Yeast in Storage: Viability and Vitality

I really, really want to thank you for conducting this study. The topic of an appropriate yeast die off rate for packages of liquid yeast (Wyeast smack-pack and White Labs tubes) is of great interest to me.

I am not a scientist by profession so I do not have a lot of experience is setting up experiments. Hopefully others (e.g., @mattbk and @phattysbox ) will chime in with their thoughts/ideas.

I took note of: “I currently have a starter of 1056 growing. I will then split it into 14 different portions. For the next two months I will open a bottle once a week and test both its Viability and Vitality.” My read is that you intend to bottle starters, is that correct? Does a difference in packaging (i.e., smack-pack, tube, bottled starter) have an effect on yeast die off rate? In other words, will the same percentage of yeast die off in a factory sealed smack pack as would occur in a bottled starter?

In prior discussions with mattbk he made mention that the accuracy of yeast counting: “but an experienced technician with good tools and an adequate dilution scheme should have a measurement uncertainty of around 5-15%”

Cheers!

Jack

 

Thank you @LeeryLeprechaun !!! I'm very excited to see what the results are!

God speed.

 

Damn.. Very big thank you for doing so..

Looking forward to seeing what you find out.

 

So you will use 8 samples in the first 2 months, can you stretch out the remainder so you have at least one sample at 6 months? I sometimes find yeast in the back of my fridge that are 6-9 months old. It seems to be a coin flip on whether or not I can bring them back to life at that point. I would definitely appreciate a more scientific approach.

 

“I would like to test Wyeast and White Lab samples of varying dates but as you can imagine that would get expensive very quickly. To avoid this expense I grew up my own starter.” I understand and appreciate that.

The discussion point I wanted to make was that yeast die off rates can be influenced by the media in which they are stored. For example, I do not know how to classify the storage media of a Wyeast smack pack (I do know they have packs which include yeast nutrient and wort in the enclosed packs). I also don’t know exactly what the media is within a White Labs tube. I am wondering whether the yeast die off rates in the Wyeast media, the White Labs media and your starter wort in a bottle will have a common yeast die off rate.

Please conduct your experiment and report back your results. As I stated in my prior post I am thankful you are willing to conduct this study.

Cheers to you sir!

 

For those keeping track: the viability would be 85% using a typical online calculator. (note that those models assume yeast stored in packs/vials, not a starter - you may argue amongst yourselves whether this is represents a best or worst-case scenario - either way - this is killer data.)

 

Would someone mind explaining to me the difference between viability and vitality in practical terms?

 

Viability is how many yeast are alive and vitality is how healthy they are/how well they can handle fermentation.

 

Just curious , did you ensue that the 1056 starter was finished with fermentation before aliquot ing into your storage bottles ? If not, you could be grossly over estimating yeast health as they would have a sugar source for propagation during cold storage.

 

This is good stuff

Would you get similar numbers from rinsed yeast from a previous batch?

 

Thanks for doing this. Great info/resource. Looking forward to seeing more data as the process continues.

 

Just caught this thread. Great experiment!