Starter Storage

I would use the Mr Malty calculator to estimate how many cells you started with and lost over the month.

 

There should be little problem with it stored in the fridge for that long. Waking the yeast up is a good idea. With a low gravity beer you will be fine.

 

500ml of starter wort may be underpitching. Presumably you have 100-200B cells, these guys really need a little more food on the table for best performance. Ideally your starters should have an inoculation rate between 40 - 125 million of cells/ml. It may still work outside this range but performance will suffer.

This isn't as hard as it sounds if you use yeastcalculator.com or BrewCipher. It actually shows you the inoc rate and warns if it reaches a danger limit (high or low). I don't know your quantity, but would guess a starter in the 1 - 1.5L range may be more appropriate. If this gives you too many cells you can pour off XX% before you chill/decant (save for next brew day) or alternately just start a portion of what is available. The yeast calculator is your friend.

 

This 2007 Zymurgy article by Jamil Zainasheff on yeast starters has tons of great info:

http://www.homebrewersassociation.org/attachments/0000/1235/MAzym07_YeastStarter.pdf

If it looks okay and smells okay then you probably stored it safely. Adding some more wort and warming it up and pitching at high krauesen and you should be golden, especially for a 1.048 beer.

 

How big was the original starter? You may need to do more than "wake up" the yeast if the original starter was small.

 

That is what I would recommend. If you had 190B a month ago that translates to 150'ish today. I would target an optimum inoc rate (available on Brewers Friend in the fine print) to insure a good re-start. If this gives you too many cells then pour off whatever the overage percentage is, typically into a mason jar. Now you have a healthy source of WLP007 that hasn't gone through a complete brew cycle . . . in theory this is healthier than washed yeast. Definitely easier than the washing process. If you really want to save an ounce or two of DME you could divide the yeast slurry in advance, use only a percentage to give you the final target count. IMO this is harder and potentially more problematic.

I do this all the time, intentionally make about a third more than I need and save for the next brew day. What you want to avoid is pitching a huge quantity of yeast into a tiny starter.

 

Are these numbers from Yeast or some other source?

 

Yes, pages 140-142. VikeMan has posted that he uses 25 million cells/ml as the bottom limit (I read the graph a little differently).

Data was from pitching 100ml of WLP001 into starters ranging from 0.5L up to 8L. In the 0.5L starter (inoc rate of 200) growth was only 12 billion cells, resulting in 112 available. But the same yeast pitched into a 1L starter (inoc of 100) growth was 52 billion cells. So by doubling the starter the growth was more than 4 times.

The authors plot all of their data points and the Yield Factor Curve is basically flat between an inoculation rate of 40 -125. In this range, growth of yeast is most optimum and results are almost linear. Yeast will certainly grow outside this range, but is less efficient and at a non linear rate.

This is why stepped starters are more efficient than a single starter. Ironically, mrmalty's calculator (copyrighted by the author of Yeast) doesn't have a step-starter menu. It will let the end result dictate a very low inoc rate, common to see results like 3 or 4 liters required which is both difficult and inefficient for homebrewers.

Yeastcalculator, Brewers Friend, and BrewCipher (three that I know of) have a very easy step menu and they will Red Flag you if you go over the edge. Because I normally only put 1.5 liters in my 2L flask, I start with the limit of my equipment and work backwards. Example: I'm restarting 50B of stored yeast for a 1.056 batch . . . 203 billion is my target. With a stir plate my most efficient pattern is a 0.9L (inoc of 56) first step followed by a 1.4L (inoc of 106). This yields ~329B, which I'll pour off the excess (1/3 of the flask) and save about 108B for the next brew day.

Some people get glazed eyes when looking at all these numbers, but a good calculator does all the heavy lifting. I find it easy to "what if" the problem and make the solution fit my equipment, usually in a minute or two. I'm under no illusion that growth is always perfect and these number may bounce around some. Even though the target is never hit exactly, I do aim at the bullseye.

 

Thanks for the detailed reply. In my own (homebrewed) brewing log sheet I have modeled both the data in Yeast and the data that Kai Troester has published. I, too, find that stepped starters seem to be the way to go -- right now I'm on the second of three stages for next weekend's lager. (My largest flask is also 2L.) I've just never thought much about min and max inoculation rates.

I've never been a fan of the Mr. Malty calculator. I always thought Yeastcalc to be much more useful, and Kai's online calculator is also quite nice (as you point out). I should look at Brewcipher's calculator.

I have yet to actually try to read Yeast, but I should probably bite the bullet and give it a go. I guess I haven't because I'm not convinced that it will add that much to my home brewing procedures or results.

 

One thing about the yeast calcs in BrewCipher... they are a little different from the others in that they automatically recommend stepped starters (and multiple step sizes) where appropriate. So it's more on auto-pilot than the others. But if you want to affect the outcome, you can of course play around with parameters on the Brewhouse paramaters tab.

 

Plus, it looks like it was designed in the MS-DOS/3.0 era . . . you know, when we had 640-480 monitors that displayed 64K colors. Don't those guys have an intern with programming skills to perk things up?

For the OP; congrats for taking the plunge into calculators. I find yeast management the single most important area for improved beer.

 

Quick question that is related to the starter question: how long can the starter sit out before needing to be refrigerated? I made a starter this weekend and won't get to brew until next weekend, can I just leave it as is?

 

Second question:
I am brewing an Irish Rye Ale, and using Wyeast 1084. I bought the first pack back in Dec (Oct 22 manufacture date), so I figured that I should get an additional pack just to be safe (Nov 8 manufacture date). BrewersFriend estimates my SG at 1074. I made only a 1L starter for this with 8oz DME, because BrewersFriend calc. told me to make a 4.9L starter with 17oz DME and that seems ridiculously big.

My question is this; am I just naive in thinking that with 2 yeast packets and the 1L starter I will still be able to pull out a 1.074 or so beer that works?

The recommended size just seems huge, and I recently brewed a beer with one yeast pack, no starter, and went from 1.066-1.022 with no problem.

 

For your two packs (used together, both ~90 days old) and 5 gallons of 1.074 wort, BrewCipher recommends a 1.9 Quart starter if Shaken, or a 1.2 Quart starter if you use a Stir Plate.

 

Great, thanks @VikeMan