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AntiMicrobial Agents Keep these questions in mind

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Major usage In salad dressings, fruit juices, cottage cheese. ... Major uses In beverages, juices, non-standard 'Jellies'. margarine. ... – PowerPoint PPT presentation

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Title: AntiMicrobial Agents Keep these questions in mind


1
Anti-Microbial Agents Keep these questions in
mind
  • Why and when do we need them?
  • What limits their use?
  • What are the principles governing their usage?
  • What choices do we have? what types of food have
    antimicrobial agents in them?
  • What foods are inappropriate for using
    antimicrobial agents? what other additives can be
    used to preserve foods and avoid the
    "preservatives", label?
  • Why do preservatives work some times and fail at
    other times ?
  • Why are processing changes important to the
    effectiveness of antimicrobial agents ?

2
Anti-Microbial Agents(Code of Federal Regulation
sections)
  • CFR Sections
  • 170
  • 172
  • 182
  • 184
  • Standards of Identity
  • 101.22 Labeling

3
Anti-Microbial Agents (AMA)
  • Generally Bacteriostatic rather the bacteriocidal
  • Consist of both acid the non-acid types
  • Acidic AMAs most common

4
FACTORS AFFECTING THE SELECTION OF ACIDIC
ANTIMICROBIAL AGENTS
  • Antimicrobial activity against different
    organisms
  • Microbial load in product
  • pKa of the AMA
  • pH of the food product
  • Food composition
  • Processing, and storage conditions
  • Solubility
  • Flavor
  • Cost
  • Marketing impact

5
Principles for Using AMAs
  • Most agents are weak acids.
  • Most work when in the un-ionized form.
  • Most are not effective above their pKa's.
  • Most affect flavor.
  • Most are affected by processing, order of
    addition distribution between oil and aqueous
    phase

6
Modified Henderson-Hasselbach
  • pH pKa log ( ineffective form / effective
    form )
  • pH pKa log ( ionized form / unionized form
    )
  • pH - pKa log ( ineffective form / effective
    form )
  • pH - pKa log ( ionized form / unionized form
    )
  • If pH is greater (Higher) than pKa, more of the
    acid is going to be in the ineffective form.
    NOTE this is a log relationship so a little
    change can mean a lot.

7
How much is effective?
  • When pH pKa then pH - pKa 0.
  • The log of 1 0, thus ineffective
    form/effective form 1
  • This means that 50 is in the effective form
    (when the pH pKa).
  • When pH - pKa 1 then U/A10 or 9.09 is
    effective.
  • When pH - pKa 2 then U/A100 or 0.99 is
    effective.

8
pH vs Effectiveness
  • pH -pKa log U/E Ineffective/Effective
    Effective
  • 2.00 2.00 100 0.99
  • 1.88 1.88 75 1.32
  • 1.70 1.70 50 1.96
  • 1.40 1.40 25 3.85
  • 1.00 1.00 10 9.09
  • 0.70 0.70 5 16.67
  • 0.40  0.40 2.5 28.57
  • 0.00 0.00 1 50.00
  • -0.30 -0.30 0.5 66.67
  • -0.40 -0.40 0.4 71.43
  • -1.00 -1.00 0.1 90.91
  • -1.40 -1.40 0.04 96.15
  • -1.70 -1.70 0.02 98.04
  • -1.88 -1.88 0.01 98.68

9
Quiz
  • If I have an antimicrobial agent with a pKa of 4
    and add this to a food having a pH of 4, how much
    do I need to add to achieve an effective
    concentration of 0.1?

10
Answer
  • 1 - What percent of the AMA is effective?
  • pHpKa so ? percent is effective
  • 50
  • If we need 0.1 then we need 2X that much
  • 0.2 X 50 effective 0.1
  • Know of any potential problems?

11
Gradys Nickel Rules
  • 1. AMA are only used at or below pH's to their
    pKa's.
  • 2. At pH pKa, only 50 of the AMA will be
    effective.
  • 3. When the pH is one unit less than the pKa,
    then about 90 is in the effective form.
  • 4. When the pH is 1 unit greater than the pKa,
    only about 10 is in the effective form. Forget
    about it!

12
Distribution Coefficient
  • Distribution coefficient
  • Organic phase / Aqueous phase
  • concentration of the component in the organic
    phase divided by the concentration in the aqueous
    phase
  • How does this impact antimicrobial agents?

13
Distribution Coefficients
  • Compound Distribution Coefficient
  • Propionic acid 0.17
  • Sorbic acid 3.0
  • Benzoic acid 6.1
  • p-hydroxybenzoic acid methyl ester 5.8
  • p-hydroxybenzoic acid ethyl ester 26
  • p-hydroxybenzoic acid propyl ester 87.5
  • Which is most water soluble? Most fat soluble?

14
Distribution Coefficient
  • Does it matter? Why?
  • Where do the bugs grow?
  • What is the effect of process?
  • What is the effect of order of addition?
  • What is the effect on kill?
  • What is the effect on order of use?

15
Most Common AMAs
  • Agent pH Range
  • Benzoic acid 2.5-4.0
  • Sorbic acid 3.0-6.5
  • Propionic acid 2.5-5.0
  • Acetic acid 3.0-5.0
  • Parabens 3.0-9.0
  • Sulfites 2.5-5.0
  • Nitrites 4.0-5.5

16
Sorbic Acid, Sorbate, Potassium Sorbate
  • pKa 4.8
  • Usage level limited to 0.1.
  •  
  • Broad spectrum against yeast and molds. Lactic
    acid bacteria at low pH.
  • Major usage In salad dressings, fruit juices,
    cottage cheese.
  • Potassium salt Is the most widely used form.
  • 182.3640 Potassium sorbate.
  • 182.3795 Sodium sorbate.
  • 182.3089 Sorbic acid.

17
Benzoic Acid, Benzoate, Sodium Benzoate
  • pKa 4.2
  • Usage level limited to less than 0.1 by
    regulation.
  • Most active against yeast and molds.
  • Major uses In beverages, juices, non-standard
    "Jellies". margarine.
  • Acid form relatively Insoluble and not used much.
  • 184.1021 Benzoic acid
  • 184.1733 Sodium benzoate

18
Acetic Acid
  • pKa 4.76
  • Usage level limited by taste.
  • More effective against yeast and bacteria.
  • Major usage In "Pickled" foods. Also In "natural"
    breads.
  • Sodium diacetate used In some breads.
  • 184.1754 Sodium diacetate.
  • Preservative labeling may not be required

19
Propionic acid, Propionate, Calcium Propionate
  • pKa 4.87
  • Usage limited to 0.1.
  • Effective against molds, but no effect on yeast.
  • Major usage In bread and baked goods.
  • Why?
  • Calcium salt most used form.
  • 184.1081 Propionic acid.
  • 184.1221 Calcium propionate.
  • 184.1784 Sodium propionate

20
Sulfite, Sulfur Dioxide, Metabisulfite
  • pKa 1.89, 7.0
  • Effective against molds, yeast, bacteria.
  • Yeast are more resistant than lactics.
  • Major usage In wines.
  • Used often for Its antibrowning and color
    stabilization characteristics. Most common use -
    remember to think about water
  • Flavor problems, hypersensitivity.
  • 182.3739 Sodium bisulfite.
  • 182.3766 Sodium metabisulfite.
  • 182.3798 Sodium sulfite.
  • 182.3862 Sulfur dioxide
  • 182.3616 Potassium bisulfite.
  • 182.3637 Potassium metabisulfite.

21
Nitrite
  • Effective against C. botulinum.
  • Used In cured meat products.
  • Reacts with myoglobin to give cured meat color
  • Nitrate is not an anti-microbial agent unless it
    is converted to nitrite
  • 172.177 Sodium nitrite used in processing smoked
    chub.
  • 172.175 Sodium nitrite.
  • 172.170 Sodium nitrate.
  • 172.160 Potassium nitrate

22
Parabens, Methyl, Propyl, Heptyl
  • pKa 8.47
  • Usage level limited to 0.1.
  • Effective against yeast and molds, gram
    bacteria.
  • Longer chain esters are more effective. Heptyl gt
    Propyl gt Ethyl gt Methyl.
  • Usage In U.S. Is not great as demonstrated by
    food labels. Found In artificial sweeteners,
    baked goods, a few salad dressings, beer?.
  • 172.145 Heptylparaben.
  • 184.1490 Methylparaben.
  • 184.1670 Propylparaben.

23
Other AMAs
  • 172.165 Quaternary ammonium chloride combination.
  • 172.130 Dehydroacetic acid.
  • 184.1061 Lactic acid.
  • 172.133 Dimethyl dicarbonate.
  • 184.1538 Nisin preparation. 172.155 Natamycin
    (pimaricin).
  • 172.155 Natamycin (pimaricin).
  • 184.1563 Ozone.
  • 173.300 Chlorine dioxide.
  • Lactoferrin application to meat carcasses SA
    GRAS 2002
  • Lysozyme GRAS
  • Lactoperoxidase - GRAS

24
Gradys AMA Nickel Rules
  • First, measure the pH
  • Remember AMAs are only hurdles
  • No amount of AMA can defeat bad sanitation
  • You may be able to use fermented products that,
    through no fault of their own, happen to contain
    antimicrobial agents

25
Anti-Microbial Agents
  • Why and when do we need them?
  • What limits their use?
  • What are the principles governing their usage?
  • What choices do we have? what types of food have
    antimicrobial agents in them?
  • What foods are inappropriate for using
    antimicrobial agents? what other additives can be
    used to preserve foods and avoid the
    "preservatives", label?
  • Why do preservatives work some times and fail at
    other times ?
  • Why are processing changes important to the
    effectiveness of antimicrobial agents ?
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