All About Salt

Let's start with a short quiz. Please answer these questions to the best of your ability, and no peeking at your neighbor's answers.

1. Salt is...

A. The only mineral commonly consumed by humans
B. Also known as halite
C. An ionic compound of poisonous gas and a volatile metal
D. All of the above

2. The only difference between ordinary table salt and gourmet sea salt is...

A. Flavor
B. Chemical composition
C. Nutritional value
D. Price

3. Choose the statements that are true:

A. Excess salt may be removed from a soup or stew by boiling a potato in the liquid
B. Salted water takes longer to boil than unsalted water
C. Only salt labeled "sea salt" actually comes from the sea
D. None of the above statements are true

If you answered "D" to all three questions, you might consider quitting your job and becoming a big ol' food writer like me. Otherwise, you might find the explanations to these answers of interest.

So, how did you do on question #1? Did you know that salt is the only mineral commonly eaten by humans? Did you also know that it is know to geologists as halite in its mineral form? I bet you knew that it's an ionic compound of chlorine and sodium called sodium chloride, didn't you? Very good, you all get gold stars.

Question #2 was a bit more controversial, and I have already received emails disputing my assertion that the only difference between ordinary table salt and gourmet sea salt is the price, so let's get down to facts. The US Food and Drug administration requires that all food-grade salt be at least 97.5% pure sodium chloride, and most of the salts on the market far exceed that number. Fans of expensive gourmet "sea salt" point out that it also contains the salts of other metals such as magnesium and calcium, and this is true. But so does regular table salt, whether mined from the earth or derived by evaporating sea water (known as solar salt). The truth is that even solar salt is almost 100% pure sodium chloride because almost all of the other mineral salts are washed away during processing. What it boils down to is this: salt is salt. Regardless of where it came from or how it is processed, salt is always salt.

So why are there so many different kinds of salt on the market? There is table salt, sea salt, iodized salt, rock salt, kosher salt, popcorn salt, margarita salt, fleur de sel... the list goes on and on. The only differences are in two areas the chemicals added during processing, and the size (coarseness) of the grains. Period. That's it.

Let's look at the additives first. The better know of these is the iodine in iodized salt. It is added in the form of potassium iodide (to a maximum of 1/100th of 1% by weight) as a dietary supplement to prevent thyroid disease, and is always accompanied by a stabilizing agent such as dextrose (yes, sugar in salt) or sodium thiosulfate. Even sea salt and kosher salt may be iodized, so read the labels carefully.

The other additives are anti-caking agents such as calcium silicate, magnesium carbonate, calcium carbonate, and other compounds. They are insoluble in water, which not only prevents them from forming clumps in humid environments (thus keeping the soluble crystals of sodium chloride separate), but also explains why water becomes slightly cloudy when salt with these additives is dissolved in it. These are all odorless and flavorless substances and contribute nothing, either positive or negative, to the taste of the salt.

So what about the coarseness of the salt? I have already explained that salt is salt, but is a tablespoon of salt always a tablespoon of salt? Ah, that's another matter.

So, salt is always salt, and except for trace amounts of additives, all the brands on the market are identical with regard to chemical composition, nutritional value, and flavor. The major difference is price, with ordinary table salt usually costing about 30 cents a pound, and some so-called gourmet salts selling for over $15 a pound. Caveat emptor.

Another difference is the size of the salt crystals, ranging from very fine* (like the salt on potato chips) to fine (common table salt) to coarse (most kosher salts and sea salts) and very coarse (rock salt). One major salt producer has over sixty grades of salt for different commercial purposes. So how do all these different grades of coarseness affect us?

Well, you see, as the grains of salt get bigger, so does the amount of space between the individual grains. In other words, a tablespoon of finely powdered salt will contain more salt by weight than a tablespoon of coarse salt because there is less air space between the small grains than the large grains. Make sense? Furthermore, the smaller the grains of salt, the faster they dissolve in a liquid-and in our mouths.

This can lead to some misleading sensory impressions. People frequently think that a certain salt tastes more or less salty than another when the coarseness of the grain is entirely responsible-not the nature of the salt itself, but rather the size of its crystals. You can easily prove this to yourself by popping a single large grain of salt into your mouth, followed by another large grain of salt which you have pulverized with the back of a spoon. The second grain of salt will dissolve on your tongue faster, giving you a faster and stronger taste of salt even though the two samples are identical in every way except for the size of the crystals.

This same factor also affects measurements. Since a tablespoon (or cup, or gallon) of coarse salt will actually contain less salt by weight than an equal volume of fine-grain salt (remember those air spaces between the grains?), precise measurements by volume cannot be relied on. Notice I almost always say "salt to taste" in my recipes? That's why. This has also led some people, including cookbook authors, food writers, professional chefs, and Madison Avenue copy writers, all of whom should know better, to pronounce that one salt is "less salty" or "more salty" than another. One more time-salt is salt-got it?

* Note These classifications are mine, and different salt producers have their own terminology for the various sizes and textures of salt crystals.

For the benefit of those of us whose memory doesn't extend beyond our last meal, here is question #3 from our quiz:

3. Choose the statements which are true:

A. Excess salt may be removed from a soup or stew by boiling a potato in the liquid
B. Salted water takes longer to boil than unsalted water
C. Only salt labeled "sea salt" actually comes from the sea
D. None of the above statements are true

Many readers took issue with my contention that D was the only true statement, so I will attempt to settle these issues to everyone's satisfaction. Let's start with the potato question.

Adding a potato to a soup or stew that is too salty was one of the first kitchen tips I ever learned, and I have tried it several times. It has never worked. Even so, this tip is still one of the more popular of kitchen old wives' tales, and even one of my favorite TV chefs (Sara Moulton, who is also executive chef at Gourmet Magazine) was recently spotted perpetuating this bit of misinformation in a 30-second promotional spot for her TV show. Come on Sara, your fans deserve better than that.

Here is what happens when you add a raw potato to an over-salted liquid: the potato cooks, and when you taste the potato it is salty. Does this mean that the potato absorbed the excess salt? No. All it means is that the potato has absorbed some salty water, just like almost anything else you would add to the soup or stew would do. Think of it this way: if you added a sponge to the liquid, and then wrung it out and tasted the liquid absorbed by the sponge, it would be salty, right? Right. But the liquid remaining in the pot is still just as salty because all the sponge did was absorb some of the salty liquid, right? Right.

I am sure you are asking yourself, "How does the Chef know all this stuff? Did he conduct scientific experiments in the vast underground Worldwide Recipes research laboratory to prove this?" The answer is that I didn't have to conduct scientific experiments because someone much better qualified than I am has already done that. A fellow by the name of Robert L. Wolke, professor emeritus of chemistry at the University of Pittsburgh and author of the Washington Post's syndicated food column "Food 101," to be precise. I won't bore you with the details of his experiment here because he does an excellent and entertaining job of explaining the whole thing here.

So, I hope that settles the old potato-in-the-salty-soup question.

You might recall that in question #3 I maintain that salted water doesn't take any longer to boil than unsalted water, and it's true... well, almost true. OK, so I fudged a bit, but let me explain. When salt (or anything for that matter) is dissolved in water, the boiling point of the water does increase and therefore requires more energy (or time) to boil. However, in order to appreciably increase the amount of time it takes to boil a pot of water, you would have to add a lot more salt than you would normally add in cooking. (No, adding a raw potato to the over-salted water won't remove the excess salt, remember?) In fact, according to Professor Wolke, a tablespoon of salt in five quarts of water will raise its boiling point by seven hundredths of a degree Fahrenheit (about 4 hundredths of a degree Celsius). I think you will agree that the additional half-second or so this adds to the clock is negligible, unless of course you happen to be entertaining your mother-in-law at the time, in which case a half-second can seem like a very long time.

There are also several cooking myths surrounding the timing of adding the salt to the water. Many otherwise reliable cookbooks and cooking pundits advise that the salt must be added before the water boils, and others insist that it only be added after the water has come to the boil. The bottom line is, it doesn't matter. Just as salt is always salt and nothing more, so boiling salted water is always boiling salted water and nothing more, regardless of when the salt was added to the water. Period.

I'll wrap up this little dissertation by asking and answering the following: Where does salt come from? The answer might surprise you, but all salt comes from the sea. I can hear you thinking, "Ah Cheffie, you have tripped up this time, you silly but adorable goof, you. I happen to know that some salt is mined from the earth because my uncle Gus used to work in a salt mine." I won't argue with your uncle Gus (and don't want your aunt Tillie to wonder where he spent his days for thirty years) because salt is indeed mined from the earth in huge quantities. Just as with the salt removed from sea water, the rock salt that is mined needs to be processed and purified before it is suitable for human consumption, but this is where much of our common table salt comes from. It is also where much of our "sea salt" comes from.

You see, that salt that comes from underground mines used to be in sea water. Millions of years ago the water evaporated from ancient inland seas, leaving the salt behind. Over the ages various geologic processes which I'm not nearly intelligent enough to understand caused this sea salt to become trapped underground, and that's why your uncle Gus had to go down and get it out. So all the salt we eat (and spread on our roads and use in over 14,000 industrial and commercial applications) was originally dissolved in sea water, whether it was extracted millions of years ago or last week.

So what's the deal with this expensive sea salt if, in reality, all salt is sea salt? Ah, that's where the ingenuity of the human mind comes into play. At some point in the near past, some marketing genius at one or more of the commercial salt producers said, "I bet people would pay more for our salt if we called it something fancy like 'sea salt,'" and the rest, as they say, is marketing history. The truth is that, depending on where you live, even the regular salt on your supermarket shelves was actually extracted from sea water, even though it doesn't carry the expensive "sea salt" moniker. (Customers in the western half of the United States are most likely buying salt processed from sea water when they buy common table salt, and people in the eastern half of the U.S. are probably buying salt that was mined.)

The long and the short of it is this: since the U.S. Food and Drug Administration doesn't have any regulations regarding the common salt/sea salt thing, some of the salt you buy as sea salt was actually mined, and some of the salt you buy as common salt was actually processed from sea water. After all, who would know better than the big salt companies that it's all the same stuff anyway? And haven't I been telling you that all along? Repeat after me-salt is salt.