From the HBD Archive
From: (Mike Meyer)
Subject: Can Dried Yeast Freeze?
Date: 1989-01-20 04:39:15 GMT

Here's one to chew on, especially the micro-bio types:

Have you ever had packets of dry yeast freeze, and if so, did it hurt
the viability of the yeast? My roommate started a batch the other night
using Red Star Lager Yeast, (the 'improved', 'faster-starting' strain they
supposedly switched to) and had one HELL of a time getting it to go, where
usually, we can get our yeast starters bubbling merrily away in far less
than an hour -- he ended up adding a packet of Kitzinger dry lager yeast
to the 2 pkts of Red Star, and pitching the still-sluggish mess a day later.

(I might add that this turn of events has provided me with a guinea pig
on the closed-vs-open fermentation question, as I convinced him that a
closed fermentation was the only way to ensure the sterility of his wort
until his yeast could take... Still hoping for some war stories, however...)

His hypothesis, one I am somewhat dubious about, is that our refrigerator,
which sometimes freezes, has damaged the packets of yeast that we have been
storing for the last 4 or 5 months. The decreased amount of viable cells
would therefore account for the problem. I see his point, though I haven't
any additional data until I try my next batch. Doesn't the drying process
reduce the amount of water in the yeast cell enough to prevent a freezing
temperature from rupturing the cell walls? (I do recall a microbiology
type or two on the list these days...)

Or might the yeast just be too old, regardless of storage temperature? We've
stored yeast for longer at room temperature and had no trouble with viability.

Mike Meyer

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