Mechanisms and effects of milk homogenisation:

• Statement (I) is true because mechanical shearing, cavitation, and turbulence break down fat globules from $1\text{--}10\,\mu\text{m}$ to $\lt 2\,\mu\text{m}$.
• Statement (II) is false because homogenisation pressures ($10\text{--}25\text{ MPa}$) do not disintegrate intact casein micelles (which are tiny colloidal particles of $50\text{--}300\text{ nm}$); instead, casein micelles and subunits adsorb onto the expanded fat globule surface.
• Statement (III) is true because increased interfacial surface area and casein adsorption increase hydrodynamic volume and milk viscosity.
• Statement (IV) is true because thousands of tiny fat globules scatter light more effectively, giving homogenised milk a whiter, richer, and more opaque appearance.

Operating temperature hierarchy of dairy unit operations:

• Bactofugation is carried out at $55\text{--}60^\circ\text{C}$ to reduce milk viscosity for centrifugal spore removal without protein denaturation.
• Homogenisation is typically executed at $60\text{--}65^\circ\text{C}$ where milk fat is completely liquid.
• Thermisation is a sub-pasteurization thermal treatment carried out at $63\text{--}65^\circ\text{C}$ for $15\text{ s}$.
• HTST pasteurization operates at $72^\circ\text{C}$ for $15\text{ s}$, followed by Sterilisation which operates at the highest thermal regimen ($115\text{--}121^\circ\text{C}$ for $15\text{--}20\text{ min}$ or UHT at $135\text{--}150^\circ\text{C}$).

Classification criteria of traditional Sandesh varieties:

• Colour and appearance vary with caramelisation and flavoring but do not define the primary grade system.
• Sandesh is classified into varieties based on body and consistency: Narampak is the soft-grade variety prepared by cooking chhana with sugar at $75^\circ\text{C}$ with higher moisture and tender consistency; Karapak is the hard-grade variety cooked at $85^\circ\text{C}$ with higher sugar content yielding a firm, compact, and brittle consistency.
• Overall quality is a composite hedonic sensory grade, not the textural class.
• Springiness is a characteristic textural attribute of spongy rasogolla rather than sandesh grades.