Exam Year:2015


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This paper consists of two sections A and B .
Answer ALL questions in section A and any THREE question from section B in the space provided in this question paper.
Each question in section A carries 4 marks while each question from section B carries 20 marks.

SECTION A (40 marks)
Answer ALL the questions in this section in the spaces provided.
1. (a) State the objective of coagulase test. (1 mark)

(b) Describe the procedure for slide technique for testing identification of the micro organisms in 1(a). (3 marks)

2. State four factors that influence the accuracy of the colony count in enumeration of micro organisms (4 marks)

3. Describe the staining procedure for a fixed smear in preparation of slides. (4 marks)

4. State four techniques of controlling mouldiness in bread during storage. (4 marks}

5. Table 1. Shows data on plate with colonies between 30-300. Calculate the standard plate count per milliliter. (4 marks)


6. Describe four factors which affect the heat resistance of spores during canning of food products. ( 4 marks)

7. Distinguish between food infection poisoning and food intoxication poisoning. (4 marks)

8. Describe four characteristics of micro-organic viruses.

9. State any four precaution observed when handling microscopes in a microbiology. (4 marks)

10. List four characteristics of clostridium botulinum. (4 marks)

SECTION B (60 marks)
Answer any THREE question from this section in the space provided after question 15.
11. Discuss the following in reference to salmonella food infection:
(a) Characteristics of the causative organisms
(b) Distribution and food sources of organisms
(c) Incubation period and symptoms of attack
(d) Control of the infection.
12. Explain how the following factors affect microbial growth:
a) Nutrients;
b) Oxygen;
c) Hydrogen ion concentration (pH)
d) Inhibition.
13. Figure 1 shows a general scheme of laboratory testing for detection of coliforms in water.
a) Explain the purpose of:
i. Presumptive test;
ii. Confirmed test;
iii. Completed test
b) Identify A,B,C,G,H and incubation condition for E.
c) Explain observation D,F and I.


14. (a) Most probable Number (MPN) is one of the method used to estimate the number of viable organisms in a sample. State:
i. TWO Applications of this method; (2 marks)
ii. Three errors associated with this method (3 marks)
iii. Three advantages associated with this method (3 marks)
(b) An experiment to estimate the number of coliforms in milk sample A,B,C,& D was done using the MPN method. The results were as shown in Table 2;

Table 2


Using the MPN table,Table 3(pg. 19 & 20), calculate the number of coliforms per gram of a sample. Show your calculation clearly and explain your working.(12 marks)

15. (a)Describe the importance of the following :
i. Direct microscopic count; (7 marks)
ii. Standard membrane filter technique.(9 marks)

(b) State four applications of standard membrane filter technique in food industries. (4 marks)

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