WBBSE Madhyamik Food Processing (Vocational) cheat sheet

Food processing is any deliberate operation that changes a raw agricultural commodity into a stable, edible, marketable form; food science is the study of the physical, chemical, and biological nature of foods and the principles behind those operations.

Unit operations (cleaning, grading, size reduction, heating, drying, freezing, mixing, separation, packaging) are the building blocks of every process line; a process flow diagram sequences them with inputs, outputs, and by-products.

Water activity (a_w) is the equilibrium relative humidity of a food divided by 100; microbial growth generally ceases below a_w 0.60, while most bacteria need a_w above 0.90.

Proximate composition reports moisture, crude protein (Kjeldahl N x 6.25), crude fat, crude fibre, ash, and nitrogen-free extract; the six fractions sum to 100 percent of fresh weight.

The Maillard reaction is a non-enzymatic browning between reducing sugars and amino groups that develops colour and flavour on heating but destroys lysine; caramelisation involves sugars alone at high temperature.

Enzymatic browning in cut fruits and vegetables is caused by polyphenol oxidase acting on phenols in the presence of oxygen; blanching inactivates the enzyme by heat before freezing or drying.

Colligative and structural properties (freezing point depression, boiling point elevation, viscosity, gelation) govern process design; starch gelatinisation and protein denaturation are the key heat-induced structural changes.

Food science disciplines map to exam topics: food chemistry (composition and reactions), food microbiology (spoilage and pathogens), food engineering (heat, mass, fluid transfer), and food technology (applied processing).

Cereal grains share a structure of bran (pericarp and aleurone), endosperm (starchy, main milling yield), and germ (oil-rich embryo); milling separates these fractions to give flour, bran, and germ.

Rice milling removes husk (dehusking) then bran and germ (polishing); parboiling soaks, steams, and dries paddy before milling and drives vitamins from bran into the endosperm, reducing milling losses.

Wheat flour quality depends on gluten-forming proteins gliadin and glutenin; hard wheat gives strong gluten for bread, soft wheat gives weak gluten for biscuits and cakes.

Pulses are legume seeds harvested dry (gram, lentil, pea, bean); they store well at low moisture but contain antinutritional factors such as trypsin inhibitors and lectins, destroyed by soaking and thorough cooking.

Fruits and vegetables are living, high-moisture commodities that continue respiration after harvest; the respiration rate correlates with perishability, and refrigeration plus controlled or modified atmosphere slows it.

Climacteric fruits (banana, mango, tomato, apple) ripen with an ethylene burst and can be ripened or ripened-then-held after harvest; non-climacteric fruits (citrus, grape, pineapple) do not ripen further off the plant.

Grading criteria for raw materials: moisture content, foreign matter, broken or damaged grains, immature or diseased produce, size, colour, and specific gravity (used to sort sound from infested or immature produce).

Maturity indices guide harvest timing: total soluble solids, acidity or TSS-to-acid ratio, firmness, colour, and days from anthesis; harvesting at the correct stage maximises storage life and processed quality.

Preservation acts by one or more of: heat destruction of microorganisms, removal or binding of water, low temperature slowing growth, acidification, addition of preservatives, exclusion of oxygen, and competitive fermentation.

Pasteurisation uses temperatures below 100 degrees C (for example 63 degrees C for 30 minutes or 72 degrees C for 15 seconds for milk) to destroy vegetative pathogens with minimal quality change; it does not sterilise.

Commercial sterilisation (canning) applies heat sufficient to inactivate Clostridium botulinum spores, typically an F0 of 3 minutes at 121.1 degrees C; low-acid canned foods need this, acid foods (pH below 4.6) need less.

Drying removes water to a safe a_w; sun drying is cheap but weather-dependent, while cabinet, tunnel, drum, spray, and freeze drying give controlled rates; case hardening occurs when surface dries too fast and traps moisture inside.

Refrigeration at 0-5 degrees C slows but does not stop microbial growth; freezing at -18 degrees C or below stops growth, and quick freezing forms small ice crystals that limit cell damage and drip loss.

Chemical preservatives include salt and sugar (lower a_w by osmosis), acids (citric, acetic, lactic), sulphur dioxide and sulphites (antioxidant and antimicrobial, restricted in use), nitrite (curing, colour and botulism control), and benzoate and sorbate for acidic foods.

Blanching before freezing or drying inactivates enzymes and removes tissue gases; failure to blanch causes off-flavours, colour loss, and vitamin degradation during storage.

Hurdle technology combines mild preservation factors (low pH, low a_w, refrigeration, preservative, modified atmosphere) so no single factor must be severe, preserving sensory quality while ensuring safety.

Cleaning removes foreign matter by screening, aspiration (air classification by density), magnetic separation, destoning, and washing; grading then sorts by size, shape, density, or quality using sieves, roller graders, or optical sorters.

Milling reduces cereal grain to flour: roller mills use paired fluted and smooth rolls with sifting between passes, while hammer and plate mills use impact and attrition for simpler, less selective grinding.

Size reduction equipment selection follows feed size and product fineness: jaw and roll crushers for coarse work, hammer mills for medium grinding, ball mills and colloid mills for fine or wet grinding and emulsification.

Mixing equipment includes ribbon and paddle blenders for powders, planetary and anchor agitators for viscous pastes, and high-shear homogenisers for emulsions; mixing index measures uniformity achieved.

Separation operations include filtration (solid from liquid using filter cloth or screen), sieving, centrifugation (cream separation, clarification), decantation, expression (oil or juice pressing), and membrane processes such as ultrafiltration and reverse osmosis.

Material balance: input mass equals output mass plus losses; a mass-balance or yield calculation (product mass divided by raw material mass times 100) quantifies process efficiency and by-product recovery.

Evaporation and distillation concentrate or separate by volatility; a multiple-effect evaporator reuses vapour from one effect to heat the next, cutting steam consumption per kilogram of water removed.

Equipment hygiene design requires smooth, non-absorbent, corrosion-resistant food-contact surfaces (stainless steel grades such as 304 and 316), rounded corners, and easy dismantling for cleaning and inspection.

Packaging functions are containment, protection from physical, chemical, and biological hazards, convenience, and communication; packaging must be compatible with the food and the process (retort, freeze, microwave).

Common materials: glass (inert, heavy, brittle), metal cans and foil (excellent barrier, needs internal lacquer for acidic foods), paper and board (poor moisture barrier, often coated or laminated), and plastics identified by resin codes 1-7.

Plastic barrier properties: PET (code 1) gives good strength and gas barrier for beverages; HDPE (2) resists moisture; PP (5) withstands heat for hot fill; PVC (3) and polystyrene (6) are restricted for fatty or hot foods; LDPE (4) is a weak moisture barrier.

Modified atmosphere packaging replaces air with a gas mix (commonly nitrogen, carbon dioxide, oxygen) to slow respiration and microbial growth; vacuum packaging removes air and relies on oxygen exclusion.

Aseptic packaging sterilises product and packaging separately and fills under sterile conditions, allowing long ambient shelf life for UHT milk and juices in laminated cartons.

A label must carry, as applicable, the product name, list of ingredients in descending order of weight, net quantity, name and address of manufacturer or packer, batch or lot code, date of manufacture and best-before or use-by date, storage instructions, allergen declaration, and nutritional information.

Storage conditions follow the product: dry grains below about 12-14 percent moisture in cool, dry, ventilated stores; canned and dry goods at ambient temperature away from sunlight; perishables under refrigeration or frozen storage with stock rotation (first in, first out).

Shelf-life testing stores samples under defined conditions and monitors sensory, microbial, and chemical markers at intervals; accelerated testing at elevated temperature uses the Arrhenius relationship to predict ambient shelf life.

Hazard categories are biological (bacteria, viruses, parasites, moulds), chemical (pesticide residues, cleaning chemicals, mycotoxins, allergens), and physical (glass, metal, stones, hair, pests).

Five keys to safer food: keep clean; separate raw and cooked; cook thoroughly; keep food at safe temperatures (below 5 degrees C or above 60 degrees C); use safe water and raw materials.

HACCP has seven principles: conduct hazard analysis, determine critical control points, set critical limits, monitor, establish corrective actions, verify, and keep records; it is a preventive, science-based system.

Good Manufacturing Practice and Good Hygiene Practice cover premises, water quality, personal hygiene, pest control, cleaning schedules, training, and traceability, and form the prerequisite programmes on which HACCP rests.

Sanitation is cleaning (removing soil with detergent) followed by disinfection (reducing microorganisms with heat or chemical sanitisers such as hypochlorite or quaternary ammonium compounds); cleaning must precede disinfection.

Personal hygiene rules: handwashing before handling food and after toilet use, clean protective clothing and head covering, no jewellery, no eating or smoking in production areas, exclusion of workers with skin infections or gastrointestinal illness.

Food-borne pathogens of concern include Salmonella, Staphylococcus aureus, Clostridium botulinum, Listeria monocytogenes, and Escherichia coli O157:H7; control relies on temperature, hygiene, and cross-contamination prevention.

Quality assurance differs from quality control: QA is the planned system ensuring quality is built in (standards, audits, documentation), while QC is inspection and testing of the product against specifications.

Intrinsic factors controlling microbial growth in food: pH, water activity, redox potential, nutrient content, antimicrobial constituents, and mechanical structure; extrinsic factors: temperature, relative humidity, and gaseous atmosphere.

Bacteria grow fastest near pH 7, yeasts and moulds tolerate lower pH, and moulds tolerate the lowest water activity; below pH 4.6 Clostridium botulinum cannot grow and produce toxin.

Growth phases in a batch culture are lag, log (exponential), stationary, and death; generation time depends on species and temperature, and the log phase is when spoilage and toxin formation accelerate.

Temperature classes: psychrophiles grow near 0-15 degrees C, mesophiles 20-45 degrees C, thermophiles 45-65 degrees C; most food-borne pathogens are mesophiles, so rapid chilling and thorough heating are critical.

Spoilage signs: bacterial slime, souring, gas and off-odours; mould mycelium and mycotoxins (aflatoxin from Aspergillus flavus in groundnuts and cereals); yeast fermentation of sugars; enzymatic browning and rancidity of fats.

Canned food spoilage types: flat sour (Bacillus species, acid without gas), thermophilic anaerobic spoilage (gas and off-odour), and putrefactive anaerobic spoilage; swelling of cans indicates gas production and the can must be rejected.

Fermentation uses controlled microorganisms to preserve and transform food: lactic acid bacteria in curd, pickle, and sauerkraut lower pH; yeasts in bread and idli; Acetobacter converts ethanol to acetic acid in vinegar.

Microbial testing methods include total plate count, coliform and E. coli counts, and pathogen-specific detection; results are interpreted against standards, and aseptic sampling technique prevents false results.

Additive classes by function: preservatives, antioxidants, colours, flavours, emulsifiers, stabilisers and thickeners, acidity regulators, anticaking agents, sweeteners, humectants, and leavening agents.

An additive is permitted only when technologically justified, safe at the intended level, and declared on the label; maximum permitted levels are set by food safety regulation and additives must not be used to disguise faulty raw material.

Examples: sodium benzoate and potassium sorbate as preservatives in acidic foods; BHA and BHT or tocopherols as antioxidants in fats; lecithin and mono- and diglycerides as emulsifiers; pectin, gelatin, and starch as thickeners.

Nutrition basics: energy from carbohydrate and protein at about 4 kcal per gram and fat at about 9 kcal per gram; a balanced diet supplies energy, protein, fat, vitamins, minerals, and fibre in adequate proportions.

Protein quality is judged by amino acid composition and digestibility; cereal protein is limiting in lysine and pulse protein in methionine, so cereal-pulse combinations improve overall protein quality.

Deficiency diseases relevant to India: protein-energy malnutrition (marasmus and kwashiorkor), vitamin A deficiency (night blindness), iron deficiency anaemia, iodine deficiency goitre, and vitamin D and calcium deficiency rickets.

Product development stages: idea generation, screening, concept and prototype formulation, laboratory trials, sensory evaluation (appearance, aroma, taste, texture, overall acceptability using a hedonic scale), scale-up, shelf-life trial, and market launch.

Fortification adds micronutrients to a staple (iodised salt, iron and folic acid in wheat flour, vitamin A in oil) to correct a population deficiency; enrichment restores nutrients lost in processing.

Cost of production per unit equals total fixed cost plus total variable cost divided by units produced; fixed cost per unit falls as output rises, while variable cost per unit stays roughly constant.

Break-even quantity equals fixed cost divided by (selling price per unit minus variable cost per unit); break-even sales value is break-even quantity times selling price.

Gross margin is sales revenue minus cost of goods sold; net profit subtracts operating expenses, depreciation, interest, and tax from gross margin; margin percentage is profit divided by sales times 100.

Working capital funds day-to-day operations (raw material, wages, power, packaging) and equals current assets minus current liabilities; a food unit needs working capital to bridge the gap between raw material purchase and payment receipt.

Small food enterprise essentials: product selection based on local raw material and demand, registration and food licence, premises layout for hygiene, quality control, branding, pricing, and record keeping.

Marketing mix elements are product, price, place, promotion, and for services people, process, and physical evidence; pricing strategies include cost-plus, penetration, and competitive pricing.

Distribution channels for processed foods range from direct sale to retailer to wholesaler and distributor networks; cold-chain integrity is essential for perishable dairy, meat, and frozen products.

Support systems for food entrepreneurs include bank loans and self-employment schemes, food parks and incubation centres, cooperative and self-help group marketing, and government food safety and standards registration.

Laboratory practice rules: wear a clean apron and closed footwear, tie back hair, wash hands, label all containers with content and date, never taste chemicals or unknown samples, and know the location of fire extinguishers and first aid.

Moisture determination: weigh a clean dry dish with sample, heat in an oven at 105 degrees C to constant weight, cool in a desiccator, reweigh; moisture percent equals (initial minus final mass) divided by initial sample mass times 100.

Ash determination uses a muffle furnace at about 550 degrees C until a white ash remains; ash represents total mineral content and indicates adulteration or contamination with sand or soil.

Titratable acidity is measured by titrating a sample against standard sodium hydroxide using phenolphthalein; total soluble solids are read with a refractometer or hydrometer and reported in degrees Brix.

Sensory evaluation uses a trained or consumer panel, coded and randomised samples, water for rinsing between samples, and a hedonic or descriptive score sheet; panelists must not be influenced by labels.

Standard workshop tools and equipment include weighing balance, oven, muffle furnace, desiccator, pH meter, refractometer, autoclave, incubator, laminar flow, sieves, mixer grinder, and sealing and packaging materials.

Project work follows the scientific format: title, rationale, objectives, materials and methods, observations in tables, calculations, results, discussion, conclusion, and references; results must be reproducible and records kept in a bound notebook.

Safe handling of glassware and equipment: check for cracks before heating, add acid to water and not water to acid, use tongs for hot items, and clean and return apparatus to its designated place after use.