Question on when to pitch yeast.

Discussion in 'Homebrewing' started by KPlen, Jan 7, 2022.

  1. KPlen

    KPlen Initiate (55) Apr 19, 2017 Colorado

    Was just doing some reading on The Modern Brewhouse website. Everything I have read and the instructions I have seen so far (in my limited experience) have all advised to aerate the wort, then pitch the yeast. However, The Modern Brewhouse advises just the opposite. So, which is correct? Pitching before aeration as stated below? Just want to make sure I am not missing something. Thanks.


    Boiling the wort
    created in the MLT adds an additional level of concern to the proceedings: It is important to control heat stress. This may come as a surprise to those who have read for years that vigorously boiling your wort is beneficial in many ways. Heat stress can serve to accelerate oxidation and affect the final flavor of the beer.

    Some of the important aspects of wort boiling in the Low Oxygen regimen are:

    • Control heat stress by limiting boil time to 60-70 minutes
    • Consider partially opened BK lid (helps limit evaporation)
    • Limit evaporation to 6-10% or less of boil volume
    • Target a “simmer” rather than a robust boil
    • Chill as rapidly as system allows to 5-6 °C
    • Do not aerate/oxygenate until yeast has been pitched

  2. venneman

    venneman Disciple (373) Dec 1, 2012 Colorado

    I pitch before aerating. Why waste the opportunity to mix the yeast in with the wort?
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  3. jbakajust1

    jbakajust1 Crusader (769) Aug 25, 2009 Oregon

    I'm not entirely sure of the science behind it, but as homebrewers we tend to follow the path of the big boys. By necessity, the pros need to oxygenate prior to pitching as it is easiest to do it inline as the wort moves from the chiller to the fermenter (lower surface area). Could you imagine the wand and stone needed to climb the side of a 50 BBL fermenter and oxygenate all that beer?

    One other consideration is that you will most likely need to bake all the steel parts for a wand and stone if used after the yeast has been pitched to ensure there is no cross contamination of different yeasts on different beers. IE, pitch a Saison yeast, oxygenate, set aside, next brew day pitch lager yeast, oxygenate, carry over Saison yeast that was in the porous stone from last brewday.
  4. JackHorzempa

    JackHorzempa Poo-Bah (5,437) Dec 15, 2005 Pennsylvania

    That is consistent with my readings and homebrewing practice. When I purchased my homebrewing kit in the 1990's I was provided with a three-ring binder which included brewing instructions. Those instruction stated to aerate first then pitch the yeast. I have been doing this ever since and it works just fine.

    My guess is that you could do it either way. Aerate first prior to pitching or pitch the yeast and aerate. You get to choose here.
    Yup, that is indeed part of the Modern Brewhouse philosophy. There are benefits to conducting a vigorous boil and I will just list a couple:
    • Properly drive off unwanted volatiles (e.g., SMM)
    • Improved clarification (improved precipitates)
    I conducted a vigorous boil when I started brewing in the 1990s and I still conduct a vigorous boil today. Entirely up to you how you want to boil in your homebrewery.

    #4 JackHorzempa, Jan 7, 2022
    Last edited: Jan 7, 2022
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  5. VikeMan

    VikeMan Poo-Bah (2,003) Jul 12, 2009 Pennsylvania

    I took a certificate course in Brewing Science from KU Leuven. While it wasn't a "LODO" course (I don't the remember the term LODO even being mentioned), it did cover heat stress and how to avoid it, including shorter, gentler boils. In commercial brewing, it's taken quite seriously. I do gentle boils, and have never detected DMS in any of my finished beers. Nor has anyone else mentioned DMS, including BJCP judges. You do need to boil enough to convert most of the SMM to DMS, which then evaporates away. (SMM is the main precursor to DMS, and is not volatile in SMM form.)
    utahbeerdude likes this.
  6. Brewday

    Brewday Initiate (168) Dec 25, 2015 New York

    I like to add the yeast to the fermenter right before I add the wort because the wort is being aerated as it's poured in and the yeast gets right to work. I don't shake or add oxygen. Does it matter. I have no clue but it works.
  7. GormBrewhouse

    GormBrewhouse Zealot (530) Jun 24, 2015 Vermont

    I add yeast while the wort is running into the fermenter. Seems to work well.

    I boil fairly hard, but when I see others boiling, I think I’m in between
  8. utahbeerdude

    utahbeerdude Devotee (419) May 2, 2006 Utah

    No one seems to have addressed why pitching then aerating might be beneficial, so I’ll take a stab. It seems to me that aeration/oxygenation after pitching could be beneficial in that there might be less oxidation of the wort/beer because the yeast will immediately begin to metabolize the oxygen. Cheers!
    MrOH, riptorn and VikeMan like this.