WBCHSE HS Vocational Food Processing cheat sheet

Food processing is any deliberate operation that transforms raw agricultural material into a stable, edible, transportable form; food science is the underlying study of the chemistry, microbiology, engineering and nutrition behind those operations.

Primary processing converts harvest into a basic stable form (milling, cleaning, grading, drying, chilling); secondary processing converts those into ready products (baking, canning, extrusion, freezing of prepared dishes).

Post-harvest loss in fruits and vegetables commonly runs 20-40% in India without cold chain; processing exists chiefly to cut this loss and add shelf life and value.

Food science sub-disciplines: food chemistry, food microbiology, food engineering/processing, food quality and safety, and food product development.

Water activity (aw) is the ratio of vapour pressure of the food to that of pure water at the same temperature; pure water aw = 1.00, most spoilage bacteria need aw above 0.90.

Perishable foods (milk, meat, fish, fresh produce) keep days; semi-perishable (potatoes, onions, nuts) keep weeks to months; shelf-stable (cereals, sugar, salt) keep months to years without special storage.

Unit operation concept: any process is a chain of discrete physical steps (size reduction, mixing, heating, separation, drying) that can be analysed and scaled independently of the specific food.

Composition of typical fresh foods (approx., wet basis): milk 87% water, 3.3% protein, 3.9% fat, 4.9% lactose; wheat grain about 12-14% water, 10-14% protein, 60-75% starch.

Macronutrients: carbohydrates supply 4 kcal/g, proteins 4 kcal/g, fats 9 kcal/g, alcohol 7 kcal/g; dietary fibre is carbohydrate but contributes little usable energy.

Water in food exists as free water (solvent, supports microbial growth and reactions) and bound water (chemically or physically held); only free water lowers aw-dependent stability.

Maillard browning is a non-enzymatic reaction between reducing sugars and amino groups of proteins, favoured by heat and intermediate aw (0.6-0.8); it produces brown pigments and flavours, and can destroy lysine.

Caramelisation is thermal decomposition of sugars without amines; enzymatic browning (polyphenol oxidase acting on phenols) is the browning of cut apples, potatoes and brinjal.

Fat oxidation (rancidity) is accelerated by light, heat, trace metals (Cu, Fe) and oxygen; antioxidants such as BHA, BHT, TBHQ and tocopherols delay it.

Essential amino acids (9 in adults): histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine; cereals are limiting in lysine, pulses in methionine.

Fat-soluble vitamins A, D, E, K are heat-stable but sensitive to oxidation and light; water-soluble B vitamins and vitamin C leach into cooking or blanching water and are destroyed by heat and alkali.

Protein denaturation by heat, acid or shear unfolds the structure without breaking peptide bonds; it changes solubility and texture (egg white setting, curd formation) but not nutritional value.

Bacteria, yeasts and moulds are the main spoilage agents; bacteria generally need aw above 0.90, pH above 4.6 and warmer temperatures, while moulds tolerate lower aw (down to about 0.60).

Danger zone for bacterial growth is roughly 5-60 degrees C; the most rapid growth is near 37 degrees C, so rapid chilling below 5 degrees C and hot holding above 60 degrees C are the core controls.

Cardinal temperatures: psychrotrophs grow near 0-7 degrees C (Listeria, Pseudomonas), mesophiles 20-45 degrees C (Salmonella, Staphylococcus aureus), thermophiles 45-65 degrees C.

Clostridium botulinum is an anaerobic spore-former whose toxin is destroyed by boiling but whose spores survive; hence low-acid canned foods (pH above 4.6) need a 12-D botulinum process such as 121 degrees C for at least 3 minutes in the cold point.

Salmonella, E. coli O157:H7, Listeria monocytogenes and Staphylococcus aureus are the key bacterial food-borne pathogens; moulds such as Aspergillus flavus produce aflatoxin in improperly stored groundnuts and cereals.

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

Cleaning removes soil with detergent and water; sanitising then reduces microorganisms with heat or a chemical sanitiser such as 100-200 ppm chlorine solution; surfaces must be cleaned before sanitising.

Personal hygiene controls in a food unit: hand washing at entry and after toilet use, clean protective clothing, no jewellery, exclusion of workers with cuts, diarrhoea or skin infection, and periodic medical checks.

Thermal processing: pasteurisation (typically 63 degrees C for 30 min or 72 degrees C for 15 s for milk) kills vegetative pathogens; sterilisation/commercial sterility destroys all pathogens and spoilage organisms capable of growing in the product.

Blanching (hot water or steam, 1-5 min) inactivates enzymes such as polyphenol oxidase and peroxidase, fixes colour, expels tissue gases and shrinks the product before freezing or drying.

Refrigeration holds food near 0-5 degrees C for short-term storage; freezing to -18 degrees C or below stops microbial growth and greatly slows enzymes; frozen foods need constant cold chain to avoid ice crystal damage.

Drying reduces aw below about 0.60 to stop microbial growth; sun drying is cheap but slow and open to contamination, while mechanical dryers give controlled temperature and airflow.

Osmotic preservation uses high sugar or salt concentration (jam, jelly, pickle, murabba) to lower aw; salt also selects halotolerant organisms, so pickles need proper acidity and oil cover.

Chemical preservatives permitted in India under FSS regulations include benzoic acid/sodium benzoate (acid foods), sorbic acid/sorbates, sulphur dioxide and sulphites (dried fruit, juice), and nitrites/nitrates (cured meat).

Fermentation by lactic acid bacteria lowers pH and produces antimicrobial compounds; examples include curd, idli batter, sauerkraut, kimchi, and vinegar production by Acetobacter.

Non-thermal methods include irradiation (doses in kGy, approved for spices, onion, potato, and some other items in India), high pressure processing, pulsed electric field, and modified atmosphere packaging with reduced O2 and raised CO2.

Size reduction equipment: jaw and roller crushers for coarse work, hammer mills and ball mills for fine grinding, colloid mills for wet pastes, and slicers/dicers for fruits and vegetables.

Mixing equipment: ribbon blenders for powders, planetary and paddle mixers for dough and batters, and high-shear homogenisers for emulsions such as milk and sauces.

Heat exchangers: plate exchangers give high heat transfer with easy cleaning for milk and juice; shell-and-tube exchangers suit higher pressures; scraped-surface exchangers handle viscous or particulate products.

Evaporation removes water as vapour below boiling point by applying vacuum; a triple-effect evaporator reuses vapour and cuts steam use to roughly one-third of a single-effect unit.

Drying equipment: tray dryer for small batches, tunnel dryer for continuous drying, fluidised bed dryer for granular solids, spray dryer for milk powder and coffee, drum dryer for flakes, and freeze dryer for heat-sensitive high-value foods.

Filtration and centrifugation separate solids from liquids; a cream separator is a disc-bowl centrifuge that splits milk into cream and skim milk by density difference.

Material balance: input mass = output product + waste + losses; energy balance: heat supplied = sensible heat to raise temperature + latent heat of vaporisation + losses.

Extrusion cooking combines conveying, mixing, shearing, heating and shaping in one barrel; it is used for snacks, breakfast cereals and textured vegetable protein.

Packaging functions: containment, protection from physical, chemical and biological hazards, convenience, and communication of information to the consumer.

Oxygen transmission rate (OTR) and water vapour transmission rate (WVTR) are the key barrier properties; metallised films and aluminium foil give near-total light and moisture barrier, while paper is a poor moisture barrier.

Modified atmosphere packaging lowers O2 and raises CO2 or N2 to slow respiration and microbial growth; vacuum packaging removes air and is used for meat, cheese and coffee.

Aseptic packaging (UHT product filled into pre-sterilised cartons) gives shelf-stable milk and juice without refrigeration until opening.

Active and intelligent packaging: oxygen scavengers, moisture absorbers, ethylene absorbers for produce, and time-temperature indicators that show whether the cold chain broke.

Storage design rules: FIFO and FEFO stock rotation, cool dry ventilated godowns, pallets off the floor and away from walls, and separate storage of raw materials and finished goods to avoid cross-contamination.

Cold chain for perishables: pre-cooling after harvest, refrigerated storage, refrigerated transport, and retail display chiller, with continuous temperature records at each link.

Transport of food requires clean, covered vehicles, no mixing with chemicals or non-food cargo, and temperature-controlled containers for frozen and chilled goods.

Quality attributes fall into sensory (appearance, colour, texture, flavour), nutritional, microbiological, chemical and physical categories; quality control monitors them against specifications.

FSSAI is the apex food regulator in India under the Food Safety and Standards Act, 2006; it issues licences and registration, sets standards, and enforces labelling rules.

FSSAI licence categories: basic registration for small turnover businesses, state licence for medium turnover, and central licence for large turnover, importers and exporters (turnover thresholds are set by FSSAI and should be checked in the current regulations).

Mandatory label information under Indian rules: name of food, list of ingredients in descending order of weight, net quantity, name and address of manufacturer/packer, batch number, date of manufacture, best-before/use-by date, nutritional information, FSSAI licence number, and veg/non-veg mark.

Codex Alimentarius, set up jointly by FAO and WHO, provides international food standards and codes of practice that national standards often follow.

BIS (Bureau of Indian Standards) issues product standards and ISI marks for items such as packaged drinking water and certain processed foods; AGMARK is a grading mark for agricultural produce.

ISO 22000 is a food safety management system standard; ISO 9001 covers general quality management; both rely on documented procedures, audits and corrective action.

Key analytical tests: moisture by oven drying or Karl Fischer, protein by Kjeldahl, fat by Soxhlet, ash by muffle furnace, pH by pH meter, and total plate count and coliform count for microbiological quality.

Cost of production = raw material + labour + utilities + packaging + depreciation + overheads; gross margin = sales revenue minus direct cost of goods sold.

Break-even quantity = fixed cost divided by (selling price per unit minus variable cost per unit); break-even sales value = fixed cost divided by contribution margin ratio.

Selling price is set by cost-plus pricing (cost plus a target margin), market/competitive pricing, or value-based pricing; food products are usually priced against local competitors.

Working capital is needed for raw material purchase, wages and stock until payment is received; a food business often needs 2-3 months of operating cost as working capital.

Market segmentation for food products is commonly by income, age, region, occasion of use and health need (for example, low-sugar, high-protein, ready-to-eat).

Distribution channels for small food processors: direct sale, local retailers, wholesalers, institutional buyers (hotels, hostels, schools), and online marketplaces; each has different margins and payment terms.

Government support for food processing entrepreneurs includes PMFME (micro food processing enterprises), PM Formalisation of Micro Food Processing Enterprises, MoFPI schemes, state subsidies, and food park facilities.

A simple project report must state product, process, capacity, machinery list with cost, raw material sources, manpower, total project cost, means of finance, projected profit and break-even period.

Moisture determination by hot air oven: weigh a dry dish, add sample, dry at 105 degrees C to constant weight, cool in a desiccator, and compute moisture percentage as (initial weight minus final weight) divided by sample weight times 100.

Total soluble solids (TSS) of juice, jam or squash are measured with a refractometer or hand-held Brix meter, corrected to 20 degrees C; Brix is approximately the percentage of sucrose in solution.

Acidity by titration: titrate a known sample volume against standard NaOH using phenolphthalein; express as percentage of citric acid for fruits (factor 0.064 for citric acid monohydrate per mL of 0.1 N NaOH).

pH is measured with a calibrated pH meter using buffer solutions of pH 4.0 and 7.0; rinse the electrode with distilled water between samples.

Total plate count: prepare serial dilutions, plate on nutrient agar, incubate at 37 degrees C for 24-48 hours, and count colonies as colony-forming units per gram or per mL.

Sensory evaluation uses a trained or consumer panel with a 9-point hedonic scale (1 = dislike extremely, 9 = like extremely); samples must be coded and served blind to avoid bias.

Project work should follow: problem statement, literature review, objective, materials and methods, observations in tables, results and discussion, conclusion, and references.

Safety in the food lab: tie hair, wear apron, wash hands, never taste unidentified samples, label all reagents, and clean and sanitise benches and glassware before and after work.