Nitrates, nitrites curing salts

Although nittate was the traditional meat curing salt, Haldane (1901) demonstrated cured meat pigment development by addition of nitrite to hemoglobin. Hoagland (1908) concluded that bacterial or muscle tissue reduction of nitrate... 

Exposure may occur through oral, dermal, ocular, and inhalation routes. People may be exposed to nitrites through foods such as cured meats and selected vegetables (e.g., broccoli, spinach, cauliflower, col-lard greens, and root vegetables). Accidental poisonings have occurred when people have mistaken sodium nitrate for table salt. 

In other working areas the reduction of airborne nitrosamines is possible, too. In a special curing process using a nitrite-nitrate salt bath for tube... 

Potassium nitrite is an antidote to cyanide poisoning. It also is a vasodilator. An important application is in the dye industry to prepare diazonium salts and azo dyes. Another use is in curing certain meat products where the salt imparts an appetizing pink color to cured meats and retards microbial growth on the meat. The commerical product is usually a nitrite-nitrate mixture, containing 85% KNO2 and 15% KNO3... 

The U.S. Food and Drug Administration (FDA) regulates the addition of nitrate and nitrite salts to fish products. Maximum permitted levels vary among products and types of fish, with up to 500 ppm residual sodium nitrate or 200 ppm sodium nitrite permitted as a preservative and color fixative in smoke cured sable fish, shad, or salmon (Code of Federal Regulations, 1981a,b Committee on Nittite and Alternative Curing Agents in Food, 1981). 

Meat. For preservation purposes, meat has been cured with added salt (NaCl) and nitrates (saltpeter) since ancient times. With the recognition that nitrate was reduced by microbial action, about 60 years ago, added nitrite began to replace nitrate. The typical red color of cured meat results from the reaction of nitric oxide with myoglobin to form nitrogen monoxide myoglobin, more frequently referred to as nitro-somyoglobin, and with heat, nitrosomyochrome. 

In the case of comminuted meat (e.g., burgers), the purpose of analysis is to characterize the main constituents (moisture, protein, fat, ash) and also to determine to what extent it differs from the intact meat. For example, typical analyses applied to comminuted meat samples might include meat species identification and determination of collagen and carbohydrate content. As the meat products move further away from the original entire meat, a range of analyses is used to characterize the food, particularly assays for nonmeat proteins, for additives such as salts, and for preservatives. In the case of cured meat and cured meat products, the important analyses are for salt, nitrite and nitrate, and other additives such as sugars and phosphorus (polyphosphates). 

The salts associated with cured meats, nitrates and nitrites, are assayed by aqueous extraction and colorimetric determination. The ISO methods involve extraction in hot water containing borax solution and deproteination of a portion of the extract with Carrez reagents. Nitrite (ISO 2918 1975) is determined directly by formation of an azo dye with sulfanilamide and N-(l-naphthyl)ethylenediamine dihydrochloride which is measured at 538 mn. Nitrate (including nitrite) (ISO 3091 1975) is determined by cadmium reduction to nitrite and azo dye formation. Reduction of nitrate to nitrite may be carried out on a special column (as in the ISO method) or using spongy cadmium. Care must be taken to prevent interference from ascorbic acid if it is present in the sample at relatively high levels (>20pgml ). 

Vegetables are not the only source of nitrate intake. Potassium and sodium salts of both nitrate and nitrite are commonly used in food industry, in curing meat, for fixing the color, for inhibiting the microbial growth, and for obtaining the characteristic flavor. ... 

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