Question

Which of the following is NOT a factor affecting keeping quality of dried milk?

• A. Fat content
• B. Initial moisture content
• C. Temperature of storage
• D. Bulk density

Hint:

Keeping quality is governed by chemical stability (lipid oxidation, browning) and biological stability.
These depend on fat, moisture, oxygen, and temperature.
Bulk density is a physical packaging property and does not affect these reaction rates.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The keeping quality (shelf-life) of dried milk powder is determined by the rate of chemical and physical deterioration during storage.
Major degradation pathways include lipid oxidation (leading to rancidity) and Maillard browning (leading to discoloration and loss of solubility).

Step 2: Detailed Explanation:
Let us analyze how each factor affects keeping quality:
- (A) Fat content: High fat content increases the susceptibility of milk powder to lipid auto-oxidation, which produces off-flavors (tallowy/oxidized).
- (B) Initial moisture content: High moisture increases water activity (\( a_w \)), which accelerates the Maillard reaction (causing browning, caking, and loss of solubility) and permits microbial growth.
- (C) Temperature of storage: According to the Arrhenius equation, higher storage temperatures accelerate all chemical degradation reactions, rapidly decreasing shelf-life.
- (D) Bulk density: This is a physical property defined as the mass of the powder divided by the volume it occupies.
While bulk density is critical for packaging design, transportation, and container sizing, it does not govern the rate of chemical or microbial degradation reactions during storage.
Therefore, bulk density is not a factor affecting the keeping quality of dried milk.

Step 3: Final Answer:
Bulk density is not a factor affecting the keeping quality of dried milk.