Lipid-oxidation-induced carboxymyoglobin oxidation

Area of Science:

• Food Chemistry
• Biochemistry
• Spectroscopy

Background:

• Brown color formation in meat products is often linked to myoglobin oxidation.
• Accurate methods are needed to quantify browning and understand its underlying mechanisms.

Purpose of the Study:

• To evaluate the ratio A503/A581 as a browning index (BI) for oxymyoglobin (OxyMb) and carboxymyoglobin (COMb).
• To investigate the impact of lipid oxidation products, specifically 4-hydroxy-2-nonenal (HNE), on myoglobin browning.
• To determine the influence of pH and temperature on HNE-induced browning in COMb and OxyMb.

Main Methods:

• Spectrophotometric analysis using a split-chamber cuvette.
• Quantification of metmyoglobin (MetMb) proportions.
• Treatment of OxyMb and COMb solutions with 4-hydroxy-2-nonenal (HNE).
• Assessment of spectral changes at varying pH (7.4 and 5.6) and temperatures (37°C and 4°C).

Main Results:

• The A503/A581 ratio showed a high correlation (r = 0.93-0.94) with MetMb estimation.
• The BI was unaffected by varying proportions of COMb and OxyMb.
• HNE treatment increased browning in both OxyMb and COMb at pH 7.4 and 37°C.
• At pH 5.6 and 4°C, HNE-induced browning was more significant in COMb compared to OxyMb.

Conclusions:

• The A503/A581 ratio is a reliable index for estimating brown color formation in myoglobin solutions.
• Carboxymyoglobin (COMb) is prone to browning induced by lipid oxidation products.
• The susceptibility of COMb to HNE-induced browning is dependent on pH and temperature conditions.