The commercial value of red-fleshed fish meat is decreased by browning, which is caused by the oxidation of myoglobin (Mb) to metMb. The formation of metMb proceeds by the SN2 reaction caused by a water molecule in the distal heme pocket attacking the heme iron in oxyMb. The higher partial pressures of oxygen and nitrogen reduce the rate of metMb formation from oxyMb. The present research was performed to determine whether free oxygen molecules could prevent oxidation of oxyMb. Simulation of the molecular dynamics of the system consisting of oxyMb with one oxygen molecule was performed. The partial oxygen pressure was estimated to be approx. 1.6 atm, causing about 40% of oxygen molecules to interact with oxyMb, and the number of water molecules in the distal heme pocket decreased to about two-thirds. Under an oxygen pressure of 1 atm, the rate of metMb formation was expected to reduce to about three-fourths compared to that under vacuum packaging.
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