UPHESC Assistant Professor Animal Husbandry & Dairying 2025 PYQs

Concept: Koestler number = (% chloride × 100) ÷ % lactose.

1. Normal milk: about 1.5–3.0; mastitic milk: above 3 (chloride rises, lactose falls as blood constituents leak in).
2. Also used for late-lactation and abnormal milk; the chloride–lactose relation keeps milk isotonic with blood.

Short trick: Koestler = Cl/Lactose × 100; > 3 → mastitis.

Concept: Dissolved lactose and salts depress the freezing point of milk below that of water: normal milk freezes at about −0.55 °C (range roughly −0.525 to −0.565 °C).

1. The question asks for the freezing temperature, but all four options are printed as positive temperatures (+0.44, +0.55, +0.66, +0.77 °C) in both languages.
2. An aqueous solution such as milk cannot freeze above 0 °C, so none of the printed values is the freezing temperature of milk; 0.55 would be right only as the freezing-point depression or with a minus sign, which is not what is printed.
3. Hence no option is correct as printed and the question is treated as a bonus (compare Q70, where the correct range is printed with minus signs).

Short trick: Milk freezes at ≈ −0.55 °C; closer to 0 = watered milk.

Concept: In the phenol-disulphonic acid method, nitrate forms nitrophenol-disulphonic acid; on making alkaline (NH₄OH/KOH) it gives a yellow colour, read colorimetrically at ≈ 410 nm.

1. Used to detect nitrates in water (and water added to milk, since normal milk is nitrate-free).
2. Intensity of yellow ∝ nitrate concentration.

Short trick: Phenol-disulphonic acid + nitrate + alkali → Yellow.

Concept: Rabri is a sweetened, concentrated whole-milk product made of layers of clotted malai. Dairy-technology course material notes that neither the PFA Rules nor BIS prescribed any compositional standard for rabri; the later FSS Regulations (2011) only define it (no added starch, fat to meet ghee constants) without a lactose limit.

1. So there is no PFA figure for lactose in rabri – the premise of the question has no legal basis.
2. Actual lactose content varies widely with the degree of concentration and the amount of sugar added; studies of market rabri report roughly 10–14% lactose, and none of 22, 15, 19 or 17% is a prescribed value.
3. As printed, no option can be identified as the PFA standard, so the question is treated as a bonus.

Short trick: Rabri – defined in the food law, but no PFA/BIS compositional (lactose) standard.

Concept: Milk is a (nearly) Newtonian liquid; its flow (fluid) property is viscosity – about 2.0 cP at 20 °C for whole milk.

1. Elasticity is a property of solids; visco-elasticity applies to gels such as curd, cheese and butter.
2. Viscosity depends on casein micelles, fat, temperature and homogenisation.

Short trick: Liquid milk → viscosity; Curd/cheese → visco-elasticity.

Concept: Agmark grades ghee as 'Special' (red label) and 'General' (green label); the acidity (free fatty acids as oleic acid) limit is 1.4% for red label and 2.5% for green label.

1. Other limits: moisture ≤ 0.3%, BR reading 40–43 (most regions), RM value ≥ 28 (region-wise).
2. Low FFA indicates fresh, well-made ghee with good keeping quality.

Short trick: Red label = 1.4% FFA; Green label = 2.5% FFA.

Concept: The vertical short-tube evaporator (Robert/standard evaporator) has a steam chest of short vertical tubes called the calandria, so it is popularly called the calandria evaporator.

1. Liquid boils up through the tubes and returns via a central downtake; circulation is natural.
2. Plate, centrifugal (Centri-therm) and falling-film evaporators are different designs.

Short trick: Short vertical tubes in a steam chest = Calandria.

Concept: Rheology is the science of deformation and flow of matter under stress – viscosity, elasticity, plasticity and visco-elasticity are rheological properties.

1. Surface tension (≈ 50 dyne/cm for milk) is an interfacial property, not a stress–deformation property.
2. Plasticity is important for butter spreadability; elasticity for cheese and curd.

Short trick: Rheology = flow & deformation (V-E-P); surface tension = surface property.

Concept: Heated surfaces get 'milkstone' – a deposit of calcium phosphate (mineral salts) bound with denatured protein. Acid detergents (nitric/phosphoric acid, 0.5–1%) dissolve this mineral–protein scale.

1. Alkaline detergents (NaOH 1–2%) mainly remove fat and loose protein soil, but they precipitate hard-water minerals.
2. So in CIP the sequence is: rinse → alkali → rinse → acid (for milkstone) → rinse → sanitise.

Short trick: Alkali for fat; Acid for milkstone (mineral + protein).

Concept: Bio-detergents (enzyme-based cleaners – proteases, amylases, lipases, polysaccharidases – and biosurfactants) degrade the extracellular polymeric matrix of biofilms; they are biodegradable, work at mild pH and temperature and are called a 'green' technology.

1. Chlorine dioxide, hypochlorite and quaternary ammonium compounds are chemical sanitisers – they leave residues/by-products (chlorinated organics) and penetrate biofilms poorly.
2. Enzyme cleaning also saves water and energy.

Short trick: Green = Bio (enzymes) – no harmful residues.