Question

Which vitamin contributes substantially to the redox potential of milk?

• A. Vitamin A
• B. Vitamin B2
• C. Vitamin B6
• D. Vitamin K

Hint:

Milk Redox Mediators: The primary vitamin establishing the Oxidation-Reduction Potential ($E_h$) of milk is VITAMIN B2 (RIBOFLAVIN), alongside Vitamin C (Ascorbic acid).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Oxidation-reduction poise of bovine milk: Vitamin B2 (riboflavin) is a major electroactive flavin coenzyme ($E_0' = -0.208 ext{ V}$) acting alongside dissolved oxygen and ascorbate to buffer milk redox potential ($E_h$).
Key Formula or Approach:
\[ \text{Riboflavin (Oxidized, Bright Yellow)} + 2e^- + 2\text{H}^+ \xrightleftharpoons{E_0' = -0.208\text{ V}} \text{Leucoriboflavin (Reduced, Colorless)} \]

Step 2: Detailed Explanation:
In milk electrochemistry and redox equilibria:
- The normal oxidation-reduction potential ($E_h$) of fresh bovine milk is $+0.25\text{ to } +0.35\text{ V}$ ($+250\text{ to } +350\text{ mV}$).
- The principal chemical redox systems that establish and buffer this potential include:
1. Dissolved molecular oxygen ($\text{O}_2$).
2. Ascorbic acid (Vitamin C) Dehydroascorbic acid.
3. Vitamin B2 (Riboflavin) (B): Milk contains $1.5 - 2.0\text{ mg/L}$ of free riboflavin and flavin nucleotides (FMN/FAD).
- Riboflavin undergoes reversible two-electron reduction to leucoriboflavin ($E_0' = -0.208\text{ V}$), acting as a primary electroactive oxidation-reduction mediator and substantially contributing to the redox poise and dye reduction kinetics of milk.

Step 3: Final Answer:
Therefore, Vitamin B2 contributes substantially to the redox potential of milk, matching option (B).