Amount of yeast for slightly smaller batches

[Lunkerking]

I have a 15 gallon brew kettle, which unfortunately is not quite big enough for some 10 gallon batches. I will have to scale some recipes where I might end up with 8 gallons of beer to bottle. This would probably be split into 2 fermenters. I know most the yeast packets are good for five gallon batches. I guess my question is do I need to scale the amount of yeast I use? I am guessing not but just wanted to check.
Thanks

 

[DudleyDoLeft]

there are several options.

*It depends* packets such as wyeast are often not technically enough even for 1. 5 gallon batch often 2 is closer to the the recommended.

a few minutes looking at a pitch rate calculator will give you an idea. http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

I recommend getting in the habit of making a starter before pitching. Just make sure whichever container is sterilized, that dry malt added to the water measures a light or moderate gravity. the starter liquid is boiled and cooled to proper pitching temps. Prepare the starter a day or 2 ahead of time.

-- after expanding options like making a starter any demand can easily be met. --
You could better consider that some styles (namely Hefe) can benefit from even under-pitching yeast. the flavors can benefit
-but even there again it takes us back to the start which is that it really can be a good boost to brewing to meet the target with active healthy yeast.

 

[RM-MN]

After you use the pitch rate calculator, read this experiment and notice the amount of over and under pitch and the results from each. https://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

Then ponder on how Gordon Strong can make a good or even drinkable lager with pitching only a single smack pack of yeast with no starter.

 

[Lunkerking]

Thanks for the info. Right now I have just brewed a few batches and have used the white labs liquid packets as a start. I imagine they would work well for a slightly smaller batch.

 

[micraftbeer]

After you use the pitch rate calculator, read this experiment and notice the amount of over and under pitch and the results from each. https://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

Then ponder on how Gordon Strong can make a good or even drinkable lager with pitching only a single smack pack of yeast with no starter.

A question that comes to my mind in the big yeast debate, is when homebrewers adamantly insist that 2 vials or 2 smack-packs are needed for a 5 gallon batch, that Wyeast and White Labs stand behind the ration of 1 portion for a 5 gallon. I've read their explanations that because how the yeast are grown in a controlled environment, there's an effect to the quality of the yeast that overcomes the quantity of yeast. So in breweries where they harvest and re-use yeast (maybe the keen homebrewers do, too), those cells are a little more worn down and not as effective as the super cells in the White Labs/Wyeast packs.

I'm sure someone will find error in the above theory of superior cell condition, but you have to wonder why Wyeast and White Labs would be so adamant that 1 pack is sufficient. It makes no sense for them commercially to try to convince people to use 1 portion when they really want to buy double that amount.

 

[filthyastronaut]

If using dry yeast, just use a pack for each fermenter. If liquid, I would just make a starter that's big enough for 8 gallons of wort. I've taken to using low gravity 2.5 gallon batches as a starter, and yesterday I just did a super low gravity table saison at 5 gallons that's already taken off. Doing it that way, you get some more beer and a LOT of yeast.

And out of curiosity, how is 15 gallons too small for a 10 gallon batch?

 

[chickypad]

... but you have to wonder why Wyeast and White Labs would be so adamant that 1 pack is sufficient. It makes no sense for them commercially to try to convince people to use 1 portion when they really want to buy double that amount.

I don't think it's as cut and dried as that. What they actually say on the Wyeast site is one pack "is designed to innoculate 5 gals of ale wort below 1.060", then have a couple pages on pitch rates depending on gravity and a calculator for starters. While labs says one pack "within proper date ranges will work for any 5 gallon batch" then right underneath that for advanced homebrewers they recommend a starter for anything over 1.048. In Chris White's book they address what you mentioned - that with a fresh laboratory grown culture and good aeration and nutrition you can use up to a 50% lower pitch rate, but then they point out that bets may be off depending on handling conditions after it reaches the LHBS.

The linked experiment is nice but it's dealing with Belgian yeast. Lots of folks underpitch those beers on purpose. For me that's very different than brewing a high gravity AIPA that you want to be extremely clean. In my completely uncontrolled and anectodal experience pitch rate does seem to make a difference in the final product, so that's what I'll continue to do. There are certainly other factors besides pitch rates that affect yeast performance, if you make great beer pitching directly then there's probably no reason to change.

 

[Lunkerking]

If using dry yeast, just use a pack for each fermenter. If liquid, I would just make a starter that's big enough for 8 gallons of wort. I've taken to using low gravity 2.5 gallon batches as a starter, and yesterday I just did a super low gravity table saison at 5 gallons that's already taken off. Doing it that way, you get some more beer and a LOT of yeast.

And out of curiosity, how is 15 gallons too small for a 10 gallon batch?

When I did a pale ale it was about 7 gallons pre boil and left me with about 5.5 gallons going into the fermenter after boil off and loss to trub. To do a batch double that I imagine it start with 13 gallons to boil and would get a boil over in a 15 gallon pot.

 

[RM-MN]

I don't think it's as cut and dried as that. What they actually say on the Wyeast site is one pack "is designed to innoculate 5 gals of ale wort below 1.060", then have a couple pages on pitch rates depending on gravity and a calculator for starters. While labs says one pack "within proper date ranges will work for any 5 gallon batch" then right underneath that for advanced homebrewers they recommend a starter for anything over 1.048. In Chris White's book they address what you mentioned - that with a fresh laboratory grown culture and good aeration and nutrition you can use up to a 50% lower pitch rate, but then they point out that bets may be off depending on handling conditions after it reaches the LHBS.

The linked experiment is nice but it's dealing with Belgian yeast. Lots of folks underpitch those beers on purpose. For me that's very different than brewing a high gravity AIPA that you want to be extremely clean. In my completely uncontrolled and anectodal experience pitch rate does seem to make a difference in the final product, so that's what I'll continue to do. There are certainly other factors besides pitch rates that affect yeast performance, if you make great beer pitching directly then there's probably no reason to change.

50% lower pitch rate? Oh yeah, that's with good aeration and fresh yeast. What about yeast that isn't so fresh? Well, then it depends on how it was handled. Refrigerated? Here's what WoodlandBrews found about veast viability. http://brulosophy.com/2015/01/19/fermentation-temperature-pt-1-exbeeriment-results/

Who would want to pitch a small amount of yeast for a high gravity beer if they wanted a clean ferment? But what really is the right amount. I've seen some recipe posted that required a 5 liter starter in a 5 gallon batch! Neccessary? Not likely. Even with no aeration you can't keep oxygen out of the wort in the homebrew world and with some oxygen you will get yeast replication. How much replication can you get?

 

[RM-MN]

When I did a pale ale it was about 7 gallons pre boil and left me with about 5.5 gallons going into the fermenter after boil off and loss to trub. To do a batch double that I imagine it start with 13 gallons to boil and would get a boil over in a 15 gallon pot.

If you took 7 gallons preboil to get 5.5 into the fermenter either you boiled too hard or left a lot in the pot with your trub. Forget the trub, dump it all in. That trub is mostly wort and the yeast seem to do better with it in the fermenter. When they are all done with it the trub will settle to the bottom, get covered in the yeast as it drops out and compact down. Leaving that trub in the pot is like throwing out beer. You shouldn't have any appreciable more boil off (your 1.5 gallons) in a 10 gallon batch than in a 5 gallon batch. Go ahead, give a 10 gallon batch a try.

 

[filthyastronaut]

When I did a pale ale it was about 7 gallons pre boil and left me with about 5.5 gallons going into the fermenter after boil off and loss to trub. To do a batch double that I imagine it start with 13 gallons to boil and would get a boil over in a 15 gallon pot.

2 gallons of space in the kettle is more than I use, I typically have a preboil volume of 6 gallons and boil down to 5, using a 7.5 gallon kettle. Regardless, if you want 10 gallons, why would you have your preboil volume at 13 gallons? Wouldn't it be more like 11? You are doubling your preboil volume when doubling the batch size, which is unnecessary. You can choose the amount of liquid you're boiling with anyway.