• Determination of Milk Density via Pycnometer:
• Pycnometer (Specific Gravity Bottle):
• precision ground-glass flask with a capillary-bored stopper used to accurately determine the specific gravity and density of fluids.
• Working Principle:

• Standardized at a controlled temperature ($20^\circ\text{C}$ or $27^\circ\text{C}$), providing high accuracy in detecting watering or skimming adulteration (normal milk density: $1.028 - 1.034\text{ g/cm}^3$).
• Conclusion: Density (Option 1).

Correct option: (1) Density

• Optical Properties and Whiteness of Bovine Milk:
• Light Scattering (Tyndall Effect):
• The characteristic opaque white appearance of milk is caused by the light-scattering properties of colloidal particles:

• Colloidal calcium caseinate micelles (diameters $50 - 300\text{ nm}$).
• Emulsified milk fat globules (diameters $1 - 10\ \mu\text{m}$).
  • Even after complete mechanical removal of fat (skim milk), milk retains an opaque, bluish-white appearance due to Rayleigh scattering by suspended calcium caseinate-phosphate micelles.

• Conclusion: Colloidal calcium caseinate (Option 3).

• Deteriorative Mechanisms in Skim Milk Powder (SMP):
• Maillard Browning Reaction:
• SMP contains approximately $50\%$ lactose (reducing carbohydrate) and $36\%$ protein (rich in free $\epsilon$-amino groups of lysine), with negligible fat ($\lt 1.5\%$).
• During storage—especially under elevated ambient temperature or moisture ($a_w \gt 0.2$)—non-enzymatic Maillard browning proceeds rapidly between reducing sugars and amino acid residues.
• Results in brown melanoidin pigments, stale/cereal off-flavors, insolubility, and loss of essential lysine bioavailability.
• Conclusion: Maillard browning (Option 4).

Correct option: (4) Maillard browning