Question

Heat denaturation of whey proteins leads to

• A. Fishy flavour
• B. Sandiness
• C. Fouling
• D. Browning

Hint:

Thermal Dairy Defects:
Whey Protein Denaturation ($> 70^\circ\text{C}$) $\rightarrow$ FOULING (Burn-on deposits on heat exchangers).
Lactose Crystallization $\rightarrow$ Sandiness.
Maillard Reaction $\rightarrow$ Browning.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Dairy processing engineering and thermal deposit kinetics: thermal denaturation of globular whey proteins ($eta$-lactoglobulin at $> 70^\circ ext{C}$) exposes reactive sulfhydryl groups that cross-link and aggregate into hard mineral-protein burn-on crusts (Type A fouling deposits) on heat exchanger plates.
Key Formula or Approach:
\[ \text{Heating Milk (} T > 70 - 75^\circ\text{C)}: \beta\text{-Lactoglobulin Denaturation} \longrightarrow \text{Aggregates with Minerals} \implies \mathbf{Fouling \text{ } Deposits on Heat Exchanger Plates} \]

Step 2: Detailed Explanation:
In dairy processing plant engineering and thermal heat exchange:
- Fouling (Heat Exchanger Deposit Formation) (C): The unwanted accumulation of thermal deposits on the stainless steel heat transfer plates and tubes of pasteurizers and UHT plants.
- Heat-induced unfolding and Thermal Denaturation of Whey Proteins (principally $\beta$-Lactoglobulin and $\alpha$-Lactalbumin) above $70^\circ - 75^\circ ext{C}$ exposes reactive thiol (-SH) groups.
- The unfolded whey proteins form intermolecular disulfide-bonded aggregates that adhere firmly to hot stainless steel surfaces together with colloidal calcium phosphate (forming Type A soft proteinaceous fouling deposits at $75^\circ - 110^\circ ext{C$}), severely reducing heat transfer coefficients and causing pressure drops.

Step 3: Final Answer:
Therefore, heat denaturation of whey proteins leads to Fouling, corresponding to option (C).