USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-1
CHAPTER 10. EXAMINATION OF HEAT PROCESSED, HERMETICALLY SEALED
(CANNED) MEAT AND POULTRY PRODUCTS
George W. Krumm, Charles P. Lattuada,
Ralph W. Johnston, James G. Eye, and John Green
10.1 Introduction
Thermally processed meat and poultry products in hermetically
sealed containers include both shelf stable products as well as
those that must be kept refrigerated (i.e. perishable product).
There are a wide variety of packages designed to totally exclude
air. These include traditional rigid containers, such as metal
cans and glass jars; semi-rigid containers such as plastic cans,
bowls and trays; and flexible containers such as retortable
pouches and bags. The microbiological examination of these food
products requires knowledge and a thorough understanding of food
microbiology, food science, and packaging technology and
engineering. Many books and scientific articles are available on
the processing and the laboratory testing of these products.
Individuals who perform these analyses should be familiar with the
current procedures and methods. Some of these references are
listed in section 10.6.
10.2 Important Terms and Concepts
a.
Shelf Stability (commercial sterility):
The term "shelf stability" traditionally has been used
by the Agency and is synonymous with the terms
"commercial sterility" or commercially sterile". Shelf
stability is defined in CFR title 9, part 318, Subpart
G, 318.300 (u) of the Food Safety and Inspection Service
(meat and poultry) USDA regulations. Shelf stability
(commercial sterility) means "the condition achieved by
application of heat, sufficient, alone or in combination
with other ingredients and/or treatments, to render the
product free of microorganisms capable of growing in the
product at non-refrigerated conditions (over 50°F, 10°C)
at which the product is intended to be held during
distribution and storage". Such a product may contain
viable thermophilic spores, but no mesophilic spores or
vegetative cells. These products usually are stable for
years unless stored at temperatures of 115-130°F (46-
55°C) which may allow swelling or flat sour spoilage to
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occur because of germination and growth of the
thermophilic spores. Many low acid canned meat/poultry
products contain low numbers of thermophilic spores.
For this reason, samples of canned foods are not
routinely incubated at 55°C because the results usually
will be confusing and provide no sound information.
Canned food lots that are to be held in hot vending
machines or are destined for tropical countries are
exceptions to this rule.
b.
Hermetically Sealed Container:
A container that is totally sealed to prevent the entry
or escape of air and therefore secure the product
against the entry of microorganisms.
c.
Adventitious contamination:
Adventitious contamination may be defined as the
accidental addition of environmental microorganisms to
the contents of a container during analysis. This can
occur if the microbiologist has not sterilized the
puncture site on the container surface or the opening
device adequately, or is careless in manipulating
equipment or cultures. Strict attention to proper
procedures is required to avoid this type of
contamination.
d.
Cured Meat/Poultry Products:
Many canned meat/poultry products contain curing salts
such as mixtures of sodium chloride and sodium nitrite.
When included in a canned meat/poultry product
formulation, sodium chloride and sodium nitrite inhibit
the outgrowth of bacterial spores, particularly
clostridial spores. Lowering the pH and increasing the
sodium chloride concentration enhance the inhibitory
action of sodium nitrite. Thus, most canned, cured
meat/poultry products are minimally heat processed and
are rendered shelf stable by the interrelationship of
heat, pH, sodium chloride, sodium nitrite and a low
level of indigenous spores. Spoilage in canned cured
meat/poultry products attributed to underprocessing is
rare. When it occurs, it is usually the result of
improper curing rather than inadequate heating. The
heat processes used for canned, cured, shelf stable
meat/poultry products are unique in that they usually
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are not designed to destroy mesophilic bacterial spores
but merely to inhibit their outgrowth.
e.
Uncured Meat/Poultry Products:
Canned uncured meat/poultry products are given a much
more severe heat treatment than canned cured products.
The treatment given to canned uncured meat/poultry
products is commonly referred to as a "full retort
cook".
10.21 Classification of Containers
a.
Metal and plastic cans with metal double sealed end(s):

Cans must be at room temperature for classification.
Cans are classified as NORMAL if both ends are flat or
slightly concave; FLIPPER when one end of a normal-
appearing can is struck sharply on a flat surface, the
opposite end "flips out" (bulges) but returns to its
original appearance with mild thumb pressure; SPRINGER
if one end is slightly convex and when pressed in will
cause the opposite end to become slightly convex; SOFT
SWELL if both ends are slightly convex but can be
pressed inward with moderate thumb pressure only to
return to the convex state when thumb pressure is
released; HARD SWELL if both ends are convex, rigid and
do not respond to medium hard thumb pressure. A can with
a hard swell will usually "buckle" before it bursts.
Hard swollen cans must be handled carefully because they
can explode. They should be chilled before opening
except when aerobic thermophiles are suspected. Never
flame a can with a hard swell, use only chemical
sanitization.
b.
Glass jars:
Classify glass jars by the condition of the lid
(closure) only. Do not strike a glass jar against a
surface as you would a can. Instead shake the jar
abruptly to cause the contents to exert force against
the lid; doing so occasionally reveals a flipper.
Scrutinize the contents through the glass prior to
opening.

Compare
the
contents
of
the
abnormal/questionable jar with the contents of a normal
jar (e.g., color, turbidity, and presence of gas
bubbles), and record observations.
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c.
Flexible containers (pouches):
Pouches usually are fabricated from laminates consisting
of two or more layers (plies) of material. Retortable
pouches are the most common type of flexible container
used for canned, shelf-stable products. Most pouches
are 3-ply: an outer ply of polyester film, a middle ply
of aluminum foil, and an inner ply of polypropylene.
The polyester functions as the heat resistant, tough
protective layer; the aluminum foil as a moisture, gas
and light barrier; and the polypropylene functions as
the food contact surface and the film for heat sealing.
The polypropylene also provides added strength, and
protects the aluminum film against corrosion by the food
product. Not all retortable pouches contain an aluminum
foil ply. Pouches and paperboard containers used for
non-retorted, shelf stable products (e.g. pH-controlled
and hot-filled product) or aseptically filled containers
may be quite different from retortable pouches in
construction. Pouches and other flexible containers are
either factory-formed and supplied ready for filling, or
are formed by the processor from roll stock.
10.22 Container Abnormalities
To determine the cause of product abnormalities, both normal and
abnormal containers from the same production lot should be
examined. All observed microbiological results should be
correlated with any existing product abnormalities (Section 10.46
a) such as atypical pH, odor, color, gross appearance, direct
microscopic examination, etc. as well as the container evaluation
findings (Section 10.46, b,c). Non-microbial swells (such as
hydrogen swells) are usually diagnosed by considering all product
attributes because culture results are negative or insignificant.
a.
Metal cans, plastic containers and glass jars:
Conditions such as "swells" are defined in Section 10.21
(a). The defects and abnormalities associated with
these containers have been extensively detailed by
others. Rather than include extensive descriptions for
each of them in this section, the analyst is referred to
several excellent references presented in Section 10.6.
These references provide detailed information on the
numerous defects and abnormalities that can occur with
these containers. The analyst should be familiar with
these conditions before beginning any analysis of a
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defective or abnormal container. The effect of
processing failures, such as overfilling, closure at low
temperature or high altitude; container damage; and
storage temperature changes, must be taken into
consideration as the analyst evaluates possible causes
for the defect or abnormality. For quick reference, a
Glossary of Terms is provided in Appendices I and II.
b.
Pouches:
A Glossary of Terms for these containers can be found in
Appendix III. It is imperative to follow uniform
procedures (Section 10.46,c) when examining defective or
abnormal pouches. The APHA, 1966 reference (Section
10.6) provides detailed information on the analysis of
pouch defects.
10.3 Analysis of Containers
The number of containers available for analysis will vary.
However, it is important that the number be large enough to
provide valid results. Unless the cause of spoilage is clear cut,
at least 12 containers should be examined. With a clear cut
cause, one half this number may be adequate. If abnormal
containers have been reported, but are not available for analysis,
incubation of like-coded containers may reproduce the abnormality.
The "normal" cans should be incubated at 35°C for 10 days prior to
examination. Incubation temperatures in excess of 35°C should not
be used unless thermophilic spoilage is suspected. This
incubation may reproduce the abnormality, and thereby document
progressive microbiological changes in the product. Examine the
incubated cans daily. Remove any swells from the incubator as
they develop and culture them along with a normal control. After
the 10 day incubation period, cool the cans to room temperature
and reclassify. Swollen, buckled and blown containers should NOT
be incubated but analyzed immediately along with a normal control.
All steps in the analysis should be conducted in sequence
according to protocol.
10.31 Physical Examination of Metal and Plastic Containers
a.
Before opening, visually examine the double end seam(s)
and side seam (if present) for structural defects, flaws
and physical damage; record pertinent observations.
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10-6
b.
Run thumb and forefinger around the inside and outside
of the double seams for evidence of roughness,
unevenness, or sharpness.
c.
Using a felt marker, make three slash marks at irregular
intervals across the label and the code-end seam.
Remove the label and copy any label code-numbers to the
side of the container along with a mark indicating the
code end of the can. Correlate any stains on the label
with suspicious areas on the side panel (can body) by
returning the label to its exact position relative to
the slash marks.
d.
Examine all non-seam areas of the can and ends for any
evidence of physical damage. If the code is embossed,
carefully examine it for any evidence of puncturing.
Circle any suspect and/or defective areas with an
indelible pen and record this information on the work
sheet. For an illustration of these defects see the
APHA, 1966 reference (Section 10.6).
10.32 Physical Examination of Glass Jars
a.
Before opening, remove the label and, using a good light
source such as a microscope light, examine the container
for apparent or suspected defects. Microorganisms may
enter jars through small cracks in the glass. Make note
of any residue observed on the outer surface and the
location.
b.
Test the closure gently to determine its tightness.
After sampling has been completed, examine the lid
(closure) and the glass rim (sealing surface) of the
jar. Look for flaws in the sealing ring or compound
inside the closure; for food particles lodged between
the glass and the lid; and for chips or uneven areas in
the glass rim.
10.33 Physical Examination of Pouches
a.
Pouches should be examined using an illuminated 5X
magnifier.
b.
Hold the pouch in one hand, examine it for
abnormalities, such as swelling, leakage, overfilling,
and defects such as delamination and severe distortion.
Record any pertinent observations.
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c.
Hold the pouch at both ends and examine both sides for
noticeable cuts, cracks, scratches, food residues,
punctures, missing labels, foreign materials or other
abnormalities.
d.
Carefully examine all seal areas for incomplete fusion.
Pay attention to such defects as entrapped product,
wrinkles, moisture and foreign material in the seal.
Particular attention should be given to the final or
closing seal.
e.
All actual and suspected defects should be circled with
an indelible marking pen for more detailed examination
after all sampling is complete.
10.4 Analysis of the Contents
Processing errors occur infrequently with canned products, but may
result in the improper processing of large quantities of product.
Swollen cans, for instance, may signal a microbial spoilage
problem. Each abnormality in a "canned" product must be
investigated thoroughly and correctly. The following procedures
should be followed carefully.
10.41 Equipment and Material
a.
Incubators 20°, 35° & 55 ± 1°C
b.
Vertical laminar flow hood
c.
Microscope, microscope slides & cover slips
d.
pH meter equipped with a flat electrode
e.
Felt-tip indelible marker
f.
Illuminated 5X magnifier
g.
Sterile Bacti-disc cutter or other suitable opening
device
h.
Large, sterile plastic or metal funnel
i.
Large autoclavable holding pans
j.
Sterile towels
k.
Clean laboratory coat and hair covering(s)
l.
Sterile wide bore pipettes or 8 mm glass tubing with
cotton plugs
m.
Sterile serological pipettes with cotton plugs
n.
Safety aspiration device for pipetting (e.g. pro-
pipette)
o.
Sterile petri dishes, beakers, and large test tubes
p.
Sterile triers, cork borers, scissors, knives and 8"
forceps. Triers can be made from the tail piece of
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chrome finish sink drain pipe, 1 1/2" in diameter,
flanged on one end and sharpened on the other end.
q.
Sterile cotton swabs with wooden handles in glass test
tubes, one per tube, or commercially sterilized swabs in
paper sleeves
r.
Sterile gloves
s.
Small wire basket to hold pouches in an upright position
t.
Seam analysis tools (micrometer, calipers, saw,
countersink meter, metal plate scissors, nippers).
u.
Vacuum gauge
v.
Light source such as a microscope light
w.
Sonic cleaning apparatus
x.
Transparent acrylic plate with a hole and tubing to a
vacuum source
y.
Bituminous compound in strips (tar type strips usually
available in hardware stores) stored in the 35°C
incubator
z.
Seamtest Type U (Concentrate), Winston Products Co., Inc
Box 3332, Charlotte, N.C., Dilute 1:300 with distilled
water for use.
aa. Wooden dowels, 1/2" diameter
bb. Gas cylinder clamp
cc. Abrasive chlorinated cleaner or a scouring pad
10.42 Media and Reagents
a.
Modified Cooked Meat Medium (MCMM) STEAM JUST BEFORE USE
b.
Brom Cresol Purple Broth (BCPB) or Dextrose Tryptone
Broth
c.
Plate Count Agar
d.
APT Agar
e.
KF Broth
f.
Strong's Sporulation Medium
g.
Gram stain reagents
h.
Spore stain
i.
Dishwashing detergent
j.
Chlorine solution, (Commercial Bleach with approximately
5% available chlorine diluted 1:100 with 0.5 M phosphate
buffer, pH 6.2)
10.43 Preparation
a.
The Analyst
i.
The analyst must wear a clean full length
laboratory coat.
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ii. Hair must be completely covered with a clean,
disposable operating room type hair cover. A
surgical face mask should be worn; if the analyst
has facial hair such as beards and sideburns, the
mask must completely cover it.
iii. Hands, forearms and face should be washed with
germicidal soap and water.
iv. The analyst should wear safety glasses or goggles,
preferably in combination with some type of face
shield when opening swollen cans or cans suspected
of being contaminated with Clostridium spp.
b.
Preparing the Environment
i.
If possible, the analysis should be done in a
vertical laminar flow hood. If a hood is not
available, the area used must be clean and
draft-free.
ii. Flat cans should be opened in the laminar flow
hood.
iii. Swells may explode or spew, therefore they should
be opened outside the hood and the container
transferred to the hood only after it is opened and
all gas released.
iv. Disinfect the work surface before beginning any
work.
c.
Preparing Metal Cans Prior to Opening
i.
Scrub the non-coded end of the metal can with
abrasive cleaner or a scouring pad. This removes
bacteria-laden oil and protein residues. Rinse
well with tap water. Cans with an "easy open" end
usually are coded on the bottom. Record the code
exactly and prepare the code end as described
above.
ii. Sanitize the cleaned end with chlorine solution
(Section 10.42 j) either by placing clean tissues
over the end and saturating it with chlorine
solution or by immersing the end in a shallow pan
containing the solution. Allow a 15-minute contact
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10-10
time; wipe dry with sterile towels or tissue. (An
alternative sanitization procedure which can be
used on Normal-appearing cans ONLY is to heat the
entire can surface using a laboratory burner or a
propane torch until the metal becomes slightly
discolored from the heat.) Proceed as outlined in
Section 10.44.
d.
Preparing Jars Prior to Opening
i.
Scrub the surface of the jar closure with abrasive
cleaner or scouring pads. Rinse well with tap
water.
ii. Sanitize the jar closure with chlorine (Section
10.42 j) either by placing clean tissues over the
closure and saturating it with chlorine solution or
immersing the closure in a shallow pan containing
the solution. Allow a 15-minute contact time; wipe
dry with sterile towels or tissue.
e.
Preparing Plastic Containers Prior to Opening
i.
Scrub the bottom surface of the container with
abrasive cleaner or scouring pads. Rinse well with
tap water.
ii. Sanitize the bottom with chlorine solution (Section
10.42 j) by placing clean tissues over the bottom
and saturating it with chlorine or immersing the
bottom of the container in a shallow pan containing
the solution. Allow a 15-minute contact time; then
wipe dry with sterile towels or tissue.
f.
Preparing Normal and Abnormal-Appearing Flexible
Retortable Pouches Prior to Opening
i.
Clean the outside of the pouch with a sanitizer and
rinse well.
ii. Sanitize the entire pouch in a suitably sized pan
with chlorine solution (Section 10.42 j). Allow a
15-minute contact time; then wipe dry with sterile
towels or tissue.
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g.
Preparing Swollen Cans Prior to Opening
i.
Scrub the non-coded end of the chilled metal can
with an abrasive cleaner or a scouring pad. This
removes bacteria-laden oil and protein residues.
Rinse well with tap water.
ii. Sanitize the cleaned end with chlorine solution
(Section 10.42 j) either by placing clean tissues
over the end and saturating it with chlorine
solution or immersing the end in a shallow pan
containing the solution. Allow a 15-minute contact
time; then wipe dry with sterile towels or tissue.
h.
Opening Devices
i.
The preferred type of opening device is the
adjustable Bacti-disc cutter (available from the
Wilkens-Anderson Company, 4525 W. Division Street,
Chicago, IL.; a similar device is available from
the American National Can Co., 1301 Dugdale Rd.,
Waukegan, IL. Order Number WT2437). The opener
should be pre-sterilized or heated in a flame to
redness. If this type of device is not available,
individually packaged and heat sterilized regular,
all metal, kitchen-type can openers may be used.
The advantage of the Bacti-disc type opener is that
it causes no damage to the double seam (simplifying
later examination) and the size of the opening can
be adjusted.
ii. Sometimes a large can (e.g. a #10 size can) may be
difficult to open. The analyst could be exposed to
pathogens or their toxins if the can is not
properly secured. The container can be held
tightly with a gas cylinder clamp secured in an
inverted position in a shallow metal drawer or tray
lined with a large disposable poly bag or an
autoclavable tray to contain any overflow. Place
the #10 container against the clamp and secure the
strap. Rotate the can and continue cutting until
the opening is completed. The metal tray and liner
may be removed for cleaning and the clamp is
autoclavable.
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10.44 Sampling
a.
Normal-Appearing Metal Cans and Jars with Metal Closures
i.
Prepare the area and can or jar closure as
described in section 10.43.
ii. Shake the container to distribute the contents.
iii. Use a sterilized opening device to cut the desired
size entry hole. Transfer samples immediately to
the selected media with a sterile pipette or swab
and proceed as outlined in Section 10.45.
iv. Aseptically transfer a representative amount of the
product to a sterile test tube or other sterile
container as a working reserve. Use a pipet or
sterile spoon to accomplish this.
v.
Caution: The contents from overfilled cans may
flow out of the hole onto the surrounding lid
surface at the time of opening. This material can
then drain back into the can when the opening
device is removed. Should this occur, terminate
the analysis.
b.
Normal and Abnormal-Appearing Plastic Containers
i.
Immediately after removing the container from the
chlorine solution and wiping the excess liquid, use
a very hot, sterilized opening device to cut the
desired size entry hole. Transfer samples
immediately to the selected media with a sterile
pipette or swab and proceed as outlined in Section
10.45.
ii. Aseptically transfer a representative amount of the
product to a sterile test tube or other sterile
container as a working reserve. Use a pipet or
sterile spoon to accomplish this.
c.
Normal and Abnormal Appearing Flexible Retortable
Pouches
i.
Place the disinfected pouch upright in a sterile
beaker and cut a two inch strip about one quarter
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10-13
of an inch under the seam edge using a sterile
scissors. If possible, use a pipette to remove
some of the pouch contents, otherwise use a swab.
Transfer the samples immediately to the selected
media with a sterile pipet or swab, proceed as in
section 10.45.
ii. Aseptically transfer a representative amount of the
product to a sterile test tube or other sterile
container as a working reserve. Fold the edge of
the opened pouch over against itself several times
and secure with tape until the microbiological
analysis is complete.
d.
Swollen Cans
i.
Cans displaying a hard swell should be chilled
before opening. Most foods spoiled by Bacillus
stearothermophilus will not produce gas (flat sour
spoilage). However, if nitrate or nitrite is
present in the meat/poultry product, gas may be
produced by this microorganism. Cold usually will
kill B. stearothermophilus resulting in no growth
in Bromcresol Purple Broth. If possible, save one
or two cans and store without refrigeration.
ii. NEVER FLAME A SWOLLEN CONTAINER - IT MAY BURST.
Place the container to be opened in a large,
shallow, autoclavable pan. The side seam, if
present, should be facing away from the analyst. A
container with a hard swell may forcefully spray
out some its contents, posing a possible hazard to
the analyst if the contents are toxic. Therefore,
these cans should be considered a biohazard and
precautions must be taken to protect the analyst.
Protective gloves should be worn and the lab coat
should be tucked inside the cuffs of the gloves or
at least secured around the wrist. Some type of
facial shield is also recommended.
iii. Place the sanitized container into a biohazard bag
and cover with a sterile towel or invert a sterile
funnel with a cotton filter in the stem over the
can. Place the point of the sterile opening device
in the middle of the container closure. Make a
small hole in the center of the sterilized
end/closure. Try to maintain pressure over the
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10-14
hole. Release the instrument slowly to allow gas
to escape into the towel or funnel.
iv. After the gas pressure has been released, enlarge
the opening to the desired size to permit sampling
and aseptically remove some of the container
contents. Sample as outlined in (a) above.
10.45 Culturing
a.
Inoculation of Culture Media
i.
The sampling and transfer processes must be
conducted aseptically; care must be taken to
prevent
contamination
during
the
various
manipulations.
ii. Transfer the sample at once to the selected media,
inoculating each tube at the bottom. Whenever
possible, use a pipet and pro-pipette to remove 1-2
ml of product for inoculating each tube of medium.
When the nature of the meat/poultry product makes
it impossible to use a pipet, use a sampling swab
(holding it by the very end of the shaft) to
transfer 1-2 g of the product to each tube. This
is accomplished by plunging the swab into the
product, then inserting the swab as far as possible
into the appropriate tube of medium and breaking
off the portion of the shaft that was handled. Use
one swab for each tube of medium. When inoculating
MCMM, force the broken swab to the bottom of the
tube by using the tip of another sterile swab.
iii. For each sample, inoculate 2 tubes of MCMM which
were steamed (or boiled) for 10 minutes and cooled
just before use and 2 tubes of Bromcresol Purple
Broth. If a tube of KF medium is inoculated at the
same time, the presence of enterococci can be
determined rapidly.
iv. As a process control, place uninoculated swabs into
each of two tubes of MCMM and BCP and one swab into
KF broth (if used). Additionally, label two
uninoculated tubes of each medium to serve as
controls. If multiple samples are cultured at the
same time, only one set of control tubes are needed
for each medium and each temperature.
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v.
After all tubes have been inoculated with a sample,
aseptically transfer approximately 30 ml or a 30 g
portion of the container contents to a sterile
tube, Whirl-Pak® or jar for retention as a working
reserve sample. Appropriately label the container
and store it in a refrigerator at approximately
4°C.
vi. Finally, transfer a portion of the container
contents to a sterile Petri plate, clean jar or
beaker for pH, microscopic, organoleptic and other
relevant analyses (10.46).
vii. Cover the hole made in the container with several
layers of sterile aluminum foil, secure the foil
with tape and then store the container in a
refrigerator at approximately 4°C. This serves as
the primary reserve. Re-enter it only as a last
resort. If the sample is a regulatory sample,
chain of custody records must be maintained on it.
b.
Incubation of Culture Media
i.
Incubate one tube each of MCMM and BCP at 35°C and
one tube each at 55°C. If used, incubate the tube
of KF medium at 35°C. For the MCMM and BCP
controls, incubate one tube at 35° and one at 55°C.
ii. Observe all tubes at 24 and 48 h. Tubes incubated
at 35°C that show no growth should be incubated for
5 days before discarding. Tubes incubated at 55°C
should be incubated for 3 days before discarding.
Subculture any questionable tubes, especially if
the
product
under
examination
contributes
turbidity.
c.
Identification of Organisms
i.
Use conventional bacteriological procedures to
characterize the type(s) of microbial flora found
in the contents of the container.
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10-16
ii. Use descriptive terms such as: mixed culture or
pure culture, anaerobic or aerobic growth, spore
former
or
non-sporeformer,
mesophile
or
thermophile, cocci or rods.
iii. Cultures should be examined using a Gram stain.
Gram stains should be done only on 18-24 h
cultures. Record the morphological types observed
and their Gram reaction. If the container contents
are examined microscopically using a methylene blue
stain, record those observations as well. If
endospores are present, the spore stain can be used
for better definition of spore type and placement.
iv. Record all biochemical test results in addition to
any characteristic growth patterns on differential
and/or selective media.
v.
MCMM tubes showing a bright yellow color with
visible gas bubbles, and containing gram positive
or gram variable rods should be suspected of
containing gas-forming anaerobes. If Clostridium
botulinum is suspected, sub-cultures should be made
and incubated for 4-5 days. The original tube
should be reincubated to check for spores. After 4
- 5 days incubation, test the cultures for toxin by
the mouse bioassay (see Chapter 14).
10.46 Supportive Determinations
a.
Examination of Container Contents
i.
Determine the pH of the sample (10.45, a, vii)
using a flat electrode. Disinfect the electrode
after taking this measurement.
ii. If applicable, determine the water activity of the
sample (Section 2.4).
iii. Examine the sample microscopically by making a
simple methylene blue or crystal violet stain. A
Gram stain is of no value since the age of the
cells is not known and Gram-stain reactions may not
be dependable in the case of old cells. Prepare a
spore stain if the contents of a swollen container
show signs of digestion and few bacterial cells.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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iv. Note abnormalities observed in the container
contents such as off-odors, off-color, changes in
consistency and texture when compared with normal
product. DO NOT TASTE!
b.
Examination of Metal and Plastic Cans
NOTE: Whenever possible a "normal" companion can should
be examined along with the abnormal one.
i.
After a reserve sample has been taken and all
examinations are complete, discard any remaining
product into an autoclavable bag and terminally
sterilize.
ii. Disinfect the inside of the container with a
phenolic disinfectant and carefully clean it with a
stiff brush or use an ultra sonic bath. Do not
autoclave the container since this may destroy any
defects.
iii. Examine the interior lining of metal containers for
blackening, detinning and pitting.
iv. The container code should have been recorded prior
to analysis; if it was not, do so now. Sometimes
embossed codes are poorly impressed and can be
revealed by rubbing a pencil on a paper held over
the code. If this does not work, place a thin
smooth piece of paper over the code, hold securely
and rub the paper with a clean finger in order to
impress the paper. Rerub the paper with a finger
coated with graphite. This is superior to using a
pencil to rub the code. If that fails, rub the
code with carbon paper. Place transparent adhesive
tape over the code and rub the tape with the back
of a fingernail. Lift the tape and transfer it to
any document requiring the can code. The latter
two techniques allow a record to be kept of any
partial numbers or symbols. It is also possible to
wait until the can is emptied, then view the
reverse of the code from the inside. If needed,
the code can be viewed in a mirror.
v.
When leakage from double seams or side seams is
suspected, remove excess metal from the opened end,
leaving a 0.5 - 1 cm flange. Dry thoroughly,
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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preferably overnight, in the 55°C incubator. Add
leak detection liquid (10.41z) to the can to a
depth of 2-4 cm. Place a microleak detector on the
open end of the container. The leak detector
consists of a transparent acrylic plate with a
vacuum gauge and connector for a vacuum source.
Place a gasket (cut pieces of an automobile tire
inner tube will do) between the apparatus and the
can. If the fit is not tight (e.g., end seam is
bent), use modeling clay to fill in the gaps.
Large cans without beading or thin metal cans
having a wider diameter than height may collapse
when vacuum is applied. To prevent this from
happening, use 1/2" wooden dowels cut to the
appropriate length to support the can sides.
Bituminous compound on the dowel ends will hold
them in place. Generally, 4 dowels are sufficient
for a #10 can. Apply the gasket and any bituminous
compound, to the open can end and fit the leak
detector plate in place. Connect the vacuum and
apply 10 inches vacuum to the can. Swirl the
liquid to dissipate bubbles formed by gases
dissolved in the liquid. Examine seams by covering
them with the diluted Seamtest. Leaks are
identified by a steady stream of bubbles or a
steadily increasing bubble size. After carefully
examining all seams for leaks, increase the vacuum
to 20 inches vacuum and re-examine the seams.
Leave the can under vacuum until a leak appears or
for a maximum of 2 h, and examine at half-hour
intervals. Mark the location of leaks on the can's
exterior using a marking pen. When reporting, note
which seam, and the distance from the side seam or
some other appropriate reference point. If no
leaks were found, note test conditions (time and
amount of vacuum drawn).
vi. Perform a tear-down examination of the double
seams. The following references in Section 10.6
will guide you through this process: APHA, 1966;
Food Processors Institute, 1988; Double Seam
Manual;
Evaluating
a
Double
Seam,
FDA
Bacteriological Analytical Manual, 1992.
vii. The tightness of double seams formed by plastic
cans and metal can ends may be evaluated by
comparing the actual seam thickness to the
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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calculated thickness of the plastic flange, neck,
or metal end. This would include three thicknesses
of plastic and two of metal. Also, assess
tightness by inspecting the pressure ridge, since
it reflects the compression of the plastic body
wall. The pressure ridge should be visible and
continuous. Each packer may have different
specifications for the finished seams; if
necessary, the analyst must call the in-plant
inspector and ask for specifications for the
container of interest.
c.
Examination of Pouches
i.
The best way to determine if a pouch has leaked is
by the type of microorganisms recovered.
ii. The pouch should be examined microscopically
looking for points of light coming through the
film. These are potential leakage sites.
10.47 Interpretation of Results
Use Tables 2, 3 and 4 to arrive at possible causes of spoilage
based on all laboratory results. Caution: The tables are based
on a single cause of spoilage. If there are multiple causes, the
tables may not help.
10.5 Examination of Canned, Perishable Meat/Poultry Products
Perishable meat and poultry products, such as hams, luncheon
meats, and loaves are packaged in hermetically-sealed containers
and then heat-processed to internal temperatures of not less than
150°F (65.5oC) and usually not greater than 160°F (71oC).
"Perishable, Keep Refrigerated" must appear on the label of these
products. Although they are not shelf stable, good commercial
processing usually will destroy vegetative bacterial cells. The
combined effects of sodium nitrite, salt, refrigeration, and low
oxygen tension retard the outgrowth of the few vegetative cells
and/or spores that may survive the process. Such products can
retain their acceptable quality for 1 to 3 years when properly
processed and refrigerated.
10.51 Analysis of Containers
See Sections 10.3 - 10.33
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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10.52 Analysis of the Contents
a.
Equipment and Material
See Section 10.41
b.
Media and Reagents
See Section 10.42
c.
Preparation
See Section 10.43
d.
Sampling
i.
Using procedures already described (Section 10.44)
remove approximately 50 g of sample with a
sterilized trier, large cork borers, scissors,
knife or forceps.
ii. Place the sample into a sterile blender jar or
Stomacher bag, add 450 ml of sterile Butterfield's
Phosphate Diluent and homogenize for 2 minutes.
This is a 1:10 dilution; make additional dilutions
through at least 10-4. Proceed with the culturing
steps given in Section 10.52 (e, f & g).
iii. After sampling, cover the container opening with
sterile aluminum foil several layers thick and
secure with tape. Place the opened sample unit in
the freezer until the analysis is complete.
e.
Aerobic Plate Counts
i.
Pipet 1 ml of each dilution prepared in 10.52 (d)
into each of two sets of duplicate pour plates
according to the instructions given in Section 3.4.
ii. Prepare one dilution set with Plate Count Agar.
Incubate this set at 35°C for 48 h.
iii. Substitute APT agar for the Plate Count Agar in the
other set of plates. Incubate this set at 20°C for
96 h.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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iv. Count and record the results from both sets as
described in Section 3.4.
f.
Gas-Forming Anaerobes (GFAs)

i.
Steam tubes of MCMM for 10 minutes and cool just
prior to use.
ii. Inoculate each tube with l ml of each dilution
prepared in 10.52 (d). Begin with the 1:10
dilution and continue with subsequent dilutions.
Use a separate pipet for each dilution. Dilutions
must be sufficiently high to yield a negative
endpoint. Be sure that the inoculum is deposited
near the bottom of the tube.
iii. Incubate these tubes for 48 h at 35°C, but read
daily.
iv. Consider any MCMM tubes showing a bright yellow
color, containing visible gas bubbles, and
containing gram positive or gram variable rods as
positive for GFAs.

v.
Based upon the highest dilution showing these
organisms, report the approximate number of
gas-forming anaerobes per gram, calculated as the
reciprocal of the highest positive dilution. If
skips occur, disregard the final actual dilution
and calculate the end point at the dilution where
the skip occurred. This is only an approximation
of the gas forming anaerobe count. A minimum of
three tubes per dilution and an MPN table must be
used for a more accurate determination.
vi. If
Clostridium
botulinum
is
suspected,
representative tubes that have not been opened
should be reincubated for a total of 4 - 5 days and
then tested for botulinum toxin using the mouse
bioassay (Chapter 14).
g.
Enterococci
i.
Transfer 1 ml of each dilution prepared in 10.52(d)
to individual tubes of KF broth. Use a separate
pipette for each dilution. Begin with the 1:10
dilution and continue with each subsequent
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-22
dilution. Dilutions must be sufficiently high to
yield a negative end point.
ii. Incubate these tubes at 35°C for 48 h. Tubes
showing a yellow color, turbidity and buttoning of
growth are presumptive positives.

iii. Confirm all presumptive positives microscopically.
Either wet mounts examined under low light or gram
stained preparations are suitable for these
microscopic determinations. Microscopic
determinations
yielding
cells
with
ovoid
streptococcal morphology shall be considered
confirmed positive.
iv. Report the approximate number of enterococci per
gram, calculated as the reciprocal of the highest
positive confirmed dilution. If skips occur,
disregard the final actual dilution and calculate
the end point at the dilution where the skip
occurred. This is only an approximation of the
number of enterococci. A minimum of three tubes
per dilution and an MPN table must be used for a
more accurate determination of organisms as
described in 10.43-10.45 and Tables 2, 3 and 4.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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10.6 Selected References
APHA 1966. Recommended Methods for the Microbiological
Examination of Foods. 2nd Edition. American Public Health
Association, Inc., New York, New York.
Bee, G. R. and Denny, C. B., 1972, First Revision.
Construction and Use of a Vacuum Micro-Leak Detector for
Metal and Glass Containers. National Canners Association,
(now NFPA), Washington, D.C.
Crown Cork & Seal. Top Double Seaming Manual. Crown Cork
and Seal Co., Inc., 9300 Ashton Road, Philadelphia, PA 19136
Cunniff, P. (ed.). 1995. Official Methods of Analysis of
AOAC International, 16th Edition. Sections 17.6 - 17.8. AOAC
International, Inc., Gaithersburg, MD 20877.
Denny, C., Collaborative Study of a Method for the
Determination of Commercial Sterility of Low-Acid Canned
Foods, Journal of the Association of Official Analytical
Chemists 55 (3):613 (1972).
Double Seam Manual. Carnaud Metalbox Engineering, 79
Rockland Road, Norwalk, Connecticut 06854
Evaluating a Double Seam. W. R. Grace and Company, Grace
Container Products, 55 Hayden Ave., Cambridge, Massachusetts
02173
Food and Drug Administration, Bacteriological Analytical
Manual, Division of Microbiology, Center for Food Safety and
Applied Nutrition, 7th ed., 1992. Association of Official
Analytical Chemists, 1111 North 19th Street, Suite 210,
Arlington, VA 22209.
Food Processors Institute 1988. Canned Foods: Principles of
Thermal Process Control, Acidification and Container Closure
Evaluation. The Food Processors Institute, Washington, D.C.
20005.
Hersom, A. C. and Hulland, E. D., 1964. Canned Foods, An
Introduction to Their Microbiology. Chemical Publishing
Company, Inc. New York, New York.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-24
National Food Processors Association, 1979. Guidelines for
Evaluation and Disposition of Damaged Canned Food Containers
Bulletin 38-L, 2nd Edition. National Food Processors Assoc.,
Washinton, D.C.
National Food Processors Association, 1989. Flexible Package
Integrity Bulletin by the Flexible Package Integrity
Committee of NFPA. Bulletin 41-L. NFPA, Washington, D.C.
Schmitt, H. P. 1966. Commercial Sterility in Canned Foods,
Its Meaning and Determination. Assoc. Food and Drug
Officials of the U.S. 30:141.
Townsend, C. T., 1964. The Safe Processing of Canned Foods.
Assoc. Food and Drug Officials of the U.S. 28:206.
Townsend, C. T., 1966. Spoilage in Canned Foods. J. Milk
Food Tech. 20 (1):91-94.
United States Department of Agriculture, Food Safety
Inspection Service. Code of Federal Regulations, Title 9,
part 318.300, Subpart G (u).
Vanderzant, C., and D. F. Splittstoesser (ed.). 1992.
Compendium of Methods for the Microbiological Examination of
Foods, 3rd Edition. Amer. Publ. Hlth. Assoc., Washington,
D.C. 20005.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-25
Appendix I
Glossary of Metal/Plastic Can Seam Terminology
for Container Components and Defects
The same terms that are used to describe an all-metal seam apply
equally well to the metal end/plastic body seam.
Base Plate: Part of a closing machine which supports cans
during seaming operation.
Beaded Can: A can which is re-enforced by having ring
indentations around the body. The bead tends to keep the can
cylindrical and helps to eliminate paneling of the can body.
Body: Principal part of a container - usually the largest
part in one piece containing the sides (thus sidewall or body
wall).
Body Hook: Can body portion of double seam. Prior to
seaming, this portion was the flange of the can.
Bottom Seam: Factory end seam. The double seam of the can
end put on by the can manufacturer.
Buckling: A distortion in a can end.
Can Size: Two systems are commonly used to denote can size:
i.
An Arbitrary system (1, 2, etc.) with no relation
to finished dimension.
ii. A system indicating the nominal finished dimensions
of a can; e.g. "307 x 512." In this example, the
first group of digits ("307") refers to the can's
diameter and the second set ("512"), the can's
height. The first digit in each set represents
inches, and the next two digits represent
sixteenths of an inch. Hence, the example can has
a diameter of 3-7/16 and a height of 5-12/16 (or 5-
3/4) inches.
Chuck: Part of a closing machine which fits inside the
countersink and in the chuck wall of the end during seaming.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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Closing Machine: Also known as a double seamer. Machine
which double seams the lid onto the can bodies.
Compound: Rubber or other material applied inside the end
curl to aid in forming a hermetic seal when the end is double
seamed on the can body.
Contamination in Weld Area: Any visible burn at one or more
points along the side seam of a welded can. This is a major
defect.
Countersink: On a seamed end, the perpendicular distance
from the outermost end panel to the top seam.
Cover: Can end placed on can by packer. Also known as top,
lid, packer's end, canner's end.
Cover Hook: That part of double seam formed from the curl of
the can end.
Cross Over: The portion of a double seam at the lap.
Cross Section: Referring to a double seam, a section through
the double seam.
Curl: The semi-circular edge of a finished end prior to
double seaming. The curl forms the cover hook of the double
seam.
Cut Code: A break in the metal of a can due to improper
embossing-marker equipment.
Cut-Over: During certain abnormal double seaming conditions,
the seaming panel becomes flattened and metal is forced over
the seaming chuck forming a sharp lip at the chuck wall. In
extreme cases the metal may split in a cut-over.
Dead-Head: An incompletely rolled finished seam. Also known
as a skip, skid or spinner.
Double Seam: The joint between the end and the can body
formed by rolling the curl under the flange (1st operation)
and then pressing the metal together (2nd operation).
Droop: A smooth projection of double seam below the bottom of
a normal seam. While droops may occur at any point of the
seam, they usually are evident at the side seam lap. A
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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slight droop at the lap may be considered normal because of
additional plate thickness incorporated into the seam
structure.
Excessive Slivers: One or more slivers which are 1/32" or
longer. This is a minor defect of welded cans.
Factory End: Bottom or can manufacturer's end.
False Seam: A seam fault where the end and body hook are not
over-lapped (engaged), although they give the appearance of a
properly formed seam. Also see Knockdown Flange.
Feather: Beginnings of a cut-over. See Sharp Edge.
First Operation: The first operation in double seaming. In
this operation, the curl of the end is tucked under the
flange of the can body which is bent down to form cover and
body hook, respectively.
Flange: The flared portion of the can body which facilitates
double seaming.
Flange Crack: Any crack at the flange or immediately adjacent
to the weld of welded cans. This is a major defect.
Headspace: The free space above the contents of a can and the
can lid.
Heavy Lap: A lap containing excess solder. Also called a
thick lap.
Hook: (i). The bent over edges of a body blank, which form
the side seam lock (ii). The body and cover hooks in a
double seam.
Internal Enamel: A coating applied to the inside of the can
to protect the can from chemical action by the contents or to
prevent discoloration. A lacquer is usually clear; an enamel
is pigmented and opaque.
Jumped Seam: A double seam which is not rolled tight enough
adjacent to the crossover caused by jumping of the seaming
rolls at the lap.
Knockdown Flange: A seam defect in which the flange is bent
against the body of the can. The cover hook is not tucked
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-28
inside the body hook, but lies outside of it. False seams,
knockdown flanges and soft crabs are degrees of the same
effect. In order to distinguish the degree of the defect,
the following terminology is suggested:
False Seam: The cover hook and body hook are not tucked
for a distance of less than an inch. Thus it may not be
possible to detect a false seam until the can is torn
down.
Knockdown Flange: As above, but more than an inch in
length. Body hook and cover hook in contact, but not
tucked.
Soft Crab: A defect in which the body of the can is
broken down and does not contact the double seam. Thus,
there is a wide open hole in the can below the double
seam where the body was not incorporated into the seam.
Lap: The soldered but not locked portions of a side seam at
the ends of the can body before seaming and removing the can
from the chuck at completion of the operation.
Lid: See Cover.
Lip, Spurs or Vees: Irregularities in the double seam due to
insufficient or sometimes absent overlap of the cover hook
with the body hook, usually in small areas of the seam. The
cover hook metal protrudes below the seam at the bottom of
the cover hook in one or more "V" shapes.
Loss of Overlap: Any observable loss of overlap along the
side seam of a welded can. This is a critical defect.
Loose Tin: A metal can which does not appear swollen, but
slight pressure reveals a looseness.
Mislock: A poor or partial side seam lock, due to improper
forming of the side seam hooks.
Neck: The thickness of the top of the sidewall (body wall) of
a plastic tub, one tenth of an inch below the junction of the
flange and the sidewall.
Notch: A small cut-away portion at the corners of the body

blank. This reduces droop when double seaming.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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Oozier: An imperfect can which allows the escape of the
contents through the seam.
Open Lap: A lap failed due to various strains set up during
manufacturing operations. Also caused by improper cooling of
the solder (See Weak Lap). A lap which is not properly
soldered so the two halves are not properly joined.
Over Lap: The distance the cover hook laps over the body
hook.
Paneling: A flattening of the can side. Also used to define
concentric (expansion) rings in can ends.
Peaking: Permanent deformation of the expansion rings on the
can ends due to rapid reduction of steam pressure at the
conclusion of processing. Such cans have no positive
internal pressure and the ends can be forced back more or
less to their normal position.
Perforation: Holes in the metal of a can resulting from the
action of acid in food on metal. Perforation may come from
inside due to product in the can or from outside due to
material spilled on the cans.
Pleat: A fold in the cover hook which extends from the edge
downward toward the bottom of the cover hook and sometimes
results in a sharp droop, vee or spur.
Pressure Ridge: A ridge formed on the inside of the can body
directly opposite the double seam, as a result of the
pressure applied by the seaming rolls during seam formation.
Pucker: A condition which is intermediate between a wrinkle
and a pleat in which the cover hook is locally distorted
downward without actual folding. Puckers may be graded the
same way as wrinkles.
Sanitary Can: Can with one end attached, the other end put on
by the packer after the can is filled. Also known as
packer's can or open top can.
Sawtooth: Partial separation of the side seam overlap at one
or more points along the side seam after performing the pull
test on a welded side seam. This is a critical defect.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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Seam Arrowing: A readily visible narrowing of the weld at
either end of the can body. This is a major defect.
Seam Width: The maximum dimensions of a seam measured
parallel to folds of the seam. Also referred to as the seam
length or height.
Seam Thickness: The maximum dimension measured across or
perpendicular to the layers of the seam.
Second Operation: The finishing operation in double seaming.
The hooks formed in the first operation are rolled tight
against each other in the second operation.
Sharp Edge: A sharp edge at the top of the inside portion of
the double seam due to the end metal being forced over the
seaming chuck.
Side Seam: The seam joining the two edges of a blank to form
a body.
Skipper / Spinner: See Deadhead.
Uneven Hook: A body or cover hook which is not uniform in
length.
Vee: See Lip.
Weak Lap: The lap is soldered and both parts are together.
However, strain on this lap (e.g. by twisting with the
fingers) will cause the solderbond to break.
Weld Crack: Any observable crack in a welded side seam. This
is a critical defect.
Worm Holes: Voids in solder usually at the end of the side
seam. May extend completely through the width of the side
seam.
Wrinkle: The small ripples in the cover hook of a can. A
measure of tightness of a seam.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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Appendix II
Glossary of Glass Container Parts
From a manufacturing standpoint, there are three basic parts to a
glass container based on the three parts of glass container molds
in which they are made. These are the finish, the body and the
bottom.
Finish: The finish is that part of the jar that holds the cap
or closure. It is the glass surrounding the opening in the
container. In the manufacturing process, it is made in the
neck ring or the finish ring. It is so named since, in early
hand glass manufacturing, it was the last part of the glass
container to be fabricated, hence "the finish". The finish
of glass containers has several specific areas as follows:
Continuous Thread: A continuous spiral projecting glass ridge
on the finish of a container intended to mesh with the thread
of a screw-type closure.
Glass lug: One of several horizontal tapering protruding
ridges of glass around the periphery of the finish that
permit specially designed edges or lugs on the closure to
slide between these protrusions and fasten the number of
lugs on the closure and their precise configuration is
established by the closure manufacture.
Neck Ring Parting Line: A horizontal mark on the glass
surface at the bottom of the neck ring or finish ring
resulting from the matching of the neck ring parts with the
body mold parts.
Sealing Surface: That portion of the finish which makes
contact with the sealing gasket or liner. The sealing
surface may be on the top of the finish, or may be a
combination of both top and side seal.
Vertical Neck Ring Seam: A mark on the glass finish resulting
from the joint of matching the two parts of the neck ring.
NOTE: Some finishes are made in a one-piece ring and do not
have this seam.
Body: The body of the container is that portion which is made
in the "body-mold" in manufacturing. It is the largest part
of the container and lies between the finish and the bottom.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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The characteristic parts of the body of a glass container
are:
Heel: The heel is the curved portion between the bottom and
the beginning of the straight side wall.
Mold Seam: A vertical mark on the glass surface in the body
area resulting from matching the two parts of the body mold.
Shoulder: That portion of a glass container in which the
maximum cross-section or body area decreases to join the neck
or finish area. Most glass containers for processed foods
have very little neck. The neck would be a straight area
between the shoulder and the bottom of the bead or, with
beadless finishes, the neck ring parting line.
Side Wall: The remainder of the body area between the
shoulder and the heel.
Bottom: The bottom of the container is made in the "bottom
plate" part of the glass container mold. The designated parts
of the bottom normally are:
Bearing Surface: That portion of the container on which it
rests. The bearing surface may have a special configuration
known as the "stacking feature" which is designed to provide
some interlocking of the bottom of the jar with the closure
of another jar on which it might be stacked for display
purposes.
Bottom Plate Parting Line: A horizontal mark on the glass
surface resulting from the matching of the body mold parts
with the bottom plate.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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Appendix III
Glossary of terms - Flexible Retortable Pouches.
Adhesive: A substance applied to ply surfaces to cement the
layers together in a laminated film: (a). Polyurethane
adhesive for the outer layer (b). Maleic anhydride adduct of
polypropylene for the inner layer.
Blisters: Bubbles/gaseous inclusions/particulate material,
may be present between layers of laminate, usually are found
in the seal area.
Bottom of Closing Seal: Portion of closing (packer) seal
adjustment to the pouch contents.
Bottom Seal: A seal applied by heat and pressure to the
bottom of a flexible pouch.
Cosmetic Seal: Area above the primary seal designed to close
the edges of the pouch thus preventing the accumulation of
extraneous material.
Cuts, Punctures, Scratches: Mechanical defects that penetrate
one or more layers of the pouch.
Delamination: Any separation of plies through adhesive
failure. This may result in questionable integrity of the
package and safety of the product.
Dirty: Smeared with product or product trapped in top edges
(where there are no cosmetic seals).
Disintegrated Container: Evidence of delamination or
degradation after retorting.
Final Seal: A seal formed by heat and pressure by the packer
after pouch filling and prior to retorting.
Foil Flex Cracks/Foil Roll Holes: Visible cracks in the
aluminum foil layer caused by flexing of the pouch or pin
holes (roll holes) in the foil caused through manufacture of
the aluminum ply.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
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Foreign Materials: Any material (solid food, condensate,
grease, voids, blemishes) that may be entrapped between the
plies but usually found in the seal area.
Fusion Seal: A seal formed by joining two opposing surfaces
by the application of heat and pressure.
Hard Swell or Blown: Distention or rupture due to internal
gas formation.
Inner Ply: Polypropylene coating bonded to the food surface
side of the aluminum foil.
Laminate: Two or more layers of material held together by
adhesive(s).
Leaker: Product leaking through any area of the pouch.
Outer Ply: The polyester film bonded to the exterior surface
of the aluminum foil.
Over Carton: A separate container (usually cardboard) in
which the flexible pouch is packaged for additional
protection.
Package Dimensions: The measurements of retortable flexible
pouches stated as length, the longest dimension (LGT), width
the second longest dimension (W), and thickness, the shortest
dimension (HGT). All are given as internal measurements.
Pin Holes, Roll Holes: Holes in the aluminum foil layer only,
originating during manufacturing; usually do not leak.
Preformed Seals: Seals formed by heat and pressure, by the
manufacturer of the pouches, along the sides and at the
bottom of the pouches.
Primary Seal: A fusion seal formed by the food processor by
applying heat and pressure immediately after filling.
Seal: A continuous joint of two surfaces made by fusion of
the laminated materials.
Seal Width: The maximum dimension of the seal measured from
the leading outside edge perpendicular to the inside edge of
the same seal.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-35
Severely Damaged: Punctures, cuts or ruptures which penetrate
all layers of the pouch and expose the product to
contamination.
Side Seals: Seals formed by applying heat and pressure to the
sides of the pouch's laminates to form the "preformed pouch".
Tear Nicks or Notch: Notches near the final seal to aid the
consumer in opening the pouch.
Wrinkle: A crease or pucker in the seal (Packer or Factory)
areas.
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-36
Appendix IV
Table 1. Normal pH Values for a Few Representative Canned
Meat/Poultry Products.
__________________________________________________________________
Kinds of Food
pH


Beans with Wieners
5.7
Beef Chili
5.6
Beef Paté
5.7
Beef Stew
5.4 - 5.9
Beef Taco Filling
5.8
Beef and Gravy
5.9 - 6.1
Chicken Noodle Soup
5.8 - 6.5
Chicken Soup with Rice
6.7 - 7.1
Chicken Broth
6.8 - 7.0
Chicken and Dumplings
6.4
Chicken Vegetable Soup
5.6
Chicken Stew
5.6
Chicken Vienna Sausage
6.1 - 7.0
Chorizos
5.2
Corned Beef
6.2
Corned Beef Hash
5.0 - 5.7
Egg Noodles & Chicken
6.5
Ham
6.0 - 6.5
Lamb, Strained Baby Food
6.4 - 6.5
Pork Cocktail Franks
6.2
Pork with Natural Juices
6.2 - 6.4
Pork Sausage
6.1 - 6.2
Roast Beef
5.9 - 6.0
Spaghetti and Meatballs
5.0
Spaghetti Sauce with Beef
4.2
Stuffed Cabbage
5.9
Sloppy Joe
4.4
Turkey, Boned in Bouillon 6.1 - 6.2
Turkey with Gravy
6.0 - 6.3
Vienna Sausage
6.2 - 6.5
Wieners, Franks
6.2
__________________________________________________________________

USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-37
Appendix V
Table 2. KEY TO PROBABLE CAUSE OF SPOILAGE IN CANNED FOODS
Group 1.- Low-Acid Foods
pH Range 5.0 to 8.0
Condition of Characteristics of Material in Cans
cans
Odor
Appearance
Gas
(CO2 &
H2)
pH
Smear
Cultures
Diagnosis
Swells
Normal to
"metallic"
Normal to frothy
(Cans usually etched
or corroded)
More than
20% H2
Normal
Negative to
occasional
organisms
Negative
Hydrogen swells
Sour
Frothy; possibly ropy
brine
Mostly
CO2
Below
Normal
Pure or mixed
cultures of
rods, cocci,
yeasts or molds
Growth, aerobically
and/or anaerobically
at 35°C., and
possibly at 55°C.
Leakage
Sour
Frothy; possibly ropy
brine, food particles
firm with uncooked
appearance
Mostly
CO2
Below
Normal
Pure or mixed
cultures of
rods, coccoids,
cocci and
yeasts
Growth, aerobically
and/or anaerobically
at 35°C., and
possibly at 55°C.
(If product received
high exhaust, only
spore formers may be
recovered)
No process given
Normal to
sour-
cheesy
Frothy
H2 and
CO2
Slightly to
definitely
below
normal
Rods, med.
Short to med.
long, usually
granular;
spores seldom
seen
Gas, anaerobically
at 55°C., and
possibly slowly at
35°C.
Post-processing
temperature abuse
Thermophilic
anaerobes
Cheesy to
putrid
Usually frothy with
disintegration of
solid particles
Mostly
CO2;
possibly
some H2
Slightly to
definitely
below
normal
Rods; usually
spores present
Gas anaerobically at
35°C.
Underprocessing -
mesophilic anaerobes
(possibility of Cl.
botulinum)
Slightly
off –
possibly
ammoniacal
Normal to frothy
Slightly to
definitely
below
normal
Rods; spores
occasionally
seen
Growth, aerobically
and/or anaerobically
with gas at 35°C and
possibly at 55°C.
Pellicle in aerobic
broth tubes. Spores
formed on agar and
in pellicle.
Underprocessing - B.
subtilis type
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-38
No
vacuum
and/or
Cans
buckled
Normal
Normal
No H2
Normal to
slightly
below
normal
Negative to
moderate number
of organisms
Negative
Insufficient vacuum,
caused by: 1)
Incipient spoilage,
2) Insufficient
exhaust,
3) Insufficient
blanch,
4) Improper retort
cooling procedures,
5) Over fill
Flat
cans
(0 to
normal
vacuum)
Normal to
sour
Normal to cloudy
brine
Slightly to
definitely
below
normal
Rods, generally
granular in
appearance;
spores seldom
seen
Growth without gas
at 55°C. Spore
formation on
nutrient agar
Post-Processing
temperature abuse
Thermophilic flat
sours.
Normal to
sour
Normal to cloudy
brine; possibly moldy
Slightly to
definitely
below
normal
Pure or mixed
cultures of
rods, coccoids,
cocci or mold
Growth, aerobically
and/or anaerobically
at 35°C., and
possibly at 55°C.
Leakage
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-39
Appendix VI
Table 3. KEY TO PROBABLE CAUSE OF SPOILAGE IN CANNED FOODS
Group 3. Semi-Acid Foods
pH Range 4.6 to 5.0
Condition of Characteristics of Material in Cans
cans
Odor
Appearance
Gas
(CO2 &
H2)
pH
Smear
Cultures
Diagnosis
Swells
Normal to
"metallic"
Normal to frothy
(Cans usually etched
or corroded)
More
than
20% H2
Normal
Negative to
occasional
organisms
Negative
Hydrogen swells
Sour
Frothy; possibly
ropy brine
Mostly
CO2
Below Normal
Pure or mixed
cultures of
rods, coccoids,
cocci, yeasts
or molds
Growth,
aerobically
and/or
anaerobically at
35°C., and
possibly at
55°C.
Leakage
Note:
Cans are
Sometimes
flat
Sour
Frothy; possibly
ropy brine, food
particles firm with
uncooked appearance
Mostly
CO2
Below Normal
Pure or mixed
cultures of
rods, coccoids,
cocci and
yeasts
Growth,
aerobically
and/or
anaerobically at
35°C., and
possibly at
55°C. (If
product received
high exhaust,
only spore
formers may be
recovered)
No process given
Normal to
sour-cheesy
Frothy
H2 and
CO2
Slightly to
definitely
below normal
Rods - med.
Short to med.
long, usually
granular;
spores seldom
seen
Gas,
anaerobically at
55°C., and
possibly slowly
at 35°C.
Post-processing
temperature abuse
Thermophilic
anaerobes
Normal to
cheesy to
putrid
Normal to frothy
with disintegration
of solid particles
Mostly
CO2;
poss-
ibly
some H2
Normal to
slightly below
normal
Rods; possibly
spores present
Gas
anaerobically at
35°C. Putrid
odor
Underprocessing –
mesophilic
anaerobes
(possibility of
Cl. Botulinum)
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-40
Slightly off
- possibly
ammoniacal
Normal to frothy
Slightly to
definitely
below normal
Rods;
occasionally
spores observed
Growth,
aerobically
and/or
anaerobically
with gas at 35°C
and possibly at
55°C. Pellicle
in aerobic broth
tubes. Spores
formed on agar
and in pellicle.
Under-
processing - B.
subtilis type
Butyric acid
Frothy, large volume
gas
H2 and
CO2
Definitely
below normal
Rods - bipolar
staining;
possibly spores
Gas
anaerobically at
35°C. Butyric
acid odor
Under
processing -
butyric acid
anaerobe
No vacuum
and/or Cans
buckled
Normal
Normal
No H2
Normal to
slightly below
normal
Negative to
moderate number
of organisms
Negative
Insufficient
vacuum, caused by:
1) Incipient
spoilage,
2) Insufficient
exhaust,
3) Insufficient
blanch,
4) Improper retort
cooling
procedures, 5)
Over fill
Flat cans
(0 to normal
vacuum)
Sour to
"medicinal"
Normal to cloudy
brine
Slightly to
definitely
below normal
Rods, possibly
granular in
appearance
Growth without
gas at 55°C. and
possibly at
35°C. Growth on
thermoacidurans
agar
Underprocessing B.
coagulans
Normal to
sour
Normal to cloudy
brine; possibly
moldy
Slightly to
definitely
below normal
Pure or mixed
cultures or
rods, coccoid,
cocci or mold
Growth,
aerobically
and/or
anaerobically at
35°C., and
possibly at
55°C.
Leakage
USDA/FSIS Microbiology Laboratory Guidebook 3rd Edition/1998
10-41
Appendix VII
Table 4. Characteristics of Normal and Abnormal Perishable Canned Meat/Poultry Products
Condition of
Cans
Odor
Appearance
pH
Smear
Cultures
Probable
Cause
Flat Cans (0 to
Normal Vacuum)
Normal
Normal
Normal
Negative to
occasional
organisms
0 to low # APC,
APT agar count
Normal product
0 to degrees of
swelling
Sour to off
odor
Normal to mushy,
possible gel
liquification
Slightly to
definitely
below normal
Mixed culture
of rods &
enterococci
Low # mesophiles,
high #
psychrophilic non-
spore formers
(enterococci,
lactobacilli
1. Prolonged storage
at low temperatures
2. Abnormal high
levels in raw
materials 3.
Substandard process
Swell
Sour or off
odor, possibly
putrid
Normal to mushy,
possible gel
liquification
Slightly to
definitely
below normal
Mixed culture
of rods, cocci
High # mesophilic
spore formers and
non-sporeformers
Product held without
refrigeration
Swell
Normal to sour
Normal
Below normal
Cocci, rods or
both
Enterococci, rods
or both
Leakage if shell
higher than core.
Underprocessing if
core higher than
shell
Swell
Off odor
Normal to off
color
Below normal
Rods
Psychrotrophic
clostridia (rarely
occurs in U.S.).
Low brine levels
Swell
Normal to
putrid,
depending on
length of
storage.
Ranges from
uncooked
appearance to
digested
Normal to low,
depending on
length of
storage.
Vary
Vary
Missed processing
cycle.
Most of these are
detected soon after
distribution.