distilled water - Yeast

[iamozziyob]

So hay all, many time listener, first time poster,

question is, why is it that distilled water is not reccomended to store or wash yeast? Ive listened to the rinsing yeast show a nimber of times and still catch on the "sterile water.. not distilled"

there must be a reason but I dont know what it is...

thought appreciated

Ozzi-Yob

[ajdelange]

In distilled water the chemical potential of anything you can think of is very low. Inside a yeast cell it is high. Thus you have a high chemical potential difference across the cell membrane and this results in high osmotic pressure which can burst the cells.

[SnowGoon99]

Leave it to AJ to blow our freaking minds...

[craigevo]

AJ - I used to store yeast slurry under beer but recently switched to distilled after reading a suggestion in the yeast book. havent had any noticable difference in performance or taste since switching - but after reading your advice I now wonder if I should switch back to beer or just use boiled/cooled tap water ?

I do notice that the slurry 'looks' like its storing better under distilled, it doesnt go brown as quick. Im not sure if this is significant or not. I normally make up a 2L 'starter' and split it into 3 or 4 small jars to store in the fridge for a few weeks. A few days before brewday I bring one jar out and make a 2L starter on a stirplate. I realise there is a limit to how long you can keep slurry in a fridge and I am probably keeping it too long, but how long would you say is too long ?

[ajdelange]

Actually, after I posted I remembered that I did too. Many years back the ATCC had an active brewing club and they sponsored a lecture/demonstration on the importance of yeast for brewing. They got their head yeast guy to give a lecture and as part of it he talked about how they had pioneered storage of yeast under simple distilled water as a means for third world breweries (i.e. those without access to cryogenic storage) to store yeast samples for up to a year at room temperature. So while it may stress them osmotically , it doesn't kill them or even damage them to the point where they are not viable.