Coarse salt

Salt in large grains

Coarse salt is food salt sold in large, visible grains. It is a description of the grain, not of a source: sea salt, rock salt and kitchen salt can all be coarse, and so can their fine versions. The Korean word is 굵은 소금, gulgeun sogeum, literally thick or coarse salt, and it is the salt that packs fish in a jar of salted anchovies. Korea's food code, which classifies food salt as solar salt, reprocessed salt, roasted or melted salt, refined salt, other salt and processed salt, treats coarse not as a type but as a size.

Whatever its grain, food salt is mostly sodium chloride. The international Codex standard defines food-grade salt as a crystalline product that consists predominantly of sodium chloride and comes from the sea, from underground rock salt deposits or from natural brine, with at least 97 per cent sodium chloride on a dry-matter basis, not counting additives. The rest is made of natural secondary products, mainly calcium, potassium and magnesium sulphates, carbonates and chlorides, in amounts that depend on the origin and the method of production. That is why two coarse salts can taste and behave slightly differently while both being salt. A cook who needs to know more than the grain has to read the packet for the origin, the method and the additions.

The oldest manufacture

People were making salt long before they were writing about it. At Poiana Slatinei, in north-eastern Romania, a salt spring of about 160 g/l, roughly six times as salty as seawater, still flows beside a mound nearly 3 m high built of ash, charcoal and burnt soil. Excavators have dated the main early Neolithic exploitation to 6050 to 5500 BC. The people there boiled the brine over fires and left hard salt cakes in pottery vessels, a method known as briquetage, and the mound is the stack of their fireplaces. It is argued to be the earliest known salt production in Europe and probably in the world; how much salt was made, and what it was for, whether food, preserving, animals or exchange, remains open. The spring was used again in the Bronze Age, around 1750 to 1630 BC, when new fireplaces were lit, and it is still in use today.

Salt and the state

Salt is heavy, necessary and easy to tax, and governments have long tried to control it. In Korea the Goryeo court issued a salt law in the second month of 1309, in the first year of King Chungseon. Salt pans held privately by palaces, temples and powerful families were to be surrendered to the state. A price was fixed: one geun of silver was worth 64 seok of salt, and a bolt of cloth two. Buyers were told to buy at the official salt stores, every county had to build a storehouse for salt, and anyone who set up a pan or traded salt illegally was to be severely punished. Counties conscripted commoners as salt households to make the salt, and the people found it very burdensome. The law counts 616 salt pans and 892 salt households across six provinces.

Salt here is a made good with a chain of production behind it: pans to make it, labour to work them, stores to hold it and officials to price and sell it. What reached a household had passed through all of that.

Sea, rock and brine

Salt comes from three kinds of source. Seawater is evaporated in shallow ponds by the sun to give solar salt. Underground deposits of rock salt are mined, or dissolved by water that is pumped down and then brought up as brine. Natural brine from springs and wells is evaporated as well. In the United States, which produced about 40 million tons in 2024, 42 per cent of the salt sold or used was in brine, 40 per cent was rock salt, 9 per cent was solar salt and 9 per cent was vacuum pan salt, made by evaporating brine in closed vessels. Reserves are large, and the oceans hold a virtually inexhaustible supply. Most of it never reaches a kitchen: about 41 per cent went to de-icing roads and 39 per cent to the chemical industry, and food processing took 4 per cent.

The route a salt takes decides more than its grain. Korea's food code separates solar salt from reprocessed salt, which is made by dissolving salt, filtering the liquid, recrystallising it and removing the water, and from roasted or melted salt, refined salt and processed salt. Food salt is also distinct from industrial salt, which is made for de-icing and for chemistry and is not covered by the food standard. The label may state the origin or the method of production, as the Codex standard permits, and that is the information that separates one coarse salt from another.

Coarse, kosher and pickling salt

The names on supermarket shelves describe different things. Table salt is fine, and in many places it is iodized; the Codex standard calls for iodization of food-grade salt in iodine-deficient areas. Pickling or canning salt is pure sodium chloride with nothing added, which dissolves easily and keeps a brine clear. Kosher salt is a coarse salt with larger crystals. Sea salts and rock salts are named for their origin, and the flaky finishing salts for their shape.

Crystals come in different shapes and sizes, so salts are not interchangeable by volume. A third of a cup of kosher salt does not weigh the same as a third of a cup of pickling salt, and the safest way to follow a recipe is to weigh the salt. Iodine and the anti-caking agents added to table salt can cloud a brine and darken or discolour vegetables. A coarse salt that is additive-free works for pickling, but only if the quantity is measured by weight or the volume is corrected for the grain.

What salt does to food

Salt changes food by dissolving in its water. Dissolved salt lowers the vapour pressure of water, and the comparison of a food's vapour pressure with that of pure water is its water activity. That is a different property from moisture content: a food can hold a lot of water and still have a low water activity if salt, sugar or other solutes hold the water. The low water activity of a salted food restricts the organisms that are sensitive to it, while others, the salt-tolerant ones, still grow.

Dry salt works in the same way on solid food. When gutted anchovies are layered with coarse salt in barrels, the salt dehydrates the flesh and seasons it, giving the fish its colour and flavour; the excess is rinsed off before the fillets are packed.

Coarse salt in curing and fermenting

Coarse salt is the traditional choice where salt is packed in layers or rubbed on. In a Gyeonggi-do method for myeolchi-jeot, salted anchovies, a jar is lined with coarse salt, the fish are packed among more coarse salt, and a brine prepared separately is poured over them. The Italian anchovy sauce colatura is made by layering fish with sea salt in oak containers under a weighted wooden disc. Traditional Korean anchovy sauce uses about 25 per cent salt, and the fish ferment for months. In one laboratory trial of the sauce, 1 kg of whole anchovies went in with 270 g of solar salt and was covered with 400 ml of a 25 per cent solar salt solution; the mixture held about 24.7 per cent salt for the 473 days of the trial. In Cantabria, fresh anchovies are salted at once to firm them, then headed, washed and left in barrels with salt for at least nine months and, for some grades, up to three years, before they are de-salted, boned by hand and packed in oil.

Salt does not stop biology; it selects it. In salted anchovy and other seafood, salt-tolerant bacteria take over as fermentation advances, among them Tetragenococcus halophilus, which is prominent in anchovy samples, while the enzymes of the fish and of the microbes break the proteins into peptides and amino acids. Different seafood develop different communities: anchovy, cutlassfish offal and croaker jeotgal are not alike. Kimchi starts from salted cabbage, flavoured with red pepper, garlic, ginger, green onion and radish, and ferments spontaneously from microbes carried on its ingredients. For fermented pickles, salt is not optional: other canned vegetables can be made without salt, but brined pickles need it.

Salt in vegetable ferments

In vegetable fermentation salt is what sets the conditions. In sauerkraut, salt draws juice out of the cabbage, which together with the salt forms the brine, and it frees fermentable sugars from the cells. It inhibits unwanted yeasts, moulds and bacteria, while the lactic bacteria that do the fermenting tolerate higher salt, so it acts as a preservative as well. The usual guidance is to weigh the shredded cabbage and use 2 to 2.5 per cent salt by weight, about 3 tablespoons per 5 pounds, with a non-iodized salt that has no anti-caking agents, and to hold the crock at a steady 68 to 72 °F for about 7 to 14 days. Warm speeds the fermentation and cool slows it.

The amount is the point. Coarse salt, with its large grains, packs into a spoon differently from fine salt, so a recipe that gives tablespoons assumes a particular salt. Weigh it, and the type of crystal stops mattering.

Choosing and keeping coarse salt

Read the label. Under the Codex standard the product is named salt, with food-grade, cooking salt or table salt close by, and the term dendritic may be added only when a ferrocyanide salt was put in the brine during crystallisation. Food-grade status, iodine, anti-caking agents and origin are all printed on the packet, and a coarse grain tells you none of them. For curing, brining and pickling choose salt without additives; for seasoning, any food-grade coarse salt will do. Weigh it when a recipe gives grams. Iodized salt keeps its iodine best when it is protected from moisture, heat and sunlight.

Sodium chloride itself is a mineral and not an allergen, but a blend or flavoured salt can include other ingredients. The packet lists them, and the ingredient statement of any processed food says what it contains. Grain size says nothing about sodium content, and the claims sometimes made about minerals in unrefined salts need a measured composition, not a grain size.

Salt is also a matter of diet. The World Health Organization recommends that adults eat less than 5 g of salt a day, about a teaspoon, and puts the global average at about 11 g in 2021. The main health effect of a high-sodium diet is raised blood pressure. The same organisation advises that all salt consumed should be iodized, for the sake of brain development in the foetus and young child, which is why the Codex standard provides for iodization in iodine-deficient areas. A coarse salt chosen for curing and pickling is a tool for the kitchen, and what goes on the table or into everyday cooking is a separate decision for each household and its health advice.