So. This is not an essay or technical paper on reduction. Rather, it’s a few thoughts, prompted by a glass of wine.
Reduction is, of course, a misnomer. It refers to volatile sulfur compounds produced by yeasts during fermentation, and it is perfectly possible to have a wine showing both volatile sulfur compounds (reduction) and oxidation
I have recently had three red Burgundies from the same producer, all 2010s, which have shown marked reduction. The latest was this evening, and the wine was close to undrinkable, although I think this is a problem that may resolve in time. Besides, this was a cask sample.
Reduction is one of the most interesting wine faults, because it’s often not a wine fault. The wine this evening didn’t have the eggy hydrogen sulfide reduction, which is nasty. [Anyway, I rarely come across that in finished wines.] It had a more complex reduction, with strong matchstick, spice and flint notes.
A quick test with an old copper penny (from 1966, when they were still made of copper) removed the reduction almost completely, suggesting it is mercaptans (aka thiols) rather than disulfides (which can’t be removed this way). I think that modern pennies are actually copper plated, so they should work as well, but to be sure, I prefer to use an old one.
What is interesting about reduction is that not only does it change the nose of a wine, but it also changes the palate. It makes it less elegant, more savoury, and distinctly tight and grippy. Even without a lot of evidence of reduction on the nose, you can find some changes on the palate of reduced wines.
I think that reduction is actually pretty common. More common than we think. But I also think it can add wonderful complexity to some wines. I don’t like it on Pinot Noir, but I quite like it on Syrah. Most of all, I love Chardonnay with a bit of matschstick reduction. It just seems to work so well.