Sulfur smell from stored yeast

I have been rinsing yeast and storing in 30ml vials for several months. Now I am getting a similar sulfur smell from all of them. All are 2-4 months old. WLP001, upon opening after 4 months, foamed over heavily and gave off a strong sulfur odor. I dumped them all, thinking they were contaminated.

I recently opened a similarly stored vial of wlp530 and found a very similar odor with a bit of foaming. I made a 1L starter out of it and found that the starter smelled fine after it really got going on the stir plate. I pitched a vial in a small test batch and it smells/tastes great.

Out of curiosity, I opend a small mason jar of 001 tonight which is 5 months old. It vented a bit of pressure and had the same smell, just not as strong. All were rinsed with boiled water and containers were thoroughly boiled as well. Any thoughts on what is going on?

Yeast die over time and will produce a sulfur odour. Just make a starter from them and you will be fine (as you found out). Lager yeast will make a strong sulfur odour during fermentation that clears quickly with conditioning and lagering.

GT

How about the excess gas? The liquid in the 001 vials was crystal clear and the yeast had only slightly darkened from that fresh off white color. They literally foamed over until most of the contents were gone. I am just curious about the reaction taking place.

Maybe fermentation creating CO2?

GT

Don't know, but it seems like there was nothing in there to ferment. That's why it was so surprising - clear, deoxygneated water + suspended yeast doesn't sound like a recipe for a spewage.

Dead yeast = new substrate for biological processes including fermentation.

GT