Alex Maltman of the Institute of Geography and Earth Sciences at the University of Wales, who has written extensively about soil and wine, presents a thorough and lengthy synopsis of “minerality” in Practical Winery & Vineyard (printed as part of Wines & Vines).
This carefully reasoned analysis focuses on the scientific challenges to an idea the author describes as “simple and romantic.” Noting that the “mineral” descriptor “has no place in the science-based schemes on wine aroma, mouthfeel and flavor,” he points out that the wine press has nevertheless embraced the term. Maltman recognizes a direct connection between geology and “minerality” in wine might seem “plausible” at first glance. He then lays out the scientific inconsistencies, starting with the observation that minerals in soil – termed geological minerals – are insoluble, noting that vines can only take up “dissolved matter.” Nutrient minerals in the plant and wine may originate with geological minerals, but only by way of “complex, protracted” processes. There is, he says, a “major disconnect between the two types of minerals.” This “disassociation” is multiplied within the vine and magnified in grape juice and during vinification. These complex relationships, the author states, undermine the notion that “minerality” expresses the minerals found in a vineyard. Minerals in wine are present in “minuscule” concentrations and are almost all “flavorless.”
Going further, Maltman points out that “licking a mineral or rock surface” can only leave a “tactile sensation” and not a taste per se. If mineral nutrients are added to distilled water in concentrations typical of wines, humans “cannot perceive their presence.” While tasters often compare “minerality” to a “flinty taste,” the scientist explains that flint is a type of silica and lacks “any taste or odor.” Moreover, vines cannot take up “inert, insoluble silica.” Similarly, he dispels the illusion of “struck flint or of gun-flint” in a wine’s aroma, which would refer to “the smell of burning iron or steel” rather than minerals. The aroma of stone is not in fact derived from the rocks themselves, but is an allusion to “kinds of organic oils” present in soils. Last, the writer mentions seashells and fossils in vineyards, pointing out that they “bring nothing different” in terms of vine nutrition or wine composition. In conclusion, Maltman admits to the “intuitive attractiveness” of “minerality” and allows for the possibility research may uncover “complex and circuitous ways” nutrient minerals influence wine flavor. However, science indicates that “minerality in wine – whatever that perception is – cannot be in any literal, direct way the flavor of minerals derived from vineyard rocks and soils.”
Ed. I highly recommend that all wine professionals, educators and journalists read the full text of this article.