Factors influencing the growth of microorganism in food

Question 1

Food spoilage organisms cause by

Answer 1

bacteria, yeasts, & molds

Question 2

Food spoilage organisms are

Answer 2

often smelled, seen, or tasted

Question 2

food spoilage organisms do not

Answer 2

cause life-threatening infection

Question 3

Foodborne pathogens do not

Answer 3

affect the taste, smell, or appearance of food.

Question 3

Foodborne pathogens caused by

Answer 3

bacteria, viruses, parasites

Question 3

Intrinsic factors

Answer 3

*Nutrient
*pH (Acidity / alkalinity)
*Water activity / moisture content
*Antimicrobial chemical
*Oxidation-reduction potential
*Biological barriers (e.g. shells)

Question 3

Extrinsic factors

Answer 3

*Temperature / Time
*Relative humidity
*Presence and concentration of gases
*Presence and activities of
other microorganism

Question 4

example Nutrients: as the sources of energy for microbes

Answer 4

(carbohydrate, protein, lipid)

Question 5

what is Bacterial Metabolism

Answer 5

The series of biochemical reactions by which the cells breaks down various biomolecules such as nutrients (carbohydrates,
fat, protein) for energy generation and the use of energy to synthesize cell material (lipids, polysaccharides, proteins) from small
molecules

Question 6

Many microorganisms are inhibited by acid conditions except

Answer 6

lactic acid bacteria

Question 7

(LAB) used in

Answer 7

fermentation process of food production

Question 8

LAB also cause spoilage of

Answer 8

unpasteurized milk and other foods

Question 9

 pH can determine

Answer 9

bacteria’s ability to produce toxin

Question 10

Pathogens do not grow,
or grow very slowly, at
pH below 4.6, except

Answer 10

• Clostridium botulinum
• Salmonella spp.

Question 11

Water activity is defined as t

Answer 11

the ratio of the vapor pressure
of water in a material (p) to the vapor pressure of pure
water (po) at the same temperature

Question 12

Modified the aw for food preservation

Answer 12

• Physical removal of water (drying, baking)
• Adding solutes (salt, sugar)

Question 13

Biological barriers in plant and animal derived food (raw) help

Answer 13

to prevent the entry and growth of
microorganism

Question 14

Some foods contain natural antimicrobial
chemicals / chemical preservative & additive that

Answer 14

inhibit microbial growth

Question 15

ANTIMICROBIAL CHEMICALS in Plant-based food:

Answer 15

Essential oils, tannin, glycosides,
resins

Question 16

ANTIMICROBIAL CHEMICALS in animal-based food:

Answer 16

 Lactoferrin, conglutinin and the lactoperoxidase system (lactoperoxidase, thiocyanate, and hydrogen peroxide) in milk - innate immunity, killing bacteria in milk
 Lysozyme in eggs and milk (enzyme that can hydrolyze the cell wall of bacteria)
 Bacteriocin (from LAB), antibiotics (from mold) –inactivate other microorganism

Question 17

Redox potential (Eh) is a

Answer 17

a measurement of the ease
for a substance to gain or loses electrons

Question 18

The redox potential of food is closely linked to

Answer 18

availability of oxygen and influences the types of microorganisms that can grow and thrive in that environment.

Question 19

Major group of microorganism based on their relationship to redox potential:

Answer 19

 Aerobes +500 to +300 mV
 Anaerobes +100 to < -250mV
 Facultative anerobes +300mV to -100mV

Question 20

Bacterial proliferation can be controlled by

Answer 20

both heat and cold temperature

Question 21

Bacteria generally do not grow at freezer temperatures but they can survive

Answer 21

 Below freezing water availability is significantly decreased
 At low temperature (above freezing) enzymatic action is very slow
or non-existent

Question 22

LOW Temperature

Answer 22

*Reaction rate for enzyme become slower
*Reduce fluidity of the cytoplasmic membrane – interfere with transport
mechanism

Question 23

HIGH TEMPERATURE

Answer 23

*Cell component denatured
*Heat-sensitive enzymes are inactivated or denatured

Question 24

The use of heat

Answer 24

Pasteurization: Sterilization:

Question 25

Pasteurization: the cooking / heat treatment of food

Answer 25

where only a certain number of bacteria are
killed (pathogens

Question 26

Sterilization: total destruction of

Answer 26

all living organisms an is only found in canned shelf stable items

Question 27

RELATIVE HUMIDITY

Answer 27

as moisture from air
can increase surface and subsurface aw of the food where
microbial growth can occur

Question 28

 Packaging - to

Answer 28

protect food from humidity and maintain its aw

Question 29

The bacterial metabolites inhibit the growth of other microbes

Answer 29

 Antibiotics
 Bacteriocins
 Hydrogen peroxide
 Organic acids

Question 30

Psychrotrophs

Answer 30

Grow well at 7ºC and have optimum growth
of 20ºC to 30ºC

Question 31

Mesophiles

Answer 31

Grow well between 20ºC and 45ºC with
optima between 30ºC and 40ºC

Question 32

Thermophiles

Answer 32

Grow well at and above 45C with optima
between 55ºC and 65ºC