Question

PER is influenced most by:

• A. Calorie intake
• B. Protein digestibility and amino acid profile
• C. Fat content
• D. Mineral content

Hint:

All main protein quality metrics—including PER, Biological Value (BV), Net Protein Utilization (NPU), and PDCAAS—depend on two core properties: amino acid composition and digestibility.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks which nutritional factors have the greatest influence on the Protein Efficiency Ratio (PER) of a food protein.

Step 2: Key Concepts and Approach:
PER is a biological assay used to measure protein quality, defined as the gain in body mass of a growing animal per gram of protein consumed:
\[ \text{PER} = \frac{\text{Weight Gain (g)}}{\text{Protein Consumed (g)}} \]
The animal's ability to turn consumed protein into body tissue is determined by how complete and usable that protein is.

Step 3: Detailed Explanation:

• Amino Acid Profile: The body needs essential amino acids in specific proportions to build tissue.
If even one essential amino acid is missing or present in low amounts (the limiting amino acid), protein synthesis stops, reducing overall weight gain and resulting in a lower PER.

• Protein Digestibility: Even a protein with an ideal amino acid profile cannot be used if the body cannot digest it.
Incomplete digestion prevents the absorption of these amino acids, lowering the protein's nutritional value.

• Standardization: In a standard bioassay, other nutrients like fats, carbohydrates, and minerals are provided in adequate amounts so they do not limit the growth rate of the animal.

Step 4: Final Answer:
Therefore, PER is influenced most by protein digestibility and the amino acid profile.