| No: 13 | January 2008 |
Nitrite and Nitrate In inorganic chemistry, nitrites are salts of nitrous acid (HNO2). They contain the nitrite ion (NO2-). Nitrites of the alkali and alkaline earth metals can be synthesized by reacting a mixture of nitrogen monoxide (NO) and nitrogen dioxide (NO2) with the corresponding metal hydroxide solution, as well as through the thermal decomposition of the corresponding nitrate. Other nitrites are available through the reduction of the corresponding nitrates.
In inorganic chemistry, a nitrate is a salt of nitric acid with an ion composed of one nitrogen and three oxygen atoms (NO3-). In organic chemistry the esters of nitric acid and various alcohols are called nitrates. Nitrate from food, especially vegetables, is converted in the human digestive tract to nitrite which reacts with amines to form carcinogenic nitrosamines.
Nitrite is a salt used to preserve meat, fish, and poultry. It is also a chemical substance in the human body, formed through normal physiological processes and the digestion of foods containing nitrite or nitrate. The latter, a salt of nitric acid, is an essential plant nutrient taken up by plants from soil as their principal nitrogen source. Nitrate is a natural component of all fruits, vegetables, and cereals. Nitrates and nitrites are nitrogen-oxygen chemical units which combine with various organic and inorganic compounds. Once taken into the body, nitrates are converted into nitrites. The greatest use of nitrates is as a fertilizer. What are the sources of nitrite and nitrate? Green leafy and root vegetables, such as spinach and carrots, provide more than 85 percent of dietary nitrate, which may be converted to nitrite by the human body during digestion. Though the majority of ingested nitrate is cleared rapidly from the body via excretion, some of it is transported to the salivary glands and secreted in the mouth. There it may be reduced by existing bacteria to nitrite and carried to the stomach upon swallowing. Dietary nitrate may also come from drinking water. Most national drinking water authorities have set a maximum limit for nitrate in drinking water to prevent high intake. The levels of nitrate in water vary greatly and may be quite high in some localities. Nitrate content in both drinking water and vegetables can be influenced by the use of nitrate fertilizers. Foods to which nitrite is added include bacon, fermented sausage, hot dogs, bologna, salami, corned beef, ham, and other products such as smoked or cured meat, fish, and poultry. On the whole, however, the dietary intake of nitrite from cured meats is only a minute fraction of the body's total exposure. A significant amount of nitrite in the body is produced endogenously (internally), rather than introduced from dietary sources. Why is nitrite added to food? Nitrite is added to certain foods to prevent the growth of the spore-forming bacterium Clostridium botulinum, whose toxin causes botulism, leading to paralysis and potentially, death. Botulinum toxins are the most toxic compounds known, 15.000 times more potent than nerve gas (100.000 times more potent than the nerve gas sarin). The word botulinum comes from the Latin word botulus, meaning sausage, which was responsible for many deaths centuries ago, before the advent of curing with nitrite. In addition to functioning as an antimicrobial agent, nitrite is used to produce the characteristic flavour, texture, and pink colour of cured meats. Directive 95/2/EC on food additives other than colours and sweeteners regulates the use of emulsifiers, antimicrobial agents and antioxidants, including nitrates and nitrites. The Directive has 6 Annexes:
The use of nitrates and nitrites in some food stuffs is placed in the "Annex III, Part C of 95/2/EC. In addition to using as food additive, nitrate is also essential growing factor for plants and therefore it is widely used for fertilizing in agriculture. Since some plants accumulate nitrate in very high amounts, e.g. spinach and lettuce, the European Commission has regulations which set maximum levels for nitrates in those plants as contaminants regulated in Commission Regulation (EC) No 1881/2006 of 19 December 2006 setting maximum levels for certain contaminants in foodstuffs References
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