When to use a yeast starter

[jrodie]

I have normally just pitched two yeast packs rather than making a starter. However I was recently told that it was a good idea to make a starter and pitch at high krausen, because it was beneficial for the yeast to be awake and actively eating when you pitch. I tried this a couple days ago. The airlock was bubbling basically immediately, but krausen didn't start to form on the wort until the typical 8-12 hours later.
I oxygenated the wort with a 2 minute shot just like I usually would. I'm wondering if oxygenating the wort was really beneficial or not, since the yeast were pitched in an active phase?
Just wondering what people's thoughts were on pitching a yeast starter at high krausen, and use of oxygen.

 

[dschoemaker]

Big proponents of both, starter plus oxygen.

Dave

 

[stratslinger]

I've been reading Jamil and Chris White's book Yeast lately, and here's the gist of what I'm getting on the subject:

1) I forget the exact numbers, but what you want when you pitch is a certain density in terms of yeast cells per mL of wort. This density ensures that you have sufficient yeast so that during the lag, or growth, phase, yeast will consume the available O2, build up their cell walls, and multiply to the concentration required for active fermentation - but that there will not be so much growth required that it'll stress out the yeast and a) possibly cause compounds that lead to off flavors and b) will generally be healthier and better able to reliably survive multiple re-pitches. Similarly, the lag phase is when the yeast typically develops its characteristic ester profile in a beer - so depending on your yeast choice and your target beer, you may occasionally WANT to underpitch to get more character, for instance.

2) On O2, that aids in the growth phase and general health of the cells once the active fermentation phase starts. But it also has significant impact on the long term health of the yeast for subsequent re-pitches. Repitching may not be something you're interested in, generally - but if you can repitch from one batch to the next in short order, it can save you some money in the long run.

As for when to pitch the starter - well, I haven't reached that part of the book to be able to share Jamil and Chris White's opinion on the matter - but I can tell you that from my own experience I really don't see a significant difference either way. With either approach, you're still only pitching a fraction of the cells that the yeast will need for active fermentation, and there's still going to be a lag phase while those cells build up to that number. But pitching the yeast at its height of starter activity or once the starter has finished chewing through all the available resources in the starter may only result in a small difference in lag time - if even that.

 

[wardens355]

I oxygenate my wort, but don't pitch my starter at high krausen. I make my starters the weekend before, let ferment for 2-3 days (the starter is typically fermented out between 1-3 days in my experience), transfer from flask to sterilized mason jars, cold crash 3-4 days, and then decant most of the spent starter wort before pitching on brew day. The starter wort always has poor flavor because I don't control temperature, so I never want it in my beer. I let the starter yeast warm up over several hours, toss a bit of cooled, fresh wort in the mason jar, and then continue to rack my wort into carboys, oxygenate, get my freezer setup, etc. Once I'm all setup, I pitch the yeast. This method works well for me.

 

[Gavin C]

For me pitching two liquid yeast packs is prohibitively expensive. $14 for yeast. No thanks. A starter not only is good practice it will save you cash.

Optimal pitch rate, optimal fermentation conditions means the yeast will do there job and be healthier for the next batch.

Or you can over build your starter and keep some back for future brews.

 

[wardens355]

Or you can over build your starter and keep some back for future brews.

+1. I always grow a starter with approximately 120-150 billion extra cells and store cultures in the fridge in mason jars. One downside for me is that my refrigerator is now overrun by hops and yeast cultures.

 

[kombat]

I was recently told that it was a good idea to make a starter

True. For liquid yeast.

and pitch at high krausen

False.

because it was beneficial for the yeast to be awake and actively eating when you pitch.

You'll have a faster start to your fermentation, but that's not necessarily desirable.

A yeast starter has exactly two purposes:

• To verify the viability of the yeast cells
• To build up the yeast biomass to the required cell count for optimum fermentation

That's it - those are the only two reasons to do a yeast starter. If you've bought enough packets, and you're confident in their viability, you don't need to make a starter. If you have a Mason jar of yeast you harvested from a batch last weekend, and you know the yeast is healthy, then you don't need to make a starter.

If you have a single vial of yeast (at most 100 billion cells), and the pitching rate calculators are telling you you need more than that, then you need to build a starter.

I tried this a couple days ago. The airlock was bubbling basically immediately

Again, that's not necessarily a good thing. You're short-circuiting their life cycle and potentially stressing them. Let them finish their job and settle out before serving up a fresh meal to them.

And oxygenating the wort is always beneficial - yeast need oxygen to multiply (and for other things). When I brew an ale over 1.060, or any lager, I always hit the wort with 60 seconds of pure oxygen in a diffuser stone. For ales below 1.060, I just whip up some foam with a Fizz-X rod on my drill.

 

[Natdavis777]

I make starters for every beer, regardless of OG. I feel it is good practice, and has made my beers taste a lot better (along with proper aeration and controlled fermentation temps). I use a calculator to make each starter specific to the OG.

Granted, the yeast still have to grow to a point to ferment the beer, the less stress the yeast have, the less off flavors. On a recent BrewStrong, JZ was talking about Brett beers and how many places were actually making clean all Brett beers bc they were pitching appropriately. They were suggesting that in order to get the Brett character (horse blanket character) they should be underpitching to stress the yeast out.

Point being, underpitching can stress yeast and lead to off flavor production, sometimes desired, sometimes not so much.