Guardian Weekend – Part of a series of 6 articles on taste and cooking with co-author Peter Barham
The idea of adding a pinch of salt to enhance the flavour of food is a fairly recent one. Our ancestors didn’t go for such subtleties. When they put salt in food, they added it by the bucketful.
Take the Romans, for example. They were very fond of fish, but their method of preparing fresh mackerel was hardly an example of haute cuisine. They would first put a neatly packed layer of mackerel in the bottom of a large terra cotta pot. Then they would cover this layer of fish completely with a layer of coarse salt. Another layer of mackerel would be put on top of this, then another layer of salt, and so on, until the pot was full.
Now for the good bit. Once the pot was full, a lid would be put on, and the pot stood out in the blazing Mediterranean sun for a year. When the pot was finally opened, all that would be present would be a yellowish, salty, fishy liquid. The Romans called it liquamen, and used it as a piquant sauce.
You can still buy liquamen today, but not in Italy. In fact, the Romans themselves must have got sick of the smell, since up until the ninth century they made most of it, not in Italy, but in England! These days, though, if you really want liquamen, you go into an Asian supermarket and ask for fish sauce. It’s still made by essentially the same methods.
Our ancestors used high concentrations of salt because salt acts as a preservative at those concentrations. This doesn’t mean that it poisons the bacteria that would otherwise grow. It works because bacteria need water to grow in, and high concentrations of salt effectively tie up the water, making it unavailable for the bacteria.
Sugar works the same way, but at high concentrations sugar still tastes delicious, whereas salt tastes terrible. There could be many reasons for this, but one possibility is that we taste salt in a different way to sugar. Sugar molecules induce a sweet sensation because receptors in our tongues recognise the shapes of the sugar molecules. Salt works in a different way. Once salt gets into your saliva-filled mouth, it divides into two bits called ions (sodium and chloride, if you must know). Those ions can transport electrical currents, and the effects of salt arise from salt-induced changes in the natural electrical currents in your mouth.
The shapes of the ions (which are practically spherical) do not influence the taste outcome, but the size certainly does. This is why salts other than sodium chloride (and there are many) don’t have such a taste effect.
The effect on electrical currents, and hence perhaps on the receptors in the mouth, may be the reason why salt not only has its own taste, but affects the taste of other things, particularly sweet and bitter things. We have already seen in an earlier column, for example, that a pinch of salt enhances the sweetness of cakes and scones.
Probably man got used to the taste of salt via the residues left from salt preservation, and these days most of us prefer salt in our savoury foods. Unless we are on a salt-free diet for medical reasons, that little pinch of salt can make all the difference, not just for its own taste, but for its effects on other tastes.
It’s partly a cultural thing, though. We prefer salted butter, for example, and our Western processed foods (such as some brands of baked beans) are loaded with salt. It’s also a taste that we acquire. Unlike the taste for sweetness, we don’t have a salt preference as children. A preference for salt is something that we adapt to, and can equally un-adapt to, even as adults.
The preference has led to some odd practices, none odder than the idea of cooking green vegetables in water with a tiny pinch of salt. This small amount of salt doesn’t make a scrap of difference, because the salt can’t get into the food. Only the salt that stays in the tiny bit of water left after the vegetables have drained contributes to the taste. As one of us frequently demonstrates in public lectures, if you compare beans cooked in a pan of water with no salt added; with a pinch of salt added to the water; and with a fistful of salt added to the water; most people can distinguish only the beans with lots of salt. Why not try your own taste test and find out how much salt you need to add to vegetable cooking water to get even a slight salty taste?
It doesn’t matter whether you use rock salt or sea salt either. Since the rock salt originally came from the evaporation of a giant inland sea, it doesn’t make tuppence worth of difference.
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