Foods deteriorate in quality due to a wide range of reactions including some that are  physical, some that are chemical, some enzymatic and some microbiological. The various  forms of spoilage and food poisoning caused by microorganisms are preventable to a large  degree by a number of preservation techniques, most of which act by preventing or slowing  microbial growth. These include freezing, chilling, drying, curing, conserving, vacuum  packing, modified atmosphere packing, acidifying, fermenting, and adding chemical  preservatives. This is section 13, Chemical food protection.  We’ll look at the other food  preservation mechanisms in future modules. 1 From the moment a food source is harvested in begins to deteriorate.  It is estimated that  25% of the worlds food is lost to microbial decay annually.  This equals more than a billion  dollars per year. 2 Salting as a means of preserving foods predates written history. The Mesopotamians were known 3000 B.C.E. generally used salt to preserve meat and fish. Early Roman writers such  as Cato (234‐149 B.C.E.) clearly explained the need to salt perishable meats and vegetables  to preserve them.  We have already seen in past chapters that salt binds water reducing  water activity and also is toxic to enzymatic and DNA processes in cells. 3 Today, nearly all manufactured foods have different chemical preservatives because it  makes financial sense. Food additives maintain or improve freshness, safety, nutritional  value, taste, texture, or appearance. Consumers demand and enjoy a food supply that is  flavorful, nutritious, safe, convenient, colorful and affordable.  4 No audio. 5 No audio. 6 In the United States, neither the Food and Drug Administration (FDA) nor the U.S.  Department of Agriculture (USDA) has labeling claim rules for “natural." The FDA explicitly  discourages the food industry from using the term. The Food, Drug, and Cosmetic Act  prohibits labeling that is false or misleading, but does not give any specifics. The USDA's  Agricultural Marketing Service has a standard for organic food, but there is no legal  definition for natural foods.  Despite no legal U.S. definition for natural foods, there are  numerous unofficial or informal definitions, none of which are applied uniformly to foods  labeled "natural". 7 So, are food chemical additives safe? 8 In 1958, the US created food additive legislation stating that the FDA must approve all food  additives and ingredients that are not generally recognized as safe.  The GRAS list contains  food additives that have been used historically and have shown no hazards during that  time.  Easily recognized examples are sodium chloride, sucrose and acetic acid.  Less easily  recognized are many of the common food preservatives such as sodium benzoate,  potassium sorbate, and calcium propionate. 9 The U.S. FDA maintains a list of over 3000 approved, generally recognized as safe, food  ingredients including food.

1. Foods deteriorate in quality due to a wide range of reactions inc
luding some that are
physical, some that are chemical, some enzymatic and some mic
robiological. The various
forms of spoilage and food poisoning caused by microorganisms
are preventable to a large
degree by a number of preservation techniques, most of which a
ct by preventing or slowing
microbial growth. These include freezing, chilling, drying, curin
g, conserving, vacuum
packing, modified atmosphere packing, acidifying, fermenting,
and adding chemical
preservatives.
This is section 13, Chemical food protection. We’ll look at the
other food
preservation mechanisms in future modules.
1
From the moment a food source is harvested in begins to deterio
rate. It is estimated that
25% of the worlds food is lost to microbial decay
annually. This equals more than a billion
dollars per year.
2
Salting as a means of preserving foods predates written history.

2. The Mesopotamians were
known 3000 B.C.E.
generally used salt to preserve meat and fish. Early Roman writ
ers such
as Cato (234‐149 B.C.E.) clearly explained the need to salt peris
hable meats and vegetables
to preserve them. We have already seen in past chapters that sal
t binds water reducing
water activity and also is toxic to enzymatic and DNA processes
in cells.
3
Today,
nearly all manufactured foods have different chemical preservat
ives because it
makes financial sense. Food additives maintain or improve fresh
ness, safety, nutritional
value, taste, texture, or appearance. Consumers demand and enj
oy a food supply that is
flavorful, nutritious, safe, convenient, colorful and affordable.
4
No audio.
5
No audio.

3. 6
In the United States, neither the Food and Drug Administration
(FDA) nor the U.S.
Department of Agriculture (USDA) has labeling claim rules for
“natural." The FDA explicitly
discourages the food industry from using the term.
The Food, Drug, and Cosmetic Act
prohibits labeling that is false or misleading, but does not give a
ny specifics. The USDA's
Agricultural Marketing Service has a standard for organic food,
but there is no legal
definition for natural foods. Despite no legal U.S. definition fo
r natural foods, there are
numerous unofficial or informal definitions, none of which are a
pplied uniformly to foods
labeled "natural".
7
So, are food chemical additives safe?
8
In 1958, the US created food additive legislation stating that the
FDA must approve all food
additives and ingredients that are not generally recognized as
safe. The GRAS list contains
food additives that have been used historically and have shown
no hazards during that

4. time. Easily recognized examples are sodium chloride, sucrose
and acetic acid. Less easily
recognized are many of the common food preservatives such as
sodium benzoate,
potassium sorbate, and calcium propionate.
9
The U.S. FDA maintains a list of over 3000 approved,
generally recognized as safe, food
ingredients including food additives. The European Union
uses a more international code
called “E” numbers. E‐numbers are the code numbers that are u
sed to identify food
additives that have been shown to be safe, and which have been
authorized for use in the
EU. The E numbers 200
through 299 refer to those additives that are antimicrobial
preservatives. Many countries that operate under the internatio
nal standard called CODEX
also use E numbers.
10
Before we get started, let’s look a moment at the antimicrobial e
ffects of chemicals. First
there can be no effect at all. Growth
of microorganisms proceeds normally. Second, a
chemical may slow growth some. Third, a chemical may stop gr
owth. In this case it is
called bacteriostatic or fungistatic
for bacteria and fungi respectively. Chemicals that are

5. sporistatic
prevent spores from germinating. The forth level is death. It is
referred to as
microbiocidal, bactericidal, fungicidal, or sporicidal.
11
It is important to note that individual
antimicrobial chemicals or other factors can make
growth difficult for a microbe. In this case it is termed a hurdle
. Basically, their growth or
progress is slowed. If a hurdle is large enough, growth cannot o
ccur and this is termed a
barrier. Sometimes multiple hurdles can be created that prevent
growth and then are
considered a barrier.
12
Let’s first look at the antifungal chemicals benzoate, sorbate, pr
opionate, and parabens.
They are primarily used in foods to prevent spoilage from yeast
and molds. Their use
generally
increases quality (no spoilage) and shelf life. It is interesting to
note that all of
these chemicals are naturally produced in foods and are easily b
roken down in human
metabolism. All are on the US FDA GRAS list, yet the “all nat
ural – no preservative” folks
ascribe many ailments to these compounds. However, if yeast w
ere allowed to spoil a food

6. they have the ability to produce some harsh chemicals naturally
including: propanol,
isopropanol, butanol, and amyl alcohol.
13
The weak acid antimicrobial theory is
based on the weak acid (benzoate, sorbate or
propionate) in its undissociated or acid form is lipophilic and ca
n easily pass through the
cells membrane. Once inside it can disassociate back into an an
ion and a proton
hydronium ion. Disassociated acids and excess protons accumu
late inside the cell reducing
intracellular pH.
As the intracellular pH lowers, cell metabolism slows and then s
tops. Since
only undissociated acids pass through the lipid membrane, the p
H of the food will
determine the effect. The white box is a chart of the percent un
dissociated acid of
benzoate at different pH levels. Resistance to weak organic aci
ds is based on either an
increase in cytoplasmic buffering or the cells ability to shed exc
ess protons.
14
Sodium benzoate was first preservative
allowed by the FDA under GRAS. It
inhibits yeasts and molds at usage level
~0.1%. It is most effective against yeast,

7. less so for mold. It has little affect on
bacteria. The antimicrobial activity of
benzoates are related to its undissociated
form. It is most undissociated at very low pH.
It is 60% active at pH 4, but only 1.5% active
pH 6. Therefore its highest usage is in acid
15
foods. Its main antimicrobial effect is believed
to be disrupting lipids in cell membranes. It is
used at 0.1% and levels above that may result
in a peppery flavor.
15
Sorbate also works best undissociated
and will disrupt cell membranes.
However, its pKa is higher than
benzoate. It will be effective below pH
6. Sorbate is most effective against
molds and is permitted to 0.2%.
Therefore it is common to combine
both sorbate and benzoate in many
acid foods. Sorbate has some
incidental antibacterial effects,
although these are minor. Sorbate
16

8. may be used as a second hurdle to
enhance other antimicrobials such as
nitrite for Clostridia.
16
Propionate, like sorbate is most
effective against molds. Its activity is
less against yeasts and there is little
activity against bacteria. Propionates
has the higher pKa than sorbate and is
effective at pH levels below 6. It is
most often used in breads, cakes, and
cookies.
17
Parabens are related to the benzoates.
Like benzoates, they are believed to
disrupt lipids and cell membranes.
They have the highest pKa and will
work at some of the highest pH levels
in foods. However, they also have an
off‐flavor making their use minimal.
18
Let’s take a look at the antimicrobial
fumigants sulfur, ethylene oxide and propylene oxide.

9. 19
Fumes from burning sulfur have been used since the ancient
Egyptian and Roman times to
sanitize fruits. Its been in continued use for more than 2000 ye
ars. When the SO2 gas
combines with water it forms sulfurous acid (H2SO3) as the anti
microbial. When dry forms
of sulfur are used, such as sulfite or bisulfite, they end up formi
ng the same sulfurous acid.
Sulfurous acid acts at the cell membrane and interacts with prot
ein enzymes causing
inactivation. Bacteria are most susceptible, while some yeasts a
nd molds are slightly
resistant. This fact explains its use in winemaking. Sulfur wou
ld more selectively kill off
bacteria and leave the natural yeast to perform the wine ferment
ation. Sulfur works best
applied on acid foods and therefore, it most often still applied t
o fruits. In the USA sulfur is
not used as much anymore due to better general sanitation and t
he fact that sulfur
residues can cause chemical sensitivity reactions in approximate
ly 10% of humans.
20
Ethylene
and propylene oxides are very effective fumigant antimicrobials
. They are
microbiocidal, sporocidal, and fungicidal. The fungi are killed i
n one or more hours of

10. contact time, while it takes longer to kill bacteria and spores. E
thylene oxide is commonly
used in many foods and non‐food sterilizations for items that ca
nnot withstand the heat of
autoclaving.
The U.S. spice industry uses Ethylene oxide
to eliminate pathogenic microbial
contaminants such as Salmonella and E.coli
in spices. When applied in a validated process,
Ethylene oxide
can be extremely effective in eliminating Salmonella and E. coli
as well as
reducing overall bacterial load, yeast and mold, coliforms, and
other pathogens. Although
exact numbers are difficult to determine, ASTA estimates that b
etween 40% and 85% of
spices in the U.S. are treated with Ethylene oxide each year. Th
e main advantage of
Ethylene oxide
is that its use on spice generally has no significant impact on th
e
appearance or flavor of the spice. The main concern over Ethyl
ene oxide use is the
production of ethylene glycol residues. Ethylene glycol is quite
toxic. Due to that fact,
propylene oxide has gained usage as an alternative. It is permitt
ed for fruits, nuts, spices,
and grains.
21
22

11. Several hundred years ago it was discovered that sea salt would
provide a pleasing red
color to smoked and dried meats. Because of the color reaction
it became more common
to use. Later it was realized that meats smoked and dried using
sea salt did not result in
“sausage poisoning”. Eventually scientists figured out that saus
age poisoning was caused
by Clostridium botulinum and that the active chemical in sea sal
t was nitrate. Nitrate was
microbially broken down into nitrite. Nitrite inhibits important
iron containing enzymes in
the Clostridia group that prevents cell germination from a spore.
When nitrite is
transformed into nitric oxide it than affects meat color. The ma
ximum usage levels in
meats are 500 ppm for nitrate and 200 ppm for nitrite.
23
In the 1970’s it was discovered that nitrosamine compounds ma
y lead to cancer. Scientists
quickly looked at many
foods for their presence. Bacon was determined to result in
nitrosamines when cooked on high heat. In response the amount
of nitrite in bacon was
dropped to a maximum of 120 ppm. Some companies lower that
further by using iron‐
binding or chelating compounds such as sodium ascorbate, EDT
A, or polyphosphate to
enhance the anti‐Clostridial activity of nitrite.

12. 24
The effects of organic acids on microbial growth inhibition have
been discussed. Two
specific organic acids have effective antimicrobial abilities agai
nst Listeria. These are
lactates and diacetates. The primary mode of action is that they
are transported into the
cell where they interfere with the acid/pH
stasis of the cell. First the cell must expend
energy to try and remove them and second the accumulation beg
ins to affect metabolism.
At lower concentrations these organic acids are listeriostatic. A
s the concentration inside
the cell rises they become listeriacidal. Lactates and diacetates
are usually used in tandem
in cured ready to eat meat products such as hot dogs. The usage
levels are usually
between zero and three percent for lactate and zero and 0.25 per
cent for diacetate.
25
Naturally occurring substances such as salt, rosemary extract, s
ugar, vinegar, alcohol, hops,
and diatomaceous earth are also used as traditional preservative
s.
26

13. As discussed previously many intrinsic factors can affect growt
h. These include pH, water
activity, nutrient
content. Sugar, salt, and other humectants can reduce the water
activity
inhibiting growth. Acids can reduce the pH reducing growth. A
lcohol is another compound
that inhibits bacteria and some yeasts. With all of the concerns
over the health status of
antimicrobial usage, manipulation of common food ingredients
would definitely be an all
“natural” means of preservation.
27
Here are some of the more novel antimicrobials that are claimed
as “natural”. These
include eugenols
a class of plant oils from clove, cinnamon, nutmeg, basil and ba
y leaf.
Allicins
are organic sulfur compounds that are antimicrobial in garlic. N
atamycin is an
antifungal agent produced during fermentation by Streptomyces
natalensis. Bacteriocins
are mostly small proteins produced by bacteria that inhibit other
bacteria. Nisin is a 34
amino acid long protein produced by Lactococcus
lactis. It has an unusual broad spectrum
of activity. Nisin
has been approved for use in some foods. The trick to get aroun
d this
restriction is to use natural fermentates. These are glucose or d
airy grown cultures of L.

14. lactis spray dried. Fermentates
are considered “fermented glucose” or “fermented milk”
and not a preservative. Bacteriophage use as antimicrobials is a
relative new approach.
Nearly all species have specific bacteriophage that infect and ki
ll them. This provides a safe
and targeted approach to microbial control.
28