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ThS. Đặng Bùi Khuê


• Selecting a food antimicrobial agent
– antimicrobial spectrum of the compound to be used
– chemical and physical properties of both the
antimicrobial and the food product
– conditions of storage of the product and interactions
– food must be of the highest microbiological quality
initially
– the toxicological safety and regulatory status


• Benzoic Acid and Benzoates
– Benzoic acid is found naturally in apples, cinnamon,
cloves, cranberries, plums, prunes, strawberries, and
other berries


• Benzoic Acid and Benzoates
– stable, odorless, white granular or crystalline powder
that is soluble in water
– Benzoic acid less soluble in water than sodium
benzoate
– Antimycotic agents
– Most yeasts and molds are inhibited by 20–2000µg
benzoic acid per mL at pH 5.0

• Benzoic Acid and Benzoates
– One yeast that it is particularly resistant is
Zygosaccharomyces bailii: up to 0.3% sodium
benzoate (salsa mayonnaise)
– Some bacteria associated with food poisoning are
inhibited by1000–2000µg/mL undissociated acid

Zygosaccharomyces bailii

salsa mayonnaise


• Benzoic Acid and Benzoates
– Benzoates are most effective at pH 2.5–4.0 and
significantly lose effectiveness at pH 4.5
– The undissociated from of benzoic acid (pKa4.19) is
the most effective antimicrobial agent


• Benzoic Acid and Benzoates
– destroyed the proton motive force of the cytoplasmic
membrane by continuous transport of protons into the
cell causing disruption of the transport system


• Benzoic Acid and Benzoates
– inhibit enzymes in bacterial cells such as those
controlling acetic acid metabolism and oxidative
phosphorylation
• α-ketoglutarate and succinate dehydrogenases in

the citric acid cycle
• lipase production by Pseudomonas fluorescens
• trimethylamine-N-oxide reductase activity of
Escherichia coli
Pseudomonas fluorescens


• Benzoic Acid and
Benzoates

Cladosporium herbarum

Pichia membranefaciens

Byssochlamys nivea


• Benzoic Acid and Benzoates
– carbonated and still beverages (0.03–0.05%)
– syrups (0.1%)
– cider (0.05–0.1%)
– margarine (0.1%)
– olives (0.1%)
– Pickles (0.1%)

relishes

– relishes (0.1%)

jams


– soy sauce (0.1%)
– jams (0.1%)
– jellies (0.1%)
– preserves (0.1%)

cider

– pie and pastry fillings (0.1%)
– fruit salads (0.1%), and salad dressings (0.1%)

pie and pastry fillings
jellies


• Glycine
• Hippuric acid
• Glucuronic acid


• Dimethyl dicarbonate
– colorless liquid
– slightly soluble in water
– primary target microorganisms: Saccharomyces,
Zygosaccharomyces, Rhodotorula, Candida, Pichia,
Torulopsis, Torula, Endomyces, Kloeckera, and
Hansenula

(CH3–O–O–C–O–C–O–O–CH3)
Torulopsis



• Dimethyl dicarbonate
– more effective than sorbate/benzoate in controlling
aerobic plate counts
– bactericidal at 30–400µg/mL: Acetobacter
pasteurianus, E. coli, Pseudomonas aeruginosa,
Staphylococcus aureus, several Lactobacillus species,
and Pediococcus cerevisiae

Acetobacter pasteurianus Pseudomonas aeruginosa

E. coli

Staphylococcus aureus


• Dimethyl dicarbonate
– Molds are generally more resistant to DMDC than yeasts or
bacteria
– 21 CFR 172.133
• wine, dealcoholized wine, and low alcohol wine that has less than
500 yeast CFU/mL at ≤ 200 ppm
• ready-to-drink teas (<500 yeast CFU/mL) at ≤ 250 ppm
• carbonated or noncarbonated, nonjuice-containing (≤ 1%),
flavored or unflavored beverages containing added electrolytes at
≤ 250 ppm
• carbonated, dilute beverages containing juice, fruit flavor, or both,
with juice content ≤ 50% at ≤ 250 ppm



• Propionic Acid and Propionates
– Swiss cheese: Propioni-bacterium freudenreichii ssp.
shermanii.
– primarily against molds
– Some yeasts and bacteria, particularly gram negative
strains
– depends upon the pH
– bread dough that causes rope formation, Bacillus
subtilis (mesentericus), was inhibited at 0.19% at pH
Bacillus subtilis
Propioni-bacterium
5.8


• Propionic Acid and Propionates
– retard the growth of S. aureus, Sarcina lutea, Proteus
vulgaris, Lactobacillus plantarum, Torula (Candida),
and Saccharomyces cerevisiae var.ellipsoideus for up
to 5 days

Sarcina lutea

Proteus vulgaris

Lactobacillus plantarum

Torula



• Propionic Acid and Propionates
– The minimum inhibitory concentration of
undissociated propionic acid against three Bacilluss
pecies, E. coli, and Staphylococcus aureus ranged from
0.13% to 0.52%
– the yeast Candida albicans, 0.29%

Candida albicans


• Propionic Acid and Propionates
– the most effective inhibitor of Salmonella serotypes
Anatum, Senftenberg, and Tennessee among acetic,
adipic, citric, lactic, propionic, and tartaric acids
– The activity of propionic acid against Aspergillus and
Fusarium was enhanced by the presence of EDTA

Salmonella

Aspergillus

Fusarium


• Propionic Acid and Propionates
– sodium propionate inhibition of E. coli was overcome
by the addition of β-alanine
– Penicillium may grow in nutrient media containing
over 5% propionic acid
– mechanism of inhibition: acidification of the cytoplasm

and inhibition of an unspecified function
Penicillium
β-alanine


• Propionic Acid and Propionates
– flour in white bread and rolls: 0.32%
– whole wheat products: 0.38%
– cheese products: 0.3%


• Phosphates
– sodium acid pyrophosphate
(SAPP)
– tetrasodium pyrophosphate
(TSPP)
– sodium tripolyphosphate
(STPP)
– sodium tetrapolyphosphate
– sodium hexameta phosphate
(SHMP)
– trisodium phosphate (TSP)


• Roles of Phosphates
– Buffering
– Acidification
– Alkalization
– Sequestration
– formation of complexes

with organic
polyelectrolytes (e.g.,
proteins, pectin, and
starch)

• Roles of Phosphates
– Deflocculation
– Dispersion
– Peptization
– Emulsification
– nutrient supplementation
– Anticaking
– antimicrobial
preservation
– leavening


• Phosphates
– Gram positive bacteria appear to be generally more
susceptible to phosphates than gram negative bacteria
– SAPP, SHMP, or polyphosphates increase the
effectiveness of the curing system (nitrite–pH–salt)
against Clostridium botulinum

Gram positive bacteria
Clostridium botulinum

Gram negative bacteria



• Phosphates
– The presence of magnesium has been shown to reverse
inhibition of gram positive bacteria by antimicrobial
phosphates
– chelating ability of polyphosphates was responsible for
growth inhibition of Bacillus cereus, Listeria
monocytogenes, Staphylococcus aureus, Lactobacillus
and Aspergillus flavus

Listeria monocytogenes

Bacillus cereus

Aspergillus flavus

Lactobacillus


• Phosphates
– Orthophosphates had no inhibitory activity against any
of the microorganisms and have no chelating ability
– inhibition was reduced at lower pH due to protonation
of the chelating sites on the polyphosphates

Orthophosphates

chelating ability