Oxygen absorbers

I have not seen anything about oxygen absorbers being used by the wine industry. They usually use an inert gas such as nitrogen to flush out air when they feel a need to do so. There are very effective oxygen absorbing compounds sold for chemical research, but I have not heard of these being used by the food industry other than for research purposes. Some of these would not be safe around foods, and any that were might require very expensive testing to gain FDA approval for food use. Wine itself, especially red, can absorb oxygen, and any oxygen in the neck of the bottle probably is consumed fairly rapidly. The main problem then is to have a very effective seal so that very little more air can leak into the bottle.Some oxygen exposure seems to benefit many reds. They often are exposed to air when being made and aging in oak casks. This seems to soften and smooth the wine, provided there is not too much contact with air. Thus I doubt if the small amount of air sealed into a red will have much effect on the quality of the wine in the long term. Leaky bottles are another matter. Wine makers who worry about the oxygen in the air in the neck of the bottle sometimes use nitrogen to flush out the air. An oxygen absorber might be more useful for beer or fruit juices that do not contain large amounts of oxygen-hungry compounds such as found in red wines.

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May not be exactly what you're thinking of, but SO2 is used in wine to prevent oxidation.

Andy

Thanks, but it was my impression that SO2 was used to kill off wild yeasts and possibly other unwanted critters (g). I don't really know how it would prevent oxidation unless you used it displace oxygen and I suspect that would lead to unwanted acidification.

Actually, SO2 (or metabisulfite as it's usually used) reacts readily with oxygen to form sulfate (oxidation of sulfur IV to sulfur VI) and water. The reaction is:

SO2 + H2O --> H2SO3 + 1/2O2 --> H2SO4

Mark Lipton

Yes, SO2 is one of the many compounds that will react with oxygen, and it is used in fairly small quantites in making many wines. However, it can be rather unpleasant in taste and smell if much is used. Also it may cause health problems for a few people. I doubt if it would be approved for use in food if it were just now being introduced. However use goes back long before most countries had many laws concerning food additives. The bright red "Maraschino" cherries sold in the US for food decoration when I was young often reeked of SO2. Ascorbic acid also will combine with oxygen. It often is added to fruit before freezing to prevent browning. Ascorbic acid, aka Vitamin C, is needed by all of us and tolerated in fairly large amounts. However it is not as good a disinfectant as SO2.

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Not "many", but all, except for the minute amount of totally sulphur free wines (which would be labelled as such, as this would be their USP). The problem with the latter is their life-span, that can be counted in weeks, seldom months, never years.

M.

If I recall my high school chemistry correctly, the last compound in the above equation is sulphuric acid, not something I would like to consume in any quantity, no matter how small.

Vino

Keep in mind that I've shown the reaction in its acid form, but at the pH of wine the reaction would be:

NaHSO3 + 1/2O2 --> NaHSO4

(bisulfite) (bisulfate)

The sodium bisulfate formed in this reaction is an FDA approved additive to food. The major problem with sulfuric acid is just that it's so strongly acidic that it damages tissue; bisulfate, being far less acidic, is harmless.

HTH Mark Lipton

Oh, I think SO2 would be easily approved. It is very useful in preserving a wide range of foods including wine and safe for the vast majority of us. Now, *alcohol* getting approval, that's a different story ;^)

Mark Lipton has already given the chemical equation involved but I thought it should be noted that you are also correct. S02 has multiple uses in winemaking. It is often used at crush for the reason you mentioned, although I believe the operative word is "stun", not "kill" since the wild yeasts aren't actually killed. The idea is to suppress the wild yeast population in order clear the field for introduction of a cultured yeast that has been selected in part for its SO2-tolerance. Most "free" SO2 is consumed during primary fermentation. Once malolactic fermentation (which cannot stand much SO2) is complete, SO2 levels are bumped back up - and often again just before bottling. The purpose then is partially to prevent unwanted microbial activity in the bottle but the more important one is to prevent oxidation. SO2 has the effect of scavenging oxygen from the wine through the reaction Mark detailed; it is mostly by preventing oxidation that SO2 makes wine ageable in terms of years rather than months.

- Mark W.

That's exactly what it is, and you drink a little of it in every glass of wine - including the wines made without added sulfites.

It's not dangerous in the concentrations present in table wines.

Look at it this way: Your stomach contains hydrochloric acid, at pH ~3, which is present to break down the food you eat into digestible liquids. You certainly wouldn't care to drink pool acid, but it's really the same stuff that naturally occurs in your stomach - just in lower concentration.

The same principle applies to sulfuric acid in wine.

Tom S

Actually, ascorbic acid has been discounted as a long term anti-oxidant for wine. I can't remember the details, but it actually contributed to oxidation after a period of time. I could probably dig up the details if anyone is interested.

I don't think many (if any) wine makers are currently using it. Supposedly, it's ok to use ascorbic acid in combination with SO2, but then why not just use SO2.

Andy

I have also read the same (but don't remember where).

Ascorbic acid is still occasionally used in "problem" wines. If a wine develops a disulfide problem due to incomplete or non-treatment of a mercaptan/hydrogen sulfide problem, ascorbic acid is required to break the disulfide bond so that copper can be used to treat the offending odor. Obviously this is only done as a last resort, but the effect can be dramatic.

Tom S

I don't doubt the validity of what you say. Sometimes (maybe most of the time; mabe ALL of the time) it's best to ignore what happens with the stuff we put into our stomachs and simply enjoy the pleasures associated with its getting there.

Vino

I suspect there are exceptions.

Back in the early part of the 20th Century there was a patent elixir on the market that supposedly had remarkable curative powers and gave its consumer a warm feeling of well being - a sort of inner glow, as it were.

The product was called "Radithor" or some such. The active principle was radium salts.

Tom S

Yes. Thanks. I forgot about about.

Of course, you still need to make sure the SO2 level is sufficient to protect the wine from oxidation.

Andy