Over Attenuative Yeast.

[Fat Bastard]

following on from this conversation between myself and Mardoo.
http://aussiehomebrewer.com/topic/80665-my-yeast-cells/
I was initially convinced that my consistent over attenuation was due to over pitching of a 2l starter wort, however now after reviewing my past reciepes and notes, I'm not so sure.

The vast majority of my beers are US styles using WLP-001, 23 litres and pitched from a 2 litre stir plate starter 24 hours old.

Reviewing past brews using yeastcalc, I've had a few that are definate over pitches, some that are definate under pitches, but pretty much all have gone well under the planned FG by around .007 or thereabouts and wound up quite dry. The exception to this has been WLP-002 in a big imperial porter that wound up at an FG 1.022, which was .005 above the predicted FG

I always use a step mash of 52/10, 62/15, 66 (or 64 or 68 depending on style)/45, 72/10, 78/10. and I think this may be where my problem is, although I'm more than pleased with the thick, persistant head it produces. Pretty certain it's not infection as there are no off flavours and I'm pretty rigourous with my sanitation.

In future I'll tune my starter more closely to the OG of the beer, but am interested in what other factors could be causing this.

Cheers,

FB.

 

[TheWiggman]

I've heard a few times that modern modified malts do the majority of conversion in the first 20 mins, so maybe the 62°C rest for 15 mins is the reason? Have you tried omitting that step - or rather, why do you do it?
Doesn't explain the 1.022 beer though assuming you maintained that schedule.

 

[Fat Bastard]

Maybe. My experience with WLP-002 has been that it's a lazy *******. I'm re brewing that one next but subbing WLP -007 which apparently has the same flavour profile, but is 10% more attenuative.

I might drop the 62 for the following brew, which will be a big red IIPA I've brewed before. Or maybe an amber.

 

[SJW]

I have the same problem with my beers, so tonight I am mashing with 30min @ 50, then the next rest is for 60min @ 70. Keeping in mind this is on a BM that raises temp 1 deg per min. So I will get plenty of B Amylase conversion between 50 deg and even some at 70 for a bit. Will be interested to see how this one ferments out.
Steve
Ps I am doing a big red American IPA also. The Evil Dead Red

 

[wynnum1]

What is the flavor of the beer like other then being dry over pitching would strip flavor if the beer has fermentable sugar then a lessor amount of yeast could convert but take longer.

 

[Mardoo]

Yes, since that conversation I've been looking at the fact that I do a protein rest as a possible source of the low mouthfeel in my beers. I'm pretty certain I have over pitched since I started using my stir plate. Calculation says I have been but I lack the means to count yeast.

However the low flavor development using yeasts with distinct flavors (1469 and French Saison in particular) suggests that I have been over pitching. I'm going to try dropping the protein rest and see what happens with mouthfeel. I realized I made a habit of the protein rest after a string of kolsches and faux lagers, for which I wanted low mouth feel. I'm still working on whether a smaller pitch improves on the flavor issue. Seems to have on my current beer but it's still finishing up so no way to tell for sure. And really, I still a noob so it's ALL learning at this point.

 

[mje1980]

A short protein rest shouldn't affect the mouthfeel too much, though it might depend how long it takes to get to the next step?. Beta is active in the high 50's so your beta rest may be longer than you think?. Interesting you're saying you're losing flavours, especially with strong flavoured yeast strains.


Tough one, hope you get it sorted.

10 years of all grain and I still think I'm a noob, just an experienced noob hahah

 

[wynnum1]

Pitching of a 2l starter when a starter is used what is needed for aeration do you want yeast to get on with it and not multiply so do not allow aeration.

 

[potof4x]

G'day,

Check out "Limit of Attenuation Test" on Braukaiser.

I got into LOA tests because of the opposite problem to the OP - constant high finishing gravity.

Originally I was convinced the problem was yeast health. So tried to remedy using yeast nutrient, varying pitches of dry yeast, stirred starters, Oxegynating and rising temperature ferments to no avail.

Then I started doing LOA tests which showed me that my beers were not getting to the desired FG because they simply were not attenuative (?) enough.

So began looking at mashing process. Using a gas BIAB setup I realized I was overshooting temps a degree due to retained heat after turning the burner off. Also went to a 90 min mash, and started taking my recipes from one source.

Changing my mash in temp/ramp stops, and getting more consistent due to realising that the next mans mash temps are not the same due to variation between systems has got the beer where I want to be now, so much so that I've had the confidence to do a run of step mashed and/or decocted lagers all of which are hitting the right FG.

Wouldn't have got to this point without knowing the limit of attenuation.

 

[lael]

How much yeast are you pitching to your stir plate?

 

[lael]

How much yeast are you pitching to your stir plate?

 

[manticle]

If you're going to do a 2 step sacch rest, you really need to target both sets of enzymes. If you move from 62-64, you are still favouring beta. Even 66 is pretty mid range.
Either drop the low and try 68 for 45, followed by 72 or shorten the low to 10 and make the alpha rest 68 for 30-40 mins.
I don't reckon it's your pitch rate with an active 2L starter unless you are beginning with way too much slurry.

 

[manticle]

I have the same problem with my beers, so tonight I am mashing with 30min @ 50, then the next rest is for 60min @ 70. Keeping in mind this is on a BM that raises temp 1 deg per min. So I will get plenty of B Amylase conversion between 50 deg and even some at 70 for a bit. Will be interested to see how this one ferments out.
Steve
Ps I am doing a big red American IPA also. The Evil Dead Red

I'd suggest both rests are too long and will work against your desired outcome. Raise the first to 52-55 and shorten to 5-10 mins. Shorten the 70 rest to 30-45 mins. Ascertain the difference in results and tweak to personal taste from there.

 

[TheWiggman]

I've only done limited batches but I do a 56°C for 15 mins then up to sacc temp whatever it may be. 64, 67 etc. for 1h then up to 76°C for MO and fly sparge at that temp. My attenuation has been almost spot on in all cases except when I under pitched once.
I've been wondering how you can correlate this to split amalyse rests. I'd guess the approach would have a large bearing in differences between target and actual FG.

 

[lael]

I always use a step mash of 52/10, 62/15, 66 (or 64 or 68 depending on style)/45, 72/10, 78/10

This is pretty much what I'm doing. I'm getting normal attenuation. 55 for the first step. 62/63.

Just tried 45 @ 63 for my last summer ale. We'll see how dry it goes. May be too much...

 

[manticle]

Target 1 low, one high, alter your timing depending on desired result. Beta is optimised high 50s - mid 60s, alpha is optimised mid/high 60s - low 70s. Beta cuts up alpha's results, alpha converts starch more quickly. A 10 min rest at 62-62 followed by 67-68 for 40 mins sees me hit the same attenuation I got from single infusion but with better body and lovely tight beaded foam formation. 15 min beta for dry beers.
Attenuation depends on yeast type, wort composition, cell numbers, oxygenation and mash profile so it's not all simple but targetting individual sacch enzymes is a good way to twesk body and attenuation.

 

[mje1980]

I did 90 mins at 61-64 on last weeks saison. Then straight to mash out. I want it dead dingos donger dry.

 

[Fat Bastard]

A little bit of an update:

Last Sunday, I brewed an imperial porter with an OG of 1.075. I followed my standard step mash of 52/10, 62/15, 68/45, 72/10, 78/10, In the past I've brewed this one with WLP-002, and always had problems with it attenuating fully, and it has always finished high, around 1.024 from my notes. This time I pitched a 2l starter made from a fresh vial of new WLP-007. According to yeast calc, this is a definate underpitch by about 120 billion cells.

Today, after 3 days in the fermenter it's sitting at 1,021, a scant 0.001 off the expected FG. Primary fermentation is showing clear signs of being well and truly over I think it will drop a few more points in the next few days, and I've raised the temp 2 degrees to help this along, as is my normal practice.

I'm going to take the speed of the ferment as a sign of lots of fermentable sugars in the wort, given that I'm now using a yeast that isn't completely lazy.

So, next beer up will be the Amber Ale. I'm not going to fiddle the recipe, but I will use a more closely tuned starter size, and an amended mash schedule, 52/10, 68/60, 72/10, 78/10 and see what difference that makes to the FG and overal taste of the beer.

I suspect I could shorten the 68 degree step, but I'm not sure if I should change too much. Any thoughts?

Cheers,

FB

 

[Fat Bastard]

Well, the amber ale has done its dash and pulled up at 1.011 from an expected 1.015 this is almost exactly the same as the last run of this beer which wound up at 1.012. That was with a 2l starter, pitched for a new vial, and the current one was with a starter calculated in yeastcalc, which was pitched from washed yeast and worked out at around 1.45 litres.

So, looks like this is mash related, although I'll persist with the calculated starters in future.

 

[black_labb]

I've found that step mashes can attenuate more than you expect unless you start adjusting for your specific system. I was doing masing similar to yours but I didn't bother with a protein rest. I was finding that the beers were very attenuative, which is an issue I've struggled to get control over until I've started mucking around a bit more and not following what I thought should be right.

I've found on my system that I usually start at about 65-68 for a rest for 15-40 mins and then ramp over 15 mins to 73 where it is held for 15 mins before a mashout. For a mild I did a 68*/15 mins, 68-73*/15 mins, 73*/15 mins then mashout which I finds gives good body in lower alcohol beers. For a brown ale I did the same temps but extended the initial 68* rest to 30 mins. I found doing rests in the low 60's ended up being to attenuative for my tastes, but I mostly brew engish ales with occasional belgian or american ales (though the american ales seem to be slanted towards english ales in therms of malt anyway)


I would reccomend playing around with more extreme mashing and see where you end up. As I alluded to I didn't find the low 60's rests did much for my brewing, even if doing a attenuative belgian. 64 is the lowest I will mash at and I won't leave it there for more than 30 minutes before I start to step up towards 73.