hist-brewing: DMS, infections in Mead, and wild yeasts

NATHAN T MOORE NTMOORE at SMTPGATE.DPHE.STATE.CO.US
Thu Jul 8 08:32:22 PDT 1999


Eric wrote:
>>DMS or dimethyl sulfide, is not the product of bacteria. 

I was expecting to get called on this one, I still dont have my literature in
front of me so I did a quick search on the HBD and found a post by Al of
all people.  I'll quote it below.

"There are primarily two sources for DMS, bacteria and the malt.  The
bacteria that generates DMS is called Obesumbacterium Proteus.  You
may have had wort infected with this bacteria all along, but since
this bacteria's activity is mostly during the earliest stages of
fermentation, when the pH of the wort is greater than 4.5, a longer
lag time on this particular batch may be all that was needed to get
the DMS in the final beer above the 30ppb human detection threshold.

Another source for DMS is from the SMM that is created when malt is
germinated.  During the kettle boil, virtually all DMS that is created
is boiled-off.  If you cover the kettle or if the boil is not a rolling
boil (just a simmer) you can retain enough DMS to detect after
fermentation.
Also, as you mentioned, fast cooling is essential to minimizing DMS
in the wort because when you take the kettle off the boil, DMS still
continues to be produced until you cool the wort below 140F, but is no
longer being boiled-off."

Nonetheless, I did miss speak when I said that bacteria was the most
common cause, Eric is probably correct in that slow cooling is probably
the more common source.

Also,

Ulfin writes in response to my claim that lag times are not as risky with
mead

>>Not sure why you would say that.  Do you think the glucose in
honey possesses some unique resistance to wild yeast?

Once again, I am not sure on this so I hope someone speaks up.

First of all, bacteria that form DMS and many other bacteria do not seem
to survive at low pH common in our musts.  And, while wort is the ideal
home for bacteria, must is not as inviting.  However, there is probably
more to it then that, and that does not even answer Ulfins question about
yeast.  Why else is it that meads have less infections then beers?  I have
read long time mead makers claim they use no sanitation at all, although
this is probably not ideal, a beer maker would have given up after the
first batch of swill that they made (unless they got lucky and caught an
exciting mix of wild strains).  And I do not think I have ever made or had a
noticably infected mead. 

AND FINNALY,

 Ulfin writes in response to me:

>>One example is making fruit wine and ciders with the natural yeasts on
>>the fruit.  Very slow start, all kinds of exposure to beasties, but the
>>results are often better then anything you could make with store
bought
>>yeast.

>Substitute "rarely" for "often" and I'd agree with you 100%.
>Wild yeasts on fruit are seldom single strains, are almost
>never saccharomyces cerevisiae, and almost always have some>
major character defect.

I strongly disagree here,  Although I have only made a few wines this
way, others do it as a religion and swear by their results.  Yes, it may
not be scientific and there is a level of risk to it, but you can make
consistently make good fruit wines with natural fermentation, no matter
what the "science" says.  The best fermented beverage I have ever had
was a pie cherry wine made by an old man in Oregon who thought a
sanitizer was hot tap water and who had never put store bought yeast
in his wines...for 50 years or so, and his father before him.  Another
example is the AHA Cider maker of the year a few years back who
thought it sacrilege to put store bought yeasts in his cider.

Nathi


 

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