3M Petrifilm 6400 Instrucciones De Producto página 4

Incubation
Incubate 3M Petrifilm AC Plates in a horizontal position with the clear side up in stacks of no more than 20. Several
incubation times and temperatures can be used depending on current local reference methods, some of which are listed in
the "Specific Instructions for Validated Methods" section.
Interpretation
1. 3M Petrifilm AC Plates can be counted using a standard colony counter or other illuminated magnifier. Count all red
colonies regardless of size or intensity.
2. The circular growth area is approximately 20 cm
than 300 colonies by counting the number of colonies in two or more representative squares and determining the
average number per square. Multiply the average number by 20 to determine the estimated count per plate.
3. High concentrations of colonies on the 3M Petrifilm AC Plates will cause the entire growth area to become red or pink.
Occasionally, on overcrowded 3M Petrifilm AC Plates, the center may lack visible colonies, but many small colonies
can be seen on the edges. When any of these occurs, record results as too numerous to count (TNTC). When an actual
count is required, plate at a higher dilution.
4. Some organisms can liquefy the gel, allowing them to spread out and obscure the presence of other colonies. If
liquefied gel interferes with counting, an estimated count should be made by counting the unaffected areas.
5. Where necessary, colonies may be isolated for further identification. Lift the top film using proper testing technique and
pick the colony from the gel. Test using standard procedures.
6. If the 3M Petrifilm AC Plates cannot be counted within 1 hour of removal from the incubator, they may be stored for
later enumeration by freezing in a sealable container at temperatures less than or equal to negative 15°C (5°F) for no
longer than one week.
For further information refer to the "3M™ Petrifilm™ Aerobic Count Plate Interpretation Guide." If you have questions
about specific applications or procedures, please visit our website at www.3M.com/foodsafety or contact your local 3M
representative or distributor.
Specific Instructions for Validated Methods
AOAC® Official Methods
Bacterial and Coliforms Counts in Dairy Products, Dry Rehydratable Film Methods)
Scope of the validations: Milk and other dairy products.
Incubate 3M Petrifilm AC Plates 48 hours ± 3 hours at 32°C ± 1°C.
Follow guidelines provided in Interpretation section of this document.
AOAC® Official Methods
Scope of the validations: In foods.
Incubate 3M Petrifilm AC Plates 48 hours ± 3 hours at 35°C ± 1°C.
Follow guidelines provided in Interpretation section of this document.
NF Validation by AFNOR Certification
NF Validation certified method in compliance with ISO 16140-2
Use the following details when implementing the above Instructions for Use:
Scope of the validation:
All human food products, pet food and industrial environmental samples.
Sample Preparation:
Use only ISO listed diluents
Incubation:
Option 1 - For testing all human food products, (including dairy products and raw shellfish), pet food and industrial
environmental samples:
Incubate 3M Petrifilm AC Plates 72 hours ± 3 hours at 30°C ± 1°C.
Option 2 - For testing all human food products, (except dairy products and raw shellfish), pet food and industrial
environmental samples:
Incubate 3M Petrifilm AC Plates 48 hours ± 3 hours at 30°C ± 1°C.
Interpretation
Calculate the number of microorganisms present in the test sample according to ISO 7218
per dilution. Estimates are outside of the scope of the NF Validation certification
(See Interpretation section, steps 2 and 4). Refer to EN ISO 7218 standard for inoculation, colony counting and calculation
and expression of results.
. Estimates can be made on 3M Petrifilm AC Plates containing greater
2
(986.33 Bacteria and Coliform Counts in Milk, Dry Rehydratable Film Methods and 989.10
SM
(990.12 Aerobic Plate Count in Foods, Dry Rehydratable Film Methods)
SM
.
5
in comparison to ISO 4833
6
3
EN
(English)
(3M 01/1-09/89)
7
for one 3M Petrifilm AC Plate
3