SECTION B : (35 marks)
11. With the aid of a flow chart, explain the biochemical pathway of how the microbial toxin of a food pathogen can trigger diarrhoea. (7 marks)
12. Non-biological contaminants can hinder the maintenance of cell cultures. Recommend five ways to prevent such contaminations. (7 marks)
13. Briefly describe seven general observations on the heat resistance of bacteria cells.
(7 marks)
14. List seven factors affecting the efficacy of a given dose of ionising irradiation on bacteria cells. (7 marks)
15. Write short notes on flat sour spoilage in canned food. (7 marks)
SECTION C : (45 marks)
16. A food microbiologist received a sample of bee hoon which is suspected to be contaminated with two types of food pathogens. The laboratory findings based on staining and biochemical methods are noted as follows:
Pathogen A
Spore-formers
Rod-shaped
Gram positive
Positive litmus milk test
Positive DNase and starch test
Pathogen B
Non spore-formers
Rod shaped
Gram negative
Negative methyl-red test
Positive citrate test
(a) Based on the findings above, name the two food pathogens. (4 marks)
(b) What are the principles involved in DNase, starch and citrate tests?
(6 marks)
(c) “Staining and biochemical methods are methods used to identify microorganisms phenotypically. There are other accurate methods to identify unknown microorganisms.” Do you agree with these sentences? Justify your answer. (5 marks)
17. List the predominant type of mould spoilage in fruit and vegetables. Name a mould responsible for each type of spoilage. (15 marks)
18. On 23 May 2005, a report by the US health officials stated that “Undercooked turkey was the likely cause of a salmonella outbreak in Camden two weeks ago that has been linked to one death and more than 300 illnesses”.
Discuss salmonellosis, giving an account for the outbreak of the disease and its symptoms. Suggest six preventive control measures to prevent salmonella food poisoning outbreak. (15 marks)
- End of Paper -
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