Double Batch to One Fermentation Vessel

I am planning on brewing two 5-gallon batches of the same beer. Can I put both batches into one 15-gallon fermentation vessel? When do I pitch the yeast, on the first run or the second run? Don't have any way to brew a 10 gallon batch.

How far apart will the two batches be brewed?

broadbill said:

How far apart will the two batches be brewed?

Click to expand...

one day brew 1st batch then 2nd day the second batch.

Pitch the yeast after you have put them both in. Make sure you prepare a large enough starter. Keep the wort from the first batch sealed up tight until you are ready to pitch and be extra careful with sanitation since it will just be sitting around until you get the second batch done.

I would think pitching the first day would hurt anything. Just my initial thought.

May I ask why you recommend he wait?

Yeah, wouldn't the first batch just become a huge starter?

had the same question and asked the brewer about this today at work. He instructed to pitch enough yeast for both batches as soon as the first batch is in and aerate extremely well. That will essentially act as a large starter and then add the second batch as soon as possible.

But you don't want your first batch to become a huge starter, you want it to be tasty beer. No one drinks the nasty run off from starters.

By simply waiting the extra day, you can combine the two batches and prepare them for yeast pitching at the same time.

Think what would happen if you have yeast happily munching away at the sugars in your wort then 1-2 days later, you throw in a bunch of wort that is potentially 5-10* hotter or colder, sloshing it around and oxidizing the beer. You are going to change the condition of the yeast and shock it.

Now doesn't it just make sense to wait that extra 24 hours and make sure everything is controlled for?

I actually use Sanke fermenters, so I use a no-chill method to double-batch. Mash, boil, dump while boiling into the Sanke, cover with orange carboy cap with holes capped. I then make a new batch right away, or I've brewed on successive nights. I try to adjust my hopping to work with some of the general rules of thumb for hopping no-chill brews.

I've also done it where I brewed two batches of the same beer, chilled in-kettle, and combined in the fermenter. A couple times that's been a two-day affair, as it's been said, if you have good sanitation, a couple days is fine.I always pitch once I have the fermenter full, and at pitching temp, and oxygenated.

I've never tried the 5 gallon starter idea, though I might give it a go on something in the future. I think the advice given, to pitch full yeast amount, aerate big on the first 5gal, then add the second batch un-aerated as soon as it's at the current fermenter temp, might result in success.

I think I might start early in the morning and batch the two in the same day. I think Jrinke has a point. It would be a good idea to blend the batches then pitch the yeast. The temperature would not effect the yeast this way. Thanks for the input.

JRinke said:

But you don't want your first batch to become a huge starter, you want it to be tasty beer. No one drinks the nasty run off from starters.

Click to expand...

huh....I guess I should not have drunk that APA that was a "starter" to get enough yeast for my RIS.

JRinke said:

By simply waiting the extra day, you can combine the two batches and prepare them for yeast pitching at the same time.

Click to expand...

Not sure what you need to "prepare"....oxygenation maybe? If that is the case, its not unusual to hit a high gravity beer with another shot of O2 24-48 hours yeast pitch.

JRinke said:

Think what would happen if you have yeast happily munching away at the sugars in your wort then 1-2 days later, you throw in a bunch of wort that is potentially 5-10* hotter or colder, sloshing it around and oxidizing the beer. You are going to change the condition of the yeast and shock it.

Click to expand...

Shock it how? 5-10 degrees difference is going to have a negligible effect, the yeast are still active so they will scrub any extra oxygen (no worry of oxidation), and I don't see what would "shock" the yeast, considering you are adding to it with a equivalent gravity wort.

Again, its not unusual for brewers of high-gravity beers to "feed" their beer fresh wort over time...even out to a month or more! Adding fresh stuff isn't going to mess anything up in my opinion.

JRinke said:

Now doesn't it just make sense to wait that extra 24 hours and make sure everything is controlled for?

Click to expand...

Not really.

The only thing I wonder about is if it would make a difference to add the 2nd batch before or after the lag phase.

I was thinking about doing something similar with a 5 gal batch. I've been doing 3 gal batches as my kettle isnt big enough to do a full 5 gal boil. Would I simply take a 5 gal recipe and split and malts and hops in half?

It would make sense to me to oxygenate and pitch on the first batch. I don't think you're going to hurt anything. I think you're running higher risk by waiting to pitch and expose your brew to contamination. I want my yeasties getting happy and to work as soon as possible.

The way this first run was described as a "starter", is a bit erroneous in my mind. You're essentially pitching the brew at a higher yeast count, but it is no where near the concentration of a starter. I think you're giving your brew a good head start by pitching in the first running; however, I wouldn't wait to brew until the next day.

If you want to brew back to back, then brew back to back and get your process smooth enough so you can do a batch before lunch, and one after lunch. You'll likely be adding the second run before your lag time expires, and minimal attenuation has occurred. I wouldn't oxygenate on the second running for risk of oxidizing any minor amount of alcohol that might have been produced - it is probably a minimal risk, but I'd try to come up with a method to keep the "sloshing" to a minimum.

A lot of breweries double, triple, quadruple, etc batch. Your goal should be to get all the wort in within 24 hrs, 36 absolute max. According to the Brewing Science Institute, for a double batch, you should oxygenate and pitch yeast as you normally would for that first brew length. The second batch goes in and only gets oxygenated if there is less than .5ºP attenuation. Some breweries will pitch enough for the total batch with the first batch but you get a lot of process loss that way...too much yeast. I would think your ester profile would also change with double pitching on the first batch.

On the other hand, I've let wort sit cold (35F) for 18 hrs before oxygenating and pitching and still made award winning beer. Just have to make sure your process is solid.

You could also do a single high gravity brew and dilute with water in the fermenter. A local brewpub does that with their light lager. That seems like something that would need some dialing-in though.