Lower RIS FG by racking to lager yeast cake?

Discussion in 'Homebrewing' started by 911CROFT, Mar 19, 2018.

  1. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    I have an AG Imperial Stout that has reached terminal gravity at 1.040 down from 1.115 I know it's finished because I've roused it, warmed it, and its been over a month in primary, plus my forced fermentation test finished at the same FG. Malt bill had a lot of caramels (14%) and roasted (14%) grains + high mash temp (69*c/ 156*f) seems to have left slightly too many unfermentables. Yeast is WLP007, I calculate the attenuation at 68% for 10% ABV so its not far off the bottom range of 70-80% published rates.

    Anyway, I'd prefer it down to the planned 1.030 if possible, so my question is... Is it worth racking to a fresh W-3470 cake? I am I correct in thinking the lager yeast is capable of eating up some of the sugars the ale yeast has left? Is it worth a shot?

  2. MrOH

    MrOH Champion (851) Jul 5, 2010 Maryland

    If it's something you're dead-set on making happen, it's worth a shot.
    I, personally, don't think it will make a difference. While the 34/70 might be able to chomp on a bit of the more complex sugars that are laying around, you'd still be pushing up on its ABV tolerance in an inhospitable environment.
  3. JackHorzempa

    JackHorzempa Poo-Bah (3,719) Dec 15, 2005 Pennsylvania

    Yes, lager yeasts will typically process a broader range of sugars. For example: “Lager yeasts can completely ferment melibiose and raffinose while ale yeast can only ferment a third of raffinose and no melibiose.”

    As to whether you will actually go from 1.040 to 1.030 it comes down to the specific types and amounts of sugars in your wort/beer.

    Whether this is a worthwhile thing to do it really comes down to your personal desires. If you truly want a drier Imperial Stout then you should go for it. I personally would be happy with a 1.040 FG Imperial Stout so I would just package what you got.

    Since you are the head brewer here you get to decide.

  4. GormBrewhouse

    GormBrewhouse Disciple (395) Jun 24, 2015 Vermont

    White labs099 yeast is super hi gravity producing, but it does take some additional work according to others who have used it.

    If interested look for post from or including @stealth . He did several brews with this yeast. I've done 1. With good results
  5. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    Thanks for the quick replies guys.
    I don’t think i’ll bother if you’re not sure it will work - another chance to oxidise between transfers. I’ve got a bit of a sweet tooth and the 90 IBU’s of Columbus should provide some balance. I’ve read some comerical brews (bourbon county) finish up in the 1.040’s too.

    @GormBrewhouse I’ve seen @stealth’s ‘none blacker’ Stout Incredible! I’ve got one planned myself but on a smaller scale, hoping to take 001 upto 15%. I’ve read 099 become wine like above 16% which is something I’d want to stay clear of.
  6. CarolusP

    CarolusP Initiate (107) Oct 22, 2015 Minnesota

    If you're adventurous, check out this post from Mike Tonsmiere: https://www.themadfermentationist.com/2007/11/courage-russian-imperial-stout.html

    In short, some Brett character is actually traditional for a RIS. So you could pitch a Brett strain and monitor gravity until it gets down to about 1.030. Then chill and add a bunch of crushed camptden tablets to kill the Brett. After a period of time, re-pitch some new yeast for bottle conditioning and package.
  7. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    Thanks for that, I like the idea of getting the funk to where you want it and then killing it off as to not over-power. I have a bottle of De Dolle Export Stout I could even culture from. Also useful if it gets stuck high I could use Brett to lower.
  8. VikeMan

    VikeMan Meyvn (1,470) Jul 12, 2009 Pennsylvania

    This is true. It's also mostly irrelevant for beer. Normal beer wort doesn't contain any raffinose. And melibiose, if it occurs at all, is in amounts too small to make much difference.

    Where it is relevant is that melibiose can be fed to yeast determine if it is a lager strain or an ale strain.
    hopfenunmaltz likes this.
  9. JackHorzempa

    JackHorzempa Poo-Bah (3,719) Dec 15, 2005 Pennsylvania

    Lager yeast strains will more fully process maltotriose than ale yeast strains:

    “Maltotriose uptake from wort by ale yeast was slower than by lager yeast. Residual maltotriose is more common at the end of ale fermentations (Zheng et al., 1994).”

    For those who may be wondering, maltotriose is a common sugar in wort:

    “In all-malt brewer’s wort, 50–60% of the total sugars are maltose, 15–20% maltotriose and 10–15% glucose (Zas-trow et al., 2001).”


  10. VikeMan

    VikeMan Meyvn (1,470) Jul 12, 2009 Pennsylvania

    Probably true for whatever strains they studied. But many ale strains are stronger attenuators than many lager strains. Doss' data showed that. And personal experience supports it.

    If you can think of a plausible reason for some ale strains (other than diastaticus) to be stronger attenuators than some lager strains, other than maltotriose utilization, I'd love to hear it.
  11. JackHorzempa

    JackHorzempa Poo-Bah (3,719) Dec 15, 2005 Pennsylvania

    Yup, it is true.
  12. hopfenunmaltz

    hopfenunmaltz Meyvn (1,387) Jun 8, 2005 Michigan

    I don’t think 34/70 will take it down as far as the OP wants.

    My recommendation is to pitch Wyeast 3711 and see if that diastaticus strain chews away at the long sugars. The OP’s beer has a lot of those.
  13. VikeMan

    VikeMan Meyvn (1,470) Jul 12, 2009 Pennsylvania

    I have a hunch 3711 would take it too far. But I'm looking forward to the experiment if the OP decides to do it.
    GormBrewhouse likes this.
  14. hopfenunmaltz

    hopfenunmaltz Meyvn (1,387) Jun 8, 2005 Michigan

    The OP could split the batch and see where it ends up. Or just pull samples and see how that works before committing the whole thing.

    Hey OP - have you pulled a taste sample? It might be pretty good now.
  15. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    I last sampled at the weekend. It tastes pretty good, I wouldn’t actually describe it as over sweet. It’s a 6.5gal batch with roughly 1lb of chocolate, 1lb of pale chocolate and 1.5lbs of roast barley. Main flavours are heavy roast, lots of coffee and a bit of dark chocolate.

    Ive made an imperial milk stout in the past with WLP005 that finished at 1.048, at first I thought it was incredible. Everyone that came over thought it was like chocolate milkshake, but they only drank small pours. I got bored of it quickly, it was a chore to get through. I ended up bottling loads off the tap and giving it away. That’s why I wanted this one to finish drier and roastier, but equally I’m not sure I want to throw Brett at it or anything too funky yet. The only wild stout I’ve had so far is Cantillon Zwanze 2015, and I didn’t really like it! I don’t have a local shop I can run to, I have to order everything online and the flat shipping on one yeast is cost prohibitive, I don’t need any other supplies either as I’ve just had everything delivered for my next stout with WLP001 (which I plan to mash lower!)

    Anyway thanks for help/ suggestions so far. I’ll probably rack it to a keg and start drinking, but could I possibly pitch a higher attenuating yeast in a month or so if I do get bored?

    I’ve not moved the lager just yet so that’s still an option, but I understand from above responses that the yeast in the cake may not be any better at fermenting the types of sugar left in my beer.
  16. VikeMan

    VikeMan Meyvn (1,470) Jul 12, 2009 Pennsylvania

    Doss didn't study 34/70 or WLP007. (He only studied Wyeast strains.) But if you consider 34/70 to be equivalent to Wyeast 2124 and WLP007 to be equivalent to Wyeast 1098, then the data says that 34/70 would actually be less attenuative than WLP007.

    Having said that, there's some debate about whether WLP007 and Wyeast 1098 are a close match. Those who think they are not sometimes say (anecdotally, I suspect) it's because WLP007 is more attenuative than 1098.

    So if WLP007 > 1098 > 34/70, I doubt that pitching 34/70 would help, unless the WLP007 crapped out prematurely for some reason.
    OTOH, there's only one way to find out for sure.
  17. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    Thanks for that breakdown. I don't think the 007 crapped out as I've taken it higher before, but from what you say most likely not worth the risk of an additional transfer.

    What i'm going to do is leave most of it untouched, lesson learnt - mash lower and longer with less crystal or more sugar next time.

    1.25 gallons I'm going to rack to a small carboy and see about inoculating with a wild strain I will cultivate from a bottle. Am I right in thinking I should leave very little headspace as there shoudn't be much krausen?

  18. VikeMan

    VikeMan Meyvn (1,470) Jul 12, 2009 Pennsylvania

    At 1.040, there's a lot of carbs left. Depending on what "wild strain" you pitch, I wouldn't assume that there won't be much activity. Personally, I'd allow for a headspace equal to about 30% of the wort volume.
  19. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    Ah of course. I was forgetting I’m basically at the SG of a session beer.
    I was thinking Orval. I like it, fresh bottles are cheap/ easy to find, young it’s not over the top funky and it’s low enough ABV% to be still have good viability.
  20. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)


    I couldn’t be bothered to cultivate from a commercial bottle in the end. What I did instead is pitch a re-hydrated packet of Lallemand Belle Saison from a local shop (which I belelive to be the dried version of 3711) It dropped the gravity down to 1.031 (additional 9 points)

    I’ve had the other 5 gals of 1.040 FG on tap for over a month now. Honestly, there’s not much in it. The 1.031 feels slightly drier/ a touch less thinner in body as expected, but the extra ABV% isn’t perceptible, there’s no real difference in flavour/ sweetness, no saison yeast qualities come through.

    Ultimately, both are very good. I wont sweat it in the future, I’ll pay closer attention to mash temps and let them finish where they finish.

    premierpro, wspscott, frozyn and 5 others like this.
  21. EvenMoreJesus

    EvenMoreJesus Champion (879) Jun 8, 2017 Pennsylvania
    Premium Trader

    Thanks for posting an update!

    Just goes to show that even moderate changes in gravity don't really impact the end product much when that end product is a high gravity one.
  22. wasatchback

    wasatchback Aspirant (271) Jan 12, 2014 Utah

    This brings up something I’ve been thinking about.. at what stage could you add a yeast strain that’s say POF+ but can handle higher alcohols and not get phenols? OP said he didn’t get any phenols but it was just a small gravity drop and obviously lots to mask any that might be there. Will phenols be created if there are basically only complex sugars left and the PH has already dropped?
  23. 911CROFT

    911CROFT Devotee (424) May 18, 2015 United Kingdom (England)

    I got absolutely no perceptible flavour contribution from the saison yeast.

    I don’t know the answer, but I’d guess at after the bulk of the fermentation has concluded, but before the initial strain dies off. I’d think a big pitch (Mine was 200BN into only 1.25G) and temp control could also limit the second yeasts impact.
  24. EvenMoreJesus

    EvenMoreJesus Champion (879) Jun 8, 2017 Pennsylvania
    Premium Trader

    Phenol production depends on two things: 1) precursors like hydroxycinnamic acids and 2) enzymes.

    However, phenols can also be masked by things, as you said, like esters. That's why aged brett beers tend to be funkier over time. The phenols were always there, there were just other things there as well.

    All that said, if you want to add a POF+ strain to an otherwise POF- fermentation and not get a lot of phenol production, you'd have to limit your phenolic precursors (like choosing grains that are low in ferulic acid and not using a lot, if any, boil hops as boiling vegetal matter will liberate caffeic acid), as phenolic yeast strains don't need (a lot of) sugar to produce phenolic compounds.