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FDSC442 > 16 - biological control of foodborn bacteria > Flashcards

16 - biological control of foodborn bacteria Flashcards

1
Q

What is biopreservation

A

The use of microorganisms, their metabolic products or both to preserve foods (exclude fermentation).

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2
Q

What is controlled aciditication

A

the production of acids by LAB and then these acids are used as a preservative in food.

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3
Q

What is microgard ?

A

it is a small bundle composed of a fermentable carbohydrte and a bacterial culture added to regfrigerated foods to for preservation

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4
Q

What are the benefits of microGARD?

A
  1. protect shelf life
  2. maintain the organileptic qualities of food
  3. meet consumer’s demand for natural products
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5
Q

what will be the factors that influence the effectiveness of microGARD?

A

1-products pH
2- buffering capacity
3- target spoilage microorganisms
4- concentration of fermentable CHO

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6
Q

T or F : the microGARD is effective against clostridium bottulinum

A

true

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7
Q

What is the wisconsin process ?

A

the reducement in nitrites in bacon by adding sucrose and LAB to prevent the growth of clostridium bottulinum

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8
Q

what are bacteriocins?

A

antimicrobial peptides that can be lethal to bacteria.

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9
Q

T or F : bacteriocins are produced virtually by all bacteria

A

true

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10
Q

What are the four classes of bacteriocins?

A

Class I-IV

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11
Q

Nisin and subtilin are found in the class ___ of bacteriocins

A

Class I

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12
Q

Nisin is effective against gram ___

A

positive

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13
Q

What is the class I of bacteriocins?

A

contains unsual amino acids like lanthionine that are produced by modification after the translation.

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14
Q

What are lantibiotics ?

A

bacteriocins that contain lanthionine rings. Lanthionine rings are amino acids that have reacted with cysteine to form thioether lanthionine.

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15
Q

What is the class II of bacteriocins?

A

bacteriocins in this class are small heat stable proteins with a consensus lader sequence

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16
Q

What are the three sub-classes of class II bacteriocins

A

IIa : bacteriocins active against listeria monocytogenes
IIb : require 2 peptides for activity
IIc : require cystein for activity

17
Q

What are the class III bacteriocins

A

really big proteins and heat liable

18
Q

What are classs IV ?

A

proteins with lipid and cho moieties

19
Q

How are bacteriocin discovered?

A

overlap of the colony producing the bacteriocin on a agar inoculated with the colony that the bacteriocin is against

20
Q

How can you be sure the inhibition zone is due to a bacteriocin

A

putting proteolyitic enzyme at the center of the inhibition zone and if there is growth then the colony was producing a bacteriocin

21
Q

Bacteriocin inhibition zone edges are _____

A

sharp

22
Q

Bacteriophage inhibition zone edges are _____

A

clear but there is no colony at the center

23
Q

Inhibition zone produced by organic acids have edges that are _____

A

fuzzy

24
Q

how does the bacteriocin produced by LAB work?

A

they work by disrupting the cytoplasmic membrane

25
Q

T or F : all the bacteriocins produced by LAB have the same mechanism

A

true

26
Q

What are the two proposed model for the perforation by LAB bacteriocins

A

1- pore formation model

2- membrane solubulization model

27
Q

What is the mechanism of action of the LAB’s bacteriocins

A

the will distrupt the integrity of the cytoplasmic membrane

28
Q

what is the mechanism of action of nisin?

A

it will make the spore germinate into the preemergent spore (which is less resistant) and will inhibit the transformation of the preemergent spore into viable cells

29
Q

T or F : nisin will allow spores to germinate and encourage germination

A

true

30
Q

what is the mechnanism of colicin

A

they wil bind to receptor and then enter the cell by the tonB toI system and then have a endonuclease action or impant voltage dependant chanels in the iner membrane

31
Q

What are the target of the endonuclease of the colicin

A
  • protein syntehsis rRNA
  • protein synthesis tRNA
  • peptidoglycan syntehsis block
  • DNA degradation
32
Q

What is nisin usually good against

A

1- anti-listerial

2- anti-clostridium

33
Q

What is nisin combined with to reduce the clostriudum and listeria

A

combined with modified atmosphere

34
Q

T or F : nisin as GRAS in several countries

A

true

35
Q

What are pediocins effective against

A

against L. monocytogenes vegetative cells

36
Q

Why is starter culture with bacteriocins good for fermentation

A

because it can inactivate the sarter culture

37
Q

what is one drawback of the use of bacteriocins

A

some bacteria can be resistant to bacteriocins

38
Q

What are the challenges of using bacteriophages

A

possible resistance

low number of bacteria in food (phage need minimal 10^5 CFU to work)

39
Q

Resistance to bacteriophages is generally created by :

A

changes in the bacteriophage receptor site

FDSC442 (19 decks)

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