On May 13, 2009, Brooklynguy wrote a post on his eponymous blog called "The Mosel and the Sulfur Stench" and asked his readers why many Mosel Rieslings, especially those from the celebrated estate of Joh. Jos. Prüm, in Wehlen, tend to have an off-putting sulfur dioxide (SO 2 ) smell. At a professional tasting of "2007 in Germany" for Wine & Spirits, he even describes one bottle of J.J. Prüm that stinks of hard-boiled eggs and another that smells bad, too—which, at the time, he also associated with SO 2 .

Back then, I replied to Brooklynguy's blog post a few times. My comments, however, could have been more thorough and better written. I also didn't know if the Prüms vinified some of their wines in pressure tanks as well.

It turns out that J.J. Prüm ferments and ages its Mosel Rieslings exclusively in stainless-steel tanks and sulfur levels have been no higher than most other producers in the region. Katharina Prüm has pointed this out more than once. As I indicated in one of my comments, the smell is often a sponti stink.

There's no question that some Mosel winemakers use high amounts of SO 2 . Many of these are for sweet wines, but not always. Other winemakers have backed off with the amount of SO 2 in the last several years. The stink from J.J. Prüm's wines isn't always one of SO 2 , though. The smell is usually different from the pungent sulfur odor of a struck match. In addition, the still very young (and very good) 2012 Willi Schaefer Graacher Himmelreich Spätlese and Graacher Domprobst Spätlese showed a little SO 2 on the palate in November 2013. In these instances, the SO 2 is noticeable, but it usually goes away with some air or time in bottle. Yet if Brooklynguy smelled hard-boiled eggs, this reduced note usually indicates hydrogen sulfide (H 2 S).

One hypothesis for this "sulfur smell" comes from an expert taster who says to Brooklynguy: "Do you know about the sulfur smell with Mosel, slate, and native yeasts?" It turns out, that the experienced taster is Peter Liem, who knows German Riesling, especially from the Mosel region. Between 2000 and 2002, he published with Kirk Wille, who works for Loosen Bros. USA, a bi-monthly electronic magazine called Riesling Report. Peter clarifies his point in a reply to Brooklynguy's post:

So as the critic who spawned this whole discussion, I suppose I ought to clarify myself. I didn't say that it was sulfur, I said that it imitated sulfur, because if you've never smelled this particular component before, the smell of sulfur is usually the closest associable thing that you can relate it to. In fact, it is an identifiably and distinctively different smell than either SO 2 or H 2 S—I disagree with brooklynguy that it smells of eggs. It has nothing to do with sulfur, but rather the sponti stink that Lars refers to. It can be accentuated by reduction, but it is not purely a reduction character either. For whatever reason—I'm not a scientist so I can't tell you—it tends to be particularly pronounced in young rieslings from the Mosel-Saar-Ruwer that have been grown on slate and fermented by ambient yeasts. (Best and most consistent examples are JJ Prüm and Nik Weis.) Unfortunately, the vast majority of people, including most wine professionals, mistake this odor for sulfur, but if you take the time to compare the two, it is easily distinguished.

Afterward, I asked Dr. Ulrich ("Ulli") Stein, what he thought might cause the J.J. Prüm wines to have a pronounced stinky aroma. On May 18, 2009, Ulli, who didn't have a lineup of 2007 J.J. Prüm wines to taste and analyze beforehand, emailed me the following explanation in layman's terms, which I've retranslated into English below:

Hi Lars, It's a very complex issue and you have to have a little knowledge about chemistry to really understand why. First, there are different types of Böckser (sulfide off-flavors) that can arise for different reasons and that come about in different ways and generate a composite impression. Individual steps during vinification add up [to form this taste impression]. To begin with, there is hydrogen sulfide (rotten eggs). This can transform into increasingly complex organic sulfur compounds to form mercaptans, which then can smell of cabbage, cheese, sweat, leather, and burnt onions, among other things. There is Hefeböckser, an off-flavor from yeasts, which arises when wines are aged too long on the lees, the yeast cells autolyse, i.e., the yeasts die and decompose. Both of these [aforementioned] wine faults can take place in the same wine. Then, there is Aromaböckser, an aroma off-flavor, that is a result from spontaneous fermentation by the formation of certain aromatic substances, which may be perceived quite positive, but if the concentration is too high or if there is a combination with other substances, they can have a negative effect. Generally speaking, off-flavors are much more likely to result during spontaneous fermentations than with fermentations from Reinzuchthefen, or selectively cultured yeasts. In addition, a long—perhaps, too long—lees contact; an airtight upbringing (in stainless-steel or fiberglass tanks—i.e., no wooden casks); and high dosages of sulfur—for example, to arrest fermentation. In cellars, "ambient yeasts" can develop that may also contribute to off-flavors. If all of this is happening at Herr Prüm's, then this explains the "stench." That is to say, the following can contribute to the development of off-flavors: molecular sulfur in wooden casks, spontaneous fermentation, ambient yeasts with enhanced reductive metabolism, stainless-steel tanks, excessive lees contact, high fermentation and storage temperatures, and high sulfur dosages. A simple test would be to put in a glass of wine a copper coin, in the other nothing. If after 10 minutes the wine with the coin no longer "stinks," it's an off-flavor from hydrogen sulfide. If the coin has no influence on the wine, then a more complicated fault, the so-called storage off-flavors (Lagerböckser), exists that are difficult to eliminate and have more complex causes. The off-flavors have nothing to do with individual vineyard sites, different soil types, or different grapes varieties. It is only a matter of vinification. If too much sulfur is perceived in the wine, then this is a rather pungent odor and not "stinky." As mentioned above, it's a complex issue that is perceived very individually. Some notice every little odor deviation from a standard vinification (excluding cultured yeasts) as a Böckser, others find the "stinky aroma" not as such, but rave about the flowery, complex flavor. I hope you can understand my remarks. I think chemical formulae won't bring you much further along, but rather the somewhat popular descriptions. Of course, I can give you formulae. I had a lot of people over at my place and only had time to write something tonight. Regards, Ulli

Though Ulli rules out that slate plays a role in typical sulfide off-flavors, there might be some truth to Peter's point as regards the combination of slate and native yeasts often resulting in stinky Mosel wines, which are termed Spontis. In a recent conversation with the wine author and Mosel authority Joachim Krieger, he says that Mosel wines were often described as having a distinct "sponti" aroma from slate soils even in 19th-century books and journals. In fact, a certain term (which I'll let Joachim reveal in an essay later) was used to describe this note of fresh, lively Mosel wines back then. ♦

>> Sponti Stink

Photograph of Ulli Stein writing formulae on a Doppelstück, taken by Tobias Hannemann.