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Food Additives
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“A food additive is a substance or mixture of substances,
other than the basic food stuff, which is present in food
as a result of any aspect of production, processing,
storage or packaging. The term does not include chance
contamination” (WHO, 1965).
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Those food additives which are specifically added to
prevent the deterioration or decomposition of a food
have been referred to as chemical preservatives.
The inhibition of the growth and activity of
microorganisms is one of the main purposes of the use
of chemical preservatives.
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Preservatives may inhibit microorganisms by:
interfering with their their enzyme activity, or
interfering with their their genetic mechanisms
interfering with their cell membranes,
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THE IDEAL ANTIMICROBIAL PRESERVATIVE
1.
A chemical preservative should have a wide range of
antimicrobial activity;
2. Should be non toxic to human beings or animals;
3. Should be economical;
4. Should not have an effect on the flavor, taste, or aroma of the
original food;
5. Should not be inactivated by the food or any substance in the
food;
6. Should not encourage the development of resistant strains; and
7. Should kill rather than inhibit microorganisms.
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ADDED PRESERVATIVES
The Federal Food, Drug, and Cosmetic Act, as
amended by the Food Additives Amendment of 1958,
defines a chemical preservative as
“any chemical which, when added to food, tends to
prevent or retard deterioration thereof; but does not
include common salt, sugars, vinegars, spices, or oils
extracted from spices, or substances added by..
woodsmoke.”
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Antimicrobial preservatives added to foods can be
grouped as follows:
1 Those added preservatives not defined as such by law: natural
organic acids (lactic, malic, citric, etc.) and their salts, vinegars
(acetic is a natural acid), sodium chloride, sugars, spices and their
oils, woodsmoke, carbon dioxide, and nitrogen.
2 Substances generally recognized as safe (GRAS) for addition to
foods: propionic acid and sodium and calcium propionates,
caprylic acid, sorbic acid and potassium, sodium, and calcium
sorbates, benzoic acid and benzoates and derivatives of benzoic
acid such as methylparaben and propylparaben, sodium
diacetate, sulfur dioxide and suffites, potassium and sodium
bisulfite and metabisulfite, and sodium nitrite.
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3 Chemicals considered to be food additives, which would
include all not listed in the first two categories.
They can be used only when proved safe for humans or animals,
and they then fall into group 4.
4 Chemicals proved safe and approved by the Food and Drug
Administration.
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Organic Acids and Their Salts
Lactic, acetic, propionic, and citric acids or their salts
may be added to or developed in foods.
Citric acid is used in sirups, drinks, jams, and jellies as a
substitute for fruit flavors and for preservation.
Lactic and acetic acids are added to brines of various
kinds, green olives, etc.
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Propionates Sodium or calcium propionate is used most
extensively in the prevention of mold growth and rope
development in baked goods and for mold inhibition in
many cheese foods and spreads.
They are effective against molds, with little or no
inhibition of most yeast and bacteria. Their effectiveness
decreases with an increase in pH, with an optimal upper
limit of about pH 5 to 6, depending on the food item.
They appear to be ideal preservatives for bread and
baked goods.
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Propionic acid is a short-chain fatty acid
(CH3CH2COOH) and, like some other fatty acids,
perhaps affects the cell-membrane permeability.
Propionic acid is found naturally in Swiss cheese, as a
developed preservative, at levels up to 1 percent.
Benzoates The sodium salt of benzoic acid has been
used extensively as an antimicrobial agent in foods. It
has been incorporated into jams, jellies, margarine,
carbonated beverages, fruit salads, pickles, relishes,
fruit juices, etc.
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Sorbates Sorbic acid, as the calcium, sodium, or
potassium salt, is used as a direct antimicrobial additive
in foods and as a spray, dip, or coating on packaging
materials. It is widely used in cheeses, cheese products,
baked goods, beverages, situps, fruit juices, jellies, jams,
fruit cocktails, dried fruits, pickles, and margarine.
Sorbic acid and its salts are known to inhibit yeast and
molds but are less a effective against bacteria.
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Dehydroacetic acid has been used to impregnate
wrappers for cheese to inhibit the growth of molds and
as a temporary preservative for squash.
Acetic acid in the form of vinegar is used in
mayonnaise pickles, catsup, pickled sausages, and pigs’
feet. Acetic acid is more effective against yeasts and
bacteria than against molds, and its effectiveness
increases with a decrease in pH, which would favor the
presence of the undissociated acid.
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Nitrites and Nitrates
Combinations of these various salts have been used in
curing solutions and curing mixtures for meats. Nitrites
decompose to nitric acid, which forms nitrosomyoglobin
when it reacts with the heme pigments in meats and
thereby forms a stable red color. Nitrates probably only
act as a reservoir for nitrite, and their use is being
restricted. Nitrites can react with secondary and tertiary
amines to form nitrosamines, which are known to be
carcinogenic.
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Preservative
Benzoic acid
Methylparaben
Propylparaben
Ethylparaben
Sodium nitrate
Sodium nitrite
Sorbates
Acetates (acetic
acid)
Propylene oxide
Ethylene oxide
Sulfites
Natamycin
Concentration allowed
0.1%, covered by good manufacturing
practices (GMPs)
0.1%, covered by GMPs
0.1%, covered by GMPs
Not authorized for use
500 ppm
200ppm
Covered by GMPs
Covered by GMPs with concentrations from
0.25 to 9.0%
300 ppm cocoa, gums, starch, spices,
processed nutmeats (except peanuts)
Residues not to exceed 50 ppm
Covered by GMPs
200 to 300 ppm as a dip, spray, or solution
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Sulfur dioxide and sulfites are used in the wine industry
to sanitize equipment and to reduce the normal flora of
the grape must.
In aqueous solutions, sulfur dioxide and various sulfites,
including sodium sulfite, potassium sulfite, sodium
bisulfite, potassium bisuifite, sodium metabisulfite, and
potassium metabisulfite, form sulfurous acid, the active
antimicrobial compound.
Sulfur dioxide has also been used in sirups and fruit juices
and, of course, wine making. Some countries permit the use
of sulfites on meats and fish.
In addition to the antimicrobial action of sulfites, they are
also used to prevent enzymatic and nonenzymatic changes
or discoloration in some foods.
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Ethylene and Propylene Oxide
Ethylene oxide kills all microorganisms; propylene
oxide, although it kills many microorganisms, is not as
effective.
They are thought to act as strong alkylating agents
attacking labile hydrogens.
The primary uses have been as sterilants for packaging
materials, fumigation of warehouses, and “cold
sterilization” of numerous plastics, chemicals,
pharmaceuticals, syringes, and hospital supplies.
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Sugar and Salt
Theses compounds lower the a and thus have an
adverse effect on microorganisms. Sodium chloride is
used in brines and curing solutions or is applied directly
to the food
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Salt has been reported to have the following effects:
(1) It causes high osmotic pressure and hence plasmolysis of
cells, the percentage of salt necessary to inhibit growth or
harm the cell varying with the microorganism,
(2) it dehydrates foods by drawing out and tying up moisture
as it dehydrates microbial cells,
(3) it ionizes to yield the chlorine ion, which is harmful to
organisms,
(4) it reduces the solubility of oxygen in the moisture,
(5) it sensitizes the cell against carbon dioxide, and
(6) it interferes with the action of proteolytic enzymes.
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Alcohol
Ethanol, a coagulant and denaturize of cell proteins, is
most germicidal in concentrations between 70 and 95
percent.
Flavoring extracts, e.g., vanilla and lemon extracts, are
preserved by their content of alcohol.
The alcoholic content of beer, ale, and unfortified wine is
not great enough to prevent their spoilage by
microorganisms but limits the types able to grow.
Liqueurs and distilled liquors usually contain enough
alcohol to ensure freedom from microbial attack.
Methanol is poisonous and should not be added to foods
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Formaldehyde
The addition of formaldehyde to foods is not permitted,
except as a minor constituent of woodsmoke, but this
compound is effective against molds, bacteria, and
viruses and can be used where its poisonous nature and
irritating properties are not objectionable. Thus it is
useful in the treatment of walls, shelves, successfully in
dried fruits, dried eggs, gelatin, cereals, dried yeast, and
spices.
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Antibiotics
Most of the better-known antibiotics have been tested
on raw foods, chiefly proteinaceous ones like meats, fish,
and poultry, in an endeavor to lengthen the storage
time at chilling temperatures. Aureomycin has been
found superior to other antibiotics tested because of its
broad spectrum of activity.
Terramycin (oxytetracycline) is almost as good for
lengthening the time of preservation of foods.
It has been recommended that antibiotics selected for
use in food preservation be other than those being used
in the treatment of human diseases.
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DEVELOPED PRESERVATIVES
The preservatives produced in foods by microbial action are
for the most part acids (chiefly lactic) and alcohol. The
preservative effect of these substances nearly always is
supplemented by one or more additional preservative
agents, such as low temperature, heat, anaerobic conditions,
sodium chloride, sugar, or added acid.
Developed acidity plays a part in the preservation of
sauerkraut, pickles, green olives, fermented milk, cheese,
and certain sausages and in various fermented foods of
plant origin.
The alcohol content of beer, ale, fermented fruit juices, and
distilled liquors has a preservative effect but was not
produced primarily for that purpose.
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