Theory question 103
Microorganisms and Health(a) A piece of raw meat was left in an uncovered bowl for seven days.
Use the information to answer questions 3(a) and 3(b).
(i) State four likely changes that would be observed in the meat.
(ii) Name the biological process that led to the changes that are observed in the meat.
(iii) On the table below, list four methods of preserving meat to prevent it from the changes stated in 3(a)(i) and mention the principle involved in the methods.
Table columns: Four methods of preserving the meat | One principle involved in the preservation method
(iv) Name two environmental factors that may be responsible for the changes in 3(a)(i).
(b) Name one method of preserving the following food items: (i) dried maize grains; (ii) fresh tomatoes; (iii) vegetables; (iv) beans; (v) milk.
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(a)(i) Any four: bad (offensive) smell; change of colour (greenish/dark); soft, slimy texture; presence of maggots; growth of moulds/microbes; liquid oozing out.
(ii) Decay (putrefaction / decomposition by bacteria and fungi).
(iii) Any four with principle: refrigeration/freezing - low temperature slows microbial growth and enzymes; drying/smoking - removes water microbes need; salting - draws water out of microbes by osmosis; canning - heat kills microbes and the sealed can keeps new ones out; cooking/boiling - heat kills microbes.
(iv) Any two: warm temperature; moisture/humidity; oxygen (air); presence of microorganisms/flies.
(b)(i) Dried maize grains: sun-drying and storing in airtight containers/silos with chemicals.
(ii) Fresh tomatoes: refrigeration (or canning as paste, drying).
(iii) Vegetables: refrigeration or drying.
(iv) Beans: drying and storage in airtight containers/with preservatives.
(v) Milk: pasteurisation, refrigeration, or drying into powder.
Each preservation method must be paired with its own principle.