From the HBD Archive
From: "Brett Lindenbach" <Brett_Lindenbach@qms1.life.uiuc.edu>
Subject: sterile vs. sanitary
Date: 1992-05-20 18:39:25 GMT

Subject:
Time:12:05 PM
OFFICE MEMO sterile vs. sanitary
Date:5/20/92
After my last post regarding the importance of scaling up starters, I
received a rash of letters with regards to the following statement:

> most homebrewers do not sterilize, but only sanitize their wort
through boiling.

For instance, someone wrote:

>I would have said that an hour's boil at something slightly above 100C
would be sufficient to sterilize the wort; it's all the other tools
that
are merely sanitized....

I would like a chance to comment and hopefully clear up any mis-
conceptions out there. The argument begins with semantics: the
definition
of sterility is the *complete* destruction of all living organisms.
ie there is no such thing as "partial sterility," it is an
all-or-nothing
thing. Anything less is considered to be sanitized, which can be
measured
in degrees. While sterility may seem like an impossible ideal, it is
a goal that can be reached. The two main factors are temperature and
exposure time. A guy named Bigelow once studied this topic, and came up
with the idea of Thermal Death Time, the shortest period of time
required to kill a known microorganism at a specific time. He then went
about calculating various TDT's. What he found is at 100C (Chip-I don't
know
about you, but my water boils at this temp (although I realize altitude
and
[sugar] will affect this, but usually lowering it)), it takes 788 to
834 minutes (average) to insure destruction of 15 typical thermophiles.
I sure hope nobody boils their wort this long! How do microorganisms do
this? Spores!
Anyways, the long and short of it is that the longer you boil, the
closer
to sterile you approach, but please do not confuse the two.
Why am I such a stickler? I hope that through brewing, people can
better
appreciate the biology behind it all. Cheers! -BDL

(brett_lindenbach.microbiology@qms1.life.uiuc.edu)



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