Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fpathogens > 4 - Factors that Influence Microbial Growth > Flashcards

4 - Factors that Influence Microbial Growth Flashcards

1
Q

What factors can be used alone or in combination to limit bacterial growth in a product?

A
  • Temperature
  • Redox potential
  • pH
  • Water activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the most important environmental factor affecting growth and survival of microorganisms?

A

Temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Microbial growth is accomplished by ______________

A

enzymatic reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Thermodynamics tells us that, in a certain range - for every ____C rise in temperature ______________ of an enzyme doubles

A

10

catalytic rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe a temperature growth curve:

A

y-axis: growth rate
x-axis: temperature
-minimum: membrane gelling; transport processes so slow that growth cannot occur
-middle: enzymatic reactions occurring at increasingly rapid rates
-optimum temperature: enzymatic reactions occurring at maximal possible rate
-maximum: protein denaturation; collapse of the cytoplasmic membrane; thermal lysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Psychrotrophs are responsible for growth and food spoilage at ___________________, but grow much faster at room temperatures

A

refrigeration temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When foods are exposed to temperatures beyond the max or min temperatures of growth cells _____

A

cells die

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Redox potential – measures the ___________________________________________

A

potential energy difference in a system generated by a coupled reaction in which one substance is oxidized and a second substance is reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The electron donor because it reduces the oxidized substance is called the reducing agent (LEO THE LION GOES GER).

A

reducing agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

_____________ and ___________ of substance are the primary means of generating energy in microbes

A

Oxidation and reduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

If there is free oxygen it acts as a _______________________, which is a high-energy reaction

A

terminal electron acceptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Redox potential in food is influenced by:

A
  • its chemical composition
  • processing treatments
  • storage condition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Fresh food and plants are in a _______ state because of the reducing potential of biomolecules (____________________-), when cellular respiration stops oxygen diffuses in and changes the redox potential

A
  • reduced

- ascorbic acid, sugars, and –SH protein groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Aerobes:

A

need free oxygen O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Anaerobes:

A

can only transfer electrons through fermentation, may die in even small amounts of oxygen (they lack superoxide dismutase necessary to scavenge toxic oxygen free radicals)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Facultative anaerobes:

A

can use free oxygen, bound oxygen (CO2, NO3 or SO4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Microaerophiles:

A

grow better in the presence of less oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The most important anaerobe in food is _______________

A

Clostridium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When oxygen is present, other organisms outcompete ________ or they make organic acids that limit its growth (it can’t grow below pH 4.0)

A

Clostridium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Clostridium ________ can cause meat putrification

A

laramie

21
Q

Clostridium __________ can cause fatal foodborne illness

A

botulinum

22
Q

Most bacteria have a pH range of _____ units

A

2-3

23
Q

T OR F: Only a few bacteria can grow at pH of less than 2 or greater than 10

A

true

24
Q

name the 3 types of bacteria based on their pH range:

A
  • acidophile
  • neutrophile
  • alkaliphile
25
Q

In general _____ and _____ can grow at lower pH than bacteria

A

yests and molds

26
Q

Gram _ bacteria can grow at lower pH than Gram _

A

positive

negative

27
Q

What do we have to look for when choosing an acid to prevent bacterial growth in food?

A

We have to look at what pH the acid gets dissociated (look at its pKa value)

28
Q

Name 5 acids commonly used in foods:

A
  • acetic
  • propionic
  • lactic
  • citric
  • sorbic
29
Q

Acids that have a lower ________ rate (weak acids) are more problematic for bacteria

A

dissociation

30
Q

Undissociated molecules are __________, they enter into the cell and dissociate to generate ___ in the _________
This causes an increase in cellular internal pH which destroys the proton gradient, and thus the ability of the cells to generate energy

A

lipophilic
H+
cytoplasm

31
Q

______ is the solvent of life

A

water

32
Q

Water is required to ________, ________, ___________

A
  • solubilize important molecules
  • carry away waste
  • carry in nutrients
33
Q

Osmosis definition:

A

water moves from an area of high water concentration to an area of low water concentration

34
Q

Cells generally have _______ solutes than the outside environments so water moves into the cells

A

higher

35
Q

Nonhalophile bacteria example:

A

E.coli

36
Q

Halotolerant bacteria example:

A

Staph aureus

37
Q

Halophile bacteria example:

A

vibrio fischeri

38
Q

Extreme halophile:

A

halobacterium salinarum

39
Q

Osmophiles, organisms are able to live in environments which are high in _______

A

sugar

40
Q

Xerophiles, organisms are to live in very ____ environments

A

dry

41
Q

What are the 3 methods for removing water from food:

A

1) Dehydration
2) Crystallization (crystal candies)
3) Adding solutes (salt, sugar, honey, starch) - jellies, honey, salami, jams

42
Q

Applying 2 or more methods of controlling microbial growth at lower levels can reduce growth, prevent growth or kill microorganisms (what is the concept behind this)?

A

the hurdle concept

43
Q

Hurdle technology is more effective when it combines_____________

A

2 stressors that act by different mechanisms

44
Q

Hurdle effects can be ______ or _________

A

additive or synergistic

45
Q

Claims of synergistic effects must be supported by a ___________ analysis, such as the use of an __________

A

quantitative

isobologram

46
Q

Experiments are conducted to determine the _______ of A and B in various _________

A

MIC

concentrations.

47
Q

If the points fall on the line the effects are _________

A

additive

48
Q

If the points fall below the line the effects are __________

A

synergistic

49
Q

If the points fall above the line the effects are _________________

A

antagonistic

Fpathogens (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions