Effect of low pH on the susceptibility of isolated cod (Gadus morhua) microsomes to lipid oxidation

Area of Science:

• Food Science
• Biochemistry
• Marine Biology

Background:

• Muscle protein isolation often involves acid or alkali solubilization, exposing cellular membranes to extreme pH levels.
• Phospholipid oxidation in muscle membranes is a concern during processing, particularly under acidic conditions with hemoglobin present.

Purpose of the Study:

• To investigate the oxidative stability of cod muscle microsomes under acidic conditions simulating protein isolate production.
• To understand the role of hemoglobin and potential inhibitors in lipid oxidation during acid solubilization.

Main Methods:

• Isolated cod muscle microsomes were used as a model system.
• Microsomes and cod hemoglobin were exposed to varying pH levels (pH 3.0 and 5.3).
• Lipid oxidation was assessed, and the effects of citric acid, calcium chloride, and cod press juice were evaluated.

Main Results:

• At pH 5.3 or lower, cod membranes showed significant sedimentation.
• Exposure to pH 3.0 reduced the susceptibility of isolated membranes to hemoglobin-mediated lipid oxidation.
• While low pH decreased hemoglobin's pro-oxidative activity, combined exposure of microsomes and hemoglobin to low pH promoted oxidation.
• Citric acid, calcium chloride, and cod press juice effectively inhibited microsomal lipid oxidation.

Conclusions:

• Acidic conditions (pH ≤ 5.3) impact cod muscle membrane stability and lipid oxidation dynamics.
• Hemoglobin's pro-oxidative potential is altered by low pH, but co-exposure with membranes can still lead to oxidation.
• Specific compounds like citric acid, calcium chloride, and cod press juice show potential as inhibitors of lipid oxidation in muscle processing.