Yeast Starter shelf life in fridge question

[dperrigan]

Hi All. My usual procedure is to create my starter, let it ferment for about 4-5 days at room temp, then cold crash it in the fridge overnight, pour off 80-90% of the liquid, then pitch the yeast. This works well for me.

My problem this time is that I'll be away until the day before I plan on making my next beer -- so I won't have time to make the starter when I get back. I'll be away for 7 days. I'm pretty sure I've read that a starter can last a few weeks in the fridge without degrading (much). So if I make it before I go, (timing it so that it finishes about when I need to leave), would it be fine in the fridge for those 7 days?

Thanks,
Dan

 

[Jack Arandir]

Short answer: Yes you're fine.

Long answer: (from Chris White's book Yeast pg 160-161) Ideally use harvested or propagated yeast within 1-3 days. After 4 weeks yeast viability is 50% or less, so the yeast should be tossed (or re-propagated). Ideally you want yeast viability of 90% or greater, so consider 14 days the maximum storage time.

 

[pvtpublic]

MoreBeer has a viability calculator on their website, if you want to get specific. Amazon has 400x microscopes if you want to get really specific.

 

[Jack Arandir]

If you can, overbuild your starter to compensate for the loss of cells during aging. You'll likely lose around 10-20%, so shoot for ~120% of the cells you'll need to pitch. Good luck!

 

[dmtaylor]

It will keep just fine for a week. Or even 2 weeks. Beyond that point, I might feed it more sugar to help wake it up again.

 

[balrog]

REal world example of exactly this topic here. I made a two step starter, second step finished 11/16, but I did not brew with it until 12/5. The calculators said it would be about 85%, but I had aimed for a very high, 2.0m cells per degree Plato, pitch rate and figured 80% was still 1.79 pitch rate and fine.

It took 4 days for the exotherm to appear, where it usually takes a day or maybe two.

 

[dperrigan]

Thanks, Everyone

 

[Northern_Brewer]

Do a vitality starter if you want the yeast to be in perfect condition, just pour off the supernatant and add some 10% w/v DME solution when you mash in. Even a few hours in new wort will allow it to hit the main wort up and running.

 

[IslandLizard]

My usual procedure is to create my starter, let it ferment for about 4-5 days at room temp,

On a stir plate, or just on the countertop, swirling a few times a day?
There's a huge difference in growth between those two "methods."

There's also the s-n-s (shaken-not-stirred) starter method. It's mostly used 24 hours (?), or thereabout, before pitching. That would be a good application in your case.

I'm pretty sure I've read that a starter can last a few weeks in the fridge without degrading (much).

That's correct!
I've stored starter slurries for months, years even. But always make a fresh starter with all or some of it, depending on age and how much there is.

Here's the pitch/growth calculator I use:
http://www.brewunited.com/yeast_calculator.php

 

[RM-MN]

Short answer: Yes you're fine.

Long answer: (from Chris White's book Yeast pg 160-161) Ideally use harvested or propagated yeast within 1-3 days. After 4 weeks yeast viability is 50% or less, so the yeast should be tossed (or re-propagated). Ideally you want yeast viability of 90% or greater, so consider 14 days the maximum storage time.

Read Chris White's book and then read this article from Woodland Brewing.

Refrigeration Effects on Yeast Viability

Note that Woodland brewing is just doing a test on the yeast viability while Chris White runs a lab that sells yeast. You decide which is the one to believe.