Food microbiology

Question 1

Food spoilage microorganisms from soil

Answer 1

spore forming species of pathogens:
clostridium
bacillus

Question 2

Shellfish bacteria

Answer 2

bacterial toxins from photosynthetic cyanobacteria

Question 3

Enteric bacteria

Answer 3

e.g e coli
- farm and town sewage
- Detection of E-coli in sea/river water is indicator of sewage contamination
-Lobster, shellfish/ muscle from costal waters pose some risk of food safety

Question 4

Campylobacter sp

Answer 4

campylobacteriosis
bloody diarrhoea

Question 5

Salmonella sp

Answer 5

Salmonellosis
bloody diarrhoea

Question 6

E. coli O157:H7

Answer 6

Haemolytic Uremic Syndrome
diarrhoea, kidney failure, death

Question 7

Y.entericolitica

Answer 7

Yersiniosis
diarrhoea

Question 8

L. monocytogenes

Answer 8

Listeriosis
meningitis, blood infections

Question 9

Mycobacterium tuberculosis

Answer 9

tuberculosis
pneumonia

Question 10

brucella sp

Answer 10

brucellosis
blood infections, heart infections

Question 11

cryptosporidium parvum

Answer 11

cryptosporidiosis
diarrhoea

Question 12

s. aureus

Answer 12

staphylococcal enterotoxin poisoning
vomiting

Question 13

coxiella burnetti

Answer 13

Q Fever
high fever, headache, muscle aches, can infect liver and/or heart

Question 14

What temperature do mesophiles operate at

Answer 14

15-40 degrees

Question 15

what temp do thermophiles act at

Answer 15

45-80
extreme thermophiles - <122°C (Topt = 80°C)

Question 16

In what condition do halotolerance at at

Answer 16

high salt

Question 17

at what temp do psychrophiles act at

Answer 17

PSYCHROPHILES 0-15°C (Topt = 5°C)
Cold-tolerant – can be found in refrigerators

Question 18

in what conditions are acidophilics found

Answer 18

high acidity

Question 19

Bacterial growth is monitored by:

Answer 19

1. Turbidity
2. Plate Count
3. Newer tech, e.g ATP-bioluminescence

Question 20

5 phases of bacterial growth

Answer 20

-Lag phase
-Acceleration phases
-Exponential growth phase – maximum rate of cell -division coincides
-Deceleration
-Stationary phases

Question 21

Intrinsic factors affecting bacterial growth

Answer 21

pH
Water availability
Redox potential
Physical properties
Antimicrobial substances

Question 22

Extrinsic factors causing bacterial growth

Answer 22

Temperature
Relative humidity (RH)
Water activity (Aw)
Atmosphere (gas)

Question 23

Hurdle Concept of preservation

Answer 23

… or hurdle technology (Leistner, 2000)
Rationale: every food product has factors that (in some way-intrinsic/extrinsic) oppose MO growth
Underpinned by homeostasis – the ability of MO’s to adapt to stresses for survival
‘hurdles’ are directly linked to factors affecting microbial growth