Nitrite preservatives

Nitrates and nitrites are spread within environmental, food, industrial, and physiological systems. Nitrate may be reduced by bacteria to nitrite, and nitrite produces carcinogenic nitrosamines. Nitrite is also commonly employed in cured meat products to provide antimicrobial action, color fixation, and preservation. Nitrite can oxidize hemoglobin iron(II) to iron(III) resulting in methemoglobin, leading to a condition known as methemoglobinemia in children mainly. In excess, nitrates and nitrites may be toxic. 

Nitrates are found in fairly high concentrations in beets, spinach, kale, coUards, eggplant, celery, and lettuce. AdditionaHy, nitrates and nitrites are commonly used in the curing solutions of bacon, ham, and other cured meats. In cured meats, nitrates and nitrites control the growth of microorganisms, particularly Clostridium botulinum, and also serve as color preservatives. 

Nitrite is part of the preserving process for cured meats. Cigarette smoke contains high levels of nitrite. 

Sodium nitrite is used to fix the colors in preserved fish and meats. It is also important (along with sodium chloride) in controlling the bacterium Clostridium botulinumy which causes botulism. Lunch meats, hams, sausages, hot dogs, and bacon are usually preserved this way. 

Potassium nitrate is also found in pills for backache and joint pain. It makes a decent plant fertilizer, providing nitrogen and potassium but no phosphorus. As an oxidizer, it is an ingredient in stump removers that hastens the decay of tree stumps. And it is used as a preservative in some salted meats like nitrites, it helps to preserve the color of the meat. 

C17-0022. Potassium nitrite is used as a food preservative. Determine the pH and concentrations of all species in an aqueous solution of KNO2 whose concentration is 0.22 M (see values in Table DM)-... 

Mirvish (53,54) discovered that vitamin C could inhibit ni-trosation reactions. The purely chemical interaction of ascorbic acid with nitrite has been studied for theoretical reasons and because of its importance in the preservation of foods. This interaction has received increased attention for minimizing the presence of nitrosamines and nitrosamides in the environment, and especially in foods. We have studied the relationship in gastric carcinogenesis between high levels of nitrite, including pickling, and of vitamin C as a protective and inhibiting element. 

Sample preservation by pasteurisation has been applied to the preservation of nitrite and nitrate in seawater [152], Samples can be stored for several months before analysis. 

Inhibitors of nitrosation generally function by competing with the amine for the nitrosating agent. An inhibitor would thus react with nitrite at a faster rate than with amines. The inhibition reaction has recently been reviewed ( 35). The ability of ascorbate to act as a potent inhibitor of nitrosamine formation has resulted in the use of the vitamin in nitrite-preserved foods and pharmaceuticals. Furthermore, the effectiveness of ascorbate in inhibiting nitrosamine formation is dependent on (1) the concentration of ascorbate (an excess is required) (2) pH (ascorbate is nitrosated 240 times more rapidly than ascorbic acid) (3) the reactivity of the amine toward nitrosation and (4) the extent of oxygenation of the system. 

They must be safe. Illness is likely to result if consumers ingest too much of them, like contaminants (see Watson, 2001). Therefore numerical limits are set for many additives in EU law. Consumers can also become ill if some additives are not used. For example preservatives such as nitrite have to be biologically-active to work. The question is are they biologically-active against us A lot of scientific work had to be done before many preservatives were allowed for use in the European Community (now the EU). Preservatives were one of the first groups of additives to have their levels controlled in food so that consumers did not consume unsafe amounts of them. 

There is a balance to be drawn between risks. Looking at nitrite again, this ion has been used since the Middle Ages to preserve meat. It is the preservative in saltpetre which helps preserve cured meats and stop those who eat them getting botulism. There has been much research to find an alternative to nitrite as it can react with some amines to form carcinogenic nitrosamines. Risk analysis, reviewed in Chapter 4, is an important tool in controlling the use of additives. 

Annex III lays down the conditions of use for permitted preservatives and antioxidants, with lists of foods and maximum levels in each case. Part A lists the sorbates, benzoates and p-hydroxybenzoates, E 200-E 219 part B lists sulphur dioxide and the sulphites, E 220-E 228 part C lists other preservatives with their uses, including nisin, dimethyl dicarbonate and substances allowed for surface treatment of certain fruits, E 249 potassium nitrite, E 250 sodium nitrite, E 251 sodium nitrate and E 252 potassium nitrate, E 280-E 283 propionic acid and the propionates part D lists the antioxidants E 320 butylated hydroxyanisole (BHA), E 321 butylated hydroxytoluene (BHT), E 310 propyl gallate, E 311 octyl gallate, E 312 dodecyl gallate, E 315 eiythorbic acid and E 316 sodium erythorbate. 

There are several routes for nitrosamine contamination in pesticides use of contaminated chemicals during synthesis, side reactions, use of nitrite as a preservative and corrosion inhibitor of metal containers and by reactions with environmental nitrosating agents. Over 300 formulations were shown to be contaminated with nitrosamines however, the main contamination was confined to 2,6-dinitroaniline herbicides, dimethylamino salts of phenoxyalkanoic acid herbicide, diethanolamine and triethanolamine salts of acid... 

Human exposure to nitrates is via exposure to food and drinking water. The nitrates in food may be present naturally or as an additive introduced for various technological reasons. Nitrite is added to foods for preservation, but is reactive in foods, whereas nitrate is quite unreactive. 

In foodstuff preserved by addition of nitrate/nitrite (namely cured meat produce and cheeses) both methods of preservation introduce nitrosating species into the food matrix. 

Pickled and salt-preserved foods, in particular plant-based products (pickled vegetables) in which microbial reduction of nitrate to nitrite occurs. Foodstuffs stored under humid conditions favouring fungal contamination, particularly the growth of Fusarium moniliforme. 

The preservation of nutrient solutions at the concentrations occurring in natural seawater is a major challenge to the routine production of a nutrient reference material. Preservation techniques must be developed that maintain concentrations stable for periods of at least one to two years. Gamma radiation will produce nitrite that is unstable. Therefore this method appears to be problematic. The feasibility of other techniques, such as autoclaving, ultra-violet or microwave radiation, freezing, and acidification, should be evaluated. 

Sodium nitrite is used as a preservative in processed meats, such as bacon, ham, and sausage. The nitrite ion, NO2U may enter the ground water in rural areas where manure is stored and be a serious health threat for infants. Draw a Lewis structure, and predict the shape of NO2X Indicate any resonance structures. 

Macrophages are cells that light invasion by foreign organisms. One way that they do this is to zap them with NO in concentrations that are toxic to the invaders. So NO is important as a component of the defense system of human beings. As it turns out, sodium nitrite, NaN02, a commonly used preservative, works by generating NO, which is responsible for its ability to preserve foods. 

Nitrates are formed when nitric acid is neutralized by a base such as sodium hydroxide (NaOH). These nitrates change form to become nitrites that are used as preservatives, particularly in canned goods and to keep meat looking fresh. 

Amines react with nitrous acid (formed by the reaction NaN02 + H HNO2) to give a variety of products. The nitrous acid isn t very stable, so generating it in place from sodium nitrite is necessary. (Sodium nitrite is a meat preservative and a color enhancer.) Under acidic conditions, nitrous acid dehydrates to produce the nitrosonium ion, NO. The NO ion is a weak electrophile that s resonance stabilized. (See Chapter 7.) Figure 13-22 illustrates the dehydration of nitrous acid. 

Nitrate, nitrite Preservative Present in vegetables form carcinogenic nitrosamines... 

It is further recommended that amine-nitrite mixtures be kept away from electrophilic carbonyl compounds and gem-di-halides capable of supporting immonium ion formation, for example in the preservation of amine-rich fish products with formaldehyde ( ) or in the use of methylene chloride as an aerosol propellant (13). It also seems advisable to avoid storing treflan and related herbicides in the presence of... 

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