Preservation and Processing Technologies
This domain tests how preservation methods extend shelf life while maintaining safety and quality. Expect comparisons of thermal processing, low-temperature storage, drying, fermentation, chemical preservation and hurdle technology.
Core concepts
- Thermal processing: pasteurisation reduces vegetative pathogens; sterilisation or commercial canning destroys spores and is used for low-acid foods. Both depend on time and temperature.
- Low temperature: chilling slows microbial growth and enzymatic reactions; freezing stops growth but does not kill all microorganisms.
- Drying and concentration: remove water and lower aw, but heat-resistant spores and toxins may remain.
- Fermentation and chemicals: acid production, salt, sugar and permitted preservatives create unfavourable conditions for spoilage organisms.
- Hurdle technology: combines several mild preservative factors for better quality and safety.
Worked example
To prepare 100 kg of pickle containing 12% salt, 12 kg of salt is needed. If a 20% brine is used, brine required = 12 ÷ 0.20 = 60 kg brine. The remaining 40 kg is prepared vegetable and other ingredients. The check is 60 kg × 20% = 12 kg salt, which is 12% of the 100 kg final batch.
Traps
Claiming pasteurisation sterilises food; forgetting that freezing does not kill all microbes; assuming drying makes a food sterile; using salt or sugar without checking the final concentration; ignoring that low-acid canned foods need a botulinum control process.