Question

The increased yield of Paneer achieved in milk heated beyond 85°C is mainly due to

• A. \(\alpha\)-lactalbumin \(\kappa\)-casein interaction
• B. Proteose-peptone \(\kappa\)-casein interaction
• C. \(\beta\)-lg \(\kappa\)-casein interaction
• D. \(\beta\)-casein \(\kappa\)-casein interaction

Hint:

Paneer Yield Chemistry: Heating milk to $85 - 90^\circ\text{C}$ induces $\mathbf{\beta\text{-LACTOGLOBULIN -- } \kappa\text{-CASEIN COMPLEX}}$ via disulfide bonding, co-precipitating whey proteins to boost curd yield.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Heat-induced whey protein-casein co-precipitation: heating milk to $85^\circ - 90^\circ ext{C}$ prior to acid coagulation thermally unfolds $eta$-lactoglobulin, which forms covalent disulfide bridges with micellar $\kappa$-casein ($eta ext{-lg}-\kappa ext{-casein complex}$), co-precipitating denatured whey proteins into the curd matrix to increase Paneer yield by 10--15%.
Key Formula or Approach:
\[ \text{Milk Heated to } 85^\circ - 90^\circ\text{C}: \beta\text{-Lactoglobulin (Free -SH)} + \kappa\text{-Casein (Disulfides)} \xrightarrow{\text{Thiol-Disulfide Exchange}} \mathbf{\beta\text{-Lg--}\kappa\mathbf{\text{-Casein Complex (Co-precipitates in Curd)}}} \]

Step 2: Detailed Explanation:
In the technology and chemistry of Paneer manufacture:
- Traditional paneer manufacture requires heating milk to 85°C to 90°C (held for 5 minutes) before cooling to $70^\circ - 75^\circ ext{C}$ for acid coagulation.
- Heating beyond $85^\circ ext{C}$ significantly increases the yield of Paneer ($18 - 22\%$) due to:
1. $\beta$-Lactoglobulin -- $\kappa$-Casein Complex Formation (C): Thermal unfolding of the major whey protein $\beta$-lactoglobulin ($\beta$-lg) exposes its free Cys121 sulfhydryl (-SH) group.
2. It undergoes covalent thiol-disulfide exchange with cysteinyl residues of micellar $\kappa$-Casein, forming a stable $\beta\text{-lg-\kappa\text{-casein complex}$}.
3. Upon acid addition (citric acid, pH 5.3), this complex co-precipitates denatured whey proteins directly with caseins into the curd matrix, retaining water and protein that would otherwise be lost in the whey serum.

Step 3: Final Answer:
Thus, the increased yield is due to \(\beta\)-lg \(\kappa\)-casein interaction, matching option (C).