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FDSC 442 > 15 - Chemical Preservatives > Flashcards

15 - Chemical Preservatives Flashcards

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1
Q

define a preservative

A

chemicals added to foods to retard the growth of, or kill microorganisms

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2
Q

most preservatives are added at levels that are _____ or _____

A

bacteriostatic; fungistatic

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3
Q

true or false: preservatives can preserve a food indefinitely

A

false

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4
Q

how are preservatives categorized?

A
  • traditional

- naturally occuring

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5
Q

what are the criteria for a preservative to be categorized as traditional?

A
  • used for many years
  • approved for use in many countries
  • are produced by synthetic processes
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6
Q

what are some traditional preservatives that can be found in nature

A
  • acetic acid

- benzoic acid (from cranberries)

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7
Q

define a naturally occuring preservative

A

when a specific food product contains a compound that extends its shelf life

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8
Q

can one chemical be both a naturally occuring and a traditional preservative?

A

yes, depending on how it was produced

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9
Q

list some traidtional antimicrobials

A
  • organic acid & derivatives
  • Dimethyl Bicarbonate (DMDC)
  • Lactoferrin
  • Lysozyme
  • Nitrites
  • para-Hydroxybenzoic Acid Esters
  • Sulfites
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10
Q

(strong/weak) organic acids are the most effective antimicrobials in their undissociated state

A

weak

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11
Q

why are weak organic acids more effective?

A

undissociated acids have no charge and can diffuse through cell membrane. then once inside, they dissociate

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12
Q

how do organic acids kill a microorganism?

A
  • the microorganism will have to spend excessive energy trying to pump out extra H
  • if it doesn’t pump, the extra H will induce structural changes to proteins, enzymes, nucleic acids, and phospholipids
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13
Q

the best acids for preservatives are _____ acids (referring to # of protons)

A

monoprotic

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14
Q

list some monoprotic acids

A

acetic, lactic, propionic, sorbic, and benzoic

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15
Q

list some multiprotic acids

A

citric, malic, tartaric, fumaric

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16
Q

the use of organic acids as preservatives is generally limited to foods with a pH of < ______ since most organic acids have a pKa of _____ to _____

A
  1. 5
  2. 0
  3. 0
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17
Q

how is acetic acid produced?

A

oxygenic fermentation

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18
Q

how is benzoic acid produced?

A

extracted from cranberries, plums, prunes, cinnamon, and cloves

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19
Q

how is lactic acid produced?

A

anoxic fermentation

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20
Q

how is propionic acid produced

A

heterofermentative fermentation

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21
Q

how is sorbic acid produced?

A

mountain ash berries

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22
Q

what kind of microorganism does acetic acid best defend against?

A

bacteria and yeast

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23
Q

where is acetic acid commonly applied?

A
  • scald tank in chicken processing (lowers salmonella)
  • bread dough for moist products (lowers Bacillus subtilis)
  • condiments, gravy, sauces
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24
Q

what kind of microorganism does benzoic acid best defend against?

A

fungi

  • some bacteria can be sensitive
  • some fungi are resistant
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25
where is benzoic acid commonly applied?
- apple cider (reduce E. coli) | - grape juice (reduces mold spoilage)
26
where is lactic acid applied?
- some studies addressed adding lactic acid to meats
27
how else does lactic acid limit microbial growth?
reduces aw
28
what microorganisms does sorbic acid best defend against?
fungi, bacteria, most yeasts; also prevents production of mycotoxins
29
how can sorbic acid be applied to foods?
dipping, spraying, dusting, incorporation into packaging films
30
where is sorbic acid commonly applied?
beverage syrups, cakes, cheese, dried fruits, margarine, pie fillings, salad dressings, wine
31
expand DMDC
dimethyl dicarbonate
32
what is DMDC?
- colorless liquid - slightly soluble with water - reactive with many substances (water, ethyl alcohol, aromatic amines, sulfhydryl groups)
33
what microorganism does DMDC best defend against?
yeasts, but is also bacericidal
34
what's the suggested mode of action for DMDC?
enzyme inactivation
35
where is DMDC commonly applied?
- apple cider - wine (prevents spoilage yeasts)
36
what is lactoferrin?
primary iron-chelating protein in milk and colostrum
37
what does lactoferrin's function?
- prevents infection of mammary glands & intestinal infection in the infant - restricts microbial access to nutrients (make iron unavailable)
38
what is lysozyme?
an enzyme. it's a peptidoglycan hydrolase
39
where can you find lysozyme?
- avian eggs - mammalian milk - tears - other secretion
40
what type of bacteria are lysozymes better at inhibiting?
Gram-positive - L. monocytogenes in meat - C. tyrobutyricum in cheese
41
what are nitrites?
salts containing NO2 - NaNO2 - KNow used in cured meat products
42
what function do nitrites have?
- primarily inhibits C. botulinum spore germination - antimicrobial properties - stabilizes cured meat color - contributes to the taste of cured meats
43
how do nitrites work?
inhibit the ability of bacterial cells to generate ATP
44
what's one drawback to nitrites?
they can form nitrosamines, which are carcinogens formed by the rxn of nitrite with secondary or tertiary amines
45
what's the real name of parabens?
para-hydroxybenzoic acid esters
46
what do parabens do?
- effective against mostly fungi; gram-positive bacteria are also sensitive
47
how do parabens work?
interfere with cytoplasmic membrane; likely interfere with electrochemical gradient
48
applications of parabens?
- beers - non-carbonated soft drinks - fruit based beverages - baked goods - fruit products - preserves - fermented foods - syrups - dressings - wines - pie fillings
49
what are sulfites?
salts containing sulfur dioxide - potassium sulfite - sodium sulfite - potassium metabisulfite - sodium bisulfite - sodium metabisulfite
50
function of sulfites?
- control growth of fermentative fungi AAB, and malolactic bacteria - have antioxidant properties (inhibit browning)
51
where are sulfites applied?
- fruit & veggie products (juices, wines) - fresh shrimp - pickles - sausages
52
what happens to sulfur dioxide when in aqueous solution?
forms sulfurous acid, which works similarly to organic acids
53
name some naturally occurring preservatives from animal and plant sources
``` animal - lactoperoxidase - chitosan plant - spices and essential oils - allicin - hops - isothiocyanates ```
54
limitations of using naturally occurring preservatives?
- not present in very high concentrations naturally - addition of these substances can negatively impact organoleptic qualities - present challenges for commercial production
55
what is lactoperoxidase?
glycoprotein enzyme found in raw milk, colostrum, saliva, other biological secretions
56
how does lactoperoxidase work?
oxidizes thiocyanate in the presence of H2O2, forming hypothiocyanite, which is a highly reactive oxidant good to use in conjunction with H2O2 use
57
what is chitosan?
natural component of fungal cell walls that can be derived from chitin
58
how does chitosan work?
chelates LPS-associated cations
59
what does chitosan inhibit?
growth of foodborne fungi and bacteria
60
where is chitosan applied?
- in combo with organic acids or antimicrobials | - edible films
61
define spices
roots, bark, seeds, buds, leaves, or fruit that are added to foods as flavoring agents
62
what spices have greatest antimicrobial activity?
- cloves - cinnamon - oregano - thyme lesser extent: sage & rosemary
63
what do cinnamon and cloves contain?
- eugenol | - cinnamic aldehyde
64
what do cinnamon and cloves inhibit?
bacteria, fungi, and yeast
65
application of cinnamon?
packaging material
66
list the antimicrobial compounds in: - oregano - thyme - sage - rosemary - basil
oregano: carvacrol thyme: thymol sage: thujone rosemary: bornel, pinene, camphene, camphor basil: linalool, methyl chavicol
67
what is allicin?
organosulfur compound found in onions and garlic
68
what does allicin do?
inhibits growth and toxin production of several microorganisms (including C. botulinum)
69
what do onions uniquely produce?
- catechol
70
how does allicin work?
inhibits disulfide-containing enzymes by oxidizing thiols to disulfides
71
what part of hops has antimicrobial activity?
- resin from hop vine contains bitter acids
72
which bacteria are sensitive to hops?
the LAB that spoil beer
73
what are isothiocyanates?
derived from brassicaceae plants when plant tissue is injured or mechanically disrupted
74
what do isothiocyanates protect against?
fungi, yeast, bacteria
75
what factors associated with the microorganism influence effectiveness of antimicrobials?
- vegetative vs. sporulated cells - interaction w/other microbes - cellular structure - biofilm formation
76
what factors associated with the physicochemistry of the preservative influence the effectiveness of antimicrobials?
- physical barriers (membranes, shells, husks, hides) - pH - buffering capacity - redox potential

FDSC 442 (14 decks)

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