Unit 1

• Buffering Capacity of Bovine Milk:
• Principal Buffering Salts:
• Milk exhibits maximum buffering capacity around $\text{pH } 5.2$ and $\text{pH } 6.6$.
• Phosphates (colloidal calcium phosphate associated with casein micelles and soluble inorganic orthophosphates $\text{HPO}_4^{2-} / \text{H}_2\text{PO}_4^-$) provide the predominant mineral buffering power across the physiological pH range.
• Citrates and casein carboxyl/amino residues provide supplementary buffering.
• Conclusion: Phosphates (Option 4).

Correct option: (4) Phosphates

• Physical Partitioning of Minerals in Bovine Milk:
• Dual Phase Distribution:
• Milk minerals exist in dynamic equilibrium partly in the soluble phase and partly in the colloidal phase.
• Colloidal phase: Two-thirds of calcium, half of magnesium, and half of inorganic phosphate are bound within casein micelles as colloidal calcium phosphate (CCP).
• Soluble phase: One-third of calcium, sodium, potassium, chlorides, and soluble citrates/phosphates are dissolved in milk serum.
• Conclusion: Partly soluble and partly colloidal (Option 4).

Correct option: (4) Partly soluble and partly colloidal