Pitch Rate Calculator, overal yeast starter questions.

[dirtyb15]

Okay, planning on brewing this weekend, and i am planning on using some washed yeast. (Did this for the first time, about 2 weeks ago). So I am not clear on how big my starter needs to be. (I have also never used a starter so this is also a first). I was tyring to use BrewTargets Pitch Rate calculator and it is saying 2.5 gallons, so not sure what i need to change there. I noticed aeration method changes results drastically. I just plan on swirling it around everyonce in a while...

Doing an 8.5 gallon batch, OG is 1.07. How do i determine the size of the starter for washed yeast, vial, or smack pack?

Thanks!

 

[LLBeanJ]

You'll need about 400 billion cells. How old is the washed yeast and how much do you have?

Edit: For that many cells, you'll likely need a stepped starter.

If you start with a fresh vial or smack pack that is say, 2 weeks old, and with intermittent shaking/stirring, you could do a 1.2L first step, then follow up with a 2.5L 2nd step. That would get you to around 409 billion.

Edit 2: Numbers obtained from http://www.yeastcalculator.com

 

[dirtyb15]

You'll need about 400 billion cells. How old is the washed yeast and how much do you have?

Thanks for the reply. That is what i am curious about, not sure how much i have exactly. I harvested the yeast about 2 weeks ago. I have 4 pint sized ball jars that are filled 3/4 each.

 

[LLBeanJ]

If your washed yeast is only 2 weeks old and you have that much (I estimate about 600ml total), then you don't even need a starter. According to mrmalty, based on a fairly thick yeast (3 billion cells/ml) and 5% non-yeast %, about 200 ml of that 2 week old yeast will do it. I'd go with one and a half jars and call it good.

Edit: Oh, wait. You said those were pint jars, didn't you? I was thinking 8 oz jars. Pint jars would put you around 1200 ml of yeast (4 x 300 ml/jar). In that case, one jar would more than do it. Do you really have that much washed yeast? Or is it just unwashed, harvested slurry?

 

[dirtyb15]

Perfect Thanks!

For the future, is there a good way to estimate how many cells are in the washed yeast volume based on age etc...? (I apologize if this is well known, i have searched and not found an answer on this.)

 

[dirtyb15]

Edit: Oh, wait. You said those were pint jars, didn't you? I was thinking 8 oz jars. Pint jars would put you around 1200 ml of yeast (4 x 300 ml/jar). In that case, one jar would more than do it. Do you really have that much washed yeast? Or is it just unwashed, harvested slurry?

I pretty much followed this guide exactly
https://www.homebrewtalk.com/f163/yeast-washing-illustrated-41768/

I was careful not to get too much trub in the jars, everything looked just like the above guide. They have been in the fridge since I washed and now there is a thin white layer at the bottom of each jar.

The pint jars are not full however, they are about 1/2-3/4 full if i remember right (im not at home or i would go look.)

 

[LLBeanJ]

Perfect Thanks!

For the future, is there a good way to estimate how many cells are in the washed yeast volume based on age etc...? (I apologize if this is well known, i have searched and not found an answer on this.)

Mrmalty.com is a good source for reusing slurry if no starter is needed. Click on the Repitching from slurry tab. If using straight, unwashed slurry, just enter your OG, batch size, harvest date, and accept the defaults on the sliders. If using washed yeast, do the same but you can bump up the yeast thickness to about 3 and lower the non-yeast % to around 5. That'll get you close enough to call it good. Others will no doubt chime in here with their recommendations, which will likely be different than mine, but they'll all get you close enough.

To convert ml to oz I will usually just take what mrmalty ouputs in ml and do a web search on Bing or Google, e.g., "Convert 212 ml to oz" and it will convert the volume for you.

 

[Calder]

Mrmalty.com is a lousy source for reusing slurry. If you use it, just dial in today as the day you harvested the yeast. The viability rates drop off so quick, that if you do follow it, you are most likely to over-pitch.

I have not checked it recently, but a while ago, it said 2 month old slurry was only 10% viable. I'll bet it is way better than that. I would expect it to be way north of 50%, so if you follow their guidance, you would over-pitch by over 5X with 2 month old slurry.

OK, I'll admit I'm not a Scientist, and have never analysed slurry to see how many live cells there are. However I have used slurry that old, and it is very healthy.

Also to support my position; if you dial in 12 month old slurry into Mr.Malty, you will get the same viability number of 10%. So ....... Mr.Malty says you need to pitch the same amount of slurry whether it is 2 or 12 months old!!!!!!

I can't fault the program for it's pitching rates for fresh yeast.

EDIT: I just checked Mr.Malty. At 2 months viability = 10%. At 12 months (365 days) viability = 10%. At 12+ months (366 days) viability = 1%.

 

[LLBeanJ]

I just checked Mr.Malty. At 2 months viability = 10%. At 12 months (365 days) viability = 10%. At 12+ months (366 days) viability = 1%.

Yeah, honestly, I don't know where it's getting numbers like that. When I plan to reuse slurry, I always wait until the new wort is in the fermenter and cooled to pitching temps before I rack the old beer off the slurry and into a keg, so I don't store my slurry at all. If I can't work it this way, I'll just use clean yeast harvested from a previous starter to make a new starter. Most of my brews are in the keg within 2 weeks of brewing, so the slurry I do repitch is only a week or so out from when active fermentation ended and has been under the beer the entire time. As far as viability date, I use pitch date + 1 week and call it good, rather than actual harvest date, but I doubt it would make much difference between a week (i.e. calculated viability date) and two weeks (actual harvest date). As a result, mrmalty's bizarre viability calculations for older slurry don't really come into play. Doing it this way seems to be working out pretty well for me, so I'll keep doing it. YMMV

 

[WoodlandBrew]

+1 to dialing the slury in as being harvested today if you use Mr. Malty. I have done the viability counts:
http://www.woodlandbrew.com/2012/12/refrigeration-effects-on-yeast-viability.html

It's good to know that I'm not the only one that doesn't trust MR. Malty 100%.

 

[megs8888]

Is there a guide somewhere as to how Mr Malty works with fresh yeast? Also how to make a starter? And how to work out exactly how much yeast is needed? Thanks.

 

[wardens355]

Is there a guide somewhere as to how Mr Malty works with fresh yeast? Also how to make a starter? And how to work out exactly how much yeast is needed? Thanks.

Are you using a commercial liquid yeast pack? Are you using a stir plate?

General Yeast Prep Info

I use this calculator sometimes

 

[dirtyb15]

Okay, so I think I have a good handle on using freshly washed yeast, or slurry. Now what about about washed yeast that has been stored for a month or two, is there a good way to estimate how many viable cells there are?

 

[WoodlandBrew]

I did some counts that should answer your question:
http://www.woodlandbrew.com/2012/12/refrigeration-effects-on-yeast-viability.html

 

[dirtyb15]

Thanks for the info!