Metmyoglobin

Metmyoglobin ( MbFe (III )) is the oxidized form of the oxygen-carrying protein myoglobin ( MbFe (II)). It is formed by autoxidation in the body of vertebrates. Metmyoglobin is the cause of the characteristic brown - gray discoloration of dead flesh, which occur during storage. To an iron (III ) ion - in the oxidation, the iron (II ) changes.

Physiology

In the body there is an equilibrium between the Fe (II) - and Fe (III ) forms of myoglobin, such that a constant ratio of two to three percent of the Gesamtmyoglobin MbFe from (III) is ( the same applies to the hemoglobin / methemoglobin ). In addition metmyoglobin can react with hydrogen peroxide (H2O2 ) can be activated to Perferrylmyoglobin, an excited state decays rapidly to ferrylmyoglobin MbFe (IV ) = O, in which iron has a coordination number of 4.

Food Chemistry

In dead muscle tissue, the concentration of Metmyoglobins increases when a lack of oxygen in the packaging is present (for example, when meat pieces are superimposed ). The normal process, reduce metmyoglobin via the pores will be blocked in this manner, and the iron contained in the meat changes color ( oxidized).

For color stabilization in meat technology formed by the addition of nitrite and nitrosyl metmyoglobin.

Together, both stable complexes bright red in color ( nitrosylmyoglobin and Nitrosylmetmyoglobin ). The process is referred to as color development.