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Yeast starters and equipment

Discussion in 'Gear and Equipment' started by Drewgong, 1/9/19.

 

  1. ABG

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    Posted 3/9/19
    @Drewgong you wont regret buying the O2 kit. As @MHB said (in more detail than I have the patience to write out for someone else), O2 is critical at the start of the fermentation process.
    Going back to your original post, if you're getting diacetyl off flavours in your beers, the most likely culprit is too short a diacetyl rest. Make sure that when fermentation is almost finished, you ramp the temperature right up to the top of the healthy range for the yeast variety you're using and give it at least 24 hours at that temperature. That rest before cold crashing will do wonders for scrubbing off some of the byproducts that yeast leave behind during their most active phase, including diacetyl. It's also worth doing a forced fermentation test to check the diacetyl has been scrubbed before you begin your cold crash. It is a little bit of extra work, but worth it in terms of ensuring your beer is going to be optimum quality.
     
  2. Drewgong

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    Posted 3/9/19
    Thanks mate i watched a video earlier on forced diacetyl testing it doesn't look that difficult.
     
  3. wide eyed and legless

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    Posted 3/9/19
  4. Drewgong

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    Posted 3/9/19
    Ill try reading that again when im sober lol . sounds like oxygen is good but not needed....ill try again tomorrow
     
  5. MHB

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    Posted 4/9/19
    Read it before, just skimmed through it again and will point up a couple of problems.
    A lot of it is right, if you put enough heathy yeast into a wort the yeast will have enough reserves to ferment the wort!

    Where we run into problems is in getting enough yeast with good reserves of stored nutrient. Without Oxygen yeast cant build stores of Sterols and Glycogen so it will use what it has onboard so to speak. Each generation will take a share of the nutrients but every daughter cell will have less than the mother... do this too long and you end up with lots of sick yeast.

    When we pitch yeast we want it to reproduce, not because we want more yeast (well that to) but because we want the yeast to consume some fractions of the wort, mainly fatty acids that if they stay in the beer will lead to premature staling and development of off flavours.

    An ideal pitch will in a well aerated wort do several things simultaneously 1/ is to remove all the DO takes less than half an hour. 2/ remove unwanted wort fractions. 3/ provide enough healthy yeast to finish the ferment quickly and cleanly (Cleanly being a technical term that means without producing unwanted side issues like VDK and a bunch of others).

    Oxygen is very much a two edged sword, it is both beneficial and a possible hazard, too much at the wrong time it will cause problems, not having any will cause problems, getting it right and we are well on our way to making better beer.

    Dried yeast is cropped at a point in the yeasts life cycle where it has the highest reserves of stored nutrients, it can be pitched into an Oxygen free wort and it will do everything we want of it. If however you cropped the yeast it wont be in the same physiological condition as the dry yeast. It will need either a starter where it has plenty of O2 to recharge, or to be pitched into a well aerated wort where it can build up its reserves.

    Over the years there have been plenty of attempts to get around this, it was this same discussion that lead to the Hull Olive Oil Thesis, (point to one brewery doing this today) where the essential sterols were provided from an exogenous source. Doesn't work long term as it is only addressing one of the yeasts needs.
    Home brewing is full of this sort of thinking, addressing one problem without regard to how the solution affects the whole process (don't get me started on the Ca/Mg argument)

    Short answer is that you can get away with pitching into unaerated wort if the yeast is setup for the job, but if you are going to be reusing the yeast at some point it needs a good recharge and for that it needs aeration.
    Mark
     
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  6. Truman42

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    Posted 10/9/19
    If I have some yeast in the fridge that Im not going to use just yet but is close to its best before date or that a yeast calculator says has low viability, is it worth making a starter for it to get some fresh healthy yeast created and decanting that off into a jar to store in the fridge? And if so will this give me another 3 months life on this yeast?
     
  7. Truman42

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    Posted 16/9/19
    Bump.... So no one does this???
     
  8. Half-baked

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    Posted 17/9/19
    I’ve done it, just make sure you ferment it out fully... more of a mini batch than a starter
     
  9. JDW81

    I make wort, the yeast make it beer.

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    Posted 17/9/19
    You will increase you cell count and have more viable yeast, but as to the shelf life it's hard to say (short of doing an actual cell count with a microscope).

    You've got nothing to lose by giving it a go. When I'm brewing regularly I often split a smacked wyeast pack into a couple of sterile vials then build a starter from the remainder (I'll step it up if I'm making a high gravity/big batch, otherwise I just make my standard 2L starter and pitch).

    You may need to make a smaller starter and step up when you re-use the yeast down the track (i.e. make a 500mL starter then pitch the dregs into a 2L starter) but if your sanitation processes are sound, then it should be fine.

    Give it a go and report back.

    JD
     
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  10. Truman42

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    Posted 17/9/19
    So when you get around to using the other vials how old can your yeast be? Ive got some yeast thats out of date so might make a starter and pitch, see if it fires up then maybe do the same thing to the slurry in 6 months time. Cheers
     
  11. JDW81

    I make wort, the yeast make it beer.

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    Posted 17/9/19
    I've never left a vial for more than about 8 weeks I'd reckon, so don't know about how long it will last. Personally I wouldn't want to leave it too long, but others may have more experience in how long you can leave it before it's totally knackered.

    I figure I spend a decent amount on grain and hops (not to mention the time spent brewing) that I'm not willing to risk a batch using yeast that is potentially past it's best just to save a few dollars here and there.
     
  12. Truman42

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    Posted 17/9/19
    Yeah I see your point. My problem is that Ive probably recently brought too much yeast and dont want to waste it and possibly wont use it all by 3 months after manufacture date. Time for an experiment.
     
  13. PaulS

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    Posted 21/9/19
    Slightly off topic question, but yeast starter related... what do you all do regarding pitching of a starter? Do you chill and decant off the beer first, then pitch the slurry, or do you pitch the whole starter while it is actively fermenting? I did read somewhere that if the volume of starter is more than 5% of the total wort volume you should decant, but of course that means you can't pitch the yeast while they are actively fermenting.
     
  14. MHB

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    Posted 21/9/19
    This is a pretty fair descriptor of how much yeast survives in a stored slurry under optimum conditions.
    What ever you get at home, it will probably be worse (you will have less of the population surviving).
    If you want to store yeast in pitchable quantities long term (other than plates/slants/stabs...) about the only practical way to do it is to freeze.
    Viability shouldn't be confused with Vitality, just because 1/2 the cells are alive doesn't mean they are healthy and ready to go to work in a wort. If the yeast is stored under beer or water for more than a couple of weeks I would strongly recommend re-vitalising the surviving yeast by running it through its full life cycle in a small ferment. Pitch into a liter or two of well aerated wort (with the right amount of nutrient added), rack off any dead yeast 24 hours after fermentation starts, allow to complete, if you have enough slurry for a direct pitch, fine, otherwise add the slurry to another starter.
    Mark
    [​IMG]
     
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  15. dibbz

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    Posted 21/9/19
    Chris White says the temperature of the pitch and first couple of days plays a big part for vdk.

    https://www.whitelabs.com/sites/default/files/Diacetyl_Time_Line.pdf

    o2 is rumored to also make yeast struggle more towards the end when the clean up happens for diacetyl and its precursors.I'm not 100% sure of this but when I do use o2 it's a massive beer and it's getting a big secondary anyway.

    I would say pitch temp is more important than o2. I just throw 2 packets of US-05 in, you are halving the growth phase.
     
  16. Grmblz

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    Posted 22/9/19
    My understanding of Chris Whites article is low O2 creates more diacetyl ? "low aeration levels when yeast is pitched will produce less healthy yeast, which are prone to higher diacetyl production" Open to interpretation I guess, I always give the wort a quick squirt, and more for a big beer.
     
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  17. dibbz

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    Posted 22/9/19
    Yea I had to read it like a dozen times.

    During both the lag and exponential phase

    yeast build amino acids
    One of the amino acids produced by yeast is valine
    An intermediate compound in valine production is acetolactate
    some will leak out of the cell and into the beer
    This acetolactate is then chemically (not enzymaticly) converted to diacetyl in the beer
    The chemical reaction is an oxidation, and high fermentation temperatures favor this reaction.
    There is a strain specific phenomena here, because given the same conditions, different strains will produce different levels of diacetyl.

    Also I first heard this from a reputable head brewer who was quoting Chris White that US-05? is under 16c for happiest pitch (may have been generically cali or 001 or something) same point tho.

    So go 16 for the first 3 days and then do what you want.

    (sorry for distracting so far away from o2).. You will certainly shorten the lag/exponential phases and lower exposure too.
     

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