Preventive control recommendations on the use of nitrites in the curing of meat products
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- Control Measures
The purpose of this document is to provide information on the use of nitrites in the preparation of cured meat products.
The Canadian Standards of Identity (CSI) Volume 7 defines the term "cured" as meaning "in respect of an edible meat product, that salt and at least 100 p.p.m. of sodium nitrite, potassium nitrite, sodium nitrate or potassium nitrate, or any combination of them, has been added to the meat product"
Nitrites, nitrate salts or both used in combination with salt (NaCl) and other curing aids are added to meat products to improve colour, texture and flavour and to prevent or delay undesirable microbial growth and toxin production.
The use of these nitrites or nitrates with salt is required when "cured" is listed as a mandatory process in Volume 7 of the Canadian Standards of Identity. The nitrite and nitrate salts may also be used as preservatives where permitted in Volume 7 of the Canadian Standards of identity and in accordance with the Food and Drug Regulations (FDR) Division 16, Table XI Part 1
Curing by standard method
Meat products can be cured using a slow curing or a rapid curing method. The nitrate and/or nitrite salts are used in slow curing processes whereas nitrites are used in rapid curing of meat products.
In the slow curing process the meat product is rubbed with a nitrate mixture, or soaked in a mixture of nitrate and water, for a period of several days or weeks. The nitrates are slowly converted by bacterial action to nitrite, which is the active curing agent. For example, dry cured hams are produced by coating hams with salt and nitrate.
The calculations for nitrate and/or nitrite in product(s) are made at the input level. Examples of calculations are provided at the end of this document.
As per the Food and Drug Regulations, in products other than side bacon, the maximum input level of sodium nitrite salts is 20 g per 100 kg of meat product, i.e. 200 mg/kg or 200 ppm. In the curing of side bacon, the maximum input level of sodium nitrite salts is 12 g per 100 kg of pork bellies, i.e. 120 ppm.
In the production of slow cured meat products, sodium nitrate salt at a maximum input level of 20 g per 100 kg of meat products, i.e. 200 mg/kg or 200 ppm, may be used in addition to the nitrite salts. An exception to the maximum level of use is permitted for dry rub cured meat products on racks. The maximum level of use permitted is 62 g of sodium nitrite salts and 186 g of nitrate salts per 100 kg of meat product.
The use of a previously cured meat product as an ingredient in excess of 10% of the batch weight will typically necessitate recalculation of the nitrite/nitrate input to account for the contribution from those ingredients.
When storing bulk nitrite or nitrate salts other than Prague powder or similar premixes, make sure you keep those salts secure and account for their use in a record log - to prevent an accidental misuse of these potentially dangerous compounds.
Curing by alternative methods
Cultured celery powder (or other cultured vegetable juice powders validated/proven by evidence to be effective for the intended purpose) can be used as an alternative source of nitrites in the production of cured or fermented meat products. Cultured celery powder contains preformed nitrites produced by bacterial action on nitrates present in the celery product. It is important to know the level of preformed nitrites present in the celery powder to determine the amount of powder to be included in the formulation to achieve the minimum levels of nitrites (100 ppm, CSI Vol 7) needed to cure the product without exceeding the maximum allowable limit (200 ppm, Food and Drug Regulations).
Non-converted celery juice powder (or other vegetable juice powders validated/proven by evidence to be effective for the intended purpose) may be used as a source of nitrates in slow curing processes provided the product meets the prescribed nitrate/nitrite limits.
Non-converted celery juice powder (or other vegetable juice powders validated/proven by evidence to be effective for the intended purpose) containing nitrates, together with a starter culture may also be used as an alternate method of curing meat products. Current regulations (SFCR and FDR) permit this method for unstandardized emulsified red meat products and standardized fermented emulsified red meat products, such as sausages. This method cannot be used to produce poultry products, or other cured meat products by pumping or injection procedures (e.g., brine injected ham). In this method, the operator determines the amount of celery juice powder/vegetable juice to be included in the formulation to achieve the minimum levels of nitrate (100 ppm, SFCR) needed to cure the product without exceeding the maximum allowable limit (200 ppm, Food and Drug Regulations). When red meat products are formulated with nitrates and are subjected to heat treatment shortly afterwards, the minimum incubation period (hold time) needs to be determined by the operator. The operator's preventive control plan will provide the minimum incubation period required for conversion of nitrates into nitrites prior to the destruction of the starter culture by the heat treatment. If the culture manufacturer has not validated the incubation period for a particular heat treated product, the operator in this case will validate that the alternative curing method achieves the same results for that product(s) as the standard curing process described earlier in this document. The validation should include:
- defined nitrate concentration, culture type and incubation period;
- two separate experiments, consisting of two batches each, of a meat product or a product representing a group of meat products. In one experiment, the batches are subject to the standard curing process, while in the second experiment, the batches are subject to the alternate process;
- for each of the batches within an experiment, residual nitrite levels should be assessed in triplicate from each batch at different time intervals i.e., at pre-incubation, post incubation, and immediately following thermal processing at day 7, 14, 30, 60, 125, 160, etc., and at the end of the shelf life of the product.
- statistical analysis should confirm that the residual levels of nitrite in the alternate curing process are not lower than the residual levels present in the standard curing process during the shelf life of the product.
Other experimental approaches can be used as long as they effectively demonstrate the safety of the alternative curing process being considered.
Note that a process validation is not required when slow curing procedures are used because these slow processes will ensure adequate conversion of nitrates into nitrites.
Examples of calculation of nitrite/nitrate salt input levels
Calculation of nitrite in sausage emulsion
Formulation: 114 kg sausage mix and 23 g sodium nitrite in bulk
Calculation: the emulsion weighs 114 + 0.023 = 114.023 kg in total
23g÷114.023kg = 201.7 mg/kg or 201.7 ppm (ppm: part per million). This exceeds the maximum level permitted.
Formulation: 114 kg sausage mix and 350 g Prague Powder
Calculation: The emulsion weighs 114 + 0.350 = 114.35 kg
Prague Powder = 6.25% sodium nitrite, therefore 350 g Prague Powder = 21.875 g sodium nitrite
21.875g÷114.35kg = 0.1913 g/kg which is equivalent to 191.30 ppm
Calculation of nitrite in injected product
Sodium tripolyphosphate: 6.41 kg + Sodium nitrite: 0.28 kg + Sodium erythorbate: 0.84 kg +
Spices: 0.70 kg+ = Total 8.23 kg Cure unit
Cure Unit: 8.23 kg + Water: 134.00 kg + Salt: 40.00 kg = Total 182.23 kg Brine
% Pump (gain) = 15
Formula 1: ppm nitrite = (weight of nitrite in kg ÷ weight of brine in kg) × [(gain × 106) ÷ (gain + 100)]
= (0.28 kg ÷ 182.23 kg) × [(15 × 106) ÷ 115)
= 0.0015365 × 0.130 × 106
= 200 ppm
Formula 2: ppm nitrite = [(weight of nitrite in g × gain in kg) ÷ weight of brine in kg] ÷ (100 kg + gain in kg)
Note Assume weight before injection = 100 kg
gain = 15 kg
weight after injection = 115 kg (weight before injection + gain)
= [(280 g × 15 kg) ÷ 182.23 kg] ÷ 115 kg
= 23.047 g ÷ 115 kg
= 0.200 g/kg i.e., 200 ppm
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