The Science of Salinity in Wine
What makes a wine taste salty? And is a salty-tasting wine actually salty? These would seem like straightforward questions with, presumably, straightforward answers. Yet they’re not. Despite all the attention in recent years paid to salinity in wine, much remains unknown.
Let’s start with the latter question. “Taste” denotes how we perceive the compounds for which our tongue has receptors (salt, sweet, acid, and bitter compounds). Though it may be easy to measure the concentration of salts, acids, or sugars in a wine, those chemical measurements do not directly correlate to how we actually experience them—each taste affects the perceived intensity of the others. Salinity increases our perception of sweetness, but reduces the perception of acid. Sweetness reduces the perception of both salinity and acidity, and acidity boosts the perception of both sweetness and salinity. So, a high salt content in a wine doesn’t just make that wine salty, but makes us perceive it as both sweeter and less acidic than it is.
Aromas, on the other hand, are sensed strictly with the nose. This includes when the wine is in our mouth as well as on the finish, after we’ve swallowed. Aromas further complicate taste perception, and may by association make us think that a wine is sweet, or even salty. For example, a wine with intense fruity aromatics may come off as sweet, when in fact it is dry.
Complicating matters even further is that any number of salts can cause salinity in wine. The main mechanism in taste buds for perceiving salty taste is responsive only to sodium ions. However, there is a secondary mechanism that responds to other ions, including potassium chloride, calcium chloride, and magnesium, which will contribute a salty taste.
These same compounds can also contribute bitterness, astringency, or a metallic taste. Salts in wine may also combine with acids, changing wine chemistry and taste.
Salty Wine Origins
Sensory thresholds of salinity in wine remain a mystery, and because other components in a wine affect how we perceive that wine’s salinity, the answer will likely be complicated and dependent on many other factors.
One of the most famous “salty” regions is northwestern Spain’s Rías Baixas, where some vineyards are mere feet away from seawater. This influences the soil, little by little adding chlorides, phosphates, and sulfates, as well as potassium, sodium, calcium and other salts. This, along with the granite soil, leads to elevated minerality and wines rich in salts, particularly chloride. The salts, then, are drawn into the roots and ultimately into the grapes.
But salts sneak into wines in other ways. Those deposited on leaves via wind, rain, or overhead irrigation are absorbed into the plant just like foliar fertilizers.
This effect is also seen in other oceanside wine regions. In Greece, on the island of Santorini, wines typically carried an intense saline aftertaste - perhaps due to the fact that the island is located in the Aegean Sea - a saltier sea than the Atlantic - and constantly blasted by gusty sea winds that get stronger as the harvest approaches.
In the Sherry region of Spain, Finos and Manzanillas sherries from chalky albariza soils also have very high salt contents. Depending on the level of calcium carbonate in the albariza, which ranges from 20 to 40 percent depending on the vineyard, you get salinity levels between 40 to 60 milligrams per liter in some Finos and Manzanillas. Albariza soils primarily contain calcium ions - hence their dazzling white color under the summer sun - but also a smaller proportion of sodium, potassium, magnesium, and other salts.
Sherry wines that are aged under a biofilm of flor yeast - including Manzanilla, Fino, Amontillado, and Palo Cortado - typically have particularly high saline characteristics. The veil of flor consumes nearly all residual sugars, can metabolize almost all of the glycerol, and eats alcohol - the three components that contribute sweetness to a wine. Flor also lowers volatile acidity and produces acetaldehyde.
All of these factors contribute to an increased perception of salinity in these already-salty wines. It’s no surprise, then, that these styles of sherry are famous for their salinity - not only do they get a high concentration of salt from the region’s soils and ocean proximity, but flor works in multiple ways to boost how we perceive it.
Salt, Soil, and Rootstocks
Rootstocks impact also the amount of salt that gets into a vine. Since phylloxera, nearly every winegrower has had to decide what rootstock to use when planting a vineyard. In general, rootstock varieties lead to differing characteristics in a wine (though they don’t have as much of an impact as grape variety). This also relates to salinity - different rootstocks allow differing amounts of soil salts into vines and have different abilities to function in saltier soils. As rainfall is needed to flush salt build-up in irrigated regions, the ability of rootstocks to function well in saltier soils becomes more important as more regions face drought pressure from climate change.
Source: https://daily.sevenfifty.com/the-science-of-salinity-in-wine/
Image credits: Pavel Neznanov