Question

Proteins are denatured if food is heated above ________.

• A. $30\text{ }^\circ\text{C}$
• B. $60\text{ }^\circ\text{C}$
• C. $100\text{ }^\circ\text{C}$
• D. $121\text{ }^\circ\text{C}$

Hint:

Most globular proteins begin to unfold and lose their biological activity at approximately $60\text{ }^\circ\text{C}$ ($140\text{ }^\circ\text{F}$), which is why egg whites begin to solidify and turn opaque around this temperature.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Protein denaturation is a process in which proteins lose their quaternary, tertiary, and secondary structures under external stress (such as heat, acids, bases, or salts), altering their functional and physical properties.
Detailed Explanation:
Thermal denaturation of globular proteins occurs when heat energy disrupts weak hydrogen bonds and hydrophobic interactions within the protein molecule.
- At lower temperatures (e.g., $30\text{ }^\circ\text{C}$), most proteins remain in their folded, native states.
- As the temperature rises above $60\text{ }^\circ\text{C}$, the kinetic energy of the molecules increases, disrupting these non-covalent bonds. This causes the polypeptide chains to unfold, aggregate, and precipitate.
- The denaturation temperature range for most food proteins (including egg albumin, whey proteins, and myosin) is between $55\text{ }^\circ\text{C}$ and $80\text{ }^\circ\text{C}$.
- While heating to $100\text{ }^\circ\text{C}$ or $121\text{ }^\circ\text{C}$ also causes denaturation, the process initiates at approximately $60\text{ }^\circ\text{C}$.

Step 2: Final Answer:
Proteins begin to denature when food is heated above $60\text{ }^\circ\text{C}$.