Question

Microfiltration is designed to retain particles in the range of

• A. 0.005 microns to 0.008 microns
• B. 0.10 microns to 5 microns
• C. 0.009 microns to 0.05 microns
• D. 0.05 microns to 0.08 microns

Hint:

Membrane Pore Size Ranges:
Reverse Osmosis = $< 0.001\;\mu\text{m}$.
Ultrafiltration = $0.01 - 0.1\;\mu\text{m}$.
MICROFILTRATION = $\mathbf{0.10 - 5.0\;\mu\text{m}}$ (Retains bacteria, fat globules, suspended colloids).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Membrane filtration pore size spectrum: Microfiltration (MF) utilizes macroporous membranes with nominal pore diameters ranging from 0.10 to 5.0 $\mu ext{m}$ (0.1--10 $\mu ext{m}$) to reject suspended fat droplets, somatic cells, and bacteria while passing soluble proteins and sugars.
Key Formula or Approach:
\[ \text{Membrane Spectrum: RO } (< 0.001\;\mu\text{m}) \rightarrow \text{NF } (0.001 - 0.002\;\mu\text{m}) \rightarrow \text{UF } (0.01 - 0.1\;\mu\text{m}) \rightarrow \mathbf{MF } (\mathbf{0.10 - 5.0\;\mu\text{m}}) \]

Step 2: Detailed Explanation:
Classification of pressure-driven dairy membrane separation processes by pore size:
1. Reverse Osmosis (RO): Pore size $< 0.001\;\mu\text{m}$ ($< 1\text{ nm}$); retains all dissolved minerals and sugars.
2. Nanofiltration (NF): Pore size $0.001 - 0.002\;\mu\text{m}$ ($1 - 2\text{ nm}$, MWCO $200 - 1000\text{ Da}$).
3. Ultrafiltration (UF): Pore size $0.01 - 0.10\;\mu\text{m}$ ($10 - 100\text{ nm}$, MWCO $1 - 500\text{ kDa}$); retains milk proteins.
4. Microfiltration (MF) (B): Designed with nominal pore diameters in the range of 0.10 microns to 5 microns (0.1 to 5.0 \(\mu\)m 0.1--10 \(\mu\)m).
- Used for cold microfiltration (bacterial spore removal at $1.4\;\mu\text{m}$), native casein micelle isolation ($0.1\;\mu\text{m}$), and fat removal from whey.

Step 3: Final Answer:
Hence, Microfiltration is designed to retain particles in the range of 0.10 microns to 5 microns, matching option (B).