Dairy Chemistry- ICAR JRF/SRF 2024

• Stokes' Law and Fat Globule Creaming Velocity:
• Governing Equation:

• $v$: creaming velocity.
• $r$: fat globule radius.
• $\rho_p - \rho_f$: density difference between milk plasma and fat.
• $\eta$: dynamic viscosity of milk plasma.
• Fat globule rise velocity is directly proportional to the square of globule radius and inversely proportional to plasma viscosity ($\eta$).
• Conclusion: Viscosity of plasma (Option 2).

Correct option: (2) Viscosity of plasma

• Partitioning of Calcium in Bovine Milk:
• Soluble vs Colloidal Distribution:
• Total calcium in bovine milk averages $120\text{ mg}/100\text{ mL}$ ($30\text{ mM}$).
• Approximately $33\%$ (one-third, $\approx 10\text{ mM}$) is present in the soluble serum phase as free ionic calcium ($\text{Ca}^{2+}$) and soluble complexes with citrate and phosphate.
• The remaining $67\%$ (two-thirds) is bound in the colloidal phase as colloidal calcium phosphate (CCP) within casein micelles.
• Conclusion: 33% (Option 4).

Correct option: (4) 33

• Whey Protein Nitrogen Index (WPNI) Classification:
• ADPI Standards for Nonfat Dry Milk:
• Measures undenatured whey protein nitrogen per gram of powder ($\text{mg WPN/g}$):
• Low-Heat Milk Powder: $\ge 6.0\text{ mg WPN/g}$ (very low level of protein denaturation).
• Medium-Heat Milk Powder: $1.5 - 5.9\text{ mg WPN/g}$.
• High-Heat Milk Powder: $\le 1.5\text{ mg WPN/g}$ (severe denaturation).
• Conclusion: ≥ 6.0 (Option 2).

Correct option: (2) 26.0