Introductory Food Technology

• 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).

• BIS Specifications for Lactometer Calibration:
• Bureau of Indian Standards (IS: 9585):
• Indian standard lactometers (such as Zeal and Quevenne types) are officially calibrated at $27^\circ\text{C}$ ($80.6^\circ\text{F}$), reflecting tropical ambient Indian dairy processing conditions.
• Temperature Correction Formula:

• Conclusion: 27°C (Option 1).

Correct option: (1) 27°C

• Determination of Solids-Not-Fat (SNF) via Lactometer Reading:
• Analytical Role:
• Corrected Lactometer Reading (CLR) measures specific gravity. Combined with Gerber fat percentage, it calculates % SNF (Solids-Not-Fat) using Richmond's equation:

• Vital rapid platform test for detecting illegal watering down or skimming of market milk supplies.
• Conclusion: SNF % in milk (Option 2).

Correct option: (2) SNF % in milk