Introduction to Food Processing and Preservation
This domain tests whether you can explain why food is processed, how preservation slows spoilage, and how to choose a method that fits a food's pH, water activity, heat sensitivity and intended shelf life.
Core rules and concepts
- Processing changes form or composition: cleaning, grading, milling, blanching, baking, extrusion, canning.
- Preservation extends shelf life by controlling microorganisms, enzymes, oxygen, moisture, heat or light.
- Primary processing turns raw produce into a stable intermediate; secondary processing makes consumer products; tertiary processing links to packaging, storage and retail.
- Hurdle technology combines mild hurdles, for example low pH plus pasteurization plus refrigeration, so no single harsh treatment is needed.
- Key preservation levers: heat, cold, water removal, acidification, fermentation, oxygen exclusion, irradiation and chemical preservatives within legal limits.
Worked example
Mango pulp has pH about 3.6. Heat it to 90°C for 1 minute, hot-fill into sterile containers, seal and cool. The hurdles are heat, acid and low oxygen. This pasteurizes the pulp but does not sterilize it, so the pack still needs a validated shelf life and cool storage after opening.
Traps that cost marks
- “Preserved” does not mean sterile.
- Refrigeration slows microbes; it does not kill them.
- Drying is only protective if water activity is low enough, usually below 0.6.
- pH 4.6 is the low-acid/high-acid boundary used in canning safety.
- A process that improves taste or texture is not automatically a preservation step.