Question

Casein is more resistant to heat than whey. Resistance of casein to heat is NOT because of the following which factor.

• A. Calcium
• B. Magnesium
• C. Citrates
• D. Nitrates

Hint:

Think of the casein micelle as a structure built with protein bricks and calcium phosphate "mortar." Citrates help control the mortar's consistency. Nitrates are irrelevant to this natural structure.

Answer 1

The Correct Option is D

Step 1: Understand the structure and stability of casein. Casein proteins in milk exist in large colloidal structures called micelles. These micelles are remarkably heat-stable. Their stability is maintained by a complex balance of interactions involving calcium, phosphate, and citrate, which hold the casein submicelles together.
Step 2: Analyze the role of the given factors in casein stability.

Calcium: Specifically, colloidal calcium phosphate acts as a "glue" that cements the casein submicelles together, contributing significantly to the heat stability of the entire micelle structure.
Magnesium: Magnesium plays a similar, though less significant, role to calcium within the micelle structure, contributing to its overall stability.
Citrates: Citrates are crucial for stability. They can chelate (bind to) calcium ions. This helps maintain the correct balance of soluble and colloidal calcium, preventing the micelles from destabilizing and aggregating when heated.
Nitrates: Nitrates are not naturally occurring components of the casein micelle system and do not play a role in its inherent heat stability. They are sometimes found in milk as contaminants but are not part of the structural or stabilizing chemistry of casein. \end{itemize}
Step 3: Determine which factor is NOT involved. Based on the analysis, calcium, magnesium, and citrates are all involved in maintaining the heat stability of casein micelles. Nitrates are not. Therefore, the resistance of casein to heat is NOT because of nitrates.