Nitrite reaction with myoglobin

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. 

The advantage of using the Micrococcaceae in fermented sausage production is a more reliable colour formation and colour stabilisation, together with enhancement of aroma. The cured colour is due to nitrosyl-myoglobin, a component obtained in the reaction of nitric oxide with myoglobin. The Micrococcaceae possess the necessary enzyme nitrate reductase that transforms nitrate into nitrite. In an acid environment, nitrite is converted into nitrous acid that is dismutated into nitric oxide. 

Cytochrome c is a heme containing protein which occurs in muscle at lower concentrations than does myoglobin. It was demonstrated some time ago (18) that oxidized cytochrome c reacts with gaseous nitrite oxide to produce a nltrosyl compound. Recent work (19, 20, 21) has examined the reactions of cytochrome c with nitrite and the contribution of the product formed to cured meat color in considerably more detail. The general conclusion is that even at the pH normally encountered in meat, the reaction can take place in the presence of ascorbic acid but probably does not affect meat color because of the unstable nature of the reaction product and the low concentration. 

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