Low attenuation and/or O2 stones

[Rob Martin]

Have a 2 part question that I think may be related.

First, last several beers have been on the lower attenuation rating scale of any yeast I use. Not any one particular yeats, just all of them. Sometimes it even is 1-5 points lower than the range the yeast is rated at. Suggestions?

Secondly, I use to use a compressed O2 tank, but stopped because it emptied (user error - need to double check that valve) and because I had 2 batches in a row that had borderline infection issues which is not normal for me. (Anybody recall the lager I brought to LBG meeting last year that tasted slightly band-aidish.)

I'm wondering if my lower attenuation is due to lack of aeration. Another reason why I stopped with the stone is because when I thought we were getting enough aeraton when we transfer from kettle to fermenter. We use a pump and whirlpool wand that is pinched on the end and causes quite a jet. While transferring, we hold the tip above the liquid line in the fermenter 2-3 feet which causes quite a bit of violent foaming. For 10 gallons, we get a good 3" foam from the air being infused into the cooled wort.

[Rob Martin]

Lastly - for those of you that use O2 stones, how do you sanitize them? Soaking them in Star San for 5 minutes didn't seem like it quite did it. I've heard of people boiling them. It is a Stainless Steel air stone.

[toolman]

i have a .5 micron o2 stone that i use with compressed o2. i sanitize it by
soaking it in starsan at the same time i sanitize my transfer hoses and stainless racking
cane that i use to fill my glass carboys. haven't needed to boil it yet. there is
always some residual starsan in the hoses and stone prior to use, that i pressure
out using the o2 when i hook it up. so if the starsan is pressurized through the
passages of the stone it should be good to go.

the positive flow of gas pressure is from the inside of the stone to the outside
of the stone, there is no flow from outside to inside, so only o2 is going through
the stone. sanitize your hoses and stone before the aeration and after the aeration
store it in a clean baggie between uses and you should be good.

i would recommend buying a stone with a mfl fitting on it, or if you already have a stone
with a barb on it, put a very short length of tube with a flare fitting so it can be taken apart
for sanitizing instead of having the stone on the end of a long length of tubing.

[Rob Martin]

Thanks Orval. The first 2 paragraphs described my setup exactly. I usually soaked the stone at the end of the hose long enough (10-30 min) that Starsan would seap into the stone and up the hose line. Then I would push the starsan back out with O2 immediately before using it.

For storage, I would place a zip lock on the end and tie it off with a wire tie. All of it stayed together as one unit on my O2 tank.

[Blktre]

First yeast attenuation percentages is relative to comparing different strains to each other using a common wort profile. So its just a guideline at best and predicting FG going by the yeast capabilities really isnt accurate way of doing it. You might want to google free amino nitrogen (FAN) to get more info about yeast growth stages and this might help answer some questions in technical detail. Since we are using different wort profiles because we are brewing different styles I would look into other areas such as your recipe's amount of fermenatables vs unfermentables and how it correlates with a low/high FG. The other area to look into and I think this is more likely the reason for your low FG's is to check your thermos. I think you are actually mashing lower than you really think you are. When calibrating I use a partial immersion alcohol/spirit filled glass lab thermo at MASH TEMP ranges and not at freezing or boiling points. A thermo in the working ranges we care about can be off.

As far as stone storage and use I always make sure o2 is flowing before and after putting it in the wort. Once removed I rinse off the wort immediately then toss the stone and tubing into a bucket of starsan until after I pitched and put away my fermenter. I then push o2 through the stone again to remove the starsan, just like sanitizing it before use. Then store. I let it air dry so no mold or bacteria can have a chance to form if it can at all. Im still using my first stone I purchased when I started brewing.

[brick]

Part of the attenuation issue may be due to the quailty of malt this year. The malting houses told us the barley crop this year was very erratic in quality and we would have to moniter it and adjust recipes for this years crop as the grain quality will effect yield and the protien to starch profile of the malt. We have seen lower attenuation recently on any beer with lots of darker malts in it at the brewery. The base malts seem to be closer to normal in results but still a little lower gravity yield.

[JMcG]

First, let me understand what you mean by "low attenuation". To me, that means you're not getting as low an FG as you thought you would (the percent of potential yield of alcohol is lower than expected). That would possibly be caused by mashing higher than you thought, instead of lower, yielding fewer fermentables.
Are the beers sweeter than you wanted or drier?
jim

[Rob Martin]

they are sweeter when I want drier.

Example:

SafBrew S-33
OG 1056
FG 1021
Attenuation 61%
Rated 70-75

WLP041 Pacific Ale
OG 1071
FG 1023
Attenuation 66
Rated 65-70

WLP001 California Ale
OG 1048
FG 1012
Attenuation 73%
Rated 73-80

It just seems to be on the low end or even below the range the majority of time.

Brick - how much does it depend on degassing the sample before measuring? The top example had a noticeable amount of residual carbonation coming out of the fermenter.

[Blktre]

First, let me understand what you mean by "low attenuation". To me, that means you're not getting as low an FG as you thought you would (the percent of potential yield of alcohol is lower than expected). That would possibly be caused by mashing higher than you thought, instead of lower, yielding fewer fermentables.
Are the beers sweeter than you wanted or drier?
jim

I misunderstood then. I bet your thermos are reading high. Almost every single time this issue comes up it ends up being thermos need calibrated.

[brick]

If there is CO2 in the sample you will get a higher reading. The more co2 in solution the higher the reading will be.

[JMcG]

I think Andy is right, the problem could be wort composition, because it sounds to me like you're getting enough O2 into the wort for the OG's you're fermenting. Assuming fermentation temps are adequate. Are you using mash stabilizer (5.2)? You might check the thermometers like Andy suggested.
jim

[bneuen]

I think Andy is right, the problem could be wort composition, because it sounds to me like you're getting enough O2 into the wort for the OG's you're fermenting. Assuming fermentation temps are adequate. Are you using mash stabilizer (5.2)? You might check the thermometers like Andy suggested.
jim

As Jim hinted, maybe it is a pH issue? Alpha-amylase is more active at higher pH's (6.7-7.0) whereas beta-amylase likes it at 4.0-5.0. So a higher mash pH would favor alpha-amylase, and thus be less fermentable. If temperature is not the issue, maybe take a look at pH. I have extra 5.2 if you need it.

Wikipedia's Amylase Article: http://en.wikipedia.org/wiki/Amylase

With the lower quality malts and strange things happening with our water over the past year, the mash pH might not balance out to what we are used to.

Does anybody else have thoughts on this?

-Bowe

[Rob Martin]

I've been using 5.2 for 4-5 years.