Discuss the principles of food preservation with suitable examples.

1. 1 · Open in two lines. Food preservation keeps food safe and acceptable for a long time while saving its nutrients, colour, flavour and texture. It rests on three principles.
2. 2 · Principle 1: prevent or delay microbial decomposition.
   • Keep microbes out (asepsis): egg shell, aseptic cartons.
   • Remove them: washing, filtering juice.
   • Hinder growth: cold, drying, sugar, salt, acid, low oxygen, chemicals.
   • Kill them: pasteurisation, canning, irradiation.
3. 3 · Principle 2: prevent or delay self-decomposition.
   • Destroy enzymes: blanching vegetables before freezing.
   • Delay chemical reactions: antioxidants, nitrogen flushing, cool dark storage.
4. 4 · Principle 3: prevent damage by insects, animals and mechanical causes. Airtight pest-proof bins, fumigation, padded crates, careful handling.
5. 5 · Draw a chart. [Chart: three principles → sub-points → one method each]
6. 6 · Add the hurdle idea. Most products combine several principles: mango pickle uses salt, oil, acid and spices together.
7. 7 · Nutrition link. Choose gentle methods that save nutrients: quick blanching keeps more vitamin C than long boiling.
8. 8 · Close in one line. Every preservation method in this course applies one or more of these principles.

Scoring tip: Write the four ways of controlling microbes in order (keep out, remove, hinder, kill); examiners look for that sequence.