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Biogenic amine toxicity a reality for histamine-sensitive consumers

In wine, biogenic amines are a byproduct of fermentation and malolactic conversion. They’re produced by yeasts and lactic acid bacteria during the process of amino acid decarboxylation, which lowers acidity and creates a more hospitable environment for the growth and survival of the bacteria.

Of the several different amines that result, tyramine and histamine
are the most frequent and problematic; together, they can cause a synergistic reaction known as biogenic amine toxicity, characterized by headaches, migraines, nausea, vomiting, and hypertension.

While not all no- and low-sulfur wines contain elevated levels of biogenic amines (and some contain none), their presence is related in part to winemaking that involves malolactic conversion. In cellars
where biogenic amine levels are high, higher-pH musts, native ferments, and the addition of no or low sulfur at the end of
malolactic conversion are the key contributing factors.

The resulting wines allow lactic acid bacteria to remain metabolically active and produce increasing amounts of amines during aging.
Casey Graybehl, R&D winemaker and production director for the Sonoma-based Obsidian Wine Co., makes three excellent low-sulfur wines for the brand’s Rabbit Hole label: Máslás, a piquette;
Pezsgö, a pétillant naturel; and Pear Blanc, a sparkling grape-and-pear wine.

Curious about amine production, he had the 2021 vintages tested. “Our winemaking practices for the Rabbit Hole wines, which are
typically wines bottled immediately after harvest, include native yeasts, low-pH musts with only a small amount of sulfur
added pre-bottling to inhibit malolactic fermentation, and zero filtration or fining,” he says.

“While this would seem like a scenario for biogenic amines to be produced, upon testing we did not see increased levels over our more standard winemaking practices. It’s very likely that our low-pH musts are inhibiting amine production.”

José Luis Ordóñez, Ana Maria Troncoso, Maria Del Carmen García-Parrilla, Raquel Maria Callejón,
Recent trends in the determination of biogenic amines in fermented beverages – A review,
Analytica Chimica Acta

Wines with normal levels of biogenic amines alone aren’t likely to tip the scales. But sensitive consumers who unwittingly pair wines that have elevated levels with foods that are rich in amines, including
aged cheese and charcuterie, are at far greater risk for adverse reactions (alcohol itself also increases their toxic effect).

Studies have shown that a mere 10 milligrams of tyramine can trigger the onset of migraines and that, given foods with different levels of histamine, symptoms of biogenic amine toxicity can occur at levels between 75 and 300 milligrams in both histamine-intolerant and healthy consumers.

Because the consumption of biogenic amines can pose a threat to human health, the Food and Drug Administration has set a legal limit of 35 parts per million of histamine in seafood products, but no
specific regulations exist for it or other biogenic amines in wine.

In a comprehensive research paper for the Institute of Masters of Wine on the use of sulfur dioxide as related to biogenic amine levels in wine, Sophie Parker-Thomson, MW, concludes, “If SO2
additions are unconscionable for the Natural Wine movement, perhaps zero-added SO2 wines should carry a mandatory high-BA
warning unless they can prove otherwise.”

Flavor-tripping with the miracle fruit

Early humans are known to have altered their consciousness with practices that some scientists believe sparked the dawn of modern human cognition. The controversial “Stoned Ape” hypothesis suggests that our ancestors may have “eaten their way to consciousness” when they ingested the naturally occurring psychedelic known as psilocybin.

As a species, we’ve been eating and drinking to intentionally alter our states of perception ever since. For generations, the indigenous peoples of the Congo, Nigeria, and Ghana have used the fruit (and leaves) of Synsepalum dulcificum, a shrub indigenous to West and Central Africa, in ethnomedicine. The taste-altering properties of this flavorless, bright-red berry—dubbed “the miracle fruit,” it’s about the size of a coffee bean—make for a fascinating sensory experience.

Asaba or Miracle berry

Ghanaians call the berries asaba and have eaten them throughout history, but the first documentation of the fruit in Western society wasn’t made until the early 18th century, when the Chevalier Reynaud des Marchais—a French cartographer, navigator, and slave ship captain who traveled extensively along the west coast of Africa—witnessed the berries being consumed by natives before eating a meal.

In Ghana, they are traditionally used to eliminate the need for sugar or any sweeteners in items like koko (a sour, spicy porridge), kenkey (fermented white cornmeal), and palm wine. During the past few decades, Ghanaian farmers have produced asaba commercially and sold it through fair trade agreements.

Asaba contains miraculin, a taste-modifying glycoprotein composed of glucosamine (31%), mannose (30%), fucose (22%), xylose (10%), and galactose (7%) that chemically is roughly 400,000 times sweeter than table sugar. When we eat asaba, the miraculin binds to specific sweet receptor cells in our taste buds, making them easily activated by acidic foods like vinegar, lemons, pickles, and mustard and enabling us to perceive these items as sweeter for about two hours. (Miraculin doesn’t, however, affect our perception of foods with a neutral pH.) For this taster, miraculin makes lemons taste like lemonade, goat cheese taste like cheesecake, and mild red wine vinegar taste like off-dry natural wine.

Beyond tricking our palates, the potential uses for miraculin, which was first synthesized in 1989, are many; it’s currently being studied by Japanese researchers to improve the flavor of less sour foods like tomatoes and strawberries.

Its applications in sensory therapy include aiding cancer patients
whose taste perception is skewed by chemotherapy, and there are anecdotal accounts that it has helped people suffering from parosmia as a result of contracting COVID-19.

Asaba currently has “novel food” status in the EU, a classification that means a given food does not have a history of widespread consumption in the region and therefore requires a safety assessment before it can be used in food products.

And while it’s technically legal in the U.S. to buy whole or powdered asaba berries and to sell them in a restaurant or cafe, distributing items that contain miraculin is still prohibited. In a questionable ruling in the 1970s, the FDA classified the miracle berry as a food additive, meaning it would need extensive testing to gain approval for its use in manufactured food products; decades later, that testing has
yet to be completed.

Learning to Perceive

Why winetasters can’t always see the forest for the trees

Professional wine evaluation is a fundamental example of perceptual learning, a process that relies on prior experience to improve our abilities, which results in long-lasting changes to our perceptual

For example, when an expert taster evaluates a wine made from Sémillon, their perceptual state includes not only the wine they are tasting but also previous wines they have tasted and their perceptions of those wines. In short, it involves far more than the immediate impressions the wine delivers to our senses; it is intrinsically bound to our prior experiences.

While perceptual learning plays an important role in evaluating wine, there’s another phenomenon related to perception that arises from the wine itself: perceptual interaction. When our olfactory system
is confronted with complex aromas, we often perceive them as a single aroma due to odor blending in a process known as configural perception (our perception of the smell of coffee as a single aroma is just one of many examples).

At the same time, we are able to isolate individual odors within complex mixtures, as in the case of detecting a fault in wine, through what is known as an elemental perception process. The rules that govern these processes are poorly understood, but the contradiction they present raises the question: How do these types of perception facilitate or complicate matters for wine tasters?

I was recently tasting a flight of eight young semi-sweet and sweet wines from Bordeaux, all of which were made from Sémillon, vinified with some percentage of botrytized fruit, and aged in oak.

While the wines were characteristically complex, they didn’t exhibit the classic markers of orange marmalade, candied orange zest, or overripe orange that are characteristic of the style and indicate the grapes were subject to noble rot.

As I compiled an aroma profile for the wines, the absence of this descriptor was puzzling to me. Recent studies concerning the aromas of noble rot–affected dessert wines have revealed the importance of a well-known phenomenon in perfumery, perceptual blending, that results in the perception of confected-orange aromas.

Researchers identified two lactones responsible in this case: One is a compound that’s associated with oak aging (3-methyl4-octanolide, a whiskey lactone that has coconut, celery, and fresh wood aromas), the other with Botrytis cinerea development (2-nonen-4-olide, a newly discovered lactone that’s oily, coconut-like, and rancid).

While it was evident that noble rot had contributed to the sweetness of the young wines I was evaluating, the two specific lactones that result in the perception of candied-orange aromas weren’t detectable in them. Yet it’s very likely they would emerge with age.

Configural perception can present a dilemma for olfactory experts of all kinds, as specific training and repeated exposure to odors mean that we are better at elemental perception of odor mixtures; we can be better at detecting the parts than we are at perceiving the whole.

This is where perceptual learning comes into play. Sensory experts are keenly aware of this adaptation and develop the ability to move fluidly back and forth between perceiving the individual elements of an aroma and perceiving the blend.

Age drives complexity in sparkling wine

After tasting the Piper-Heidsieck Hors-Série 1971 ($499), a rare, late disgorged Champagne that spent 49 years resting peacefully on its lees, I was inspired to delve deeper into the role yeast autolysis plays in the flavor development of sparkling wine.

The wine, which is the first release of the new Hors-Série range, was made by then-cellarmaster Claude Demiere; an equal blend of Chardonnay and Pinot Noir that was sourced from 12 different Grand Cru villages and did not undergo malolactic conversion, it is characterized by concentrated aromas and flavors attributed to
the low-yielding vintage.

Émilien Boutillat, who was appointed chief winemaker in 2019, disgorged the wine in February 2021, selecting a 2019 Chardonnay for the Brut dosage of 10 grams per liter. Describing autolytic characteristics in wine that has undergone lengthy periods of aging on the lees can be tricky, largely because these aromas and flavors aren’t part of a routine sensory experience and are inherently more challenging to pin down as a result.

Because Boutillat and I were tasting different bottles that showed slight variations, we compared notes during our Zoom session to compile a summary of descriptors for the wine: delicate yet complex aromas of honeysuckle, golden hay, dry garrigue, hazelnut, quince paste, and caramel; beautifully balanced and intense flavors of toast, baked apple, nutmeg, orange zest, and prune; and chalky minerality with lemon pith that persists through an incredibly lengthy finish. For this taster, it was the epitome of mineral expression.

In addition to the Hors-Série 1971, I also tasted the Telmont 2006 Blanc de Blancs Vinothèque ($209) with Telmont president and shareholder Ludovic du Plessis. In a joint partnership with Rémy
Cointreau, du Plessis is reviving a house he describes as “a sleeping beauty” by reducing the winery’s carbon footprint and converting the estate to organic viticulture by 2025.

The 2006 Vinothèque, which spent a minimum of three years on the lees and another 12 in the cellar, is a vinous wine with miniscule bubbles and notes of marzipan, brioche, young pineapple, and lip-smacking Granny Smith apple that culminate in a toasty, savory, umami-driven finish.

While du Plessis is planning comparative tastings to zero in on the sweet spot for lees aging at Telmont, which he believes is highly dependent upon vintage, this wine is a prime example of what researchers in Tasmania and South Africa have discovered about lees aging post–secondary fermentation: namely, that the base wine plays the dominant role in determining the complexity of a late-disgorged sparkling wine and that overall wine age has a much greater impact on the development of the characteristic flavors most commonly associated with sur lie aging.

While lengthy aging on the lees contributes to sensorial changes, enhanced foaming properties, and the development of the characteristics that winemakers refer to as autolytic, these researchers found that aging base wine on or off the lees produced similar aroma profiles irrespective of grape variety.

To better understand the impact of lees aging on flavor development, expert tasters participating in the trial were asked to evaluate base wines and tiraged wines for six sensory characteristics: autolytic, spicy, toasty, honeyed, nutty, and earthy.

Chardonnay base wine aged without lees showed significantly more intense nutty and honeyed flavors and, after 24 months of aging, its concentrations of compounds associated with malty, cooked, potato-like, honeyed, and floral aromas were more than 99% higher than those in the base wine aged on the lees.

While Pinot Noir aged on the lees had intense honeyed character and positive aromas of nuts and vanilla, it didn’t fare as well over time, showing increased levels of sweaty, cheesy, and rancid notes after 24
months. Having focused only on yeast-derived volatiles, researchers are now calling for further study on the effects of fruit-derived volatiles on the perception of flavor in sparkling wine.

The duality of-smell phenomenon

Our sense of smell is based on two delivery pathways, orthonasal and retronasal; that makes it the only “dual sense modality” we possess, one that provides information about things both external and internal to the body.

When it comes to evaluating as well as marketing wines, the duality of smell has important consequences for perception. Not surprisingly, there are differences in the odors resulting from orthonasal and retronasal olfaction, even though they are processed in the same way.

While both pathways deliver volatile aroma compounds to the same receptors, the quality of those odors and our thresholds for detecting them differ due largely to the airflow patterns that the molecules follow, the temperature differences of the air traveling through each pathway, and the different enzymes found in our saliva and the membranes of our mouth and throat.

 The Nasothek is Copenhagen, Denmark takes its name from the Latin for “nose” and Greek for “container.”

Researchers at Ohio State University have determined that food odors elicit similar responses through orthonasal and retronasal olfaction—but that’s not the case with non-food odors such as floral aromas. Participants in the study were asked to match an identified scent, such as rose, with one of four unknown scents using two methods: by drinking a solution to activate the retronasal sense of smell through the internal nares, or nostrils, at the back of the throat and by sniffing from a vial to activate the orthonasal sense of smell through the nose.

Participants were presented with the reference aromas of honeysuckle, lavender, rose, and jasmine labeled in three different ways: with their common names, with their Latin or species name, and with a letter. When the routes of delivery differed, for example by smelling one sample and tasting another, participants made more mistakes, which were attributed to the differences in those delivery systems affecting their ability to match the scents.

Regardless of how the samples were labeled, the best results were achieved when aromas were introduced in the same way, either through sniffing them in a vial or drinking them in a solution.

However, researchers were surprised to find that the less participants knew about the reference aromas—that is, when they were labeled with their species name or a letter—the better their chances of correctly identifying a match when using different routes of delivery. The unexpected finding suggests that aroma detection (and thus perception) involves learning, memory, and cognitive strategy.

Researchers point to cues provided by familiar labels as the cause of cognitive
interference from the brain’s language centers, which has a negative impact on our ability to identify aromas: Even when the same aromas are activating the same receptors, albeit through different pathways, we still can’t make a match.

That discovery and its relation to the duality of-smell phenomenon is further illustrated by a small study conducted by Cornell University researchers in tasting rooms in New York’s Finger Lakes region, which showed that both the volume and value of wine sales were higher when tasting sheets omitted sensory descriptors like “dry and full-bodied, with decadent flavors of pink grapefruit, honeysuckle and lemon meringue” in favor of details on the climate in which the grapes were grown and the foods the wines in question paired with.

Their conclusion: Sensory descriptors are likely intimidating to inexperienced
consumers, who get frustrated when they can’t identify the aromas and flavors used to describe the wine. The consumers studied had a better tasting experience and purchased more wine when they had less information about the sensory attributes of the wines they were tasting.

In short, the challenges created by the duality-of-smell phenomenon in combination with cognitive dissonance are at least partly responsible for the confusion consumers experience when they have difficulty identifying non-food aromas ascribed to wines.

We’re losing Rotundone’s peppery notes

As the climate strains, wine complexity wanes

Wine professionals use the markers that differentiate grape varieties as
guideposts when assessing quality and style and/or when blind tasting. Wine enthusiasts relish the complexity of their favorite expressions, a factor that contributes significantly to their enjoyment.

Wine is one of the foods richest in volatile aroma compounds, linked to as
many as 1,000 of them. That said, only 80 or so—including the monoterpenols responsible for the floral notes in Muscat (among other varieties) or the thiols that impart passion fruit and grapefruit aromas
to Sauvignon Blanc—have been widely studied.

“Now the days of comparing a

glass of Northern Rhône Syrah to

a strip of peppered bacon appear

to be coming to an end.”

In fact, the molecule responsible for the pronounced peppery notes found
in several French grapes—including Syrah from the Northern Rhône; Gamay from Beaujolais; and Duras, Fer, Négrette, and Prunelard, grown in the southwest—was only recently discovered.

Until 2008, knowledge of the aromatic compounds that account for the varietal character of red wines, especially free compounds directly extracted from grapes,was limited to methoxypyrazines, the culprit responsible for undesirable green notes in Bordeaux varieties. The discovery in an Australian Syrah of rotundone, a sesquiterpene responsible for those peppery notes, shed new light on its sensory significance.

Rotundone had been hiding in plain sight; it had remained undetected by
researchers in not only wine but food products such as Piper nigrum, or black
pepper, which has more than 50 volatile compounds. These researchers speculate that several factors complicated its detection, including the fact that 1) the molecule appears late during sensory evaluation sessions, when judges no longer expect to encounter any molecules of interest and therefore may be less attentive, and 2) there is a specific anosmia for it, with 30% of tasters unable to detect it.

But now the days of comparing a glass of Northern Rhône Syrah to a strip of
peppered bacon appear to be coming to an end: Researchers at the École
d’Ingénieurs de PURPAN in Toulouse, France, anticipate that the peppery notes attributed to rotundone in Syrah grown in warmer climates will be lost due to increased temperatures and less precipitation during the ripening stage.

Unlike other aroma compounds in grapes that are derived from odorless precursors released during production or formed during fermentation, rotundone is directly extracted from berry skins during winemaking. In the context of climate change, strategies are being proposed in both the vineyard and the winery to help produce wines with consistent rotundone levels.

In addition to developing drought-tolerant rootstocks, the Toulouse researchers have identified specific clones that produce higher concentrations of rotundone, including Duras clones 554 and 654; they are also focusing on later-ripening clones of varieties like Tardiff, because later picking dates appear to be another significant factor in maximizing rotundone in wines (as do extended macerations in the cellar).

If we lose the peppery notes that we know and love in Syrah and Gamay wines, producers will have the option of recreating those characteristics by blending with wines made from varieties such as Duras and Tardiff.

Loss of complexity is just one indicator of the impact that climate change is having on the characteristics that we associate with benchmark wine styles. And this unfortunate scenario isn’t confined to the warmest growing regions of France. It’s hard to imagine tasting Grüner Veltliner without its characteristic notes of white pepper or losing the fragrant green peppercorn
that is found in Cabernet Franc. Without them, differentiating between
grape varieties will become increasingly more difficult, and consumers will be
forced to look elsewhere for their favorite complex flavors.

Italian Wine Podcast: Get US Market Ready talks with Deborah Parker Wong

Get US Market Ready host Steve Raye talks with Slow Wine Guide USA National Editor Deborah Parker Wong about her journey and work as an educator, journalist and much more. The 2023 Slow Wine Guide USA is available through Slow Food USA.

Italian Wine Podcast

Alvarinho’s Authentic Terroir

Despite its close proximity to the Atlantic Ocean and the Minho River, the Monção e Melgaço subregion of Portugal’s Vinho Verde DOC has a Mediterranean climate, with hot summers and mild, rainy winters. The horseshoe-shaped Gerês Mountains, home to Portugal’s oldest and largest national park, encompass the area in a natural amphitheater that opens northeast to the Minho River and the border with Spain.

The mesoclimate created by those mountains, which reach elevations of up to 1,550 meters, is utterly unique within the Vinho Verde region and is a defining factor in the character of the Alvarinho wines produced there. The peaks protect the vineyards from the cool maritime influence of the Atlantic coast and create a rain shadow that delivers 1,178 millimeters of rain during the winter months—less than half of the annual precipitation received by other Vinho Verde sub regions.

Average temperatures during the growing season in Monção e Melgaço are also warmer, resulting in an ideal climate for producing a range of styles of Alvarinho. The area’s soils—a combination of shallow, weathered granite and coarse sand from colluvial runoff and aeolian erosion—don’t have much water-holding capacity and are naturally high in acidity, with low levels of phosphorus. Winegrowers use terraces and natural fertilizers to enrich the soil, but the low vigor ultimately works in their favor.

The Minho River valley in the region of Monção e Melgaço

Above 500 meters, the terrain is notoriously rugged and inhospitable,
so vineyards around the towns of Monção and Melgaço are typically
sited below 300 meters—Soalheiro, for instance, produces its aptly named
Alvarinho Granit from sites above 200 meters. Alvarinho, which originated
in the Minho River valley, dominates the plantings here, producing wines
with extraordinary minerality and physiologically ripe fruit character but
without searing levels of acidity.

The range of styles includes both light, fresh wines like the Adega de Monção
2020 Deu la Deu—offering lime and tangerine flavors and a suggestion of
pétillance—and richer expressions that show marked intensity and purity of
fruit as well as minerality, such as the Valados de Melgaço 2019 Alvarinho
Reserva laden with peach, apricot, and just-ripe tropical fruits; these can age gracefully for several years.

Winemaking techniques also play a role in the range of styles characteristic of the region. While most fermentation takes place in stainless-steel tanks, winemakers do allow higher-temperature fermentations that result in less overtly floral wines and greater focus of flavors on the palate.

The reserve wines typically undergo bâtonnage and aging on the fine lees to help build body and add complexity. Alvarinho produced in its native terroir is incomparable to expressions of the variety grown elsewhere. But it may ultimately prove to be on a trajectory similar to that of Pinot Gris, which is renowned for producing light, delicately floral wines in Italy’s Collio region and wines of great mineral intensity and fruit purity in Alsace. Time will tell.

Shochu: the spirit of the Summer Games

When Japan hosted its first Summer Olympic Games in 1964, saké was served freely on opening day as part of a festive ceremony known as kagami biraki. This ancient tradition, which dates to the 17th century, is an integral part of Japanese culture, taking place at celebrations throughout the year.

Japan has since played host to two Winter Olympics—1972 in Sapporo and 1998 in Nagano, where saké and shochu were the drinks of choice—but it will make history this year as the only Asian nation to host a second Summer Games. Because Americans won’t be able to attend in person, they’ll be seeking ways to experience the tournament from afar—and, surely, raising their own toasts to the occasion.

Official logo of the 2020 Summer Games

In fact, they already are. According to a market research report from Kalsec, a leading producer of natural spice and herb flavor extracts, pandemic travel restrictions are fueling dining and drinking trends that emphasize cultural authenticity.

Interest in Japanese cuisine in particular is growing; take, for example, the newfound popularity of “sandos,” or katsu sandwiches, and sudachi, a Japanese citrus fruit from Tokushima Prefecture that’s being touted as the new yuzu.

As these foods grow in recognition, saké and shochu are also gaining traction
in the U.S. market—and for consumers who are increasingly drawn to the
stories behind the products they purchase, iichiko, Japan’s most popular shochu brand, has what they’re looking for in spades.

The Spirit of Umami

While saké is a fixture at all of life’s important moments in Japan, the similarly lengthy history and traditions of shochu have made it the nation’s distilled spirit of choice—and iichiko its most notable producer.

With a name that translates as “it’s good,” iichiko conveys a level of complexity that few white spirits can rival thanks to its barley base and koji backbone. It’s distilled on the island of Kyushu in O¯ita Prefecture, but because the area lacks the cold winters that were once so essential to fermentation, shochu became the key alcoholic beverage, as warmer weather wasn’t a factor in the distillation process.

The shochu capital of Japan, Kagoshima

That said, the two-row barley used to produce iichiko is treated very similarly to saké rice in that it’s polished, steeped, and steamed in soft, iron-free water, preparing it for the addition of barley koji. The koji initiates the fermentation process, releasing the rich flavor of the grain and creating citric acid, which protects the shochu from bacteria that causes spoilage.

To produce its two expressions, iichiko uses a mix of low- and high-pressure distillation techniques at different temperatures, resulting in raw shochus with different characteristics. These are then blended to create Silhouette—which, at 25% ABV, offers notes of melon, grapefruit, and herbs with a smooth, elegant flavor profile and nutty finish—and Saiten, a 43% ABV shochu that shows aromas of honeydew melon, white grape, pickled watermelon rind, Kabosu citrus, and umami notes of soy and barley as well as flavors of jasmine tea, white peach, minerals, and earth.

Saiten was developed specifically for mixology, while Silhouette is frequently
mixed with oolong or matcha tea, showcased in a classic Highball with soda or fruit juice, or served on the rocks. Together, they reinforce shochu’s undeniable versatility.

As an ambassador of Japanese culture, iichiko has a unique story to tell. From its heritage grains and traditional production methods to its affinity for pairing with umami-rich foods, iichiko is a metaphor for Japan itself: a place where the enduring past sets the stage for the future.

Unraveling Geologic Metaphors

The discovery of more naturally-occurring compounds found both in soil and in wine prompts winegrowers to abandon their geologic metaphor and take credit for winemaking choices that reflect their terroir.

In addition to water and alcohol, wine is composed of fewer than 4% of minor components, many of which are only present in miniscule amounts. The dozen or so minerals that are present as nutrient elements—typically metallic cations (positively charged ions)—such as potassium, phosphorus, and calcium are only distantly related to geological minerals found in vineyards, which are complex crystalline compounds.

However, research is showing that some of the same volatile compounds
found in rocks can also be found in wines described as “mineral.” (I covered the best known of them, petrichor, in my October/November 2019 column.)

Although there is no single term for the source of mineral expression in wine,
one thing wine professionals and consumers do agree upon is the use of certain words to describe such characteristics.

Careful study of the lexeme for the word “mineral” has produced a list of relevant descriptors, including: flint, matchstick, smoke, kerosene, petrol, rubber eraser, slate, granite, limestone, earthy, tar, charcoal, graphite, rock dust, wet stones, salty, metallic, steely, and ferrous.

One of the most romantic yet misguided geologic metaphors employed by
winemakers attributes mineral expression to the soil vines grow in. For example, flint and pebbles contain polysulfides and, more specifically, hydrogen disulfane, compounds that give them odors of flint, gunpowder, and matchstick.

Photo credit: Benoit Roumet

Despite the widespread use of the term “flinty” to describe them, the odors of these sulfanes had previously never been studied in the context of food products—largely because the sulfanes are highly volatile and unstable, making them challenging to work with—until researchers who were studying toilet malodors realized they were on to something.

Flint is formed from sediments rich in hydrogen compounds as a result of
the bacterial reduction of sulfates in an anaerobic environment. When it’s scraped or struck against another rock, the presence of iron from clay minerals releases those compounds as iron sulfides and other sulfur forms.

This is the source of the easily detectable gunflint odor that the winegrowers of Sancerre metaphorically assign to the aromas found in the wine that comes from the area’s silex soils. Flinty aromas in Sauvignon Blanc are attributed to benzene methanethiol (or reduction), but hydrogen disulfane can also play a role.

The abovementioned researchers confirmed the presence of hydrogen disulfane in two dry white Chasselas wines that were described by wine professionals as the most mineral from among 80 samples.

When tested, in addition to containing this polysulfide, these wines were found to have higher concentrations of malic and lactic acid. While hydrogen sulfide is present to some degree in all wines, the compound hydrogen disulfane is more abundant in wines defined as mineral.

Given its presence in both them and the soils they hailed from, the intrepid winegrowers of Sancerre can now revise their metaphor and take credit for winemaking choices that reflect their terroir