Buyers rarely come to calcium, magnesium and manganese salts for the mineral claim on the label. They come because the salt does a job on the line: it sets the tofu, keeps a canned tomato from collapsing in the retort, carries magnesium into a sports drink without wrecking the taste, keeps a powder free-flowing, or feeds a fermentation. Which of those jobs a given salt can do is fixed by two things that have nothing to do with the cation. The anion fixes solubility and taste. The hydrate fixes how much of the cation you actually receive per kilogram. Choose the wrong one and a 25 kg bag fails in a way that looks like a process problem.
The ten grades, and the job each one is bought for
| Product | CAS No. | E / INS | Cation | Solubility in water | Taste | Bought for |
|---|---|---|---|---|---|---|
| Calcium Chloride (anhydrous) | 10043-52-4 | E509 | Ca 36.1% | 74.5 g/100 mL (20 °C) | Salty, faintly bitter | Firming agent, cheese coagulation aid, brine |
| Calcium Sulfate (food gypsum) | 7778-18-9 | E516 | Ca 23-29% (see hydrate note) | 0.21 g/100 mL (20 °C) | Practically tasteless | Tofu coagulant, dough conditioner, firming agent |
| Calcium Gluconate | 299-28-5 | E578 | Ca 9.3% | 3.5 g/100 mL (25 °C) | Neutral | Calcium in drinks and plant milks; firming without bitterness |
| Calcium Acetate | 62-54-4 | E263 | Ca 25.3% | Over 30 g/100 mL (20 °C) | Faint acetic, salty | Firming agent with a preservative side effect; low-sodium blends |
| Magnesium Chloride (hexahydrate) | 7791-18-6 | E511 | Mg 12.0% | 54.3 g/100 mL (20 °C) | Clean but saline-bitter | Nigari-type tofu coagulant, magnesium source |
| Magnesium Sulfate (monohydrate) | 14168-73-1 | E518 | Mg 20.2% | 35 g/100 mL (20 °C) | Bitter | Magnesium source, brewing water, fermentation nutrient |
| Magnesium Gluconate | 3632-91-5 | E580 | Mg 5.9% | Freely soluble | Neutral | Magnesium in RTD drinks, syrups, effervescent tablets |
| Magnesium Carbonate | 546-93-0 | E504 | Mg 28.8% | Practically insoluble | – | Anti-caking agent, alkaliser, magnesium in powders |
| Manganese Sulfate (monohydrate) | 10034-96-5 | – | Mn 32.5% | Readily soluble | Astringent, metallic | Manganese in infant formula and cereals; fermentation micronutrient |
| Manganese Gluconate | 6485-39-8 | – | Mn 12.3% | Soluble | Neutral | Manganese in supplements and beverages |
Cation percentages are calculated on the hydrated form named in the product. The hydrate is dealt with in its own section below, because it is the most common source of a shipment that assays "correctly" and still does not work.
The solubility ladder decides how you feed the powder
Three tiers, three different pieces of plant equipment.
- Highly soluble, over 30 g/100 mL: calcium chloride, magnesium chloride, magnesium sulfate, calcium acetate. These can be dosed as a stock solution through a metering pump, which is why they dominate continuous processes. The price of that convenience is that a dosing error is instant and local - a slug of calcium chloride hits the soy milk or the brine as a concentrated bolus and leaves a bitter patch that no amount of blending will remove.
- Moderately soluble, 2 to 5 g/100 mL: calcium gluconate. Soluble enough for a beverage, slow enough that it needs agitation and warm water. One gram dissolves slowly in about 30 mL at 25 °C, and a supersaturated calcium gluconate concentrate will precipitate on standing. If you run it as a liquid, keep it warm and inspect it before use.
- Practically insoluble, under 0.3 g/100 mL: calcium sulfate and magnesium carbonate. These cannot be dosed as a solution at all. They go in dry, as powder or suspension, and they react where the particle sits. That sounds like a handicap and is often the whole point: the 0.21 g/100 mL of gypsum is exactly why it coagulates soy milk slowly and evenly instead of flashing to a coarse curd.
Tofu: one cation, three textures
Soy protein is coagulated by bridging the acidic groups on glycinin and beta-conglycinin with a divalent cation, so the texture decision comes down to which salt you use and how fast it releases its cation. Salt coagulants are dosed at roughly 1.5 to 5.0 g per kg of soy milk, at 75 to 85 °C.
| Coagulant | Typical dose | Behaviour | Result in the block |
|---|---|---|---|
| Calcium sulfate (gypsum) | 0.2-0.4% of soy milk | Slow and uniform, because solubility is only 0.21 g/100 mL | High water retention, smooth surface, delicate structure - soft and silken styles; the tofu becomes a genuine calcium source |
| Magnesium chloride (nigari) | 0.3-0.5% of soy milk; about 2-5 kg per 100 kg of dry soybeans on industrial lines | Fast and strong; the tighter network contracts as it sets | Lower water retention, firm springy curd - pressed and dried tofu; adds magnesium rather than calcium |
| Calcium chloride | Same range as magnesium chloride | More soluble than the sulfate, so faster than gypsum | Firm curd at the lowest cost, but the chloride leaves a salt-and-bitter edge |
Two operating notes. First, nigari is not a pure chemical: it is evaporated seawater bittern, and its magnesium chloride content varies with the source, which is why large plants buy refined magnesium chloride instead of relying on a traditional material. Second, the dose is a property of the bean as much as of the salt. Soybeans with a higher 11S to 7S subunit ratio set at a lower coagulant level, so a specification that fixes the dose and ignores the incoming protein will drift from lot to lot.
Firming agents: calcium without the bitter edge
In canned and frozen vegetables the target is texture. Calcium ions bridge the carboxyl groups of pectin in the cell wall into a calcium pectate network that survives the retort, so the piece keeps its shape instead of going to pulp. It is the same egg-box chemistry that gels alginate, which we set out in our guide to alginates and chitosan.
- Calcium chloride (E509) is the workhorse for canned tomatoes, potatoes, carrots, beans and peppers: cheapest, most soluble, approved as a firming agent and sequestrant. Its limitation is taste - the chloride reads as salt and, at the top of the range, as bitterness.
- Calcium gluconate (E578) is the answer where flavour is the constraint. It is neutral in taste, does not destabilise proteins, which is why plant-based milks use it rather than the chloride, and it firms without a salty note. It is authorised in the EU as E578 and in the United States under 21 CFR 184.1199.
- Calcium acetate (E263) firms and carries a mild antimicrobial effect, and is also used in low-sodium salt blends where the acetate replaces part of the chloride.
- Calcium sulfate (E516) is used as a firming agent for tomatoes, potatoes, carrots, beans and peppers where a neutral taste and a slow release are wanted.
The dosing trap: firmness rises with calcium only up to the point where the pectin is saturated. Beyond that the extra calcium is not bound, it is tasted - bitter, chalky, sometimes described as soapy. Dose on the pectin content and the retort schedule, not on the percentage printed on the certificate.
Electrolytes and supplements: choose the anion that keeps the drink drinkable
Magnesium is where the anion choice is most visible to the consumer. Magnesium chloride and magnesium sulfate are the cheapest magnesium in the catalogue, and both are strongly saline-bitter. Both are also osmotic laxatives, and the sulfate is the more aggressive of the two. That is acceptable in a 25 kg bag destined for a brewery or a fermentation tank. It is not acceptable in a 500 mL bottle.
- The gluconates - magnesium gluconate (E580) and calcium gluconate (E578) - are neutral in taste and freely soluble, which is why they hold the ready-to-drink beverage, syrup and effervescent tablet segment.
- The trade you make for that taste is weight. Magnesium gluconate carries only about 5.9% magnesium, so a 200 mg magnesium claim needs some 3.4 g of salt. Magnesium sulfate monohydrate at 20.2% needs roughly 1 g for the same claim. Quote both, and compare price per milligram of magnesium rather than price per kilogram.
- Manganese has the narrowest window of the three. Under GB 14880 it is permitted as manganese sulfate at 1.32-5.26 mg/kg expressed as Mn in infant formula, 0.92-3.7 mg/kg in dairy and 0.5-1.0 mg/kg in beverages, with an upper limit of 8 mg/kg for older-infant formula. Read the specification on the manganese basis, never on the salt basis.
- Manganese is also a strong pro-oxidant at trace level, so it belongs in an aqueous premix or a mineral blend, not in a fat-phase blend sitting next to an oil rich in unsaturated fatty acids.
Iron has the same problem in a more extreme form, and the salt choice there is even less forgiving; we set out the four iron salts separately.
Hydration state: the same name, two different products
Every one of these products is bought as a hydrate, and the hydrate is what turns a name into a number. The form you receive decides the cation per kilogram, the freight per unit of mineral, and the handling.
| Product | Forms | CAS No. | Cation | Practical consequence |
|---|---|---|---|---|
| Calcium chloride | Anhydrous / dihydrate | 10043-52-4 / 10035-04-8 | 36.1% / 27.3% Ca | The anhydrous grade delivers about a third more calcium per kg, but it is deliquescent and must stay sealed |
| Magnesium sulfate | Monohydrate / heptahydrate (Epsom salt) | 14168-73-1 / 10034-99-8 | 20.2% / 9.9% Mg | The monohydrate carries about twice the magnesium, so half the bags and half the freight for the same magnesium; the heptahydrate effloresces and cakes in dry air |
| Manganese sulfate | Monohydrate / tetrahydrate | 10034-96-5 / 10101-68-5 | 32.5% / 24.6% Mn | Declare the form on the order or the assay will not reconcile with the premix |
| Calcium sulfate | Anhydrous / dihydrate / hemihydrate | 7778-18-9 / 10101-41-4 / 10034-76-1 | 29.4% / 23.3% / 27.6% Ca | Three forms behind one name on a purchase order, and a different setting behaviour in dough for each |
What belongs on the purchase specification
| Line on the spec | What to require | Why it matters |
|---|---|---|
| Assay and hydrate form | For example CaCl2 min 94% anhydrous; MnSO4.H2O min 98% | The form sets the cation per kg; an assay without a form is not a specification |
| Water of crystallisation or loss on drying | A stated range, checked on your receiving sample | The fastest way to catch a heptahydrate shipped against a monohydrate order |
| Heavy metals | Pb max 2 mg/kg and As max 2 mg/kg for the food grades | GB 1886.6-2016 for food-grade calcium sulfate sets Pb max 2.0 mg/kg, As max 2.0 mg/kg and Se max 0.003% |
| Fluoride | A declared ceiling on calcium chloride | Fluoride follows the limestone through the process and concentrates in the calcium salt |
| Water-insoluble matter | A ceiling on the soluble grades | Insolubles settle in tanks, foul plate heat exchangers and cloud clear beverages |
| Particle size and bulk density | A range for anything entering a dry blend | A coarse hydrate segregates away from fine actives in a premix drum |
| Manganese basis | Declared as Mn, not as manganese sulfate | The regulation is written on the element, so the certificate should be too |
| Food-additive standard | GB 1886.6-2016 and GB 29208 for the manganese grade; the E number for the EU; 21 CFR 184 for the US | Which standard the batch is tested against is a purchasing decision, not a technicality |
Selection checklist
- Decide first whether the salt is a nutrient or a processing aid. If it is a processing aid, taste and solubility outrank the cation percentage every time.
- Match the anion to the flavour budget: chloride is cheapest and saltiest, sulfate is cheap and bitter, gluconate is neutral and costs the most per kilogram of cation, acetate sits in between.
- For coagulation and firming, choose by reaction rate - insoluble sulfate for slow and uniform, soluble chloride for fast and firm.
- For anything going into a beverage or a supplement, rule out chloride and sulfate before you look at the price.
- Price every offer per milligram of the element, after correcting for the hydrate form.
- Put the hydrate form and the testing standard on the purchase order, and verify loss on drying on the first delivery of every new lot.
Grades we supply
- Calcium Chloride (10043-52-4), anhydrous and dihydrate
- Calcium Sulfate (7778-18-9), food-grade gypsum
- Calcium Gluconate (299-28-5), E578
- Calcium Acetate (62-54-4), E263
- Magnesium Chloride (7791-18-6), hexahydrate
- Magnesium Sulfate (14168-73-1), monohydrate
- Magnesium Gluconate (3632-91-5), E580
- Magnesium Carbonate (546-93-0), E504
- Manganese Sulfate (10034-96-5), monohydrate
- Manganese Gluconate (6485-39-8)
Tell us the application, the target dose and the destination market, and we will quote the grade, the hydrate form and the documentation package that go with it. Samples of 1 kg are available for bench work.