Explain the principle and applications of food irradiation.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Open in two lines. Food irradiation exposes food to controlled ionising radiation to kill microbes and insects, stop sprouting or delay ripening, without heating the food.
2 · Sources and principle.
Gamma rays from cobalt-60 (or caesium-137), electron beams, X-rays.
Rays damage microbial DNA directly and through free radicals.
Food is not made radioactive; a 'cold' process; works through packs.
3 · Dose unit. Gray: 1 joule per kg; 1 kGy = 1000 Gy; up to 10 kGy overall average judged safe by the 1980 expert committee.
4 · Draw the dose chart. [Chart: low (<1 kGy) sprout and insect control → medium (1-10 kGy) radurisation and radicidation → high (>10 kGy) radappertisation]
High: sterile meals for astronauts and hospital patients.
6 · Advantages, limitations and labelling. Cold, residue-free, works on packed food; costly, consumer fear, some vitamin loss, no effect on toxins; Radura logo required.
7 · Nutrition link. Safer spices and seafood; sterile meals for immune-compromised patients; vitamin losses are small.
8 · Close in one line. Irradiation is a safe, cold method that supports, but does not replace, good hygiene.
Scoring tip: The three dose bands with one example each are the heart of the answer; add the Radura.
