Food Preservation, Processing and Storage
What this domain tests
The exam checks whether you know why food spoils, which preservation principle each method uses, and how to store foods safely at home.
Causes of spoilage
Microorganisms (bacteria, moulds, yeasts), enzymes, insects and rodents, moisture, oxygen, and rough handling.
Principles of preservation
- Asepsis - keeping out microorganisms (clean handling, sealed containers).
- Removal of moisture - drying, solar drying, salting.
- Low temperature - refrigeration, freezing (slows, not kills, microbes).
- High temperature - boiling, canning, sterilization.
- Chemicals - salt, sugar, oil, vinegar, spices, permitted preservatives.
- Irradiation - controlled, approved use.
Common methods
Jam, jelly and murabba use sugar; pickle uses salt, oil, vinegar and sunlight; papad and vegetables use drying; milk uses pasteurization (63 °C for 30 minutes, or 72 °C for 15 seconds) followed by quick cooling.
Worked example
Mango pickle spoiling within a week. Reasoning: moisture entered and oil floated low. Correction - use fully dry mango pieces, dry salted pieces in sunlight, use enough salt and oil to cover, pack in a dry sterilized jar, keep a layer of oil on top, and use a dry spoon.
Traps that cost marks
- Confusing pasteurization with sterilization: pasteurization does not make milk sterile.
- Believing a refrigerator kills bacteria - it only slows growth.
- Home canning low-acid foods without proper heating risks botulism.
- Storing onions and potatoes together - both spoil faster.