Metmyoglobin reducing activity.

Meat colour is a major factor that influences the purchase decision by consumers. Many intrinsic and extrinsic factors contribute to the final colour of meat. The role of the MetMb reducing system in maintaining meat colour has been controversial and a considerable amount of work has been published since [Giddings, G. G., 1974. Reduction of ferrimyoglobin in meat. CRC Critical Reviews in Food Technology 5, 143-173] classic review. Historically, the activity of MetMb reductase was classified under different names, for example, diaphorases, aerobic and anaerobic reducing systems, cytochrome b(5) MetMb reductase, and NADH dependent metmyoglobin reducing enzyme system. Several techniques have been proposed to measure the enzyme activity including reflectance spectrophotometry and absorbance spectrophotometry. However, the variations in the reductase systems and techniques used to measure them have yielded inconsistent results from different investigators. This review seeks to characterize the current understanding of metmyoglobin reduction in meat especially with reference to recent developments in this area. Because many systems (different enzymatic systems and non-enzymatic systems) have been reported to reduce MetMb, the term MetMb reductase is not appropriate to be used to reflect "the MetMb reducing activity" in meat. The need for a standardized approach for measuring MetMb reduction is discussed in order for future research to ensure a greater understanding of this important reaction.