Question

____________ is much more rapidly oxidized during browning of meat.

• A. Hemoglobin
• B. Myoglobin
• C. Ferroprotoporphyrin
• D. Methmyoglobin

Hint:

Fresh meat color changes from purple (Deoxymyoglobin) \(\rightarrow\) bright red (Oxymyoglobin) \(\rightarrow\) brown (Metmyoglobin).
This browning is caused by the oxidation of the ferrous iron (\(\text{Fe}^{2+}\)) in myoglobin to ferric iron (\(\text{Fe}^{3+}\)).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The color of fresh meat is determined primarily by the state of its pigment proteins, particularly myoglobin.
Browning occurs when the iron atom in the heme ring of myoglobin is oxidized, changing the meat's color from bright red to brown.

Step 2: Detailed Explanation:
Myoglobin is the primary oxygen-binding hemoprotein found in skeletal muscle, and is responsible for about 80--90% of the pigment in red meat.
The color of myoglobin depends on the chemical state of its heme iron:
- Deoxymyoglobin (reduced state, containing \(\text{Fe}^{2+}\)): Displays a deep purplish-red color in vacuum-packaged meat.
- Oxymyoglobin (oxygenated state, containing \(\text{Fe}^{2+}\)): Displays a bright cherry-red color when meat is exposed to oxygen.
This state is highly unstable over time.
In the presence of oxygen, light, and lipid oxidation products, oxymyoglobin and deoxymyoglobin undergo rapid oxidation.
During this oxidation, the ferrous iron (\(\text{Fe}^{2+}\)) is oxidized to its ferric state (\(\text{Fe}^{3+}\)), converting the pigment into metmyoglobin (or methmyoglobin) (D).
Metmyoglobin is a stable pigment that displays a dull brown color, which is undesirable to consumers.
While hemoglobin (A) is a similar oxygen-carrying protein, it is found primarily in blood and is mostly removed during slaughter, leaving myoglobin as the primary pigment that oxidizes during meat browning.
Therefore, myoglobin is the protein that undergoes rapid oxidation during browning.

Step 3: Final Answer:
The primary muscle pigment that undergoes rapid oxidation during the browning of meat is myoglobin.