Curing: How Salt, Sugar and Nitrite Preserve Food

Curing is preserving meat or fish with salt, usually along with sugar and often sodium nitrite or nitrate. The cure draws out moisture, makes the food hostile to spoilage bacteria, and changes its flavour, texture and colour. Bacon, ham, corned beef, gravlax, salami and prosciutto are all cured.

How salt preserves

Bacteria need available water to grow. Salt dissolves into the meat's moisture and binds it, lowering the water activity so most microbes can't multiply. Through osmosis, salt also pulls water out of cells, which firms the texture. That's why gravlax turns from soft and raw to silky and sliceable.

Salt also dissolves some muscle proteins, which is why cured ham holds together in clean, dense slices.

Why sugar is there

Sugar balances salt's harshness, adds browning potential and binds a bit of water too. In a gravlax cure it's often equal to the salt by weight.

What nitrite does

Sodium nitrite does three jobs:

• Safety: it strongly inhibits Clostridium botulinum, the bacterium behind botulism, which loves the low-oxygen centre of a ham or sausage.
• Colour: it binds to myoglobin, creating the stable pink of ham and bacon instead of the grey of cooked pork.
• Flavour: it creates the "cured" taste and slows fat from going rancid.

Curing salts are sold as Cure #1 (6.25% sodium nitrite, for short cures) and Cure #2 (nitrite plus nitrate, for long dry cures). They're dyed pink to prevent mix-ups. Use them at the weighed rate a tested recipe gives; for Cure #1 that's typically 0.25% of meat weight.

Dry cure vs wet cure

• Dry cure: salt mix rubbed directly on the meat. Concentrates flavour and is used for bacon, prosciutto and gravlax.
• Wet cure (brine cure): meat sits in salty water with cure dissolved in it. Gives juicier, more evenly seasoned results, as with corned beef and many hams.

An "equilibrium cure" uses a weighed amount of salt, around 2.5–3% of the meat's weight, so it can never get too salty no matter how long it sits.

Safety notes

Keep curing meat in the fridge at 1–4 °C / 34–40 °F unless a recipe is built for controlled drying. Long, uncooked dry cures (salami, whole-muscle hams) need precise salt, nitrate, temperature and humidity control. Start with bacon or gravlax before you try them.