Chapter 18: Food Technology and Food Safety
Food composition and spoilage
Foods contain water, carbohydrates, proteins, fats, vitamins, and minerals. Spoilage is caused by microorganisms (bacteria, yeasts, moulds), enzymes in the food, oxidation (rancidity), and physical damage. Microbial growth depends on nutrients, moisture (water activity), temperature, pH, and oxygen; food preservation works by controlling one or more of these factors (Chapter 9).
Preservation methods
| Method | Principle | Examples |
|---|---|---|
| Heat treatment | Kills microorganisms and enzymes | Pasteurization, sterilization, canning, blanching |
| Cooling and freezing | Slows or stops growth | Refrigeration, freezing of fish and meat |
| Drying and dehydration | Removes water | Dried fish, dried fruit, spices |
| Salting and sugaring | Lowers water activity | Salted fish, jam, candied fruit |
| Acidification and pickling | Lowers pH | Pickles, chutney |
| Fermentation | Desirable microbes make acid or alcohol | Yoghurt, curd, vinegar, toddy products |
| Chemical preservatives | Inhibit growth | Permitted additives such as benzoates, sorbates |
| Modified atmosphere and packaging | Controls oxygen and moisture | Vacuum packs, sealed pouches |
| Irradiation | Ionizing radiation | Spices, some produce (where permitted) |
Pasteurization of milk uses mild heat (for example 63 °C for 30 minutes, or 72 °C for 15 seconds) to destroy disease-causing organisms with little change in flavour; sterilization (UHT, canning) destroys all organisms. For canning, high-acid foods (pH below about 4.6) can be processed at boiling temperature, whereas low-acid foods need higher temperatures in a pressure vessel because spores of Clostridium botulinum survive boiling.
Processing of major food groups
Cereals: milling (paddy to rice, wheat to flour), parboiling, baking, extrusion.
Fruits and vegetables: washing, peeling, blanching, pulping, juice extraction, jam making (fruit, sugar, acid, and pectin boiled to the right solids), dehydration.
Milk: collection, cooling, pasteurization, standardization, and manufacture of yoghurt, curd, butter, and cheese.
Meat, poultry, and fish: hygienic slaughter and handling, chilling, freezing, curing, canning.
Spices and plantation produce: cleaning, drying, grinding, and packaging of cinnamon, pepper, and others; tea and coconut processing.
Packaging and labelling
Packaging protects, preserves, informs, and sells. Materials include glass, metal, paper, plastics, and laminates, each with strengths and limits. A label must give the name of the food, ingredients (in descending order of weight), net quantity, manufacturer’s name and address, batch number, date marking (best before or expiry), storage instructions, and nutrition or allergen information, as required by national food law and standards.
Food safety systems
Food hazards are biological (Salmonella, E. coli, norovirus), chemical (pesticide residues, cleaning chemicals, toxins), and physical (glass, metal, stones). Basic controls are Good Hygiene Practice and Good Manufacturing Practice: personal hygiene, clean premises and equipment, pest control, safe water, correct temperature, and separation of raw and cooked food. HACCP (Hazard Analysis and Critical Control Points) is a systematic approach built on seven principles (Codex Alimentarius Commission, 2020):
Conduct a hazard analysis.
Determine the critical control points (CCPs).
Establish critical limits.
Establish monitoring procedures.
Establish corrective actions.
Establish verification procedures.
Establish documentation and record keeping.
Example: for pasteurized milk, the CCP is the heating step, the critical limit is 72 °C for 15 s, monitoring is by a continuous temperature recorder, and the corrective action is to divert under-heated milk back for re-heating. Traceability, recall procedures, laboratory testing, and compliance with national food law and the Sri Lanka Standards Institution (n.d.) standards support safe food. Clean water and clean hands remain the most important controls.
Nutrition and sensory quality
A balanced diet includes energy foods, body-building foods (proteins), and protective foods (vitamins and minerals), with adequate water and fibre. Processing can improve safety and shelf life but may reduce some nutrients, so the methods should preserve quality. Sensory evaluation (appearance, aroma, taste, texture) is used to test and improve products.
Common mistakes
Cross-contamination of raw and cooked food.
Using too little acid or heat in home canning.
Keeping perishable food in the “danger zone” (roughly 5–60 °C) too long.
Practice questions
State the seven principles of HACCP.
Explain why low-acid foods need higher temperatures for safe canning.
Identify the critical control point in making canned fruit.