How long can yeast be left.

[loady]

I have rehydrated my yeast but my wort is still over 30 degrees and it will take a good few hours to cool. The yeadt is in a sterile enviroment.

 

[BreadMurderer]

If this yeast is in a sterile environment, like you say, then that shouldn't be an issue at all. Creating my yeast starter is done 24/48hrs before I do my actual brew day.

 

[jonnymorris]

I think your only concern is going to be temp of the yeast when you come to pitch it. I believe you want it to be similar to that of the wort.

 

[rpt]

We need to distinguish between rehydrated dried yeast and a yeast starter (usually made from liquid yeast). The latter can be left for days because there is food for the yeast to grow but the former is meant to be used within about an hour. I'm sure it will still be fine after a few hours but the yeast will be depleting their reserves.

 

[jonnymorris]

A liquid yeast starter will consume the food, i.e. ferment within 12-18 hours and once it has done do it won't grow anymore. I'm not sure rehydrating dried yeast will deplete any of its reserves seeing as it is only rehydrating and not ferementing. Either way, 15mins is ideal but I doubt an hour will cause much drama.

 

[rpt]

The instructions for Danstar Nottingham yeast say to sprinkle the yeast on 10 times its weight of water at 30-35C and leave for 15 minutes, stir and leave for 5 more minutes and then adjust it to the temperature of the wort:

Attemperate in steps at 5 minute intervals of 10C to the temperature of the wort by mixing aliquots of wort. Do not allow attemperation to be carried out by natural heat loss. This will take too long and could result in loss of viability or vitality.