Maharashtra SSC Milk & Milk Products (MSBSHSE) cheat sheet

Average cow milk composition: water 87%, fat 3.5–4.5%, protein 3.2–3.5% (casein ~80% of protein), lactose 4.6–4.9%, ash 0.7%.

Buffalo milk is higher in fat (6–7%) and total solids (~16–17%) than cow milk (~12–13% total solids); buffalo milk lacks carotene, so it appears whiter.

Milk density at 20°C is 1.028–1.032 g/mL; adding water lowers density, while skimming raises it, so density alone cannot detect adulteration.

Titratable acidity of fresh milk is 0.14–0.16% lactic acid; rise above ~0.18% indicates bacterial souring or added acid.

pH of fresh milk is 6.6–6.8; freezing point is −0.53 to −0.55°C, and added water raises the freezing point toward 0°C (cryoscopy test).

Milk is an oil-in-water emulsion of fat globules (1–10 µm) stabilised by the milk fat globule membrane; casein micelles (~100 nm) form a colloidal dispersion.

Lactose is a disaccharide of glucose and galactose; fermentation converts it to lactic acid, lowering pH and coagulating casein at the isoelectric point ~pH 4.6.

Milk is opaque due to light scattering by fat globules and casein micelles; homogenisation increases whiteness and reduces cream separation.

Clean milk production depends on udder hygiene, teat dipping, dry-hand milking or machine milking, sanitised utensils, and rapid cooling to 4–5°C.

Platform tests at collection centres: organoleptic, Clot-on-Boiling (COB), alcohol test (68–70% ethanol), and Specific Gravity by lactometer.

Methylene Blue Reduction Test (MBRT) grades bacterial quality: reduction time over 5 h is very good, 2–5 h fair, under 30 min poor.

Resazurin test uses colour change from blue to pink/white; faster decolourisation means higher bacterial load.

Gerber method measures fat: sulphuric acid dissolves protein, isoamyl alcohol aids separation, and the fat column is read in a butyrometer at 65°C.

Kjeldahl method measures nitrogen for protein; milk protein = total N × 6.38.

Adulteration tests: starch with iodine (blue-black), cane sugar with resorcinol (red), urea with urease/para-dimethylaminobenzaldehyde, detergent by froth and methylene blue.

Milk must be weighed and tested before pooling; two-axis pricing pays on both fat and SNF content to discourage watering and skimming.

Filtration removes visible dirt and somatic cells using cloth or membrane filters; clarification uses centrifugal force to remove fine sediment and leucocytes without separating fat.

Centrifugal separation works on density difference between fat (~0.9 g/mL) and plasma (~1.03 g/mL); a cream separator yields cream and skim milk, adjusted by cream screw position.

Standardisation adjusts fat content by blending whole milk, skim milk and cream to a target, calculated by the Pearson square method.

Homogenisation forces milk through a valve at 150–250 bar, reducing fat globule size to under 2 µm and preventing cream layer formation.

HTST pasteurisation: 72°C for 15 s; LTLT: 63°C for 30 min; both achieve alkaline phosphatase inactivation, which is the pasteurisation test.

UHT treatment: 135–150°C for 2–5 s followed by aseptic packaging gives commercial sterility with a shelf life of several months at ambient temperature.

Sterilisation of milk in bottles typically uses 110–120°C for 15–20 min; it causes more browning (Maillard reaction) than UHT.

Cooling after pasteurisation to below 5°C is essential; residual phosphatase and surviving thermoduric organisms cause spoilage if cooling is delayed.

Cream grading by fat: light 18–25%, medium 25–40%, heavy 40–50%; whipping cream is usually 35–40% fat.

Butter is made by churning cream (30–40% fat) to invert the emulsion; finished butter must contain at least 80% fat and under 16% moisture.

Ghee is clarified butterfat made by melting butter and removing moisture and curd; BIS requires ghee to have under 0.3% moisture and Reichert–Meissl value of 28–32.

Curd (dahi) is set by lactic cultures (Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus) at 37–42°C until pH reaches about 4.6.

Paneer is produced by acid coagulation of hot milk (85–90°C) with citric or lactic acid, then pressing the curd; yield is roughly 18–20% of milk weight.

Khoa is made by continuous open-pan evaporation of milk to 65–70% total solids; it is the base for burfi, peda and gulab jamun.

Spray drying produces milk powder: concentrate to 45–50% solids, atomise, dry in hot air, then instantise by agglomeration for easy reconstitution.

Ice cream mix is pasteurised, homogenised, aged (2–4°C for 4–24 h), frozen with overrun (air incorporation 30–100%), then hardened at −20 to −25°C.

Plate heat exchangers are used for HTST pasteurisation; flow is arranged so pasteurised milk is heated by hot milk leaving the regenerator, saving 80–90% energy.

A cream separator is a disc-bowl centrifuge; bowl speed and disc stack determine separation efficiency, and back-pressure regulates cream fat.

Homogenisers are positive-displacement pumps with a homogenising valve; two-stage homogenisation (first stage 150–200 bar, second 30–50 bar) prevents cluster formation.

Bulk milk coolers (BMC) hold milk at 4°C; direct expansion tanks use refrigerant coils, while ice-bank units use chilled water.

Milk cans, silos and pipelines should be of stainless steel grade AISI 304 or 316 to resist corrosion and permit cleaning.

Automatic milk analysers (e.g., MilkoScan) use infrared spectroscopy to measure fat, protein, lactose and SNF in seconds.

CIP circuits require a return pump, flow velocity above 1.5 m/s, and conductivity sensors to confirm detergent concentration.

Freezing point cryoscope and somatic cell counter are standard quality instruments in a dairy laboratory.

CIP sequence: pre-rinse with warm water, alkaline wash (1–2% NaOH at 70–80°C), intermediate rinse, acid wash (0.5–1% nitric or phosphoric acid), final rinse with potable water.

Alkaline detergent removes fat and protein; acid detergent removes milk stone (calcium phosphate scale).

Sanitisers include hypochlorite (100–200 ppm available chlorine), peracetic acid and hot water at 80–90°C; contact time is typically 5–10 min.

Cleaning efficiency depends on four factors: time, temperature, concentration and mechanical action (flow velocity); all must be balanced.

Swab tests and ATP bioluminescence verify hygiene; standard plate count on equipment surfaces should be low after CIP.

Personnel hygiene: hand washing, clean protective clothing, head covering, no jewellery, and health screening for food handlers.

Pest control, fly screens, foot dips and separation of raw and pasteurised zones prevent cross-contamination.

Water used in dairy plants must meet potable standards; hardness causes scale and reduces cleaning effectiveness.

Pasteurised milk is packed in glass bottles, pouches (LDPE/LLDPE film), or PET bottles; pouch filling machines form-fill-seal under hygienic conditions.

UHT milk requires aseptic packaging such as multi-layer cartons or pre-sterilised bags to maintain commercial sterility.

Cold chain for pasteurised milk: 4°C from plant to consumer; any break above 10°C shortens shelf life and risks spoilage.

Milk powder is packed in nitrogen-flushed, moisture-barrier bags or tins to prevent oxidation and caking.

Ghee is packed in tinplate or food-grade plastic; exposure to light and air causes rancidity.

Ice cream requires a deep-freeze chain at −18°C or below, including during transport and retail display.

Date marking, batch coding and first-expiry-first-out (FEFO) rotation reduce wastage in distribution.

Refrigerated vans and insulated boxes with eutectic plates maintain temperature during rural milk collection routes.

FSSAI is the apex food regulator in India under the Food Safety and Standards Act, 2006; it issues licences and sets standards for milk and milk products.

BIS (Bureau of Indian Standards) publishes product specifications such as IS 1479 for pasteurised milk and IS 3508 for milk powder.

HACCP is a preventive system with seven principles: hazard analysis, CCP identification, critical limits, monitoring, corrective actions, verification, and record keeping.

A Critical Control Point (CCP) for pasteurisation is the time–temperature combination (72°C/15 s); failure triggers a hold-and-divert valve.

Good Manufacturing Practices (GMP) and Good Hygiene Practices (GHP) are prerequisite programmes that support HACCP.

FSSAI mandates labelling requirements: product name, ingredients, net quantity, nutrition information, FSSAI licence number, and date of manufacture.

Adulteration of milk is an offence under the FSS Act; penalties include fines and imprisonment depending on severity.

Traceability and recall systems are required so that contaminated batches can be withdrawn from the market.

Cost of milk production includes feed, labour, veterinary care, depreciation and interest; feed alone typically accounts for 60–70% of the cost.

Two-axis milk pricing pays farmers on fat and SNF content, encouraging quality rather than volume alone.

The Anand pattern cooperative (Amul model) has three tiers: village dairy cooperative society, district milk union, and state milk federation.

Cooperative societies collect milk twice daily, test it, and pay farmers based on fat and SNF, sharing profits as dividends.

Value addition (ghee, paneer, flavoured milk) raises margins but requires capital for processing and cold chain.

Break-even analysis compares fixed and variable costs against sales revenue; dairy plants need high capacity utilisation to be viable.

Government support includes the National Dairy Plan, subsidies for milk processing units, and loans under schemes for dairy entrepreneurs.

Market demand for milk products is rising with urbanisation; branded and packaged products command premium prices over loose milk.

Dairy plant hazards include slips on wet floors, burns from steam and hot water, rotating machinery entanglement, and chemical exposure from detergents.

Lock-out/tag-out (LOTO) procedures isolate energy sources before equipment maintenance.

Dairy effluent has high BOD and COD due to milk solids, whey and detergents; it must be treated before discharge.

Effluent treatment plants use screening, equalisation, biological treatment (activated sludge or UASB), and sludge handling.

Whey from cheese and paneer production is a valuable by-product; it can be dried into whey powder or used for lactose and protein recovery.

Biogas generation from dairy waste converts organic matter into energy and reduces disposal costs.

Personal protective equipment (PPE) includes gloves, goggles, aprons and safety shoes for handling chemicals and hot surfaces.

Noise, dust and ammonia from refrigeration plants are monitored to protect worker health.

Gerber fat test: measure 10 mL sulphuric acid, 10.75 mL milk and 1 mL isoamyl alcohol in a butyrometer, centrifuge 5 min, and read the fat column at 65°C.

Determination of total solids: weigh milk, dry in an oven at 100°C to constant weight, and calculate percentage solids; SNF = total solids − fat.

Acidity titration: titrate 10 mL milk with 0.1 N NaOH using phenolphthalein to a pink endpoint; % lactic acid = (mL NaOH × 0.009) / 10 × 100.

Specific gravity by lactometer: read at 20°C and correct for temperature; normal range 1.028–1.032.

COB test: boil 5 mL milk in a test tube; clotting indicates high acidity or unstable protein.

Alcohol test: mix equal volumes of milk and 68–70% ethanol; coagulation indicates acidity above ~0.2%.

Project assessment criteria typically include aim, methodology, observation tables, calculations, interpretation and conclusion.

Laboratory safety: never add water to acid, handle glassware carefully, and label all reagents clearly.