ZIMSEC O Level · Food Technology and Design · Form 3, Form 4
Preservation prevents or slows spoilage so food lasts longer.
Principles
Remove one or more conditions bacteria need: water, warmth, oxygen, or a suitable pH; or kill micro-organisms with heat.
Methods
- Drying: sun-drying vegetables (mufushwa), fruit, fish (kapenta/matemba) and meat (biltong) removes water.
- Heat: boiling, pasteurisation (milk heated to about 72 °C for 15 seconds), canning and bottling.
- Cold: refrigeration slows bacteria; freezing stops their growth.
- Chemical: salting, sugaring (jam), pickling in vinegar, smoking, and approved preservatives.
Food processing and value addition
Turning raw food into products with a longer life and higher value: peanut butter, tomato sauce, dried mango, mahewu, yoghurt, juices and baked goods.
Packaging and labelling
Packaging protects food and attracts customers. Labels must show the product name, ingredients, net mass, manufacturer's details, date marking (best before/use by) and storage instructions.
Exam tip: Explain how each method works – which bacterial need it removes – not only what it is.
Check yourself
- How does sugar preserve jam?
- State the conditions for pasteurising milk.
- Name four items that should appear on a food label.
Show answers
- High sugar concentration draws water out of micro-organisms (osmosis), so they cannot grow.
- About 72 °C for 15 seconds, then rapid cooling.
- Any four: name, ingredients, net mass, manufacturer, date marking, storage instructions.
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