High-purity sodium nitrite curing salt

01

Set the food-grade purity specification

The JECFA specification for sodium nitrite (INS 250, CAS 7632-00-0, NaNO2, formula weight 69.00) requires an assay of not less than 97.0% on the dried basis, loss on drying of not more than 0.25% (over silica gel, 4 h) and lead of not more than 2 mg/kg. It describes the substance as white or slightly yellow, hygroscopic and deliquescent granules, powder or fused sticks, freely soluble in water, with functional uses as an antimicrobial preservative and colour fixative. [1]

JECFA established an ADI of 0–0.06 mg/kg body weight in 1995 and states that nitrite should not be used for infants below 3 months; its metals and arsenic specifications were revised in 2004. [1]

Because the material is hygroscopic and the loss-on-drying limit is tight, state the packaging and storage the supplier must use to keep it within specification, and ask for the assay, loss on drying and lead results on each lot certificate. [1]

Give the supplier the specification to meet (for example JECFA INS 250 or a national food additive standard), form (crystals, powder, curing salt mix and its nitrite concentration), lead and other contaminant limits, particle size, packaging and lot size, labelling language, and the documents required with each lot.

02

Dose the nitrite within the limits for each product

US rule 9 CFR 424.21 lists sodium or potassium nitrite to fix colour in cured meat and poultry products, not in baby, junior or toddler foods, at up to 2 lb per 100 gal of pickle at a 10% pump level, 1 oz per 100 lb of product in a dry cure, or ¼ oz per 100 lb of chopped meat, meat by-product or poultry. Nitrites, nitrates or both may not result in more than 200 ppm of nitrite, calculated as sodium nitrite, in the finished product; bacon follows separate provisions. Supplies of nitrite and mixtures containing it must be kept under the care of a responsible employee, with their nitrite content known and clearly marked. [2]

For fish and home curing, 21 CFR 172.175 limits sodium nitrite to 10 ppm in smoked cured tunafish; 200 ppm (with no more than 500 ppm sodium nitrate) in smoked cured sablefish, salmon and shad; and, in home meat-curing preparations, directions that keep nitrite to no more than 200 ppm in the finished product. The label must name the additive and state its concentration in any mixture; household retail packs need directions for use and the statement "Keep out of the reach of children". [3]

Editorial calculation: with 16 oz in 1 lb, ¼ oz per 100 lb is 0.25 ÷ 1,600 ≈ 156 ppm ingoing nitrite, and 1 oz per 100 lb is 625 ppm; 200 ppm is 20 g per 100 kg of finished product. [2]

03

Know the EU safety basis behind nitrite limits

The European Food Safety Authority (EFSA) re-evaluated nitrites and nitrates as food additives and reported on 15 June 2017 that existing safe levels are "sufficiently protective for consumers". It re-established the acceptable daily intake (ADI) for nitrites at 0.07 mg/kg bw/day, close to the existing ADI of 0.06 mg/kg bw/day, and kept the ADI for nitrates at 3.7 mg/kg bw/day. Sodium and potassium salts of nitrite and nitrate (E 249-252) are authorised as food additives in the EU, used in meat, fish and cheese products. [4]

EFSA lists the purposes of these additives as hindering microbial growth, "in particular to protect against botulism", keeping meat red and enhancing flavour [4]. The US rule sets a different kind of number: no more than 200 ppm of nitrite, calculated as sodium nitrite, in the finished product [2]. An ADI limits what a person takes in per kilogram of body weight, while the US figure limits the product, so the two cannot be converted into each other without consumption data.

For a buyer of food-grade sodium nitrite these figures explain why the purity and labelling requirements are tight. JECFA requires an assay of not less than 97.0% on the dried basis [1], and the US rules require the nitrite content of mixtures to be known and marked [2] [3]. Ask the supplier which market's additive rules the product and its labelling are made for (E 250 in the EU, 21 CFR 172.175 in the US).

Editorial calculation: for a person weighing 60 kg (an example weight), an ADI of 0.07 mg/kg bw/day corresponds to 4.2 mg of nitrite a day, and the previous 0.06 mg/kg bw/day to 3.6 mg. [4]

Values are from EFSA's news release of 15 June 2017; the full scientific opinion was not reviewed.

04

What to ask a sodium nitrite supplier

Ask for a certificate of analysis against the JECFA limits (assay not less than 97.0% on the dried basis, loss on drying not more than 0.25%, lead not more than 2 mg/kg) and for moisture-tight packaging, since the salt is hygroscopic and deliquescent. [1]

Ask any supplier for the food additive specification met, lot certificates showing assay, loss on drying and lead, nitrite concentration of any curing mix, carrier salt grade, particle size, packaging and moisture protection, shelf life, labelling, and dangerous goods classification for transport.

05

Assay, drying loss, lead, mix strength, finished-product limit and storage control

Three requirements apply to the salt itself (assay, drying loss, lead) and three to its use in food, where 9 CFR 424.21 caps finished meat and poultry products at 200 ppm nitrite, calculated as sodium nitrite. [1] [2]

06

Purity, drying loss, lead and solubility for food-grade sodium nitrite

JECFA supplies four of the values here; particle size, bulk density, pH, shelf life and packaging are not set in the reviewed sources and have to be agreed with the supplier. [1]

07

Send the specification, use and packaging data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Specification: [JECFA INS 250; national standard]
Form: [pure sodium nitrite; curing salt mix at __% nitrite]
Use: [cured meat; poultry; fish; market]
Limits: [assay; loss on drying; lead]
Packaging: [pack size; moisture barrier]
Documents: [lot certificate; label text]
Quantity: [kg per order]

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