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7791-18-6
Magnesium chloride hexahydrate
7791-18-6
project | information |
Chinese name | Magnesium chloride |
English name | Magnesium chloride |
Alias | Brine (Nigari / Bittern – a bitter residue from seawater after salt production) |
Molecular formula | MgCl₂·6H₂O (hexahydrate – the most common form) |
molecular weight | 203.30 (hexahydrate) |
CAS number | 7791-18-6 (hexahydrate) |
Appearance | Colorless or white crystals, flakes or granules – extremely hygroscopic (water will appear on the surface within minutes of being exposed to air). |
Solubility | It is extremely soluble in water—54.2 g/100 mL (20°C), and its aqueous solution is neutral to slightly acidic. |
smell | Extremely bitter and salty—more intense than magnesium sulfate—is the source of the highest exposure to magnesium ions in taste. |
Magnesium content | Approximately 12.0% (hexahydrate, calculated as Mg) |
The chemical principle behind magnesium chloride as a tofu coagulant is extremely simple:
Soy protein (negatively charged) + Mg²⁺ → protein-Mg²⁺-protein cross-linking → gelation → tofu
But the speed of this process is the key difference between brine tofu and other types of tofu:
coagulant | Solubility (cold water) | Release rate of Mg²⁺/Ca²⁺ | solidification rate | Tofu network structure | Characteristics of tofu |
Magnesium chloride (brinest) | Extremely high (54 g/100mL) | Extremely fast—impact within seconds | Quick – 1-3 minutes | Crude protein rapidly aggregates | Firm and chewy – Northern tofu/Kapok tofu |
Magnesium sulfate (E518) | High (26 g/100mL) | Fast - relatively mild | Medium – 5-8 minutes | finer | Middle – In between |
Gypsum (CaSO₄·2H₂O) | Extremely low (0.2 g/100mL) | Extremely slow – sustained release | Extremely slow – 15-20 minutes | Extremely fine – the protein fully expands and absorbs water. | The most tender and smooth – soft tofu/silk tofu |
GDL (gluconolactone) | Extremely high | Extremely slow (requires heating for hydrolysis) | Slow – heating gradually | Even and delicate | Super tender – silken tofu |
Details of the production process of brine tofu
Key parameters for making salt brine tofu at home:
Soy milk temperature 70~80°C (the higher the temperature, the faster it coagulates);
The amount of bittern used is 0.5% to 1.0% of the weight of soy milk (Ngari concentration is about 15% to 20% - added after dilution);
Besides tofu, magnesium chloride is also used as a coagulant in the production of certain soy products—such as dried tofu and bean curd sheets—in the pre-coagulation process. In these cases, where stronger coagulation power and a denser protein network than gypsum are required, magnesium chloride is one of the preferred choices.
Magnesium chloride is the most "brutal" of all magnesium sources—12% magnesium, 0% mild, and 100% bitter. Therefore, in food magnesium fortification—it almost exclusively appears in tofu—because in this context its bitterness is diluted to an imperceptible level in the final tofu (tofu itself is virtually tasteless).
In mineral water, beverages, and liquid supplements—if magnesium chloride is added—consumers will reject it from the first sip. This is why magnesium lactate and magnesium gluconate are far superior in terms of "mildness," but brine tofu still cannot be replaced—because the bean flavor and chewiness of tofu made with magnesium chloride cannot be replicated by any mild organic magnesium source.
Magnesium chloride (food grade / E511 / CAS 7791-18-6) has only one truly irreplaceable function in food – making tofu. But it is irreplaceable in this function – without magnesium chloride, there is no soft, cottony texture in Northern tofu, and no two-thousand-year-old tofu flavor tradition in Northern China.
Scene | What did magnesium chloride do? |
Salt brine tofu | Mg²⁺ coagulates soy protein within 1-3 minutes – resulting in a firm, chewy texture and a rich soy flavor. |
Japanese Kapok Tofu | Nigari's braising sauce—it won't break when picked up with chopsticks—it won't fall apart when cooked in hot pot. |
Family Kitchen | Pour the crystals into the soy milk—a few minutes later—the transformation from liquid to solid is complete. |
It's bitter and salty—a disaster in beverages. It's hygroscopic—water forms on its surface within minutes of being exposed to air. It's practically absent in any food other than tofu. But in the world of tofu—it's irreplaceable. Its extremely rapid coagulation isn't a flaw—it's the chemical basis for the chewy texture and bean flavor of tofu. This is E511—a food additive that does only one thing, but has done it in a way that has been irreplaceable for two thousand years.
