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Winemaking (rec.crafts.winemaking) Discussion of the process, recipes, tips, techniques and general exchange of lore on the process, methods and history of wine making. Includes traditional grape wines, sparkling wines & champagnes.

burnt rubber problem -- mercaptan or disulfide?



 
 
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  #16 (permalink)  
Old 12-12-2003, 05:25 PM
Ed Marks
Usenet poster
 
Posts: n/a
Default burnt rubber problem -- mercaptan or disulfide?

That's a good lesson for all of us to learn.

Ed

"Richard Kovach" wrote in message
om...
Thanks for all the info guys! I'll try and filter earlier vs later,
and in the meantime consider the carbon option.

In my case the problem came from being careless and leaving the wine
on the gross lees too long and without regular stirring. Just got too
busy with other things and pushed my luck too far. Won't be letting
*that* happen again!

Cheers,
Richard



  #17 (permalink)  
Old 13-12-2003, 06:34 PM
Tom S
Usenet poster
 
Posts: n/a
Default burnt rubber problem -- mercaptan or disulfide?


"David C Breeden" wrote in message
...
Ed Marks ) wrote:
Dave,


I'm certainly not an expert here, but here's what I was told by the Wine
Lab - they said that the aggregate copper & sulfide can separate again

after
a few months, and the only way to avoid this is to add deodorizing carbon

to
bind with these and then remove them by filtration with a polish grade
filter. They suggest trials with the carbon to find the minimum amount

that
will remove all traces of the sulfide odor and minimize the impact on

other
characteristics of the wine. In their sulfide treatment instructions,

they
state loudly: "WITHOUT CARBON, DISULFIDES USUALLY RE-EMERGE" (emphasis

is
theirs).


Ed



Hmm. Thta seems weird. I usually trust the Wine Lab, but that just
doesn't even seem coherent to me, even less actually right.


Unfortunately, they're right. I've observed this effect myself.

Tom S


  #18 (permalink)  
Old 13-12-2003, 09:11 PM
David C Breeden
Usenet poster
 
Posts: n/a
Default burnt rubber problem -- mercaptan or disulfide?

Tom S ) wrote:

"David C Breeden" wrote in message
...
Ed Marks ) wrote:
Dave,


I'm certainly not an expert here, but here's what I was told by the Wine
Lab - they said that the aggregate copper & sulfide can separate again

after
a few months, and the only way to avoid this is to add deodorizing carbon

to
bind with these and then remove them by filtration with a polish grade
filter. They suggest trials with the carbon to find the minimum amount

that
will remove all traces of the sulfide odor and minimize the impact on

other
characteristics of the wine. In their sulfide treatment instructions,

they
state loudly: "WITHOUT CARBON, DISULFIDES USUALLY RE-EMERGE" (emphasis

is
theirs).


Ed



Hmm. Thta seems weird. I usually trust the Wine Lab, but that just
doesn't even seem coherent to me, even less actually right.


Unfortunately, they're right. I've observed this effect myself.


Tom S



Hi Tom,

I wasn't disputing (or meaning to dispute) that Cu-S compounds can
decompose over time. What I was disputing was the idea that because
this can occur, it's a good idea to treat all wine you've treated
with copper with activated charcoal. THAT, to my mind, is insane.

I also pointed out that if the copper worked, there's no way to do a
bench trial to determine what amount of charcoal to add. There's no
way to look for a loss of something that isn't there.

The other possibility, for wines that have been successfully treated
with copper but then later (in the bottle) start to stink again, is
that not all (or any, if ascorbic isn't used) of the disulfides were
broken and made available to the copper. The olfactory threshold
for disulfides is enough higher than that for mercaptans or H2S
that you can have disulfides, not know it, use copper to treat
mercaptans and H2S, and later have the disulfides (under reductive
conditions) break back into mercaptans which you CAN smell.

Without having done GC/MS before treating with copper, I don't know
how you'd distinguish this situation from the one described by the
Wine Lab. In both cases, a wine would appear to have been
successfully treated with copper, but would then start to smell of
mercaptans later.

Dave
************************************************** **************************
Dave Breeden
  #19 (permalink)  
Old 13-12-2003, 11:15 PM
Rex Franklin
Usenet poster
 
Posts: n/a
Default burnt rubber problem -- mercaptan or disulfide?

Is deodorizing carbon the same as activated carbon? Ed quoted the WL as
using deodorizing while Dave referred to activated :-(

--
Regards,
Rex Franklin
"David C Breeden" wrote in message
...
Tom S ) wrote:

"David C Breeden" wrote in message
...
Ed Marks ) wrote:
Dave,

I'm certainly not an expert here, but here's what I was told by the

Wine
Lab - they said that the aggregate copper & sulfide can separate again

after
a few months, and the only way to avoid this is to add deodorizing

carbon
to
bind with these and then remove them by filtration with a polish grade
filter. They suggest trials with the carbon to find the minimum

amount
that
will remove all traces of the sulfide odor and minimize the impact on

other
characteristics of the wine. In their sulfide treatment instructions,

they
state loudly: "WITHOUT CARBON, DISULFIDES USUALLY RE-EMERGE"

(emphasis
is
theirs).

Ed


Hmm. Thta seems weird. I usually trust the Wine Lab, but that just
doesn't even seem coherent to me, even less actually right.


Unfortunately, they're right. I've observed this effect myself.


Tom S



Hi Tom,

I wasn't disputing (or meaning to dispute) that Cu-S compounds can
decompose over time. What I was disputing was the idea that because
this can occur, it's a good idea to treat all wine you've treated
with copper with activated charcoal. THAT, to my mind, is insane.

I also pointed out that if the copper worked, there's no way to do a
bench trial to determine what amount of charcoal to add. There's no
way to look for a loss of something that isn't there.

The other possibility, for wines that have been successfully treated
with copper but then later (in the bottle) start to stink again, is
that not all (or any, if ascorbic isn't used) of the disulfides were
broken and made available to the copper. The olfactory threshold
for disulfides is enough higher than that for mercaptans or H2S
that you can have disulfides, not know it, use copper to treat
mercaptans and H2S, and later have the disulfides (under reductive
conditions) break back into mercaptans which you CAN smell.

Without having done GC/MS before treating with copper, I don't know
how you'd distinguish this situation from the one described by the
Wine Lab. In both cases, a wine would appear to have been
successfully treated with copper, but would then start to smell of
mercaptans later.

Dave

************************************************** **************************
Dave Breeden




 




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