Question

Which of the following are characteristics of whey protein?
A. Whey proteins are proteins which are insoluble at pH 4.6
B. Whey prepared by gel permeation chromatography does not contain lactose & soluble salts
C. Acid whey contains glycomacropapetide
D. Acid whey contains \(\gamma\)-casein and proteose peptone
E. Ultrafiltration is used for the preparation of whey protein isolate
Choose the most appropriate answer from the options given below:

• A. A & C are correct
• B. B & D are correct
• C. C & E are correct
• D. A, B & D are correct

Hint:

Whey Protein Characteristics:
Soluble at pH 4.6 (Casein precipitates).
Sweet (Rennet) Whey = Contains GLYCOMACROPEPTIDE (GMP).
Acid Whey = NO GMP; contains $\gamma$-casein and proteose peptone.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Chemistry of whey proteins and whey processing: whey proteins remain soluble in milk serum at pH 4.6, and acid whey contains $\gamma$-caseins and proteose peptones liberated during acidification without glycomacropeptide (GMP is exclusive to sweet rennet whey).
Key Formula or Approach:
\[ \text{Sweet (Rennet) Whey} = \text{Contains Glycomacropeptide (GMP)} \quad \longleftrightarrow \quad \mathbf{Acid \text{ } Whey} = \mathbf{\gamma\text{-Caseins} + \text{Proteose Peptones (NO GMP)}} \]

Step 2: Detailed Explanation:
Evaluating characteristics of whey proteins and whey processing:
1. A. False: Whey proteins ($\beta$-lactoglobulin, $\alpha$-lactalbumin, BSA, Igs) are by definition the milk serum proteins that remain soluble in milk serum at pH 4.6 at $20^\circ ext{C}$ (caseins are insoluble and precipitate at pH 4.6).
2. B. True: Gel Permeation Chromatography (Size-Exclusion Chromatography) fractionates molecules by size; high-molecular-weight whey proteins elute in the void volume while small lactose and mineral salts are retained, yielding desalinated, de-lactosed pure protein.
3. C. False: Glycomacropeptide (GMP) is formed strictly by chymosin cleavage of $\kappa$-casein and is present only in sweet (rennet) whey, NOT in acid whey (mineral/lactic acid coagulation).
4. D. True: Acid coagulation causes minor partial solubilization of $\gamma$-caseins and proteose-peptones into the acid whey serum.
- Therefore, statements B and D are correct.

Step 3: Final Answer:
Thus, B & D are correct, matching option (B).