Studies in Dumbness

If you're adding enough SO2 to prevent a re-fermentation of residual sugar by yeasts, then a re-fermentation by malo-lactic bacteria (of residual malic acid) shouldn't be a problem as malo-lactic bugs are far more sensitive to SO2 than are wine yeasts.
If you're (sterile) filtering to remove malo-lactic bacteria, then you'll also be removing any yeasts that could cause a re-fermentation of residual sugar since these yeasts are larger than the MLF bacteria. Typically any filtration that passes wine through a filter medium of 1.0 micron pore size or less is considered "nominal sterile" as this would remove wine yeasts. In order to remove MLF bacteria you'd probably need to pass the wine through a filter of pore size 0.45 microns or less.
[NB: This all assumes that bottling line sanitation is as it should be, with necessary steps taken prevent re-introduction of microbes downstream from the filter.]

It is my understanding that high SO2 levels in German wines are primarily vestigial, a hold over from the days before sterile filtration equipment was readily available for the average winegrower. The technology was developed in the 50s, and it took a while for the procedures and materials to morph into affordable, workable forms necessary for the use to spread. By the mid-80s, though, I think everyone in Germany who wanted to use such technologies could probably do so.
In the late 80s when I visited a number of estates in Germany there were people who were using both sterile filtration AND high SO2 additions, still adding very high levels of SO2 "as insurance", which I think was more a lack of trust in the newish technology of sterile filtration than anything else. There were also some who thought a use of very high level of SO2 for stabilization was preferable to sterile filtration. Many of these were taking the traditionalist approach.... "If the grand wines of the past were made that way then I will continue". Others were thinking beyond the simple act of maintaining the past, theorizing what benefits might actually come from such high levels of SO2. At that time Carl von Schubert was wondering aloud whether some of the complexity of great aged Riesling was due to the very high SO2s added at the outset of the wine's life.

Haven't been back to Germany in a while. so I dont know what the current thought is on this.

Regards,
 
Thanks for the post, Bruce. I have a good friend who is sensitive to it and can't get near a young German wine. In spite of that, my understanding is that the EU rules now force considerably lower levels of SO2 than in the old days.
 
Claim: "Elemental sulfur is in no sense an oxidant."

An oxidant is simply any molecule for which there exists a capable reductant. Sticking to "uncomplicated" ionic examples, note that sodium sulfide is prepared by treatment of elemental sulfur with sodium metal in liquid ammonia.

There is chemistry outside of aerobic, aqueous environments...
 
originally posted by David M. Bueker:
I will try to quiz Johannes Selbach and any other amenable German vintners (esp. Mosel) when I see them next month.
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Look forward to your report. Many must be sympathetic towards natural wine trends, but while nothing prevents them from being organic in the vines, perhaps they feel their hands are tied in the cellar because of rs, at least for the non-trockens.

There's a site (www.velier.it) that lists the (total) sulfur for some (mostly organic or BD) wines. For Clemens Busch, the SO2 for three Trockens (two of them Spatlese) is around 120 mg/l, rising to 275 mg/l for an 07 Auslese and 259 mg/l for an 06 Beerenauslese. Weingut Wittman, a BD estate, lists only Trockens at 130 mg/l.

Huet also seems to use relatively high levels, and not just for the sweeter cuves. 06 Le Mont Sec has 161 mg/l, compared to 176 mg/l for the 96 Moelleux and 231 mg/l for the 05 Constance.

06 Coulee de Serrant has 105 mg/l, whereas 07 and 08 both have 60 mg/l, so even a strict BD producer appears to vary the level of SO2 according to the vintage.
 
If there is one thing I have learned over the years it's that reading the figures (whether SO2, total acidity, rs, extract) tells me nothing about the wine drinking experience. I was fascinated with the numbers for a few years, and now I just don't care (except for price!).
 
originally posted by David M. Bueker:
If there is one thing I have learned over the years it's that reading the figures (whether SO2, total acidity, rs, extract) tells me nothing about the wine drinking experience. I was fascinated with the numbers for a few years, and now I just don't care (except for price!).
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I think, for the most part, you're right.
Although, when I'm trying to figure out how long to cellar, some of those numbers can be helpful.
Best, Jim
 
originally posted by MLipton:
originally posted by Ian Fitzsimmons:
Sorry, I should have read more carefully.

There are bugs that earn their living using sulfur as an oxidizing agent, but I gather that reaction is limited to anaerobic environments.
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Define what form of sulfur you're talking about. Elemental sulfur is in no sense an oxidant.

Non-sequitur, but in animal metabolism, does the oxidation of carbohydrates (leading to the conversion of ATP to ADP) create energy in the form of an electron flow (i.e., a current) or in some other way? (Some goes to heat, of course, but I mean energy used for work).
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Or perhaps a non-sequitur? The energy is released in the form of metabolic energy, the conversion of one chemical species to another. You're a bit cornfuzzled, though. Glycolysis converts glucose to pyruvate, thereby releasing energy that is harnessed to form ATP. ATP is the energy currency used in many different endothermic biochemical processes. For instance, ATPase converts ATP to ADP to drive the export of protons out of a cell to maintain proper pH balance in the cell.

Mark Lipton
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I was thinking specifically of sulfide oxidation, e.g.:
HS(-) + 202->S04(2-) + H(+) (sorry for the irregular notation)
I'm not a lab rat and argue here from authority, the authority being Eby discussing Thiobacillus thiooxidans - PM me if you want more detail.

As to metabolizing carbs, I believe we're saying the same thing: the energy bound up in carbs by photosynthesis (up the food web) is moved first into ATP, then released for work by converting to ADP. Perhaps I should have written "eventually leading to ..."

I see that my fancy of electron flow is misguided, however. Still, citing 'metabolic energy' sounds a bit like evoking the 'dormative principle' to explain why sleeping pills work. What form does the released energy take and how are its effects coordinated for, say, the muscular work of acquiring food? Is a pressure gradient created that drives mechanical motion? This doesn't sound right.

Really, I should look this stuff up instead of asking the board, though. Thanks for your comment.
 
originally posted by Arjun Mendiratta:
OxidantsClaim: "Elemental sulfur is in no sense an oxidant."

An oxidant is simply any molecule for which there exists a capable reductant. Sticking to "uncomplicated" ionic examples, note that sodium sulfide is prepared by treatment of elemental sulfur with sodium metal in liquid ammonia.

There is chemistry outside of aerobic, aqueous environments...
Click to expand...

Agreed. See my mea culpa to Joe. 'Twould have been better to have said "sulfides are in no sense oxidants" since my point was simply that we needed to know the form of sulfur being referred to.

Mark Lipton
 
originally posted by Ian Fitzsimmons:

I was thinking specifically of sulfide oxidation, e.g.:
HS(-) + 202->S04(2-) + H(+) (sorry for the irregular notation)
I'm not a lab rat and argue here from authority, the authority being Eby discussing Thiobacillus thiooxidans - PM me if you want more detail.
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OK, that makes sense. But please note that in your example sulfides are being used as reducing agents, not oxidizing agents. The sulfur atom is being oxidized, which is coupled to the reduction of elemental oxygen to the oxides of the sulfate ion. An oxidizing agent (oxidant) oxidizes other things; a reducing agent, conversely, does the opposite. In any redox reaction, something is being oxidized while something else is being reduced, in compensatory fashion.

As to metabolizing carbs, I believe we're saying the same thing: the energy bound up in carbs by photosynthesis (up the food web) is moved first into ATP, then released for work by converting to ADP. Perhaps I should have written "eventually leading to ..."

I see that my fancy of electron flow is misguided, however. Still, citing 'metabolic energy' sounds a bit like evoking the 'dormative principle' to explain why sleeping pills work. What form does the released energy take and how are its effects coordinated for, say, the muscular work of acquiring food? Is a pressure gradient created that drives mechanical motion? This doesn't sound right.
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Yes, we're saying more or less the same. I use the term "metabolic energy" to describe the transfer of energy through the formation of unstable (high energy) chemical species rather than through the generation of current, heat or electromagnetic radiation (to name but a few alternative forms of energy).

No problem asking questions here: I'm done with teaching until the Fall.

Mark Lipton
 
Yes, after sulfide oxidation, the sulfur is with the reduced product.

The free energies released by reactions going from less to more stable molecules must be converted to electricity or mechanical work at some point.
 
originally posted by Ian Fitzsimmons:
Yes, after sulfide oxidation, the sulfur is with the reduced product.

The free energies released by reactions going from less to more stable molecules must be converted to electricity or mechanical work at some point.
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Of course. This is why I refer to ATP as "energy currency." It's used to fuel many mechanical processes. For instance, ATPase employs an absolutely fascinating mechanism to pump protons across a plasma membrane. If you haven't seen the structural model of ATPase, you should take it upon yourself to find it: it's absolutely fucking beautiful. Likewise, ABC transporters such as pGP use ATP to fuel the exportation of small molecules across plasma membranes. There are many more instances, of course, but these two give you a taste for the sort of mechanical work ATP is put to in vivo.

Mark Lipton
 
Thanks again, Mark. Yes, I know ATP stores energy at a scale that makes it practical for celluar operations, relative to carbohydrates, and facilitates relatively efficient release of the stored energy. I don't know about the proton pumping, though - is there an animated video of the process available on-line, or can you recommend an account in print? I wonder if it's at all related to tree root proton pumping, which is part of their soil nutrient uptake protocol, and also a product of metabolic activity.

Do you have a favorite book on the topic of metabolism and cellular process that is not over-the-top technical?
 
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