Curing of meat

Curing of meat (Соління м'яса; also meat curing, salting) is treatment with salt, often with nitrite, applied dry, in brine or by injection. Spanish law distinguishes salting (salazón), which aids dehydration and keeping, from curado, treatment with salt possibly with nitrites and nitrates (Real Decreto 474/2014). According to FAO, curing also gives a heat-stable red colour.

FAO describes three methods. Dry curing: the meat is rubbed with curing salt and piled in layers with salt at 0 to +4 °C; it is used only for cured-raw products, followed by drying and ripening of 3–6 months, some hams up to 24. Wet curing: a brine of 15–20 % curing salt; the dry-wet variant needs about 2 days per kilogram of the biggest piece. Injection is fast, but the flavour comes out milder, the texture softer and the shelf life clearly shorter. The result is Jamón, Prosciutto crudo and other Dry-cured hams and shoulders.

So what do salt and nitrite actually do? Salt hardly kills bacteria; it binds water. Below a water activity of 0.91, roughly 15 % salt, microbes stop growing. Nobody can eat that much salt, so it is combined with drying and acidity. Nitrite curing salt is 99.5 % table salt and 0.5 % sodium nitrite, which comes to about 150 mg/kg nitrite in the product. The nitrite forms nitric oxide, which with myoglobin gives a heat-stable red. Bacteria must first reduce nitrate to nitrite, so nitrate goes only into long-ripened products such as Dry-cured sausages.

How much nitrite is allowed? According to the guidance of the Irish authority FSAI (Guidance Note 43, 2025), which reproduces Regulation (EU) 2023/2108, from 9 October 2025 meat products may carry 80 mg/kg of added nitrite and 45 mg/kg residual (as the NO2 ion); for sterilised ones 55 and 25 mg/kg. Before that the limit was 150 mg/kg. For traditionally cured products the residual is generally 30 mg/kg. Nitrates are not permitted in heat-treated meat products.

Prosciutto di Parma, by contrast, does without nitrite entirely: it is salted with sea salt alone, no additives, and the label reads «pork and sea salt». The ham ages at least 14 months. On other labels look for E250 (sodium nitrite) or E252 (potassium nitrate).

Why does this matter to you? According to EFSA (2017), the acceptable daily intake is 0.07 mg/kg body weight for nitrite and 3.7 for nitrate. Nitrate from additives is under 5 % of all dietary nitrate; the rest comes from vegetables and water. IARC (WHO) classes processed meat in Group 1.