Question

Which one of the following products has the highest density?

• A. Whole milk
• B. Skimmed milk
• C. Cream
• D. Whey

Hint:

Higher SNF increases milk density, whereas higher fat content decreases milk density. Skim milk is therefore denser than whole milk.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The density of milk and derived dairy products depends directly on the relative proportions of fat and solids-not-fat (SNF).

Step 2: Key Formula or Approach:
The individual densities of milk constituents at $20^\circ\text{C}$ are given by:
\[\rho_{\text{fat}} \approx 0.93\,\text{g/cm}^3,\quad \rho_{\text{water}} \approx 1.000\,\text{g/cm}^3,\quad \rho_{\text{SNF}} \approx 1.616\,\text{g/cm}^3\]

Step 3: Detailed Explanation:
Milk fat is lighter than water ($\rho \approx 0.93\,\text{g/cm}^3$), whereas proteins, lactose, and ash have densities exceeding $1.6\,\text{g/cm}^3$.
Skimming removes the low-density fat fraction, concentrating the heavy SNF fraction in the continuous phase.
At $20^\circ\text{C}$, representative densities are:
- Skimmed milk: $1.034\text{--}1.037\,\text{g/cm}^3$
- Whole milk: $1.028\text{--}1.032\,\text{g/cm}^3$
- Whey: $1.024\text{--}1.028\,\text{g/cm}^3$
- Cream: $< 1.000\,\text{g/cm}^3$

Step 4: Final Answer:
Consequently, skimmed milk possesses the highest density among the listed products.