81 Species-specificity in metmyoglobin reduction

Abstract Myoglobin is the primary sarcoplasmic protein responsible for meat color. Previous research has reported that myoglobin oxidation is species-specific. Metmyoglobin reducing activity is an inherent property to limit myoglobin oxidation. However, limited research has determined species specificity in metmyoglobin reducing properties. The objective of current study was to compare metmyoglobin reducing properties of eight different species such as beef, porcine, bison, deer, emu, equine, goat, and sheep in vitro. Myoglobin was isolated from eight different species via ammonium sulfate precipitation. The pH of the myoglobin was adjusted by passing through a column pre-calibrated with 50 mM phosphate buffer at pH 5.6. All species myoglobin were converted to metmyoglobin, and the metmyoglobin reduction was determined by two different approaches, non-enzymatic metmyoglobin reducing activity (NMRA) and oxidation-reduction potential (ORP). In the first method, NADH (electron donor), EDTA, and methylene blue (electron carrier), were added in a cuvette and increase in absorbance at 582 nm was monitored using a UV-Vis spectrophotometer. In the second method, the ability of the heme to get reduced was determined using an RedoxSys analyzer, in which electron was directly transferred to heme. The NMRA and ORP experiments were replicated five times. The data were analyzed using the Mixed Procedure of SAS, with species as the fixed effect. There were species-specific differences (P < 0.05) in NMRA and ORP. Bovine myoglobin had the greatest (P < 0.05) NMRA compared with sheep, equine, goat, deer, bison, pork, and emu. There were no differences (P > 0.05) in NMRA among equine, goat, deer, bison, pork, and emu. ORP studies indicated that beef and porcine myoglobins had the greatest ability to get reduced (P < 0.05) compared with other species. Hence, use of different techniques and approaches will help to elucidate the mechanistic basis of metmyoglobin reduction.