How do you know how many cells are in a starter?

[supermoth]

I washed and saved some yeast from a beer I just bottled, and I'd like to use it for next weekend's brew. I've been reading up on how much yeast to use (per mL of wort per Plato and all that), but what I haven't seen is how to determine how many cells are actually in my starter.

I do have access to hemacytometers and stuff at work, and I guess I could check out my starter under the microscope at work, but is there another, simpler method?

 

[alpo]

I just count them one at a time

 

[Bob]

Leaving Alpo's helpful answer aside, I'm afraid the only way to know is to do a methylene blue stain count with a haemocytometer.

However, there are some Rule of Thumb estimates for your harvested and washed yeast. Fix, in Principles of Brewing Science, states that one can expect about 4.5 billion cells in 1ml of washed yeast or yeast solids. That's simply a count of how many cells can fit in a given amount of space. Of course, that can change, because slurry can be thin like pancake batter or thick like cookie dough; still 4.5 billion is a good estimate number.

Now, to complicate matters. While one can expect 4.5 billion cells, even in the base of circumstances about 10% of those cells will be non-viable. Here's where your ability to use the haemocytometer will come in handy: you can perform a viability test on your harvested yeast. Then it's a matter of doing the arithmetic based on the Rule of Thumb number.

Do the cell count on, say, Thursday. If it comes up not-so-healthy, that gives you Thursday night into Sunday to build up a starter from your less-than-optimal culture. If you build a fresh starter using your washed sample, you can then decant the starter 'beer' and calculate how much fresh slurry to pitch.

Make sense?

Bob

 

[Laughing_Gnome_Invisible]

Do the dead cells decay and dissipate over time? Or do they continue to build up as yeast is re-used?

 

[Bob]

Much of 'stuff' from dead cells is metabolized by live yeast. This is the dreaded 'autolysis', in which process the live yeast throw off some very weird flavor compounds.

However, autolysis is practically only a problem if the yeast is stored in warm conditions or for very, very long times under cold conditions. If the colony is chilled to dormancy, autolysis takes quite a long time to develop.

Dead cells and other detritus tends to build up with every generation. That's why washing is important to long-term viability. You can pitch out to ~10 generations, practically speaking, without washing. But washing is best for the home brewer.

Cheers,

Bob

 

[Laughing_Gnome_Invisible]

Much of 'stuff' from dead cells is metabolized by live yeast. This is the dreaded 'autolysis', in which process the live yeast throw off some very weird flavor compounds.

However, autolysis is practically only a problem if the yeast is stored in warm conditions or for very, very long times under cold conditions. If the colony is chilled to dormancy, autolysis takes quite a long time to develop.

Dead cells and other detritus tends to build up with every generation. That's why washing is important to long-term viability. You can pitch out to ~10 generations, practically speaking, without washing. But washing is best for the home brewer.

Cheers,

Bob

Soooooo.... I obviously want to remove as many dead cells as possible....At what level do dead cells rest in the slurry when they come out of suspension? I ask this because I am wondering if my already washed and refrigerated yeast would benefit from re-washing before making a starter if that is at all possible. My concern being, that I want to know that I have done everything possible to maintain the highest possible ratio of viable/dead yeast. I hope that makes sense.

 

[Bob]

I wouldn't worry about your already-washed sample, as the process of washing in theory rids the sample of trub and other detritus. I'd just build up a starter from a portion of that sample. The process of building up the colony should reduce the percentage of non-active cells to an amount so small it won't make a difference.

You dig?

Bob

 

[Laughing_Gnome_Invisible]

I dig.

Cool. I was hoping for an answer that meant I didn't have to worry about it......And I got it!

 

[supermoth]

So, N3QX, would it make sense to make lots more starter than I need before doing a cell count? Once I know how many cells per mL, I can decide from there how much starter to pitch, without having to go back and regrow my starter if my cell count is too low. That way I can put starter on the stir plate Thursday, measure it Friday, and brew Saturday. Would you foresee any adverse effects from doing it that way? And is one day long enough to grow it up, or is 2 better?
Thanks!

 

[McKBrew]

I'm not sure how techical you are trying to get. If your only real concern is pitching enough yeast, then the yeast pitching calculator at Mr. Malty might be all you really need.
Mr Malty

 

[beerthirty]

I just count them one at a time

I tried that but ran out of fingers and was afraid I would lose count if I stopped to take off my shoes.

 

[supermoth]

I'm not sure how techical you are trying to get. If your only real concern is pitching enough yeast, then the yeast pitching calculator at Mr. Malty might be all you really need.
Mr Malty

honestly, McKBrew, I'm getting WAY more technical than I need to, but sometimes it's fun to geek out and do a little science! Especially when I have all the equipment I need and Fridays are really slow at work

 

[vespabrew]

I am doing my first starter and I am not sure if I am doing it right. I followed the steps for the wort and pitching, I think that is okay, but I am not sure if I accidently carbonated it. I put a tin foil cover on, but I pretty much sealed the bottle off. I am now at hour 46 of 46. While at work today the wort went from brown to tan. All the little yeast build up at the bottom seems to have depleted. When I shook it this morning it overflowed - left it covered pretty tight last night. Can I still use this starter? is this what it is supposed to do? I am trying to make a starter for a tripel so i need the count pretty high and if I just damaged my yeast I want to start again before I ruin the wort.
Thank you for any help. I am severely stressed.

 

[Bob]

So, N3QX, would it make sense to make lots more starter than I need before doing a cell count? Once I know how many cells per mL, I can decide from there how much starter to pitch, without having to go back and regrow my starter if my cell count is too low. That way I can put starter on the stir plate Thursday, measure it Friday, and brew Saturday. Would you foresee any adverse effects from doing it that way? And is one day long enough to grow it up, or is 2 better?
Thanks!

Well, yeah, it would make sense. You don't want to pitch the entire starter anyway; I know it's mentioned in the literature, but it's never made sense to me. Why pitch all that diluent into your beer? Chill the whole starter flask, decant the starter 'beer', and pitch the slurry.

So: If you want to ensure you have enough yeast for a Saturday brew, first calculate how much slurry you need. You can use the Mr Malty online pitching calculator or you can do the arithmetic yourself - see my brief tutorial in the HBT Wiki.

Once you've determined how many ml of yeast slurry you'll need to inoculate your wort, you can estimate how much bother you'll need to go through with your starter. If, to follow the Wiki example, you determine you need 228 ml of slurry, you need to modify the amount because your starter slurry is a lot more pure than slurry harvested from a ferment. Harvested slurry is only about 25% yeast; your starter culture is - should be - almost 100% pure. So you can reduce the amount needed accordingly. If you want to be conservative - and who doesn't? - call it 80% pure. And since 1 ml of yeast solids contains approximately 4.5 billion cells, you can easily compute the amount of slurry you require.

Brewing up the starter in a measured container means you can start your starter a week before brewing. If you discover the first go-round has produced enough yeast, just cover it and keep it refrigerated. If the first go-round hasn't produced enough, you've got several days to step up the starter.

Brew it up, ferment it, chill it, see how much slurry settles out. If you need more, repeat. Simple!

Bob

 

[WBC]

If you want to really get into yeast then this article on Maltose Falcons website is really helpful. I now have a microscope and a hemocytometer and use them for counting and when I really want to know how my yeast is doing. You can see if there is bacteria too. If you really love brewing beer like I do then this is a great way to do it. I bought my 1000x microscope on EBAY and the hemacytometer too. The microscope was about $200.00 and you can get one for less than that but I wanted binocular style with a camera mount. Hemacytometers are under $70.00. Some petri dishes and agar are also needed for yeast ranching and a nichrome wire is nice for handling the yeast. You also need some small test tubes for diluting the sample to count yeast. Once you get used to this it is easy to know the health and numbers of yeast cells per ML of sample. The ability to know if you have bacteria is priceless. Yes the price is a bit high to get started but you can maintain a nice group of yeasts and almost never have to buy yeast. I would never recommend this to people who don't like technical activities as it does take patience and persistence to obtain good results when yeast ranching.

 

[Laughing_Gnome_Invisible]

You lost me at $200

 

[Bob]

I forgot gnomes are cheap.

Odd, though, that this situation should have come up. According to various online reference sources, gnome "is said to derive from the New Latin gnomus and ultimately from the Greek gnosis, meaning knowledge."

Which means you are hereby disqualified from asking any more questions, since you're supposed to know everything and....well....all that.

Either that or you're not really a gnome....are you?



Bob

 

[supermoth]

ok, so I started my starter Wednesday, put it on the workplace stir plate, and looked at it under the microscope with the hemacytometer this morning. I calculated that I have 170 million cells per mL, which means I'd need just under 500 mL for my 2 gallon batch I'm doing tomorrow. The 500 mL is settling in the fridge right now. I got to see lots of the cells budding, it was so cute! Little yeastlings!

 

[Islandboy85]

I wonder if I could bribe someone at my fiance's hospital to check my yeast with some homebrew...that would save me a lot of hassle buying and storing all the extra equipment.