Reason for over attenuation?

[JoeyBagOfDonuts]

I brewed a 6 gallon IPA batch all grain. OG was estimated to be 1.076. My grains weren't milled well enough I believe- my OG ended up at 1.062. I mashed at 151F for 90 minutes. My FG ended up at 1.005 (estimated- 1.018). Wyeast 1056 was used (made a 4L starter and decanted)

1. Hydrometer was used (Checked and it is 1.000 in plain water)
2. Fermentation temperature 69F (Room temperature in my house)
3. Highly doubt infection (Tasted it during transfer and it had no off flavors and was very clear)

Is it possible that the exothermic yeast fermentation heated the fermentation enough to cause that much attenuation? Or more likely a infection? Something else I'm missing?

 

[SoCal-Doug]

Big attenuation for 1056. But stranger things have happened. If it doesn't taste "off", it should be fine. Just a bit dryer and higher ABV. Here's a few things that pop into my head when it comes to over-attenuation...

Was the OG measured at, or corrected for, your hydrometer temperature?
When you checked your hydrometer, did you use tap water or distilled water?
Was the hydrometer test done at the temperature the hydrometer was calibrated for? (it should say the temp somewhere on it)
Were there sugars or juices used in your recipe? (sounds strange in an IPA but one never knows)
Have you recently brewed a different batch using a Belgian or Saison yeast?
Was there a lot of water in the hydrometer tube? Maybe from rinsing or something?
When pulling your FG sample, was it post kegging (mixed up good)? Is it possible there was some stratification?
Did your sample contain a bunch of hop schmutz in it?

 

[Qhrumphf]

+1 on the Saison question.

I use Chico ALL the time (using a different supplier ATM but it was WY1056 for a long time), and routinely getting 85% apparent attenuation (lots of low mash temps). But 91% screams var diastaticus.

 

[Smellyglove]

I'm supporting the diastaticus question.

 

[JoeyBagOfDonuts]

First off, thank you for your reply.

Was the OG measured at, or corrected for, your hydrometer temperature? -- Yes
When you checked your hydrometer, did you use tap water or distilled water? -- Distilled
Were there sugars or juices used in your recipe? -- No
Have you recently brewed a different batch using a Belgian or Saison yeast? -- No, last batch brewed in that fermenter was US-04. Have really only used US-04 and 1056 in the past 3 months.
Was there a lot of water in the hydrometer tube? -- No
When pulling your FG sample, was it post kegging (mixed up good)? Is it possible there was some stratification? --I checked today while siphoning to secondary. The beer was very clear, no hops or anything. I don't believe it was stratified but that could be a possibility.

It tastes about what I expected so I know it's not a big deal. I've never had such high attenuation. I fear a hidden infection that is going to cause problems later on. Hopefully it's a stratification issue like you mentioned. I plan to recheck after kegging and mixing.

 

[JoeyBagOfDonuts]

Will diastaticus cause off flavors? I haven't heard of it before really. I really don't want to toss my fermenters. But will do if necessary. Can you bleach or oxiclean and then soak in star san to get rid of it?

Edit: Now that I'm thinking about it.. My 2nd extract batch a couple years ago when I still bottled I had bottle bombs which was fun. I stopped brewing for ~8 months then started kegging only.

 

[Dland]

I have hit 1.005 at that ABV, mash temp on the low side with US-05. Nice to have some of the summer ales with a kick.

The main question is; how does it taste? If it has an infection or flavor you don't want, you can find out now.

If it tastes OK, it will probably be a enjoyable beverage if it is put up well(bottles or kegs), and conditioned. Drier high ABV beers usually benefit if served aged and served cold and with some carbonation.

 

[SoCal-Doug]

Will diastaticus cause off flavors? I haven't heard of it before really

Generally not a cause of flavors. It's basically a gene within the DNA of certain yeasts (primarily of some of the Saison and Belgian types) that cause fermentation of more things than standard yeasts tend to chew on. Those types of yeasts tend to attenuate very highly.

 

[Dland]

One other thing I'll add, (in abundance of caution, as they say): if you are bottling, make sure it is done working. Kegs are more forgiving, brew might be undrinkable, but will not make too much of a mess.

There are some wild critters that will ferment your brew to almost zero, and if put in glass at 1.005, they would be exploders or terminal gushers.

 

[Smellyglove]

First off, thank you for your reply.

Was the OG measured at, or corrected for, your hydrometer temperature? -- Yes
When you checked your hydrometer, did you use tap water or distilled water? -- Distilled
Were there sugars or juices used in your recipe? -- No
Have you recently brewed a different batch using a Belgian or Saison yeast? -- No, last batch brewed in that fermenter was US-04. Have really only used US-04 and 1056 in the past 3 months.
Was there a lot of water in the hydrometer tube? -- No
When pulling your FG sample, was it post kegging (mixed up good)? Is it possible there was some stratification? --I checked today while siphoning to secondary. The beer was very clear, no hops or anything. I don't believe it was stratified but that could be a possibility.

It tastes about what I expected so I know it's not a big deal. I've never had such high attenuation. I fear a hidden infection that is going to cause problems later on. Hopefully it's a stratification issue like you mentioned. I plan to recheck after kegging and mixing.

You will not see any stratification post fermentation. There's been a lot mixing and stirring going on by the yeast. You can do a sample from both bottom and top and they should read the same. I've tried this myself several times, if your readings are different I'd be very surprised.

And since you mentioned hops. solid matter has no impact on the gravity readings. The same way you don't float more easy if more people jump in the same pool as you. But salt water makes you float more easily since the salt is dissolved in the water making the water denser.

 

[RM-MN]

You used a 4 liter starter, decanted, on a 6 gallon batch. That sounds like an over-pitch to me. You then fermented a big beer with it without active temperature control. That is a recipe for over-attenuation for sure. At peak fermentation your beer temperature probably reached between 75 and 80 degrees.

 

[SoCal-Doug]

^^^ +much

Your home may be set to 69F but fermentation generates it's own heat and was most likely much higher. But on the good side, if you taste it and like it, no harm done. Look at the bright side, it's an IPA. You wont taste anything except hops anyway

 

[Vale71]

You used a 4 liter starter, decanted, on a 6 gallon batch. That sounds like an over-pitch to me. You then fermented a big beer with it without active temperature control. That is a recipe for over-attenuation for sure. At peak fermentation your beer temperature probably reached between 75 and 80 degrees.

Why? Neither pitch rate nor temperature are going to suddenly turn regular Saccharomyces into something that can ferment complex sugars. Once fermentables are exhausted any non-overattenuating yeast will stop working, no matter what conditions it's in.

I'm afraid that a 92% apparent attenuation in a recipe with no refined sugar adjuncts and barring gross measurement errors is simply a clear indication of an infection going on.

 

[Eric_S]

Is your sample degassed? Carbonation in the sample will mess up the reading. Run it through a coffee filter, helps remove solids (hops and yeast) and carbonation - which helps for both hydrometer and refactometer readings.

 

[ESBrewer]

I wonder when all the people in homebrewing circles started calling it an infection. I even see it in many hb publications. I always use the the term contaminated as infection in biology refers to the invasion of harmful micro-organisms inside the tissues or cells of an organisms, causing damage or an immunological response. If virus enters the individual yeast cells by traversing the cell membrane then the yeast culture may be infected. Otherwise (scientifically) cell cultures are just contaminated by some unwanted microbia.

 

[JoeyBagOfDonuts]

You guys are awesome. Thank you all for the many suggestions!!

I have always been under the impression that pitching more yeast cells does not cause over attenuation. I pretty much always do a 3.5-4L starter and pitch the yeast cake and have never had it happen. The exothermic reaction during yeast fermentation heating up the wort did cross my mind. I may have to look into getting a fridge for temperature control.

ESBrewer--
I'm a pharmacist and have had much lab and classroom experience and I've thought about this. "Infected" (adjective) can mean unwanted bacteria/yeast that are present in whatever. However "infection" (noun) is what you explained. "I have an infected beer" is a correct statement but "My beer has an infection" is technically not. But when it comes down to it, contamination requires further explanation while infection does not so it just makes things easier and more widely understood.

 

[Vale71]

Uncontrolled temperature rise during fermentation is not going to cause overattenuation either. By the time you pitch yeast wort composition is fixed and will not be altered unless you add synthetic enzymes or your wort is "contaminated" by bacteria that can release such enzymes.

That said, temperature control is always advisable to improve quality/repeatability.

 

[JoeyBagOfDonuts]

Uncontrolled temperature rise during fermentation is not going to cause overattenuation either. By the time you pitch yeast wort composition is fixed and will not be altered unless you add synthetic enzymes or your wort is "contaminated" by bacteria that can release such enzymes.

That said, temperature control is always advisable to improve quality/repeatability.

I've heard that yeast are more active at higher temps and can obviously lead to more esters/off flavors. I also assumed that with a more active yeast that they would eat up more (if not all) of the consumable sugars. What you say makes sense because a 0.013 overattenuation likely wouldn't account for the extra conversion from a "more active yeast" of the few left over sugars after fermentation is complete. Will be picking up some iodophor as well.

 

[mcl]

Why? Neither pitch rate nor temperature are going to suddenly turn regular Saccharomyces into something that can ferment complex sugars. Once fermentables are exhausted any non-overattenuating yeast will stop working, no matter what conditions it's in.

I'm afraid that a 92% apparent attenuation in a recipe with no refined sugar adjuncts and barring gross measurement errors is simply a clear indication of an infection going on.

I get 83% attenuation. That plus the 90 min mash seems perfectly normal to me.

 

[Calder]

I'm afraid that a 92% apparent attenuation in a recipe with no refined sugar adjuncts and barring gross measurement errors is simply a clear indication of an infection going on.

I disagree. I regularly get 90% attenuation with normal ale yeasts. If you mash low you can get a very attenuative wort. 145 F for 90 minutes will get you there. I like my IPAs dry.

I'm suspecting the mash temperature may have been lower than the OP thought. Maybe a thermometer error?

 

[SoCal-Doug]

If you mash low you can get a very attenuative wort. I'm suspecting the mash temperature may have been lower than the OP thought. Maybe a thermometer error?

Very plausible!

It could also be a low/missed strike temp and took a while to come up to the desired temp, where by then it was too late. The majority of conversion takes place very quickly and early in the mashing. When i've sampled and plotted a typical batch (measuring every few minutes), 75% of the OG was reached within the first 15 minutes. Once the beta's have done their thing, there isn't much left for the alpha's.

 

[JoeyBagOfDonuts]

It could also be a low/missed strike temp and took a while to come up to the desired temp, where by then it was too late.

Yeah, that's probably it. I missed my strike temp which was initially at 146-148F, had to heat up more water which took 5-10 minutes before I had the right temperature. Didn't realize that could be so detrimintal. I still plan to iodophor all my equipment just in case. Many thanks to everyone for your help.

 

[SoCal-Doug]

Didn't realize that could be so detrimintal

Wait… who said "detrimental" You just made a different beer. More dry and more alcohol. I can't stand IPA's but you may have a "brut ipa" there that you'll really like. Remember what you did just in case.

 

[jfolks]

Did you dry hop? (Hop creep could explain this)

 

[JoeyBagOfDonuts]

It's been kegged now. Actually turned out to be the best batch I've brewed so far out of 15 batches or so. Funny how things work.