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FDSC 442 > 15 - Chemical Preservatives > Flashcards

15 - Chemical Preservatives Flashcards

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
Q

where is benzoic acid commonly applied?

A
  • apple cider (reduce E. coli)

- grape juice (reduces mold spoilage)

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26
Q

where is lactic acid applied?

A
  • some studies addressed adding lactic acid to meats
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27
Q

how else does lactic acid limit microbial growth?

A

reduces aw

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28
Q

what microorganisms does sorbic acid best defend against?

A

fungi, bacteria, most yeasts; also prevents production of mycotoxins

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29
Q

how can sorbic acid be applied to foods?

A

dipping, spraying, dusting, incorporation into packaging films

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30
Q

where is sorbic acid commonly applied?

A

beverage syrups, cakes, cheese, dried fruits, margarine, pie fillings, salad dressings, wine

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31
Q

expand DMDC

A

dimethyl dicarbonate

32
Q

what is DMDC?

A
  • colorless liquid
  • slightly soluble with water
  • reactive with many substances (water, ethyl alcohol, aromatic amines, sulfhydryl groups)
33
Q

what microorganism does DMDC best defend against?

A

yeasts, but is also bacericidal

34
Q

what’s the suggested mode of action for DMDC?

A

enzyme inactivation

35
Q

where is DMDC commonly applied?

A
  • apple cider
  • wine
    (prevents spoilage yeasts)
36
Q

what is lactoferrin?

A

primary iron-chelating protein in milk and colostrum

37
Q

what does lactoferrin’s function?

A
  • prevents infection of mammary glands & intestinal infection in the infant
  • restricts microbial access to nutrients (make iron unavailable)
38
Q

what is lysozyme?

A

an enzyme. it’s a peptidoglycan hydrolase

39
Q

where can you find lysozyme?

A
  • avian eggs
  • mammalian milk
  • tears
  • other secretion
40
Q

what type of bacteria are lysozymes better at inhibiting?

A

Gram-positive

  • L. monocytogenes in meat
  • C. tyrobutyricum in cheese
41
Q

what are nitrites?

A

salts containing NO2
- NaNO2
- KNow
used in cured meat products

42
Q

what function do nitrites have?

A
  • primarily inhibits C. botulinum spore germination
  • antimicrobial properties
  • stabilizes cured meat color
  • contributes to the taste of cured meats
43
Q

how do nitrites work?

A

inhibit the ability of bacterial cells to generate ATP

44
Q

what’s one drawback to nitrites?

A

they can form nitrosamines, which are carcinogens formed by the rxn of nitrite with secondary or tertiary amines

45
Q

what’s the real name of parabens?

A

para-hydroxybenzoic acid esters

46
Q

what do parabens do?

A
  • effective against mostly fungi; gram-positive bacteria are also sensitive
47
Q

how do parabens work?

A

interfere with cytoplasmic membrane; likely interfere with electrochemical gradient

48
Q

applications of parabens?

A
  • beers
  • non-carbonated soft drinks
  • fruit based beverages
  • baked goods
  • fruit products
  • preserves
  • fermented foods
  • syrups
  • dressings
  • wines
  • pie fillings
49
Q

what are sulfites?

A

salts containing sulfur dioxide

  • potassium sulfite
  • sodium sulfite
  • potassium metabisulfite
  • sodium bisulfite
  • sodium metabisulfite
50
Q

function of sulfites?

A
  • control growth of fermentative fungi AAB, and malolactic bacteria
  • have antioxidant properties (inhibit browning)
51
Q

where are sulfites applied?

A
  • fruit & veggie products (juices, wines)
  • fresh shrimp
  • pickles
  • sausages
52
Q

what happens to sulfur dioxide when in aqueous solution?

A

forms sulfurous acid, which works similarly to organic acids

53
Q

name some naturally occurring preservatives from animal and plant sources

A 
animal
- lactoperoxidase
- chitosan
plant
- spices and essential oils
- allicin
- hops
- isothiocyanates
54
Q

limitations of using naturally occurring preservatives?

A
  • not present in very high concentrations naturally
  • addition of these substances can negatively impact organoleptic qualities
  • present challenges for commercial production
55
Q

what is lactoperoxidase?

A

glycoprotein enzyme found in raw milk, colostrum, saliva, other biological secretions

56
Q

how does lactoperoxidase work?

A

oxidizes thiocyanate in the presence of H2O2, forming hypothiocyanite, which is a highly reactive oxidant

good to use in conjunction with H2O2 use

57
Q

what is chitosan?

A

natural component of fungal cell walls that can be derived from chitin

58
Q

how does chitosan work?

A

chelates LPS-associated cations

59
Q

what does chitosan inhibit?

A

growth of foodborne fungi and bacteria

60
Q

where is chitosan applied?

A
  • in combo with organic acids or antimicrobials

- edible films

61
Q

define spices

A

roots, bark, seeds, buds, leaves, or fruit that are added to foods as flavoring agents

62
Q

what spices have greatest antimicrobial activity?

A
  • cloves
  • cinnamon
  • oregano
  • thyme
    lesser extent: sage & rosemary
63
Q

what do cinnamon and cloves contain?

A
  • eugenol

- cinnamic aldehyde

64
Q

what do cinnamon and cloves inhibit?

A

bacteria, fungi, and yeast

65
Q

application of cinnamon?

A

packaging material

66
Q

list the antimicrobial compounds in:

  • oregano
  • thyme
  • sage
  • rosemary
  • basil
A

oregano: carvacrol
thyme: thymol
sage: thujone
rosemary: bornel, pinene, camphene, camphor
basil: linalool, methyl chavicol

67
Q

what is allicin?

A

organosulfur compound found in onions and garlic

68
Q

what does allicin do?

A

inhibits growth and toxin production of several microorganisms (including C. botulinum)

69
Q

what do onions uniquely produce?

A
  • catechol
70
Q

how does allicin work?

A

inhibits disulfide-containing enzymes by oxidizing thiols to disulfides

71
Q

what part of hops has antimicrobial activity?

A
  • resin from hop vine contains bitter acids
72
Q

which bacteria are sensitive to hops?

A

the LAB that spoil beer

73
Q

what are isothiocyanates?

A

derived from brassicaceae plants when plant tissue is injured or mechanically disrupted

74
Q

what do isothiocyanates protect against?

A

fungi, yeast, bacteria

75
Q

what factors associated with the microorganism influence effectiveness of antimicrobials?

A
  • vegetative vs. sporulated cells
  • interaction w/other microbes
  • cellular structure
  • biofilm formation
76
Q

what factors associated with the physicochemistry of the preservative influence the effectiveness of antimicrobials?

A
  • physical barriers (membranes, shells, husks, hides)
  • pH
  • buffering capacity
  • redox potential

FDSC 442 (14 decks)

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