From the HBD Archive
From: Darryl Richman <darryl@ism780c.isc.com>
Subject: re: dry v. liquid yeasts (was 200 gallons)
Date: 1989-07-26 15:42:13 GMT

From: "Allen J. Hainer" <ajhainer@violet.waterloo.edu>
" I also had an interesting conversation about yeasts with Kelly. According
"to him, the major difference between dry and liquid yeasts is the way they
"are started. Dry yeasts are usually pitched directly into the wort. Because
"of the packaging, liquid yeast is usually started before being added to the
"wort. If dry yeasts are started before being added in, they will perform
"as well as liquid yeast (he still used liquid yeast). This is because
"most of the unwanted flavours are produced by the yeast in the first hour
"or so. This seems to agree with Papazian who says that the yeast produces
"esters only at the beginning of fermentation.

The major difference beween liquid and dry yeast is that liquid yeast is
handled properly. Brewer's yeast does not sporulate. It does not take to
drying and rehydrating. Furthermore, cheap dry yeast comes from yeast
that breweries no longer consider clean enough to continue to pitch. The
drying process kills a large amount of the yeast and thereby emphasizes
any thermophilic wild yeast or bacteria that may be present. Those yeast
that do survive are more likely to mutate. This is why dry yeast is such
a gamble. You may have gotten a package of perfectly good yeast that the
brewmaster threw out because he was conservative. Or you may not.

" Kelly also told me that culturing yeast from one batch to another was very
"important. From his experience, the yeast actually improve after three or four
"batches. This is because the stronger yeasts are the ones that survive. He
"has been able to keep some yeasts going for up to fifteen batches before
"mutations start to detereorate the quality of the beer (producing sulphers).

This theory is flawed, however, because any wild yeast that might be
present will certainly have better vigor than the specialized brewer's
yeast. Eventually they will overcome the brewer's yeast and produce
thinness or off flavors/aromas. (This will happen anyway, because you
cannot guarantee sterility and purity, but the difference is that you
know that the first pitch is pure, and you are likely to be able to
repitch several times safely without a tremendous amount of care. I
have routinely pitched the same yeast into 5 batches. If I were brewing
twice a week, with professional equipment in a real brewery, I would
feel secure doing it much more often.)

--Darryl Yeast Bigot Richman

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