Are There Rocks in My Wine?

Wine Making Talk

Help Support Wine Making Talk:


Victim of the Invasion of the Avatar Snatchers
Sep 19, 2013
Reaction score
near Milwaukee
Here is something I wrote a while ago:

I have a few disjointed thoughts.

Lalvin suggests that RP15 may enhance minerality. I can't say that I know this to be the case.

I have always thought that commercial wines from Washington State and Chile's Central Valley had a pleasant degree of minerality. There are lots of kits available from Washington (see the CC Showcase series, for example) and from Chile. You could give either of those a try.

Your question made me search for what is believed to confer the mineral taste to wines. Of course, it was long thought you were quasi-directly tasting the soil that the grapes were grown in. The new school of thought is that this proposition is scientifically impossible. Instead, the thought is that, believe it or not, trace amount of thiols (AKA mercaptans) in wine are responsible. Now, thiols (sulfur-bearing compounds, R-SH) are generally a wine fault, but evidently small amounts of some of them confer a "gunflint" aroma.

Where do the thiols (i.e., mercaptans) come from? From having a must that is somewhat poor in nutrients, specifically, low in yeast-assimilable nitrogen, as I explained here:

From my reading of the primary and secondary literature, this is my understanding of H2S production and its relation to N deficiency. Proteins are made of amino acids, and two important amino acids contain sulfur. The yeast has to provide the sulfur to form these compounds to the proper organelle during protein synthesis. It does so in the form of H2S, which it extracts from more complex sulfur-containing compounds. One organelle passes the H2S off to the organelle responsible for protein synthesis.

However, nitrogen is a major component of amino acids (hence the root amine, from ammonia.) If there is a dearth of N, the organelle responsible for synthesizing the sulfur-containing amino acid cannot do its job; this results in a surfeit of H2S, which the yeast then excretes.

Note that soils that are very high in minerals, very chalky, limestone-y, slate-y, ALSO tend to be low in nitrogen. That could explain why wines from mineral-dominated soils themselves taste of minerality, although the link is surprisingly indirect.

Now, of course, I am not suggesting that you should use poor nutrient management. However, it may be that you really do want a must that is moderately low in YAN to emphasize mineral notes.