Attenuation ?

My last 2 batches have failed to ferment down to the predicted FG. In fact they have been .008-.01 short. Upsetting a little I had high hopes for the most recent beer, I hit the OG dead on (first time ever).

My procedure is this. I make a 1000ml starter 2-3 days prior to brewing. I always use the instructions on the back of the Wyeast pack for doing so. I cool my wort to 72-74° before pitching. I aerate using oxygen for about 30 seconds prior to pitching. My beers usually begin aggressively fermenting 12-24 hours. They ferment at 65-70°.

I realize that 1000ml is not huge for a starter. That would however affect the lag time more than the attenuation correct? That said I would assume then I am not aerating correctly then. What do you guys do?

Cheers!!!

Follow up... Is there anything I can do with my beer in the fermenter. It has been there going on 4 weeks.

If you're mashing, I'd guess that your mash is more likely the culprit and not your yeast. Mash temperature, pH, water/volume ratio, etc can all affect the fermentability of your wort.

I'm having the same problems as you.

I'm going to get an O2 kit because I thought aeration was my problem, but it sounds like you are using O2 and still having issues.

I'll still do that, but maybe I need to pay more attention to my mash. I haven't been having any problems there, so I don't know what it could be.

I'm also going to do an extract kit or two. If I do not have any problems with them then I'll know its the mash.

I had this same issue when I first started using my brewery... I was mashing too high (temp).

Some time ago I wrote this article to answer exactly your question. Let me know if it helped or not. I may have to add some more info.

One thing to take away is the forced ferment test. This is not widely practiced in american home breweing but It can give you very valuable information about the FG that you can expect and if you don't hit it it tells you to look for the problem in the wort (mash or extract) or in the fermentation.

The attenuations given for the yeasts, and on which most FG predictions are based on, are only a very rough guideline and don't take mashing into account.

Kai

Kaiser said:

Some time ago I wrote this article to answer exactly your question. Let me know if it helped or not. I may have to add some more info.

One thing to take away is the forced ferment test. This is not widely practiced in american home breweing but It can give you very valuable information about the FG that you can expect and if you don't hit it it tells you to look for the problem in the wort (mash or extract) or in the fermentation.

The attenuations given for the yeasts, and on which most FG predictions are based on, are only a very rough guideline and don't take mashing into account.

Kai

Click to expand...

Kai - I read your article when you first posted it. I think its a good discussion of attenuation and I found it informative.

From the perspective of a homebrewer who has had some trouble with attenuation, I thought it would benefit from including a discussion of factors that a homebrewer can control that directly impact attenuation. For example, mash temp, fermentation temp, pitching rate, yeast choice, yeast nutrients, aeration, etc.

It would be great if each of these could be discussed separately and ranked in terms of their affect on attenuation. I'm not sure if the data exists to make a rigorous comparison, but that's OK. It would still give a homebrewer a checklist to work through when trouble shooting an attenuation problem.

I guess what I'm thinking of is something along the lines of a more general discussion of factors that ensure a good fermentation, like in Palmers book (here). That may be taking an article on attenuation too far afield.

Anyway, thanks for the article. It did help.

I notice that for the most part my attenuation is higher than anticipated. My brews usually finish a bit lower than targeted. My average AT is around 80%-85%. I'm pretty sure this is due to my mini-mash temps though. I tend to err on the lower side of the temp as opposed to the higher. I guess I'm always irrationally concerned about overly sweet brews or tannin extraction.

Nate said:

If you're mashing, I'd guess that your mash is more likely the culprit and not your yeast. Mash temperature, pH, water/volume ratio, etc can all affect the fermentability of your wort.

Click to expand...

Thanks Guys!

First off I am at work and haven't the chance to read the links. (I will).
I was thinking that if I hit the OG that would "tell" if the mash is correct. Are you guys saying there is more to it?
Again sorry I am posting without reading the links.

Please let me know how the extract goes Beertoven I will be interested to find out.

Cheers!!!

Assuming you are doing all grain the single factor you have the most control over is your mash temp. As everyones system and process differs recommended mash temps are a guide only. You will need to know your system and adjust accordingly. For instance if I mash at Jamil's "sweet spot" of 154 I end up 0.002-0.003 points higher then target so my "sweet spot" is 152 - a little lower which increases fermentability and attenuation.

GT

Well it might have been the mash in my case.

2 brews ago I missed the OG .007 on the low side. (Having less sugars to convert may have been the issue).

The Last brew had an S-load of corn (20%). Palmer says many times beers with a lot of adjuncts are sometime low on minerals the yeast need.

What do you guts think???
I guess the attenuation issues might have been 2 separate problems with the same result. Regardless of all that I am going to aerate the crap out of my next batch.

A hydrometer cannot tell the difference between fermentable and unfermentable sugars. Hitting your OG only means you had good starch (sugar polymers) to sugar conversion and good sparging. I was having an attenuation problem & discovered all three of my thermometers were reading low.

If the dump truck weights 56,000 lbs, you know it's full, but you don't know if is rock or sand until it washes out*.

*We had the "storm of the decade" last week. Had one last year, also

Oh no please don't get my going on thermometers again. I have the whole anxiety about them being wrong.
I am going to go home tonight and test them all in boiling water.

Of course it was the yellow one I used to mash.
<EDIT> Now that I think of it that is probably the one that was right... that is boiling water.

I'm sorry I am not trying to post whore...

I am just a little thick headed (really a lot).
OK what you guys are saying is that I should be looking at my mash technique. Find where the hole is.
That 30 seconds with oxygen should be enough. If the Oxygen was low it would show up in my lag time.

If that is the case I am at a loss. It looks as if the thermometer I use while mashing is correct. I guess I had better go back to the books and see where I am missing the mark.

If anyone is interested below was my mash.
10g batch 20.15# of grain
Added 25.25 quarts at 171° - Mash at 155° for 60 min. (It came out a few degrees high but a few minutes of stirring got it down to 155°)
Sparged 2 equal batches of 5g 168° (added 178° water to get this)

Chris_Dog said:

Of course it was the yellow one I used to mash.
<EDIT> Now that I think of it that is probably the one that was right... that is boiling water.

Click to expand...

I've used had big problems with that yellow thermometer. My first one failed, they sent me a new one, and that one is off now too. I just gave up on that type of thermometer all together.

Beerthoven said:

From the perspective of a homebrewer who has had some trouble with attenuation, I thought it would benefit from including a discussion of factors that a homebrewer can control that directly impact attenuation. For example, mash temp, fermentation temp, pitching rate, yeast choice, yeast nutrients, aeration, etc.

Click to expand...

That's a good point.

Kai

Beerthoven said:

It would be great if each of these could be discussed separately and ranked in terms of their affect on attenuation. I'm not sure if the data exists to make a rigorous comparison, but that's OK. It would still give a homebrewer a checklist to work through when trouble shooting an attenuation problem.

Click to expand...

I added a section about affecting attenuation. Look it over and let me know if this is what you were looking for.



Kai

Chris_Dog said:

I'm sorry I am not trying to post whore...

I am just a little thick headed (really a lot).
OK what you guys are saying is that I should be looking at my mash technique. Find where the hole is.
That 30 seconds with oxygen should be enough. If the Oxygen was low it would show up in my lag time.

If that is the case I am at a loss. It looks as if the thermometer I use while mashing is correct. I guess I had better go back to the books and see where I am missing the mark.

If anyone is interested below was my mash.
10g batch 20.15# of grain
Added 25.25 quarts at 171° - Mash at 155° for 60 min. (It came out a few degrees high but a few minutes of stirring got it down to 155°)
Sparged 2 equal batches of 5g 168° (added 178° water to get this)

Click to expand...

A couple of thoughts:

1) How much and what types of specialty grains are you using?

2) Where did the FG estimate come from?

3) My earlier post should have been clearer. It is not about the accuracy (or lack thereof) of your thermometer that determines your "sweet spot" Everyones system and process differs so even if you hit an accurate and identical mash temp your attenuation may not be the same. If I brew someones recipe with a mash temp of 155 and it doesn't attenuate enough I drop the mash temp a few degrees until I hit it. This does of course assume you have a consistent process.

GT

1. Recipe: Bass Clone - BYO
Brewer: Chris
Asst Brewer:
Style: English Pale Ale/Strong Bitter
TYPE: All Grain
Taste: (35.0)

Recipe Specifications
--------------------------
Batch Size: 10.00 gal
Boil Size: 13.20 gal
Estimated OG: 1.053 SG
Estimated Color: 13.1 SRM
Estimated IBU: 31.3 IBU
Brewhouse Efficiency: 72.00 %
Boil Time: 90 Minutes

Ingredients:
------------
Amount Item Type % or IBU
14.00 lb Pale Malt (2 Row) UK (3.0 SRM) Grain 69.48 %
4.00 lb Corn - Yellow, Flaked (Briess) (1.3 SRM) Grain 19.85 %
2.00 lb Caramel/Crystal Malt - 60L (60.0 SRM) Grain 9.93 %
0.15 lb Roasted Barley (462.0 SRM) Grain 0.74 %
2.25 oz Northern Brewer [6.90 %] (60 min) Hops 28.2 IBU
0.50 oz Northern Brewer [6.90 %] (15 min) Hops 3.1 IBU
2.00 tsp Irish Moss (Boil 15.0 min) Misc
1 Pkgs London Ale (Wyeast Labs #1028) [Starter 12Yeast-Ale

2. The FG estimate came from Beersmith... I would expect better that 1.020 anyway.

3. I would agree that everyones brewery is different. However I am thinking this is not a fine tuning issue. Of course I could be wrong I have been so far.

Thank you guys for all the information!!!

It happened again... I hit my predicted OG dead nuts. God I hope this one attenuates the way it is supposed to.

Kaiser said:

I added a section about affecting attenuation. Look it over and let me know if this is what you were looking for.

Kai

Click to expand...

That's great! Thanks, Kaiser.

Thanks Kaiser

My latest batch has had crazy attenuation. I mashed it too low accidentally (147 degrees) and had a stuck sparge that led to it being effectively mashed for two hours before the wort was even put on to boil. It started out at 1.074 and went down to 1.008 using US-05.

This is going to be one super-dry light-bodied IPA (even with the carapils used), but I also threw some melanoiden malt in there originally so it should have some good malty flavor without the sweetness that usually comes with it.

How much can I expect the beer to attenuate after the active fermentation is over?
Yoopers DFH 60. https://www.homebrewtalk.com/showthread.php?t=25709

I brewed Sunday 1:30PM (Thursday now 6:30PM)
1.071 OG
I just a gravity reading 1.021.
I know the question is impossible to answer accurately. I am just wondering roughly. I'm I looking at a few .001's or .01's? or maybe it is done for the most part?

Chris_Dog said:

I know the question is impossible to answer accurately. I am just wondering roughly. I'm I looking at a few .001's or .01's? or maybe it is done for the most part?

Click to expand...

No, it's not impossible. Perform a forced ferment test. Take a lot of yeast and a sample of the beer. put this in a flask or botle and keep it at a warm place. Some brewers put it on top of the cable box, but be very careful that it won't foam over.

Once it is done you won't get any more bubbles from it when you shake it and it will lay completely still. Give it one more day and take a reading. This will be your limit of attenuation and your actual FG should be slightly higher.

As I mentioned before I always do this now, even with my ales. I currently have a pale ale fermenting at 66 *F and it seems to be taking its time. After 8 days its gravity is at 3.5 *P. From the FFT, which was done after 4 days, I know that it can't go below 2.0 *P which means that it will soon be done. I can even start chilling and dry hopping before the fermentation is completely done as long as the remaining fermentable extract less than necessary for carbonation. At bottling time I measure the current extract level, calculate the difference to the expected FG and consider this as priming sugar that is already in the beer.

Kai

Thanks again Kai!

That makes perfect sense. Take a sample and force ferment it to see what the limit of attenuation will be. I am assuming the force ferment will attenuate faster than the cooler beer. I wouldn't imagine there would much point otherwise.

I had to read the last paragraph several times to understand. (not that it was poorly written just over my head a bit). I am fortunate in that I don't have to worry about priming or bottling to much because I keg my beers. I have never used the Plato scale before so I can't relate to the numbers. I do understand what you are saying though.
Thanks again & Cheers!!!

Chris_Dog said:

I had to read the last paragraph several times to understand. (not that it was poorly written just over my head a bit). I am fortunate in that I don't have to worry about priming or bottling to much because I keg my beers. I have never used the Plato scale before so I can't relate to the numbers. I do understand what you are saying though.
Thanks again & Cheers!!!

Click to expand...

Sorry about the complication. The basic idea is, that I know where the yeast has to stop. But keep in mind that the yeast is not expected to ferment it down all the way. Some fermentable sugars in the beer are desired.

To roughly convert between plato, multiply Plato by 4 and use this as your gravity point. 2 *P ~ 1.008 SG and 3.5 *P ~ 1.014 SG. I have switched to the Plato scale as it is very close to the extract % scale. If you work with Plato or % it becomes easy to calculate sugar amounts in your head. For example 10 *P is about 10 % extract. This means that there is about 0.1 kg extract in 1L of 10 *P wort. Gotta love the metric system .

Kai

I think what it comes down to is that your mash temp is just too high period (not because of a faulty thermo). When you say your target was155 but it was initially higher, you have to consider that the higher the mash temp the faster the conversion takes place. If you missed by say 4º high at 159ºF for even 10 minutes, you're making a lot of long chain sugar really quickly. Even if you drop it to 155 (which I still think is high), you're more "averaged" at something like 157 in the grand scheme of the mash. Anytime I flirt with mash temps nearing 155, I never attenuate where I want it. I've decided that my range between dry and sweet is between 149 and 153 and that's that.

Chris_Dog said:

How much can I expect the beer to attenuate after the active fermentation is over?
Yoopers DFH 60. https://www.homebrewtalk.com/showthread.php?t=25709

I brewed Sunday 1:30PM (Thursday now 6:30PM)
1.071 OG
I just a gravity reading 1.021.
I know the question is impossible to answer accurately. I am just wondering roughly. I'm I looking at a few .001's or .01's? or maybe it is done for the most part?

Click to expand...

Here it is 13 days from brewing and the beer attenuated like I expected. 1.071-1.021 (Wyeast 1056). Beersmith expected the FG to be 1.017. At any rate I am going to rack today and dry hop. 6.67 ABV rather than 7.12 expected. Not god awful but just once I would like be higher rather than lower. 69% Apparent Attenuation-75% predicted.

Bobby this batch I mashed at 152°

I don't expect you guys can solve my issue with out dissecting my entire process. I am brewing a SN clone tomorrow.
I know when problem solving that you are only supposed to change 1 thing at a time. However I am changing two.
1. To take my yeast and starter process out of the equation I am using dry yeast US-05.
2. I am not using my digital thermometers at all. I got a nice through hull dial thermometer that I will be using on my HLT. (I need to calibrate it today). Floating type "Mercury?" for the mash.

I am convinced that after this last brew the problem lies in the temprature... like you guys said. I have had way to many problems with the digital thermometers to rule them out.

We will see how this goes.

A buddy of mine brewed a porter that finished around 1030 so we have been contemplating attenuation rates and there's something we're wondering: To truly get an accurate measure of attenuation and/or FG, shouldn't you calculate it based on the amount of fermentable sugars and not the total OG? Here's an example to illustrate my point:

Porter with OG of 1.072. Approx 14 gravity pts come from unfermentables. Let's suppose you get attenuation of 75%. Most software predict FG as 72-(.75x72) = 18, right? But you know that 14 of the 72 pts won't ferment. Shouldn't the calculation be FG = 72-[(72-14)x.75] = 28.5?

Alternately, you would calculate % attenuation from OG and FG as follows: (OG-FG) / (OG - pts from unfermentables). In by friend's porter example, (72-30) / (72-14) = 72.4%. I think Promash is calculating his attenuation as (72-30)/72 = 58%.

This doesn't seem like any huge revelation to subtract unfermentables out of the attenuation calculation, but we've never seen it done. Anyone know why this isn't done?

Thanks,
SP

ESPY said:

This doesn't seem like any huge revelation to subtract unfermentables out of the attenuation calculation, but we've never seen it done. Anyone know why this isn't done?

Click to expand...

It's not done b/c the amount of unfermentable extract is unknown unless you make a corret fast ferment test to find the limit of attenuation. If it would be common to do such a test, brewers would also through around the difference between limit of attenuation and actual attenuation as a parameter when analyzing beer.

It's similar to the different definitions for Efficiency between German and American brewres. German brewers like to express brewhouse efficiency as amount of extract gotten from the total weight of the grain. Americans express it as amount of extract gotten from the limit of extract they could have gotten from the grain (based on laborarory analysis of the grain).

Kai