Lipid oxidation occurs through three main mechanisms: autoxidation, enzyme-catalyzed oxidation, and photo-oxidation.
Here's a breakdown of each:
Mechanisms of Lipid Oxidation
| Mechanism | Description | Importance (e.g., in meat) |
|---|---|---|
| Autoxidation | A continuous free-radical chain reaction. | Most important. |
| Enzyme-catalyzed oxidation | Oxidation reactions catalyzed by enzymes (e.g., lipoxygenases). | Significant. |
| Photo-oxidation | Oxidation initiated by light, often involving a photosensitizer. | Relevant. |
1. Autoxidation
According to the reference, autoxidation is the most important process of lipid oxidation, especially in meat. It's a continuous free-radical chain reaction. Here's what that means in simpler terms:
- Initiation: A free radical (an unstable molecule with an unpaired electron) is formed.
- Propagation: This free radical reacts with a lipid molecule, creating another free radical and continuing the chain reaction.
- Termination: Two free radicals react and neutralize each other, stopping the chain reaction.
2. Enzyme-Catalyzed Oxidation
Certain enzymes, like lipoxygenases, can speed up the oxidation of lipids. These enzymes are naturally present in many foods, and their activity can lead to off-flavors and rancidity.
3. Photo-oxidation
Light, particularly in the presence of a photosensitizer (a molecule that becomes excited by light and then transfers energy to another molecule), can initiate lipid oxidation. This process can occur on the surface of foods exposed to light.
In summary, lipid oxidation can occur via autoxidation (a free-radical chain reaction), enzyme-catalyzed oxidation (sped up by enzymes like lipoxygenases), and photo-oxidation (initiated by light). Among these, autoxidation is considered the most significant mechanism in meat.
