For those who produce commercially or for their own consumption, it is extremely important to know and be able to estimate the reduction rate of sodium nitrite(present in curing salt) added in production. To better understand this issue, I listed some studies that present this reduction or conversion of sodium nitrite in cured meats from production to storage.
Residual nitrite in meat products is regulated in Brazil at a maximum of 150ppm in the product to be consumed. Low concentrations of nitrite can increase the chances of microbiological contamination of meat products, so it is important to use the recommended amount. Nitrite is converted to nitric oxide, which in turn reacts with myoglobin and hemoglobin. For this reason, the level of residual nitrite in products decreases over time. To better understand sodium nitrite and the recommended amount of use, also read Curing salt, what it is and how much to use.
A study carried out in Sweden, which focused on evaluating exposure to nitrite in 4-year-old children, monitored the reduction in nitrite added to meat products from the day of production until their final expiration date.
In the graph below it is possible to see the progression of nitrite reduction through residual analysis in the products used in the study.
After 24 hours of adding nitrite at the time of production, nitrite levels were reduced to approximately 55%, 45%, 35% and 15% of the initial level, that is, there was a drop of up to 85% in 24 hours. It is also noted that chicken meat had the slowest reduction.
The CMC – Canadian Meat Council cites that between 10% and 20% of added nitrite remains present immediately after the production process. This concentration decreases over time. In Canada, product surveys were carried out in different cities and the results were similar to another study published in 2012 by the North American Journal of Agricultural and Food Chemistry. In this study, 470 products containing cured meats were purchased in stores in the 5 largest metropolitan cities in the United States. The average concentration result was 37 mg/kg nitrate and 4.5 mg/kg nitrite.
A classic North American study from 1973 called “Changes in residual nitrite in sausage and luncheon meat products during storage“, analyzed the reduction in nitrite concentration in various products. This same study reports that between 20% and 25% of the added nitrite is already reduced during the mixing of the ingredients in the production plant.
The study presents reductions in different products over time. Day 0 determines the start of storage.
Beef Frankfurter Sausage
Addition (ppm): 110 nitrite and 119 nitrate
0 days: 27 ppm
10 days: 16 ppm
20 days: 13 ppm
31 days: 11 ppm
Bologna (Mortadella)
Addition (ppm): 126 nitrite and 135 nitrate
0 days: 20 ppm
6 days: 18 ppm
12 days: 17 ppm
17 days: 25 ppm*
*The addition of sodium nitrate to products that do not undergo long curing has been abandoned. The increase is probably related to the conversion of sodium nitrate to sodium nitrite, which is currently a well-known fact.
Beef Frankfurter Salami
Addition (ppm): 126 nitrite and 136 nitrate
0 days: 42 ppm
10 days: 12 ppm
21 days: 6 ppm
30 days: 6 ppm
Smoked sausage
Addition (ppm): 123 nitrite and 132 nitrate
0 days: 30 ppm
5 days: 30 ppm
8 days: 26 ppm
15 days: 19 ppm
Nitrate and Nitrite in the human body
On a study in the United States, carried out by medical institutes, universities and health agencies, which aimed to analyze the sources of nitrite and nitrate in the North American diet, evaluating the sources from various vegetables. Below is the relationship and result.
The concentration of nitrite/nitrate in vegetables, according to the 2009 North American study, noted differences in conventional and organic vegetables taken from five metropolitan cities. The nitrate levels of broccoli, cabbage, celery, lettuce and spinach were 394.38, 417.56, 1,495.48, 850.46 and 2,797.18 ppm, respectively, while their organic versions averaged 204.29 , 551.97, 911.94, 844.06 and 1,317.73 ppm. To give a comparison, the residual nitrite allowed in a meat product processed in Brazil is 150ppm, while organic spinach has more than 1300 ppm of naturally present nitrate.
The study concludes that vegetables contribute 80% of nitrate intake in the North American diet.
The Canadian CMC (Canadian Meat Concil) mentions that vegetables constitute, by far, the largest source of nitrate in the human diet, providing more than 85% of daily intake. Additionally, nitrate and nitrite are synthesized by human metabolism. Nitrate produced by human metabolism is secreted by saliva. Nitrate is chemically reduced to nitrite by bacteria present in the mouth. Normally, about 20% of the nitrate produced by saliva and food is converted to nitrite. This conversion represents more than 90% of the total nitrite ingested, the remainder comes from sources external to the body.
Sources of nitrite and nitrate
The vegetables with the highest nitrate concentrations, from 1,000 to 2,500ppm, are:
Escarole, lettuce, spinach, red beetroot, radish, celery, rhubarb, parsley, chard and turnip;
Vegetables with medium concentrations, 500 to 1,000 ppm), include:
Cabbage, leeks, pumpkin and turnip;
Examples of low concentration, from 200 to 500 ppm, are:
Broccoli, carrots, cucumber, cauliflower, pumpkin, eggplant, chives, chives, melon
Other foods with less than 200ppm are:
Potatoes, peppers, sweet potatoes and tomatoes
Nitrite and nitrate in processed meats
The results published by the North American study indicate that:
The weighted averages of nitrite and nitrate levels across all processed meat categories were 4.54 and 37.07 ppm.
The lowest nitrite levels in the North American study were observed in fermented, dry-cured meat products, averaging between 0.64 and 1.95 ppm. Higher nitrite levels were observed for cooked and uncooked whole sausages and muscles, averaging between 6.86 and 7.31 ppm.
References
Time-dependent depletion of nitrite in pork/beef and chicken meat products and its effect on nitrite intake estimation
A National Survey of the Nitrite/Nitrate Concentrations in Cured Meat Products and Nonmeat Foods Available at Retail – NPB #08-124
Canadian Meat Council
Changes in residual nitrite in sausage and luncheon meat products during storage
English 
Português do Brasil
How long does the pancetta need to be smoked after applying the curing salt?
Ricardo, see the nitrite conversion times in this post. Even after smoking or cooking, nitrite continues to be converted, so it is not necessary to wait before finishing the preparation, but rather wait before consuming. See in the post that after 2 or 3 days the nitrite will already be converted in large quantities. Nitrite conversion time in cured meats
In all cup recipes, you have to wash the meat after 15 days.
Is this washing process to remove the salt or cure? If so, in the studies presented, does this process exist?
Hi Leandro. Washing after the first curing stage is optional, the seasoning and additives will have already been absorbed by the meat and little will remain on the surface. It's another option for those who want the outside of the product to be cleaner when placed in the casing, but it's not mandatory.
Goodnight. I have a question regarding the use of nitrite and the storage of fresh sausages at a temperature of -18 degrees C. In the table above, the test was carried out with storage at 2-3 degrees C. With the storage temperature at -18 degrees and in vacuum packaging, with the use of nitrite in adequate quantities, this shelf life can reach how many days ?
The same as a commercial frozen sausage from a refrigerator, that is, around 120 days. You can check similar products on the market and take the same durability as a basis.