Slow Yeast Starter - OK or Wild?

[DigitalGiraffe]

I made up a yeast starter on Saturday using some WLP001 that I'd washed and have had int he fridge since January (A long time I know). I oxygenated the wort prior to pitching the yeast and there was little to no activity and I'd all but given up on it. Yesterday while I was at work it came to life. Do you think it just took a while for things to wake up or is it more likely to be wild yeast? I'm only mentioning the possibility of wild yeast as sometimes I leave a 100mm sample on the windowsill and after a week or so it begins to ferment on its own?

 

[MHB]

If it's been in the fridge for 9 months or so the population and the health of the yeast would be a lot poorer than a fresher yeast. No surprise if it takes a while to kick off.
It would be a good idea to start an older yeast in a smaller starter before stepping up, probably only a couple of hundred mL and at a lower gravity (say 1.020) than for fresher yeast, old yeast is stressed yeast and needs to be coddled a bit.
Mark

 

[DigitalGiraffe]

If it's been in the fridge for 9 months or so the population and the health of the yeast would be a lot poorer than a fresher yeast. No surprise if it takes a while to kick off.
It would be a good idea to start an older yeast in a smaller starter before stepping up, probably only a couple of hundred mL and at a lower gravity (say 1.020) than for fresher yeast, old yeast is stressed yeast and needs to be coddled a bit.
Mark

Cheers Mark. Would you bin it? I have some new yeast on the way just in case.

If you have yeast stored for extended periods of time do you think there any benefits in waking it periodically in a starter then returning it to the fridge for later use?

 

[MHB]

Good rule of thumb is that if you aren't going to use a slurry in a couple of weeks, don't use it!
If you have a look at any of the yeast calculators and the viable cells over time it's pretty easy to get into a set of diminishing returns. Perhaps some other method of storage would be more suitable (like freezing) for long term storage.

I would be very cautious with restarting a slurry too often, the odds of picking up an infection would go up, the possibility of depleting the yeasts reserves are too high for comfort. I think it is important for health to run yeast through the entire life cycle and select out the yeast that sediments at or near the terminal gravity.

Without a lot of care it's easy to end up with a lot of unhealthy yeast, we as brewers would be much better off on working toward less of happier yeast.
Mark