Nitric Oxide and Cured Meat Color

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 

Production of Nitrosylmyoglobin from Sodium Nitrite or Potassium Nitrate  

A nonmitochondrial muscle diaphorase has also been described (Koizumi and Brown (1971), capable of forming NOMb in solutions containing nitrite and Mb, using methylene blue as a nonspecific electron carrier. NOMb formation by both the mitochondrial and mtnmitochondrial diaphorase enzyme systems requires the presence of reduced NADH. 

In canned meats, ascorbate also enhanced NOMb production (Reith and Szakaly, 1967b). Without ascorbate, a Mb nitrite molar ratio of 1 5 was needed for optimum formation of NOMb. With ascorbate, a ratio of 1 Mb 3 nitrite was sufficient for maximum NOMb formation. Sodium erythorbate was equivalent to sodium ascorbate for NOMb formation. Canned meats formulated with potassium nitrate showed no formation of cured meat pigment. 

Ascorbate, cysteine, hydroquinone, and NADH are capable of acting as re-ductants for NOMb formation in model systems containing sodium nitrite and Mb (Fox and Ackerman, 1968). Ascorbate, cysteine, and hydroquinone all form nitroso-reductant intermediates which released NO, forming a NO-MMb complex which was then reduced to NOMb. Release of NO from the reductant-NO complex was rate limiting in production of NOMb. For NADH as reductant, reduction of NOMMb to NOMb was the rate limiting step. In summary, two reduction steps were required, the reduction of nitrite (as nitrous acid or its anhydride, N2O3) to NO, and reduction of NOMMb to NOMb. 

---