Unit 3

• 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

• Ultrasonic Membrane Cleaning Frequency:
• Acoustic Cavitation Mechanics:
• Power ultrasound de-fouls filtration membranes (UF/RO) by inducing acoustic cavitation—microscopic bubble formation and violent collapse producing localized shock waves and high-velocity microjets that dislodge foulant foul cakes.
• Operates in the low-frequency power ultrasound regime of $20 - 40\text{ kHz}$.
• Conclusion: 20-40 KHz (Option 2).

Correct option: (2) 20-40 KHz

• Fundamental vs Empirical Rheological Properties:
• Fundamental Rheological Properties:
• Well-defined physical quantities independent of sample geometry, instrument dimensions, or test speed (e.g., shear modulus, true viscosity, fracture stress / true failure stress).
• Empirical Texture Profile Analysis (TPA) Properties:
• Hardness, chewiness, adhesiveness, and gumminess are empirical, instrument-dependent sensory descriptors measured via two-bite force-time curves.
• Conclusion: Fracture stress (Option 4).

Correct option: (4) Fracture stress