How much yeast to use in a 1 gallon brew?

Discussion in 'Beginners Brewing Forum' started by Jonny the Brewer, Jun 5, 2020.

  1. Jonny the Brewer

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    Hi guys.

    I'm a bit confused. In the one gallon brew I am doing tomorrow I'm using a sachet of US 05 yeast. Now, it says on it that the sachet is 11.5g and it's to be added to 20-30 litres of wort. I like a strong ABV so I'll calculate it as per 20 litres.

    A few sums - 20 / 11.5 = 0.575g of yeast per litre. There is 4.55 litre in a gallon, so 0.575g x 4.55 = about 2.62g of yeast I will need to pitch into my one gallon of wort.

    However I was reading something yesterday that said to use a third of the sachet per gallon. Is this correct? Yeast is tricky stuff so my question is - Do you work it out by dividing it like I've done, or is it not as simple as that?

    Any help appreciated as I worry I've got a couple of beers fermenting from last weekend and the weekend before that that have too little yeast and will be very low ABV. Thanks all!

    Jonny
     
  2. BrewPatgonia

    BrewPatgonia Well-Known Member

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    your calculation works. I always calculate and measure my yeast on a gram scale.
    the package is a typical 11.5 gms. The manufacturer recommends 50 to 80 gms per hectoliter, therefore, .5 - .8 gms per liter.
    if you use a third of the package, it gives some additional insurance for a decent fermentation, but if the yeast is fresh.. 2 gms per gallon is good enough. if the ABV is above 7%, then I would be more comfortable with a higher pitch rate... 1/3 of the package for 1 gallon.
     
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  3. Nosybear

    Nosybear Well-Known Member

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    Flipside: While you can overpitch, it's hard to do so and its effects are not as severe as underpitching. Me, I'd guesstimate a half-sachet and call it good.
     
  4. Bubba Wade

    Bubba Wade Well-Known Member

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    I make 2.5 gallon batches. Some of the time, I drop a whole 11g packet in the fermenter, but other times, I pitch approximately half the packet and tape the other half up for later use. I have been using the half packet method more and more as it seems that yeast is one of my more expensive ingredients.

    I have made the same beers with both the full and half packet, and I have noticed no discernible differences in taste or fermentation time.
     
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  5. Frankenbrewer

    Frankenbrewer Well-Known Member

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    Hey BWade, I have a half packed of S-04 from last year. Do you think it is still good? It is double taped and in a ziplock bag in the frige.
     
  6. Jonny the Brewer

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    Great advice guys thanks. I didn't realise it was ok to chuck in a half packet! I might just do that from now on.

    Last weekend's brew stopped bubbling completely after 4 days... I think I might have under-pitched it. Do you think I could add more yeast to it now, a week later?
     
  7. Nosybear

    Nosybear Well-Known Member

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    No. The yeast likely used up all the sugars. Take a gravity reading, if possible, and I'll bet you're near your final gravity.
     
  8. BrewPatgonia

    BrewPatgonia Well-Known Member

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    to Franken, I think you would be OK with the -04 a year old, but better to make a starter with it to be sure. I am using some -05 which I purchased 2 years ago... (I purchase 500 gm packs)... and using a starter with dry yeast isn't necessarily normal..but it is my way to verify activity as well as grow more cells. with 2 yr old yeast... I am getting good activity 70 percent of the time. I store mine in vacuum packed packaging..near 33 deg F. Not a normal situation, but I couldn't use what I had purchased due to work assignments.

    to jonny, mirroring what 'nosy' stated; you should be fine without pitching more yeast; most likely fermentation is complete. if you cannot verify with sg readings, it is better to wait a week at least, to let the active yeast clean up... prior to bottling, etc.. only positive results can occur with reasonable patience.
     
  9. Bubba Wade

    Bubba Wade Well-Known Member

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    Most likely. But as stated previously, making a starter is a pretty good idea if it’s that old. I try to use my half packets within two or three months. But the dry yeast is pretty hardy. It will likely work without a starter given how you stored it.
     
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  10. Jonny the Brewer

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    Even if I didn't pitch enough?

    Is it possible to add not-enough yeast, and still have it eat all the sugar? Yeast is very confusing!

    And how would I know when I'm at FG? For me I just take an OG and an FG and work out the ABV - I wouldn't know how to aim for an ABV.

    I am guessing the two factors are the sugar (grain) and the yeast... varying the types and quantities of each make variations in ABV?
     
  11. Bubba Wade

    Bubba Wade Well-Known Member

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    Yeast will reproduce. That's why you can make a starter to increase the number of cells. Unlike the other ingredients, you can sometimes add too much or too little yeast and the batch will taste as expected.

    But there is a range. And the upper and lower limits are not generally clear cut. So, we usually try to stick to the guidelines for yeast quantity.
     
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