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7647-14-5
futurechem
7647-14-5
project | information |
Chinese name | Sodium chloride/table salt |
English name | Sodium chloride / Common salt |
Molecular formula | NaCl |
molecular weight | 58.44 |
CAS number | 7647-14-5 |
Appearance | Colorless transparent cubic crystals or white crystalline powder |
Solubility | Easily soluble in water—35.9 g/100 mL at 25°C—solubility hardly changes with temperature. |
Sodium content | Approximately 39.3% (as Na) |
smell | Pure saltiness—the only one of the five basic human tastes almost entirely defined by a single chemical substance. |
Food Additive Number | Most countries exempt "table salt" from E-numbers. |
Sodium chloride is the purest source of saltiness—Na⁺ ions are recognized by the ENaC sodium channels on the taste buds of the tongue—generating a salty taste signal that is transmitted to the brain. Salt does more than just "make food salty"—at trace levels (< 0.5%), it can suppress bitterness—a classic indirect function of salt in the food industry: adding a trace of salt to a pot of stale sugar water makes it sweeter; adding a few grains of salt to a cup of bitter coffee reduces its bitterness.
Salt was the earliest food preservative used by humankind—predating freezing, canning, and synthetic preservatives thousands of years earlier.
Anti-corrosion mechanism | principle |
Reduce water activity (Aw) | Na⁺ and Cl⁻ provide strong hydration—binding water molecules tightly around their ions—making it unusable for microorganisms—inhibiting the growth of bacteria, yeast, and mold. The salt content in cured meats is typically 2% to 6%—Aw decreases from >0.95 to 0.85-0.90. |
Osmotic pressure destruction | High salt concentrations create a hypertonic environment outside microbial cells—water is "drawn out" from the bacterial cells—leading to cell dehydration and death. |
Selective antibacterial | Salt inhibits most spoilage bacteria and pathogens (Salmonella, Escherichia coli, Listeria), but its inhibitory effect on some beneficial bacteria (lactic acid bacteria) is weaker—this is the microbiological basis of naturally fermented pickled foods (sauerkraut, kimchi, pickled cucumbers). |
In meat processing, salt (usually in synergy with phosphates) plays an irreplaceable role in protein chemistry:
Role | mechanism |
Protein dissolution and extraction | The ionic strength effect of NaCl at high concentrations (2%–3%) causes myofibrillar proteins—primarily myosin and actin—to partially dissolve from muscle fibers. Upon heating, the dissolved proteins form a continuous gel network—fixing water and fat within the network. |
Emulsion stability | The extracted proteins coat the surface of fat particles, forming a protein film that prevents fat from clumping and separating ("oil seepage") during heating. The delicate texture of sausages and emulsified sausages comes from this protein emulsion film. |
Gel formation | Heating denatures the extracted proteins, forming a three-dimensional gel network that locks in water and fat. This is why ham and sausages are juicy and tender – the protein gel network keeps the juices within its structure. |
In dough—salt is added at 1.5% to 2% of the flour weight—its function is dual:
effect | mechanism |
gluten strengthening | Na⁺ and Cl⁻ shield the charges on gluten proteins—reducing electrostatic repulsion between molecules—bringing protein chains closer together—forming stronger hydrophobic interactions and disulfide bonds—resulting in a denser and more resilient gluten network. |
Fermentation control | Salt inhibits some yeast activity, slowing down fermentation and preventing the bread from over-proofing before baking. It also gives the gluten enough time to form a stable air cell structure, resulting in a more even and delicate bread texture. |
In the pickling of vegetables and fish, the high osmotic pressure of salt creates a driving force for moisture to migrate outward from the surface of the food.
Vegetables (sauerkraut, kimchi): Salt draws water and some soluble sugars from the vegetable tissues—the sugars provide a carbon source for subsequent lactic acid bacteria fermentation—the lactic acid bacteria produce acid, lowering the pH—further inhibiting bacterial growth. The first step is the physical dehydration by salt—the second step is the chemical fermentation by bacteria;
Fish (salted fish): After being cured with high salt, the water activity is as low as 0.75~0.85 - spoilage bacteria are almost completely inhibited - fish relied on salt to "winter" in the days before cold chain.
In traditional fermented condiments, salt acts as a microbial selector. The salt content in the fermentation liquid of soy sauce, bean paste, and fish sauce is typically between 12% and 18%—at this salt concentration, most spoilage and pathogenic bacteria are inhibited—while salt-tolerant yeasts and lactic acid bacteria become the dominant flora—these are the true "flavor makers" of these fermented condiments. Salt doesn't kill all bacteria—it "selects the right bacteria."
In cheese making, salt is added in various ways:
Some varieties are directly mixed with curd particles;
Some varieties involve soaking the entire curd in brine, while others involve rubbing salt onto the surface.
The role of salt in cheese:
Continue to extract whey from the curd—controlling the final moisture content—to determine whether the cheese is soft (like Brie) or hard (like Parmesan).
During fermentation and aging—salt selectively inhibits unwanted microorganisms—it provides a competitive advantage for specific molds (such as Penicillium roqueforti in blue cheese) and bacteria;
The cheese rind is formed by soaking in brine to dehydrate the surface, thus forming a natural outer shell.
Sodium chloride is the first compound in the history of food additives—predating any modern food regulations, chemistry as a science, and the invention of the word "additive." It is the chemical carrier of saltiness, one of the five basic human tastes, the oldest food preservative, the architect of the protein structure of meat products, the rhythm controller of bread fermentation, and the microbial selector of fermented flavorings.
Scene | What does salt do? |
The juicy texture of the ham | The 2% salt extracts myosin—after heating, the gel network locks in water and fat. |
Evenly spaced air pockets in the bread | The 1.5% salt slowed down the yeast's pace—allowing the gluten to keep up with the rising action. |
The sour and crunchy taste of kimchi | Salt draws out water and sugar—lactic acid bacteria consume the sugar and produce acid—putrefactive bacteria are kept out by the acid. |
The umami flavor of soy sauce | The 15% salt content selected salt-tolerant yeasts and lactic acid bacteria—which produce all the amino acids and aromas. |
Marble pattern of blue cheese | Salt gave Penicillium roqueforti the advantage in the competition. |
Of all the additives in the food industry—sodium chloride is the only "grandfather"—it doesn't require safety assessments because humans have conducted all the testing themselves over thousands of years. Its chemical formula is the shortest in chemistry textbooks—NaCl, two atoms per bond. Yet, it has participated in more food chemical reactions than any other food additive.
