PHYSICOCHEMICAL CHARACTERISTICS OF NITROSOMYOGLOBIN - WATER-EXTRACTABILITY AND STABILITY TOWARD AN OXIDIZING-AGENT OF MYOGLOBIN DERIVATIVES

To clarify the mechanism of the insolubilization of nitrosomyoglobin ( NOMb) formed in meat during curing, the extractability of myoglobin (M b) derivatives with water coexisting with NOMb in cured meat was compa red, and the effects of an oxidizing agent on heme pigments were inves tigated. Cured meat was prepared by adding nitrite, sodium chloride an d sodium ascorbate to porcine skeletal muscle. In spite of the low ext ractability of NOMb from the cured meat, the other Mb derivatives were significantly more extractable with water. On adding potassium ferric yanide at 1 %, most of the heme pigments in the cured meat were oxidiz ed to metmyoglobin (MetMb). NOMb formed during curing could not be ext racted with water, even after being oxidized to MetMb with ferricyanid e. NOMb thus appears to react strongly with endogenous muscle componen ts, especially myofibrils, in cured meat. NOMb and oxymyoglobin (MbO(2 )) were prepared as model solutions and to both ferricyanide (0-0.5 %) was added. One reaction mixture was incubated at pH 5.5 and the other , at pH 7.0, followed by measurement of absorption spectra. Under the experimental conditions used, Mb was completely nitrosated, but the ox ygenation of Mb did not proceed to 100 %. In a 90 % MbO(2) solution at each pH, all MbO(2) was oxidized to MetMb by 0.5 % ferricyanide. This treatment failed to oxidize NOMb completely. These results clearly sh ow that NOMb is more stable toward oxidizing agents than MbO(2).