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I ordered four extracts from NB and received four Wyeast liquid yeast smack packs. There website specifically recommended against purchasing liquid yeast from them during the summer but I did so anyways.

The yeast/package was shipped on Monday and arrived Friday night, where I immediate smacked two of the packets and put the other two in the fridgerator. The two I smacked that night inflated as normal and I made yeast starters out of them, which I just pitched yesterday.

After pitching yesterday, I took the remaining two smack packs out of the fridge (both are Wyeast 1084 Irish Ale), smacked them, went to a movie and when I came back they were not inflated. I went to bed, and 8 hours later they were still not inflated. I made yeast starters out of them this morning (and verified the inner pouch was punctured), and its been about 8 hours now and there is no activity.

Is it just a coincidence that the two smack packs I used last week right from the UPS package inflated while the two that I had stored in my refrigerator for a week did not?

Main question: Does a smack pack which does not inflate suggest that the yeast died, or rather became unusable?

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  • An important detail when discussing yeast, especially liquid yeast is the manufacturing date or BBE. Can you provide these dates for the various packs?
    – mdma
    Jul 8, 2014 at 16:50
  • @Mdma Yes I'll dig through my trash after work :)
    – Matthew Moisen
    Jul 8, 2014 at 17:17
  • I have had these same yeast die on me, although in my case is was in the fridge for >6 months. I smacked, let it sit, put some in a starter and few drops on an agar plate - nothing ever grew.
    – Pepi
    Jan 20, 2015 at 4:26

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I'd say you were too impatient. There's no reason to assume that the pack will inflate that fast. The ROT is to give it one day for every week past manufacture. So even if the pack was only a couple weeks old, that would have been at least to days for it to inflate. And 8 hours in a starter is too soon to determine there's no activity. The packs might or might not have been OK, but you didn't wait long enough to find out.

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  • Yes, always check the manufacturing date to set your expectations of how quickly it will start.
    – jalynn2
    Jul 7, 2014 at 16:39
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    @DennyConn 36 hours in and I am seeing activity.
    – Matthew Moisen
    Jul 8, 2014 at 2:04
  • I'm not surprised.
    – Denny Conn
    Jul 8, 2014 at 14:41
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A pack that does not inflate could be ok. Some strains are slower to start. But, if you made a starter and there's still no activity, the yeast may be inactive. I wouldn't risk it in my batch. I'd get another pack or 2. Maybe throw in a dry yeast.

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I'd say it was the fact you put it in the fridge, which will cause the yeast to go dormant. I usually leave for at least 24 hours if they have been stored in the fridge.

I think the yeast were dormant, not dead, and needed some more time to get up to speed compared to the packs that were not put in the fridge.

If you had left the pack 72 hours and still no result then that does indicate yeast were not viable. But in your case, I think it was simply too little time before pitching into the starter.

Also WLP004 can be a slow starter - I have had lag times in excess of 48 hours with that strain.

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  • I have serious doubts that putting the yeast in the fridge had anything to do with the problem. I keep Wyeast in the fridge for weeks or longer before smacking it and it's never seems to have any effect on how long it takes the pack to inflate. AAMOF, storing it in the fridge is the recommended method.
    – Denny Conn
    Jul 7, 2014 at 19:44
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    @mdma good news -- it has been 36 hours and I've spotted activity in my two yeast starters.
    – Matthew Moisen
    Jul 8, 2014 at 2:03
  • @Denny, so you think that if you smacked two packs - one cold, and one at room temp, they would both be at the same level of inflation in 8 hours time? Common knowledge says the warm one will start sooner, since it doesn't need to warm up first. While storing in the fridge is the way to go, it also says on the instructions that the pack should be incubated at 70-75°F (21-24°C). (wyeastlab.com/hb_productdetail.cfm?ProductID=16)
    – mdma
    Jul 8, 2014 at 15:28
  • Yes, but incubation is after you smack it. In that case, both would be at room temp. while one that was at room temp before smacking might start to swell a bit before one that was stored in the fridge, after a couple hours there would be equal activity, given identical packs to start with.
    – Denny Conn
    Jul 8, 2014 at 16:27

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