WHENEVER I’m flying home and the plane passes over the south end of San Francisco Bay, my eyes can’t linger long enough over its startling patches of orange and red.
They’re sea salt ponds, cultivated to produce pure snow-white sodium chloride for industry and for the table. The colors in the ponds come from unusual microbes that thrive in the evaporating brine and produce pigments to cope with the intense sunlight.
A few months ago I finally encountered the colors of that briny life up close, in a jar of salt from the Murray River region in southeastern Australia. The remains of salt-loving bacteria and algae give the crystals a beautiful pink blush and a faint, pleasant aroma.
These days, salts come from all over the world, in many hues and crystal forms and textures. But this welcome blizzard is borne on a whirlwind of obfuscatory hype.
We now have “selmeliers” to expound on the flavors and textures of all these salts, the terroir of rock salts and the “meroir” of sea salts.
And the salt expert and purveyor Mark Bitterman has called into question the palates of the many chefs and cookbook writers who routinely recommend the use of kosher salt, which he views as an industrial, soulless product that tastes bad. In his recent book “Salted,” an entertainingly opinionated, frustratingly undocumented tour through the new world of salts, Mr. Bitterman offers vivid tasting notes. He describes the flavor of pink Murray River salt, for example, as “distinct sunshine sweetness; tingle of warm minerals.”
And the flavor of kosher salt? “Metal; hot extract of bleach-white paper towel; aerosol fumes.”
Is this just hyperbole from a seller of artisanal salt? Or is it true that pure salt can have other flavors beyond simple saltiness? And can less refined salts taste so much better that they might be worth a hundredfold multiple in price?
These aren’t new questions for cooks, but at last sensory scientists have taken an interest and run careful taste tests to answer them. It seems as if most salts taste pretty much the same, but no salt, even the most pure, is merely salty.
Culinary salts generally come either from the oceans or from solid underground deposits of ancient seas. Both sources contain many different minerals, but the predominant one is sodium chloride. Most standard table salt is produced by injecting water into mines to dissolve the minerals, heating the brine to evaporate the water, and then handling the minerals as they precipitate to separate sodium chloride from the others, which generally have a bitter taste. Table salt is more than 99 percent sodium chloride.
Sea salts are produced from ocean water, either by slow evaporation in shallow ponds to make what is known as solar salt, or by rapid boiling over high heat.
Both kinds of salt may be made on artisanal or industrial scales, and both can end up more or less refined (more or less pure sodium chloride) depending on countless details of the process. The least refined sea salts, with the largest proportions of other minerals and moisture, are gray and clumpy rather than white and free-flowing. Flakes of highly regarded fleur de sel, or flower of salt, are harvested from the surfaces of salt ponds.
If salt crystals develop while submerged in brine, they turn out compact and solid, like the cubic crystals of table salt. If they develop at the surface of the brine, they form flat flake-like masses or hollow pyramids.
Then there are treated salts: salts to which manufacturers add other materials to provide color or flavor. Red salts are coated with iron-rich red clay, black ones with activated charcoal. Some salts are smoked or roasted; some are flavored with a variety of other ingredients, including herbs and spices and wine.
Even the least refined salt is still mostly sodium chloride, and its traces of potassium, calcium, magnesium, iron and zinc are nutritionally insignificant compared with what we get from the foods it seasons.
But what about taste? If you’re not a salt expert, can you tell the difference between cheap table salt and French fleur de sel?
Late last year, scientists at North Carolina State University in Raleigh published a study of 38 salts from all over the world in the Journal of Sensory Studies. Stephenie L. Drake and MaryAnne Drake analyzed the chemical composition of each salt, and had a trained panel compile a set of relevant flavor descriptors and then taste the salts simply dissolved in distilled water. They found that different salts do indeed have different tastes, even when the solutions had the same concentration of sodium.
Many less refined salts tasted less salty than table salt, but some actually tasted saltier. This suggests that trace minerals can either suppress or accentuate the saltiness of sodium chloride.
The researchers also found that all salts, including the most refined, were slightly astringent, and all had some slight umami taste, the mouth-filling savoriness generated by MSG. The New Zealand “organic” salt ranked notably high in both saltiness and umami. A small handful were slightly bitter. And many of the unrefined salts had a detectable metallic smell, like a penny or rusty nail. All told, the panel noted a total of 10 different tastes and smells in the salts, many fewer than the wine-like profusion of qualities celebrated by salt specialists.
Curiously, the taste differences didn’t seem to correlate with the mineral compositions of the salts, with the exception of iron and the metallic smell. And the differences themselves were generally small. So with some experience and effort, you might be able to distinguish among salts you taste on their own.
What if you’re a nonexpert in your kitchen or at the table tasting foods, which are full of their own minerals and flavors? At the Culinary Institute of America in Hyde Park, N.Y., Christopher Loss, a sensory scientist, and David Kamen, a chef, have been studying the role of salt in cooking and enjoying food. They shared their most recent, still unpublished findings with me earlier this month.
The Hyde Park team used kosherg salt and several French sea salts to make different batches of five foods. They served the batches side by side not to a trained taste panel in a lab, but to staff members, students and visitors in several different settings, including a food conference and a restaurant during lunch service. These everyday tasters then rated their liking for each batch.
The tasters significantly preferred chicken broth and bratwurst made with an inexpensive white sea salt over the ones made with kosher salt. Batches of those two foods made with gray sea salt, or sel gris, and fleur de sel fell in between.
For fresh tomato juice, mashed potatoes and lima bean purée, the tasters had no clear favorites among the salts.
Considered together, the two studies suggest that it would take an unusually sensitive palate to be offended by the taste of ordinary salt, or to notice a difference in foods prepared with different salts. So there’s probably no need to rewrite all those cookbooks or throw out the kosher salt.
Still, with such diverse versions of this universal ingredient available, why not explore? The price difference can seem crazy: sel gris and fleur de sel are 100 to 200 times more expensive than table salt, and really esoteric salts 500 times, well over $100 a pound. But this is still just pennies a serving when you use them by the pinch as last-minute garnishes. (If, as Mr. Bitterman suggests, you use sel gris to make a salt crust for a rib steak for two, the salt alone will cost you $12.)
With their great variety of crystal sizes and shapes, specialty salts shine as garnishes in appearance, texture and taste. The thicker the crystal, the more it crunches between the teeth, the slower it dissolves, and the more gradually and gently it delivers its saltiness. Standard table and kosher salts dissolve fast and can seem harsh for that reason.
If you choose to use specialty salts in general cooking as well, don’t simply substitute spoonful for spoonful. Because compact crystals pack together more densely than broad flaky ones, a given volume of one salt may contain twice as much sodium chloride and saltiness as the same volume of another. (It’s good to know that even among industrial salts, 1 spoon of table salt is the equivalent of 2 spoons of Diamond Crystal brand kosher salt, but 1 1/2 spoons of denser Morton kosher salt.)
Start with less than you think you’ll need, then taste and keep tasting as you add more. And beware of using gray or colored salts in any clear or lightly colored dish, or in pickling brines; the colors don’t dissolve and leave unappealing deposits and scums.
Salt is the rare ingredient that can enhance the flavor of pretty much any food it’s sprinkled on. Sensory scientists have found that beyond supplying its own taste, salt in small amounts enhances our perception of sweetness and sourness while suppressing bitterness, a talent that helps balance the flavor of everything from brussels sprouts and grapefruit to caramel and chocolate and coffee. It brings out the flavor of food by helping expel its volatile molecules, so there’s more aroma to fill our noses.
And I enjoy bringing a bit of Central Asia or the Mediterranean to my California table, or faintly speckling a morning egg with the pigments that paint the Bay. There’s more to salt than the taste.
April 27, 2011
Copyright 2011 The New York Times