferment towards the cool side to control esters and fusel alcohols. But towards the end I will jack up the temp to reduce the diacetle and for full ATTENUATION. If you have been cold crashing (in some cases even if it just slips a few degrees) or transferring the beer off the yeast to a secondary it could effect the attenuation.

maida7 said:

Fermentation temp is also important. I like to start ferment towards the cool side to control esters and fusel alcohols. But towards the end I will jack up the temp to reduce the diacetle and for full ATTENUATION. If you have been cold crashing (in some cases even if it just slips a few degrees) or transferring the beer off the yeast to a secondary it could effect the attenuation.

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True but if his basement is 69, then the ferment probably got up to at least 72. My guess is this is a case of underpitching.

Killervector said:

Not a huge deal in my most recent beer, but a problem nonetheless, since the problem is so consistent.

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Are you beers coming out as dry to taste as you like them, or is the residual sugar problematic?

If the former - and your target ABV is really the only thing you're not getting - then I'd think a logical solution would be to just bump up the grain bill a hair. Since the problem is so consistent, it seems to me that you're in a position to accurately determine just how much of an increase is required to hit your numbers.

JonK331 said:

True but if his basement is 69, then the ferment probably got up to at least 72. My guess is this is a case of underpitching.

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I agree on the pitching rate. I even brought it up in one of my earlier posts.

But if the temp were to fluctuate and it dipped down to the low 60's one night. And if said dip coincided with the later stages of fermentation. Then the yeast could fall out prematurely and BLAM! poor attenuation.

Thanks for all the tips. I'm gonna check the mash ph, as I feel its the only place left to look. As far as the starters... I make em all the time... and it doesn't seem to matter a whole lot. I just didn't have time this last time. I'll update you next week when i brew.

Chad

A question that nobody did yet, what brewing tool (software) are you using?
Have you always used the same?
Do you often use Crystal, carapills or any known unfermentable malt/sugars?
Do you know (as far as I know), most if not all brewing tools DO NOT differ fermentables from non-fermentables sugars?
That is, if you plug in 5lb of 2row and 5lg of carapills, it will apply the yeast attenuation (default % by the way) to the whole thing? That means your real FG will be much higher than the toll predicts.
From malt spec sheets, fermentability can be estimated from the "glassy" caracteristics of the malt. Malts that have a high glassy number, provide very low fermentables, like Crystal, that I estimate to be 5% fermentable only, depending on the toasting level. Carapills and lactose are 0% fermentables, as well as highly toasted malts (above 120L).
Also, the same tools DO NOT care for your mashing temp, so it uses the same attenuation across the board, regardless of what temp you mashed in.
That said, I like using non-fermentables like carapils, lactose, crystal malt, and gave up on these tools and built my own. I hit FG every time within a point or two.

check here:
http://beertech.blogspot.com/2009/12/considerations-when-predicting-final.html
http://beertech.blogspot.com/2010/05/malt-analysis-and-potential-calculation.html