Dairy Chemistry- ICAR JRF/SRF 2024

• Chemical Origin of Cooked Flavor in Heated Dairy Products (Khoa):
• Volatile Sulfur Compounds:
• Thermal denaturation of whey proteins (specifically $\beta$-lactoglobulin and bovine serum albumin) uncoils globular chains and activates buried cysteine sulfhydryl groups (-SH).
• Oxidation of these exposed sulfhydryl moieties yields volatile sulfides (hydrogen sulfide $\text{H}_2\text{S}$, methanethiol, dimethyl sulfide), producing the characteristic cooked, rich caramelized aroma in khoa.
• Conclusion: Sulphhydryl (Option 1).

Correct option: (1) Sulphhydryl

• Iron Concentration Calculation in FAS Solution:
• Molecular Formulation:
• Ferrous ammonium sulfate hexahydrate, $(\text{NH}_4)_2\text{Fe}(\text{SO}_4)_2 \cdot 6\text{H}_2\text{O} = 392\text{ g/mol}$.
• Dissolving $21\text{ mg}$ ($0.021\text{ g}$) in $500\text{ mL}$ ($0.5\text{ L}$):

• Expressing concentration on a parts-per-million (ppm) basis ($1\text{ ppm} = 1\text{ mg/L}$):

• Conclusion: 6 ppm (Option 2).

Correct option: (2) 6 ppm

Evaluating the Assertion and Reason concerning Milk clotting enzymes from different sources – microbial:

The correct answer is Option 1: Both (A) and (R) are true and (R) is the correct explanation of (A).