Guest Lecture Nisin

Question 1

what are the important aspect for food antimicrobials

Answer 1

antimicrobial activity should be selective, neg effect on sensory properties, safe for human consumption

Question 2

what are the limitations in using nicin? (6)

Answer 2

1. lack of stability at neutral pH (highly soluble and stable at pH 2-3)
2. potential for nisin to partition to fat because its hydrophobic, so no longer available against bacteria
3. cationic nisin binding to anionic proteins
4. presence of divalent cations in the foods, these cations can interact with phospholipids of the cell and inhibit nisin insertion.
5. degradation of nisin by food components-ingredients (sodium metabisulfite, titanium dioxide and proteolytic enzymes)
6. potential of nisin resistance

Question 3

what are the strategies to improve nisin efficiency (6)

Answer 3

1. combination of non thermal techniques
2. encapsulation
3. active antimicrobial packaging
4. combination with antimicrobials
5. bioengineering
6. nanotechnology

Question 4

what is the encapsulation of nisin + advantages

Answer 4

incorporation of nisin in a polymeric shell. it compensate for solubility issues at neutral pH

Question 5

what are the benefits of incorporating nisin in packaging (2)

Answer 5

1. better stability and release of the antimicrobial

2. reduce interaction of nisin with food

Question 6

give 2 examples of packaging materials used with nisin

Answer 6

chitosan and liposome

Question 7

name a food that nisin can be used with in active antimicrobial packaging

Answer 7

cheese

Question 8

what does bioengineering on nisin focus on + provide an example

Answer 8

modifying the structure of nisin to enhance efficacity against pathogens and microorganisms. Modified nisin combined with carvacrol were effective to reduce Ecoli 0.157:H7

Question 9

combination of nisin with other antimicrobial has 3 advantages, name them

Answer 9

1. low cost
2. minimal sensory effect
3. maintain desire level of safety of the product

Question 10

example of combination of nisin with other antimicrobials

Answer 10

combination of nisin with p anisaldehyde showed synergistic effect against S aureus.

Question 11

what is endolysin - how is it used with nisin?

Answer 11

it is an enzyme capable of degrading the bacterial cell wall (peptidoglycan). Bacteriophages use endolysins to kill the host. Modified nisin and endolysin completely eliminated Listeria Monocytogenes in cheese.