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Starter question - is it dead, Jim?

Northern Brewer General
#1

I’m not a noob to brewing but I am new to doing this starter thing. I figured I’d try it and see what the fuss was about!

Thursday at about noon I made a starter wort following the instructions in the FAQ, and when it was cool to 75 degrees I added about a 1/4 C of US-05 yeast cake that I had collected from a primary a week ago and kept in the fridge. I then put the jug (a gallon wine bottle with an airlock) in a 75-degree spot & covered it up. That thing was bubbling in less than an hour, and was going like gangbusters after 3 hours and formed a 2-3 inch krausen. I left it on the counter all night, and this morning it wasn’t bubbling at all (or barely bubbling). I did swish/shake the bottle a couple of times last night, and gave it a shake today, but still no more activity. The krausen has collapsed by 50% as well.

So, I planned to brew tomorrow afternoon. Should I still use this starter, or make a new one since I can probably guess pretty accurately as to when it will be ready. I guess I’m worried that my yeast has died of alcohol poisoning (and of course I didn’t take an OG of this wort so taking another reading wouldn’t be of much use). I still have about 3/4 C of that US-05 yeast cake on hand and had even thought about just pitching some of that in directly.

So what are your thoughts on this? Oh, FWIW, I’m using US-05 on purpose, and I figured that if I’m going to try something new, I may as well learn on a cheaper yeast in case I crash and burn. :roll:

#2

All you’re seeing is that 1/4 cup of yeast is a TON. You don’t really need a starter with that amount of yeast, at least not for an average-gravity ale.

#3

So roughly how much yeast should I add if I wanted to make a starter (for all the reasons they give for making a starter)? The instructions just say “add your yeast packet” without saying how much that would be.

#4

If your yeast cake was only a week old, you could have taken about 1/3 of it and added it to your new brew without a starter. I am no expert, but what I am understanding is that you don’t need to make a starter unless the yeast cake is about a month old. I guess in your case you could “test” the yeast by adding 4-6 oz of new wort to the yeast cake and if you have rapid activity, the yeast is good to go.

#5

I’m planning to brew later today, so I haven’t done any real damage yet. This is my first time collecting and reusing yeast so I’m a bit timid. I think that what I observed with this starter made Thursday shows that the yeast is raring to go. Shoot, when I took the jar out of the refrigerator to let it warm up a little bit, I saw large bubbles begin to form after about 20 minutes.

Anyway, it had crossed my mind to just pitch a good dollop of this cake directly into my new beer. Thanks for your thoughts on this! :cheers:

#6

The MrMalty calculator has an option for repitching slurry. If you want to build a starter, you could just let it estimate how many cells are in the slurry and then manually plug that number into the viability field of the liquid yeast tab.

BTW, you don’t want to use an airlock on a starter.

#7

Cool - I’ll check into that. Thanks!

:? But won’t it go BOOM? I’m just going by the instructions on the FAQ.

#8

Sanitized foil or a foam plug work great.

#9

I’ve seen that before, but I have a stopper and airlock that fit - so why not use it? You guys are really confusing me here!

#10

I’ve seen that before, but I have a stopper and airlock that fit - so why not use it? You guys are really confusing me here![/quote]

The specific reason that you do not want an airlock on a starter is that you WANT to let oxygen in to allow rapid yeast growth. The airlock would push the oxygen out very quickly and keep it out.

#11

[quote=“a10t2”]The MrMalty calculator has an option for repitching slurry. If you want to build a starter, you could just let it estimate how many cells are in the slurry and then manually plug that number into the viability field of the liquid yeast tab.

BTW, you don’t want to use an airlock on a starter.[/quote]

The problem that I have with this is…what is the real definition of “slurry” in these calculations? It is the unwashed yeast cake and trub? Is it washed yeast? I find that part pretty confusing for this calculation.

#12

That’s why Jamil’s calculator lets you set the slurry density and non-yeast percentage. For density, I’ve found that almost all slurries will compact to around 4 billion/mL after a few days in the fridge. The default of 2.4 is probably about right for yeast that’s been harvested that same day. Non-yeast percentage you can pretty much eyeball, or just set it to 0 if the yeast has been rinsed.

The bottom line is that without a cytometer you’re making assumptions on cell counts anyway. But by using your best guesses you can get “close enough”.

#13

Hmmm… not sure what happened b/c my post 6 hours ago isn’t here, so I will try again.

I understand the idea of wanting O2 to encourage the yeast, but wouldn’t said O2 also bring with it a risk of contamination? Also, wouldn’t the positive pressure created by the CO2 prevent oxygen from entering through a foam plug or a fairly well-sealed foil cover?

I’m not looking for fisticuffs or anything, :wink: just trying to sort out everything I’ve read so far and all the contradictions.

Thanks!

#14

Technically, yes, but everything you do to the wort carries a risk of contamination. Remember, bacteria and wild yeasts can’t fly. In order to get into the wort they have to fall in. As long as nothing drops into the wort, the risk of contamination is basically zero. Unless there are fruit flies in the area, nothing is getting past a loose foil cap.

As long as there’s no airlock, there’s no positive pressure.

Aeration and Yeast Starters


#15

CO2 is heavier than air.
any resistance on top of the flask will create back pressure into the flask. if you see the foil bobbing or flapping, that is a result of positive pressure in the flask.

as the yeast does its thing, it will create a layer of co2 above the wort which will, eventually, seal out O2, or ambient air, from getting to the krausen.

use an airlock or dont
it sounds like it makes no difference.

btw
i never make starters
all of my beers have turned out horrible and completely undrinkable. for as long as ive been brewing ive never actually drank an entire 5 gallons of my own beer. i just brew them and dump them into the toilet.

if i brew a beer larger than .065 then i use 2 smack packs.
im just lazy and dont want the added work of making a starter.

#16

[quote=“swirly_commode”]
if i brew a beer larger than .065 then i use 2 smack packs.
im just lazy and dont want the added work of making a starter.[/quote]

2 smack packs = $12 - $15
Starter with 1 smack pack ~ $6.50 + about $1 of DME
Starter reusing yeast about $1.00 This is why I make starters and it is not to much trouble to probably make my beer a little better.

Making a starter takes me around 1-2 hours and not all that time is consumed in making the starter. Some is waiting for the heating or cooling.

As to the original question there was a lot of yeast and it consumed the wort quickly. It is not dead and ready to go.
The oxygen the yeast will need will get past a foil cover or through a foam stopper before the co2 shuts it out. An airlock will stop that transfer sooner.

Using the slurry to mrmalty’s amounts will be adequate. Making a starter with fairly fresh slurry is unnecessary as stated. Doing it for the practice is probably a good idea.

#17

[quote=“swirly_commode”]
as the yeast does its thing, it will create a layer of co2 above the wort which will, eventually, seal out O2, or ambient air, from getting to the krausen.[/quote]
That simply is not how gaseous diffusion works. There is no ambiguity or lack of consensus on this.

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