Assam HS Skill Food Processing cheat sheet

Food processing converts raw agricultural material into a stable, safe, palatable form; preservation specifically extends shelf life by controlling microbial growth and chemical/enzymatic deterioration.

Water activity (aw) is the ratio of vapour pressure of food to that of pure water at the same temperature; most bacteria need aw above 0.90, most yeasts above 0.88, xerophilic moulds can grow down to about 0.60.

Preservation hurdle concept: combining low aw, low pH, low temperature, preservatives and modified atmosphere gives a cumulative inhibitory effect so no single hurdle need be severe.

pH classes: high-acid foods pH below 4.6 (botulinum spores cannot germinate), acid foods 4.6-5.2, low-acid foods above 5.2 and therefore needing pressure thermal processing.

Perishable foods (milk, meat, fish, fresh vegetables) have shelf life of days; semi-perishable (potatoes, nuts) weeks to months; shelf-stable (cereals, sugar, salt) months to years.

Blanching is a mild heat treatment (70-100 °C, 1-5 min) that inactivates polyphenol oxidase and peroxidase, expels tissue gases and shrinks product before freezing or drying; it is not a sterilisation step.

Primary processing (cleaning, grading, milling, hulling) prepares raw material; secondary processing (baking, canning, extrusion, fermentation) makes consumer products; tertiary processing adds convenience and packaging.

HACCP has seven principles: hazard analysis; determine CCPs; set critical limits; monitor CCPs; establish corrective actions; verify; keep records.

A CCP is a step where control can be applied and is essential to prevent, eliminate or reduce a significant hazard to an acceptable level; a control point is any step controlling a hazard but not essential for safety.

Critical limits must be measurable (temperature, time, pH, aw, chlorine ppm); typical example is 121 °C retort centre temperature held for a defined Fo value.

Pre-requisite programmes (GMP, SSOP) must be in place before HACCP; HACCP is not a stand-alone substitute for hygiene infrastructure.

Biological hazards include Salmonella, Listeria monocytogenes, E. coli O157:H7, Clostridium botulinum, aflatoxin-producing moulds; chemical hazards include pesticide residues, cleaning chemicals, allergens; physical hazards include glass, metal, stones.

Cleaning follows the sequence dry clean, pre-rinse, detergent wash, rinse, sanitise, air-dry; sanitising reduces, not sterilises, and works only on a clean surface.

Personal hygiene rules: no jewellery or street clothes, hand wash with soap after toilet or handling waste, no work with exposed wounds, health declaration for diarrhoea, jaundice or skin infection.

Maillard browning occurs between reducing sugars and amino groups of proteins at pH above about 6, accelerated by heat and intermediate aw (0.4-0.7); caramelisation needs only sugar plus heat.

Lipid oxidation is autocatalytic via free radicals (initiation, propagation, termination); antioxidants such as BHA, BHT, tocopherols and ascorbic acid interrupt propagation.

Protein denaturation by heat, acid or shear unfolds the native structure; it changes solubility and texture but does not break peptide bonds, unlike hydrolysis.

Energy values (Atwater): carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g; dietary fibre about 2 kcal/g.

Water in food is bound, capillary or free; only free water supports microbial growth, which is why aw, not moisture percentage, predicts stability.

Starch gelatinises in excess water at 60-75 °C (irreversible swelling), then retrogrades on cooling giving staling and syneresis; retrogradation is slowed by emulsifiers and by holding above about 60 °C.

Vitamins differ in heat sensitivity: vitamin C and thiamine are heat labile, riboflavin is light sensitive, fat-soluble vitamins A, D, E, K are sensitive to oxidation and rancidity.

Bacterial growth curve phases: lag, exponential (log), stationary, death; generation time for mesophiles is commonly 20-30 min under optimum conditions, so one log increase occurs in that time.

Temperature classes: psychrophiles grow below 15 °C, mesophiles 20-45 °C (optimum about 37 °C), thermophiles 45-70 °C; refrigeration selects psychrotrophic spoilage organisms (Pseudomonas, Listeria).

Canned food spoilage groups by pH: flat-sour thermophiles in low-acid cans, TA spoilage (Bacillus thermoacidurans) in acid cans, putrefactive anaerobes and sulphide spoilage in low-acid under-processed cans.

Osmophilic yeasts and xerophilic moulds spoil jams, honey and dried fruit; halophilic bacteria spoil salted fish; lactic acid bacteria cause souring of milk and vegetable fermentations.

Moulds grow at lower aw and wider pH than bacteria, tolerate low oxygen and produce mycotoxins such as aflatoxin (Aspergillus flavus) and ochratoxin; visible mycelium means the whole soft food should be discarded.

Spore formers survive boiling: Clostridium botulinum spores need 121 °C (Fo 3 min for a 12D reduction); Bacillus cereus spores survive cooking and cause emetic or diarrhoeal illness.

Indicator organisms: coliforms and E. coli indicate faecal or post-process contamination; standard plate count and yeast-mould count show overall hygiene and remaining shelf life.

Pasteurisation: 63 °C for 30 min (vat) or 72 °C for 15 s (HTST) for milk; ultra-high temperature 135-150 °C for 2-5 s gives commercial sterility with aseptic packaging.

D-value is time at a given temperature to reduce the population by 90 percent (one log); z-value is the temperature change giving a tenfold change in D; Fo is equivalent time at 121 °C.

Drying rate curve: constant-rate period controlled by external mass transfer, then falling-rate period controlled by internal diffusion; case-hardening occurs when surface dries too fast and traps moisture.

Freezing: water freezes near -1 to -2 °C in tissue; rapid freezing gives many small ice crystals and less drip loss, slow freezing gives large extracellular crystals and cell damage.

Freeze-drying (lyophilisation) sublimes ice under vacuum below the triple point (0.006 atm, 0.01 °C); it preserves structure and aroma but is energy intensive.

Irradiation doses: up to 1 kGy for sprout inhibition and insect disinfestation, 1-10 kGy for pathogen and spoilage reduction, above 10 kGy for sterilisation; the process is cold and leaves no radioactivity.

Evaporation and concentration remove water at boiling point under vacuum to protect heat-labile components; multiple-effect evaporators reuse vapour and cut steam consumption per kg of water removed.

Canning process order: raw material preparation, blanching, filling, exhausting, seaming, retorting, cooling, labelling; the double seam integrity is the critical safety barrier.

Modified atmosphere packaging lowers O2 (typically 1-5 percent) and raises CO2 to slow respiration and microbial growth; vacuum packaging relies on oxygen exclusion, not on gas addition.

Active packaging interacts with the product or headspace (oxygen scavengers, ethylene absorbers, moisture regulators); intelligent packaging indicates a condition such as time-temperature history.

Glass is inert and impermeable but heavy and breakable; tinplate gives strength and heat resistance; retort pouches (aluminium foil laminate) give fast heat penetration and light weight.

Chemical preservation: salt and sugar lower aw, acidulants lower pH, sulphites inhibit browning and moulds (not recommended in foods for asthmatics), nitrite inhibits C. botulinum in cured meat.

Curing and smoking combine salt, nitrite, dehydration and antimicrobial smoke phenols; the combination, not one agent, delivers stability and colour.

Fermentation preservation relies on lactic acid bacteria lowering pH below 4.6 (sauerkraut, kimchi, curd, idli); salt concentration and anaerobiosis select the desired flora.

Milling: rice milling removes husk, bran and germ to give head rice; degree of milling controls yield, whiteness and loss of thiamine and minerals concentrated in bran.

Pulse milling splits dehusked grain into dal; pretreatments (oil, water, heat) reduce breakage; dhal recovery is the key economic index.

Milk composition: cow milk about 3.5 percent fat, 3.2 percent protein, 4.6 percent lactose; buffalo milk has higher fat and total solids and gives higher paneer and ghee yield.

Dairy products: pasteurised milk, curd (fermented by Lactobacillus), paneer (acid-coagulated, citric acid or lactic), khoa (heat-concentrated), ghee (clarified butter fat), ice cream (frozen foam with overrun).

Fruit and vegetable products: jam (55-65 percent soluble solids with pectin and acid), jelly (clear fruit extract), marmalade (with peel), squash and syrup (preserved by sugar, acid and preservative), chutney and pickle (salt, acid, oil).

Value addition turns low-value raw produce into higher-margin products: tomato to paste and ketchup, mango to pulp and leather, potato to chips and flour, maize to starch and breakfast cereal.

Bakery and extrusion: dough development depends on gluten hydration and kneading; extrusion cooking gelatinises starch and denatures protein under high shear, temperature and moisture.

Quality attributes group as sensory (colour, flavour, texture), nutritional, safety and functional; quality assurance is process-focused, quality control is product-testing focused.

Proximate analysis: moisture by oven drying or Karl Fischer, fat by Soxhlet, protein by Kjeldahl (nitrogen times 6.25), ash by muffle furnace, crude fibre by acid-alkali digestion.

Rapid instruments: refractometer for soluble solids (Brix), hydrometer for milk density, lactometer for milk adulteration, pH meter, colorimeter, texture analyser, moisture balance.

Microbiological testing uses plate count agar for total count, VRBA or MacConkey for coliforms, and selective media for pathogens; results are reported as CFU per g or per ml.

Sensory evaluation uses trained panels with hedonic or descriptive scales; triangle test detects a difference, duo-trio and paired comparison are simpler discrimination tests.

Sampling must be representative: random sampling from the lot, sufficient sample size, and a documented chain of custody; a single grab sample cannot certify a lot.

Calibration and traceability: instruments are calibrated against certified reference standards at defined intervals, and records must allow a result to be traced to sample, method, analyst and date.

Material selection: 304 stainless steel for general food contact, 316 for chloride or acid service; food-contact surfaces must be smooth, non-absorbent, non-toxic and corrosion resistant.

Equipment classes: size reduction (crusher, hammer mill, pulveriser, slicer), separation (sieve, cyclone, filter, centrifuge), heat exchange (plate, shell-and-tube, scraped surface), conveying (belt, screw, bucket elevator, pneumatic).

Plate heat exchangers give high heat-transfer area per volume and are easily opened for cleaning; they suit pasteurisation but not high-viscosity or particulate products.

Preventive maintenance is scheduled by calendar or running hours; predictive maintenance uses vibration analysis, thermography, oil analysis and ultrasonic leak detection to act before failure.

Utilities: steam (boiler, pressure, dryness fraction), chilled water and refrigeration (compressor, condenser, expansion valve, evaporator), compressed air (oil-free for food contact), potable water, and effluent treatment.

Boiler efficiency improves with feedwater treatment (softening to prevent scale), blowdown control, economiser and condensate recovery; steam traps remove condensate without losing live steam.

CIP (clean-in-place) uses defined flow velocity, temperature, detergent concentration and contact time; verification by conductivity, turbidity and swab tests rather than visual inspection alone.

Business plan components: product and market analysis, technical process and capacity, location, plant and machinery, project cost, means of finance, working capital, break-even and profitability projections.

Break-even quantity equals fixed cost divided by (selling price minus variable cost per unit); contribution margin per unit drives the calculation.

FSSAI licence type depends on turnover and activity: basic registration for small petty food business, state licence for medium turnover, central licence for large turnover, importers, exporters and certain categories.

FSSAI mandates labelling with product name, ingredients list, net quantity, nutrition information, veg/non-veg logo, FSSAI licence number, batch, date of manufacture, best-before or expiry, and storage instructions.

Standards referenced in India include Food Safety and Standards Regulations for contaminants, additives, packaging and labelling, plus BIS standards for many processed products.

Marketing mix (4P): product (quality, pack size), price (cost-plus or competitive), place (distribution channel, cold chain), promotion; branding and certification marks aid differentiation.

Support ecosystem: PMFME and similar schemes for micro food processing, food parks, cold chain and incubation support, plus MSME registration, GST and food testing laboratory access.