UPHESC Assistant Professor Animal Husbandry & Dairying 2025 PYQs

Concept: A synbiotic (printed 'symbiotic') is a product that combines probiotics (live beneficial microbes, e.g. Lactobacillus, Bifidobacterium) with prebiotics (non-digestible substrates such as inulin, FOS, GOS) that feed them.

1. The prebiotic improves survival and colonisation of the probiotic.
2. Antibiotics kill microbes; abiotic means non-living; biostatic means growth-inhibiting.

Short trick: Pro + Pre = Syn(biotic) – 'synergy'.

Concept: Cheese hardness depends mainly on moisture content. If only a small part of the whey is expelled (little cutting, cooking, pressing), the curd keeps much moisture and a soft cheese results.

1. Soft cheeses (Cottage, Camembert, Brie) have > 50–55% moisture; hard cheeses (Cheddar, Parmesan) < 40%.
2. The amount of milk used affects yield, not texture.

Short trick: Less whey removed → more moisture → softer cheese.

Concept: Rennet, extracted from the fourth stomach (abomasum) of suckling calves, contains about 80–90% chymosin (rennin) and 10–20% pepsin.

1. Chymosin specifically cleaves κ-casein at Phe₁₀₅–Met₁₀₆, destabilising micelles so that milk coagulates.
2. Plasmin is the native alkaline protease of milk; catalase is an indicator of mastitis/heat.

Short trick: Rennet = Chymosin (κ-casein 105–106).

Concept: For a therapeutic effect, a probiotic food should contain at least ${10}^6$ cfu per ml (or g) of viable organisms at the time of consumption (daily intake about ${10}^8$–${10}^9$ cells).

1. FSSAI and most international guidelines use ≥ ${10}^6$ cfu/g (some ≥ ${10}^7$).
2. ${10}^{15}$ or ${10}^{20}$ cfu/ml is physically impossible – far more cells than can fit in 1 ml.

Short trick: Probiotic 'therapeutic minimum' = ${10}^6$ (million) per ml.

Concept: Co-precipitates are made by heating skim milk (to bring whey proteins down with casein) and precipitating with CaCl₂ and/or acid. High-calcium co-precipitates are poorly soluble.

1. Calcium cross-links casein (calcium caseinate–phosphate bridges), so the higher the Ca, the lower the solubility.
2. Low-calcium (acid-precipitated, neutralised with alkali) co-precipitates are the soluble types used in foods.

Short trick: More Ca = more cross-links = less soluble.

Concept: Protein content of cheese rises as moisture and fat fall: soft/semi-hard < hard < very hard skim-milk cheese.

1. Sapsago (Swiss Schabziger) is a very hard, dried skim-milk cheese, so it has the highest protein – 49.4%.
2. Parmesan (grated, very hard, part-skim, ~30% moisture) – 41.6%.
3. Cheddar (≈ 37% moisture) has more protein than the moister Gouda (≈ 41–43%): Cheddar 29.6%, Gouda 26.0%.
4. Code: a – 1, b – 3, c – 2, d – 4.

Short trick: Drier and leaner the cheese, higher the protein: Sapsago > Parmesan > Cheddar > Gouda.

Concept: Butyric acid (C4:0) is the characteristic short-chain fatty acid of ruminant milk fat; in buffalo milk fat it is about 3.6% (by weight of fatty acids), slightly higher than in cow milk fat (≈ 3.0–3.4%).

1. Butyric acid is the basis of the Reichert–Meissl value (volatile, water-soluble fatty acids) used to detect ghee adulteration.
2. It is absent from vegetable oils and body fats, so its presence identifies milk fat.

Short trick: Buffalo fat butyric ≈ 3.6 > cow ≈ 3.2.

Concept: The Farrall index is the standard microscopic measure of homogenisation efficiency: a diluted milk sample is examined and globules larger than 2 µm are counted.

1. Farrall index 0–10: lower values mean better homogenisation (< 4–6 is acceptable for market milk).
2. Other checks are the USPHS test (fat difference between top 100 ml and the rest after 48 h) and the NIZO method; 'creaming index' is not the recognised index for homogenisation.

Short trick: Homogenisation efficiency → Farrall index (microscope, globules > 2 µm).

Concept: Homogenisation (≈ 2000–2500 psi at 60–65 °C) breaks fat globules from 2–10 µm (avg ≈ 3.5 µm) to below ~1–2 µm, so their number rises about 10,000-fold.

1. Number ∝ $1/d^3$ for the same fat volume, so even a modest cut in diameter multiplies the number enormously.
2. Surface area increases 4–10 times; new membrane is formed from casein and whey protein, so no cream line forms.

Short trick: Homogenisation: ~10,000× more globules, no cream line.

Concept: In standard dairy texts, homogenised milk is defined as milk in which fat globules have been reduced to 2 µm or less in diameter, so that no visible cream layer forms in 48 h.

1. Raw milk globules: 0.1–15 µm, mostly 2–6 µm (average 3–4 µm).
2. That is why the Farrall index counts globules larger than 2 µm as un-homogenised.

Short trick: Homogenised milk = fat globules < 2 µm.

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.