Higher than expected Final Gravity

[Brew49411]

I am having a reoccuring problem with highe than expected final gravities. If I am shooting for 2.5P I get around 3.5P. If I am shooting for 3.5P I get around 4P. I have done everything I can think of as far as using servomices, checking the yeast, and I still can't get to where I am looking to be.

Any suggestions???

Nicholas Mladucky
Head Brewer
Miami Gordon Biersch

[johnstuart]

I would check the fermentabililty of your wort first. Do a forced fermentation of your production wort in a 2l flask on a spinner. Hyper-pitch it with a sample of the same yeast crop. After it's done fermenting, check the forced sample's final grav, and compare it to the final of the production batch.

If the two are within a tenth P or so, and still too high, you can start investigating your wort composition.

If the forced sample attains your projected final, and the production batch does not, start looking at things relating to ferment methods.... ie calibrating your thermos, checking pitch rates... etc

HTH,

[Bham Brewer]

What is your mash temp? Mash time? Aeration schedule?

[Brew49411]

10 min @ 52 C
30 min @ 62 C
10 min @ 68 C
30 min @ 72 C
10 min @ 78 C

As for the aeration, I use about 30lbs throughout the knockout.

[Bham Brewer]

What kind of beer are you making that you are opting for a step mash? You might find you have a more fermentable wort if you extend your time around 65C. What 0.G. on the beers in question? What does your yeast supplier expect for apparent attenuation of the strain you use?

I might also say 'be careful what you wish for' I can't tell you how many brewers I've know say they were shooting for a lower terminal gravity, only to hear them whine about their beer not having enough body... huh?

[Moonlight]

I've had crappy yeast performance (including attenuation) when my aeration stone gets a bit plugged so that the bubbles are big instead of fine. The fine bubbles dissolve more thoroughly, and the course bubbles mostly just blow out the fermenter. The result is the same oxygen flow rate in cfm's but less gets dissolved in the wort, hence less feeds the yeast, and poor viability. I always try to watch the sightglass to see how the stone is behaving.
Just another idea...

[crassbrauer]

Body is dependent upon protein molecules. If you have a long protein rest, your body will suffer. Some brewers cut their fermentations a little short in order to increase body. This only results in beers which are sweeter and more apt to infection.

A step mash is a "normal" choice outside of ale brewing. I assume since you're at Gordon-Biersch that you're brewing a lager or Weissbier? Since you are step mashing, you have a choice as to where your rests land. If you're not brewing a Weissbier, then you may want to try no protein rest at all. How's your foam and mouthfeel? If satisfactory, then don't do a protein rest. Definitely avoid 65 C, because it is at the high end of the optimum for an enzyme you don't want working in your mash, namely lipase. Hit 62 C, the optimum for beta-amylase, then rise immediately to 72, the optimum for alpha-amylase. Don’t stop at 68 C. If you need to reduce the time you spend at each of these optima.

If you’re comparing your gravities to those of brewers who’ve used a British-style single temperature mash, then you will be getting better extract efficiency from your malt. If you still feel they’re too high, check your mash pH, it should be around 5.2 to 5.3. If you want even less, there is a mash program used in Germany for lowering final gravity: mash in at 52 C, then immediately rise to 72 C without stopping at the beta-amylase optimum.

[pennbrew2]

If you want even less, there is a mash program used in Germany for lowering final gravity: mash in at 52 C, then immediately rise to 72 C without stopping at the beta-amylase optimum.

This would raise the final gravity, bypassing the beta-amylase step would decrease the fermentability of the wort.

[Brew49411]

I only have the problem with my lagers. The Hefe that I brew never has a problem finishing where I need it which is making me think it is the yeast. I have checked with other brewers using White Labs and they seem to have had some yeast issues with German Lager strains from there. I can't figure out if its me or the yeast. I am going insane!!!

[crassbrauer]

Sorry, my bad. With "less" I obviously meant less fermentable sugar/lower final attenuation. I typed that quickly before running for the bus... :o

[crassbrauer]

The first thing I would try, before you go insane, would be to reduce the time of each of your maltose rests and cut out the 52 C rest. (This rest can break down proteins which are encapsulating carbohydrate molecules or are bound to them.) It probably won't work, but you never know, and it'd be the easiest solution.

Is anything on the malt analysis which is different from previous ones? (indicating that it's overly modified?) A shot in the dark: Since top fermenters don't break down maltotriose but bottom fermenters do, the malt could be modified to the point that there is a lot of maltotriose in it, which is feeding the lager yeast but not the Weissbier yeast.

Grow up some fresh lager yeast, as well. Pitch around 20 million cells/ml. You want your fermentation to go quickly and for the pH drop rapidly to around 4.3 or so. Your yeast should be happy, so that everything goes according to plan. Aerate them well (but be careful with O2). Most poor fermentations can be avoided by doing this. Try to ensure there are no other microbes present that can break down dextrines, for instance, which would drop the gravity substantially.

Are there any odd flavor characteristics about your lagers?

Those are the first ideas that come to mind. If the problem persists, then perhaps you could post again with more information. Good luck.

[jarviw]

crassbrauer> I think you are missing the point here.. he has low attenuation in his lager, not trying to increase the body or anything about his weizen.


.......


it makes sense your lager yeast ferment differently from your weizen yeast. Actually, a lot of sources do recommend higher yeast pitching rate for lager yeast... so you probably really shouldn't expect the same mashing schedule to work across yeast strains.


I would try cutting out the rest at 72C... it's too hot for amylases anyway, and if you want more fermentable sugar, you need longer rest at lower temps... try:

10 min @ 52 C
*45 min @ 62C
*25 min @ 68C (or until iodine test negative)
10 min @ 78 C


I would also second that -- calibrate your thermometers!

[crassbrauer]

Wow...thanks jarviw! Maybe I need more sleep. For some reason, I scanned the first post in this thread and assumed the reverse problem. My bad, again. Sorry, I’ll try to read more carefully. Mentioning yeast problems made my mind jump to possible infection problems. Now I think my head’s on straight, though… :o

Actually, the reverse did happen to someone I know in a brewery in Germany, is maybe why I had it in my mind. His problem ended up being microbial, and he had to scrap his yeast and clean some problem spots really well.

Anyway, everything I mentioned in my previous post would be good to do except, of course, cutting your rests down. Do cater to the needs of your yeast, as mentioned – pitch healthy yeast, pitch enough (at least 20 million cells per ml) and aerate them well, especially for higher gravity lagers (>12%). Try to see that they become evenly distributed in your wort. You may just need more cells per ml to get the job done. Remember that top-fermenters tend to reproduce at a faster rate than bottom-fermenters, primarily due to the difference in the pitching/fermentation temperatures. This would explain why your Weissbier's OK.

Of course, as jarviw mentioned, you will want to increase the two amylase rests and keep the protein rest. Really, 30 min per rest should probably do it, but you can try longer ones if you think you need them. Not much happens after 30 min, though, unless you’ve mashed in very thick. The thinner your mash is the more sensitive the amylases will be to heat, but the more quickly they work. Try mashing in at a ratio of 100 kg (1 deciton) of malt to 3.5 or 4 hectoliters of water (i.e. 1:3.5 to 1:4), if your mash tun will hold it. German lager brewers traditionally mash in thinner than British ale brewers.

It is better to go a little higher than 68 °C for the α-amylase rest, though. It’s closer to the lipase and the β-glucan-solubilase optima, two enzymes that you don’t want working near their peak in your mash. 70 – 72 °C is about in the middle of the optimum for α-amylase in mash, which is around 65 – 75 °C (however, this optimum is different, for example, in a sugar solution). If you want to be right in the middle, then you can rest at 70 °C instead of 72 °C. (For 10 min at 80 °C in mash, one notices α-amylase activity starts to fall off – it is about 30% as effective as at its optimum.) Keep in mind that the pH optima for the amylases are 5.4 – 5.6 for β and 5.6 – 5.8 for α. Lowering the mash pH to below these optima is standard and advantageous for a variety of reasons, but perhaps not with the trouble you’re having. Maybe you should try shooting for 5.4 – 5.5, then acidify your wort at the end of the boil to around 5.2. A lower pH going into fermentation gives lagers better drinkability and also reduces the chance of infection.

And, yes, as mentioned above, check your thermometers both in the brewhouse and fermentation cellar. Hopefully it's something as easy as that.

[Fred Scheer]

We have some great posts here regarding your problem.
I simply think you got a problem with your temperatures during mashing, i.e., to high. Check your thermometers...........check your pH.
If you in the range of 149 - 154*F and using American Malt, most likely your FG will be in the range of 1.012 As our Malt is well modified, you don't need a Protein rest, the FAN is in a good range, >175 ppm.
Your pH should be in the range of 5.4 - 5.6 at mash in.
KO pH will be in that case ~ 5.1, follow through Fermentation.
Did you had a good start of Fermentation?
Keep your runnings at 2.8 gal/min and vs vs your sparge flow.
During the runnings, cut your bed at least 3 to 4 times very gently.
Make the iodine test with your spent grain at different layers.

Good luck

Fred

[Sulfur]

I would also try to find out the gelatinization temp of the malt you're using. The latest Malt I used had a gelatinization temp of 66.7 deg C, hence we changed our mash programm accordingly.