Lecture 1

Question 1

What is a food ecosystem?

Answer 1

Food is an ecosystem composed of the environment and the microorganisms living in it.

Question 2

What are intrinsic factors?

Answer 2

Characteristics inherent to the food itself

Question 3

What are examples of intrinsic factors

Answer 3

Water activity, pH and nutrients

Question 4

What are extrinsic factors?

Answer 4

Environmental factors that affect food.

Question 5

What are examples of extrinsic factors?

Answer 5

Time, temp, microorganisms, packaging, gases

Question 6

True or False. Intrinsic factors and extrinsic factors can be manipulated to preserve food.

Answer 6

True

Question 7

True or False. Food may contain multiple microenvironments.

Answer 7

True

Question 8

What can affect gene expression of cells?

Answer 8

Acidity

Question 9

The _______ the pH, higher energy is required by the cell to maintain cell intracellular pH neutrality and less energy is left for growth.

Answer 9

lower

Question 10

Acidic food requires _______

Answer 10

milder

Question 11

What is preshock?

Answer 11

The exposure to mild acid.

Question 12

What type of pH intrinsic factor involves shifting cells directly from alkaline conditions to acidic?

Answer 12

Acid shock

Question 13

What is free water?

Answer 13

Water that is available for microbial growth and chemical reactions.

Question 14

What is bound water?

Answer 14

Water that is not available for microbial growth or chemical reactions

Question 15

What is the measure of available water or energy of water in food?

Answer 15

Water activity

Question 16

What foods are susceptible to bacteria?

Answer 16

Foods with high protein and water activity

Question 17

How do cells protect themselves from osmotic stress?

Answer 17

Compatible solutes intracellularly

Question 18

what not only controls growth rate but also regulates bacterial gene expression?

Answer 18

Temperature

Question 19

What is multiple hurdle technology?

Answer 19

The use of two or more intervention measures to ensure a reduction of potential bacterial growth

Question 20

What are the benefits of multiple hurdle technology?

Answer 20

Higher efficacy
Better taste
Save energy
Allows use of milder treatments

Question 21

Why use enrichment?

Answer 21

Bacteria may be present in a low amount, some pathogens have very low infective doses.

Question 22

What cell type is this: cells exposed to sub-lethal conditions, lose the ability to grow on selective media but can grow on non-selective media.

Answer 22

Injured Cells

Question 23

Can injured cells recover and cause an outbreak?

Answer 23

Yes

Question 24

What cannot be cultured on any culture media?

Answer 24

VBNC

Question 25

What are 3 ways we can detect VBNC?

Answer 25

Cytological methods, viability staining, reverse transcription RT-PCR

Question 26

What is biofilm?

Answer 26

Aggregation of bacteria or groups of bacteria living together on a solid surface

Question 27

What are the steps in biofilm formation?

Answer 27

1. Solid surface conditioning
2. Adsorption of bacterial cells on a surface by biopolymer formation
3. Microcolony formation: adsorbed cells multiply and form microcolonies

Question 28

What are cells that can detach and move on to form biofilm at different locations?

Answer 28

Planktonic Film