Question

Match the Milk constituent in List-I with the corresponding wavelength used for its estimation in the Infrared Milk Analyzer (IRMA)

List-I	List-II
(A) Fat A	(I) 3.5
(B) Fat B	(II) 5.7
(C) Protein	(III) 9.5
(D) Lactose	(IV) 6.8

Choose the correct answer from the options given below

• (A) - (IV), (B) - (III), (C) - (II), (D) - (I)
• (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)
• (A) - (III), (B) - (II), (C) - (I), (D) - (IV)

Hint:

Remember the characteristic infrared absorption bands for milk analysis:
- \(3.5\ \mu\text{m}\) \(\rightarrow\) \(C-H\) bonds (Fat B).
- \(5.7\ \mu\text{m}\) \(\rightarrow\) \(C=O\) ester bonds (Fat A).
- \(6.8\ \mu\text{m}\) \(\rightarrow\) Amide peptide bonds (Protein).
- \(9.5\ \mu\text{m}\) \(\rightarrow\) \(C-O\) carbohydrate bonds (Lactose).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Infrared milk analyzers (such as the IRMA) are spectrophotometric instruments used for the rapid, automated analysis of milk components.
These instruments measure the absorption of mid-infrared radiation at specific wavelengths corresponding to the characteristic molecular vibrations of milk lipids, proteins, and carbohydrates.

Step 2: Detailed Explanation:
Let us match each milk constituent with its characteristic absorption wavelength:
-(A) Fat A (Carbonyl channel):
Fat A represents the absorption of ester carbonyl bonds (\(C=O\)) present in the triglyceride molecules of milk fat.
These carbonyl groups exhibit a strong stretching vibration at a wavelength of approximately \(5.7\ \mu\text{m}\).
Therefore, (A) matches with (II).
-(B) Fat B (CH-stretching channel):
Fat B represents the absorption of carbon-hydrogen (\(C-H\)) bonds in the hydrocarbon chains of fatty acids.
These aliphatic groups exhibit a characteristic stretching vibration at a wavelength of approximately \(3.5\ \mu\text{m}\).
This measurement is less sensitive to variations in fatty acid chain length and unsaturation compared to the Fat A channel.
Therefore, (B) matches with (I).
-(C) Protein:
Milk proteins contain peptide bonds with characteristic amide groups.
The Amide I absorption band, which primarily arises from the carbonyl stretching vibration (\(C=O\)) of the peptide linkage, is measured at a wavelength of approximately \(6.8\ \mu\text{m}\) (or \(6.5\ \mu\text{m}\) depending on the instrument configuration).
Therefore, (C) matches with (IV).
-(D) Lactose:
Lactose is a disaccharide containing multiple hydroxyl (\(-OH\)) and carbon-oxygen (\(C-O\)) groups.
The stretching vibration of the \(C-O\) bond of the secondary hydroxyl groups exhibits a strong absorption band at a wavelength of approximately \(9.5\ \mu\text{m}\).
Therefore, (D) matches with (III).
This matching sequence corresponds to Option (B).

Step 3: Final Answer:
The correct matching sequence is (A) - (II), (B) - (I), (C) - (IV), (D) - (III).