Casein Protein

Casein is the predominant phosphoprotein found in mammalian milk.

• It comprises roughly 80% of the total protein in cow’s milk and 40% of human milk.
• Casein forms a micellar complex that slows gastric emptying.
• This provides a prolonged release of amino acids, sustaining muscle protein synthesis for up to 7 hours after ingestion.
• It is a favored “slow-digest” protein for recovery and overnight nutrition.

• Casein is a family of phosphoproteins (α-S1, α-S2, β, κ) with molecular weights ranging 19–25 kDa for each subunit.
• The overall empirical formula for a typical casein protein (average) can be approximated as C₁₁₇H₁₈₇N₃₁O₁₉S₁ (e.g., α-S1-casein).
• It contains ~3 % phosphorus (as phosphoserine residues) and ~1 % calcium bound in phosphoserine clusters, conferring high water-binding capacity.
• The protein is rich in proline, glutamine, and leucine, with a high proportion of hydrophobic residues that promote micelle formation.
• Casein’s isoelectric point (pI) is ≈4.6, allowing precipitation at acidic pH (used in cheese making).
• The tertiary structure is predominantly α-helical with β-sheet content, lacking a defined tertiary fold, which contributes to its resistance to gastric proteases.

• Commercial casein is most commonly derived from bovine milk.
• It is obtained through acid precipitation (pH ≈ 4.6) or ultrafiltration of skim milk.
• This is followed by spray-drying to produce micellar casein or whey-casein blends.
• Alternative sources include goat, sheep, and camel milk, though bovine remains >90 % of market supply.
• Extraction methods aim to preserve the native micellar structure (micellar casein) or produce hydrolyzed forms (casein hydrolysate) for faster absorption.
• Quality considerations: protein purity ≥90 % (Nitrogen-to-protein conversion factor 6.38), low residual lactose (<0.5 %), and minimal heavy-metal contamination (<0.2 ppm arsenic, lead).
• Certifications such as GMP, ISO-22000, and third-party testing (e.g., NSF, Informed-Choice) are recommended to assure purity and safety for athletes and health-conscious consumers.