FT 3103 Food Microbiology

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FT 3103 Food Microbiology

• Present by Mai Thuy Linh 4525522
• Bui Vinh Hoang Chuong 4325742

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Topic Surface Monitoring
30/6/2004
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The need to maintain food contact surfaces in a
hygienic state is of obvious importance.The
primary problem that has to be overcome when
examining surfaces or utensils for microorganisms
is the removal of significant percentage of the
resident flora.The most commonly used methods
for surface assessment in food operations are
presented below.
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• Test can have a microbiological, chemical or
  physical basic.
• Microbiological tests are hotly debated issue.
• Surface monitoring is used to verify the
  efficiency of and end of shift clean up.
• These tests are not specific for a given
  microorganism.
• Trend is toward more rapid tests.
• Most effective when applied as part of overall
  Hazard Analysis critical Control point( HACCP)
  program.

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Some kinds of microorganisms
examination of
surfaces
Swab/ swab Rinse methods
Agar
Syringe/ Agar Sausage methods
Other surfaces methods
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Swab/ swab rinse Methods

• Swabbing is the oldest and most widely used
  method for the microbiological examination of
  surfaces not only in the food and dairy
  industries but also in hospitals and restaurants.
• The swab rinse methods was developed in 1917 by
  W. A. Manheimer and T Ybanez.

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Either cotton or calcium alginate swabs are
used.If one wishes to examine given areas of a
surface, templates may be prepared with openings
corresponding to the size of the area to be
swabbed. Example 1 in2 or 1cm2
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Swab Test KitsSterile swabs and buffer for
microbiological monitoring of surfaces and
process operations such as equipment sanitation
and changeovers. Easy to use - simply swab the
surface and place back into the sterile buffer.
Pour the buffer into a sterile membrane device
and filter.
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The sterile template is placed over the surface,
and the exposed area is rubbed thoroughly with a
moistened swab.

• The exposed swab is returned to its holder
  containing a suitable diluents and stored at
  refrigerator temperatures until plated.
• The diluents should contain a neutralizer.

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• The swab method to be best suited for flexible,
  uneven, and heavily contaminated surfaces.
• The ease of removal of organisms depends on the
  texture of the surface and the nature and types
  of flora.
• The swab rinse method remains a rapid, simple,
  and inexpensive way to assess the microbiological
  flora of food surfaces and utensils.

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• Samplers and Swab Test Kits for Food and Beverage
  ApplicationsSamplers use self-contained dip
  testers to monitor microbiological organisms in
  liquids Swab Test Kits use Swab and Sampler
  combination to monitor microorganisms on
  equipment and other surfaces Easy to use - simply
  sample, incubate and count.

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Contact plate

• The replicate organism direct agar contact
  (RODAC) method employs special Petri plates,
  which are poured with 15.5-16.5 ml of an
  appropriate plating medium, resulting in a raised
  agar surface.
• When the plate is inverted, the hardened agar
  makes direct contact with the surface.

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• Originated by Gunderson and Gunderson in 1945, it
  was further developed in 1964 by Hall and
  Hartnett.

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• When surfaces are examined that have been cleaned
  with certain detergents, it is necessary to
  include a neutralizer in the medium.
• Once exposed, plates are covered, incubated, and
  the colonies enumerated.
• The RODAC plate has been shown to be the method
  of choice when the surfaces to be examined are
  smooth, firm, and nonporous.

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Re-thermalization cart (stainless steel) with
contact units note the round heating unit
surfaces as part of the tray support system in
the cart.
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• The RODAC plate has been shown to be the method
  of choice when the surfaces to be examined are
  smooth, firm, and nonporous.
• Contact plates give better results where low
  numbers exist.
• In terms of ranking of surface contamination, the
  two methods correlated well.

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Agar syringe/ agar sausage
methods.

• The agar syringe method was proposed by W.
  Litsky in 1955 and subsequently modified.
• By this method, a 100 ml syringe is modified by
  removing the needle end to create a hollow
  cylinder that is filled with agar.

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• A layer of agar is pushed beyond the end of the
  barrel by means of the plunger and pressed
  against the surface to be examined.
• The exposed layer is cut off and placed in a
  petri dish, followed by incubation and colony
  enumeration.

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The agar sausage method

• The agar sausage method proposed by ten Cate is
  similar but employs plastic tubing rather than a
  modified syringe.
• The latter method has been used largely by
  European workers for assessing the surface of
  meat carcasses, as well as for food plant
  surfaces.

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• Both methods can be viewed as variations of the
  RODAC plate, and both have the same
  disadvantages spreading colonies and
  applicability limited to low levels of surface
  contaminants.
• Because clumps or chains of organisms on surfaces
  may yield single colonies, the counts obtained by
  these methods are lower than those obtained by
  methods that allow for the breaking up chains or
  clumps.

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Other surface methods

• Direct surface
• Sticky film
• Swab/ agar slant
• Ultrasonic devices
• Spray gun

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Direct surface

• Angelotti and Foter proposed this as a reference
  method for assessing surface contamination
• And it is excellent for enumerating particulates
  containing viable microorganisms.

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Sticky film

• The sticky film method of Thomas has been used
  with some success by Mossel.
• The method consists of pressing sticky film or
  tape against the surface to be examined and
  pressing sticky the exposed side on an agar
  plate.
• It was shown to be less effective than swabs in
  recovering bacteria from wooden surfaces.

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Swab/agar slant

• The swab/agar slant method described in 1962 by
  N. H. Hansen has been used with success by some
  European workers.

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• The method involves sampling with cotton swabs
  that are transferred directly to slants.
• It requires a template, a comparator disc, and
  reference table, making it a bit more complicated
  than the order methods notes.

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Ultrasonic devices

• Ultrasonic devices have been used to assess the
  microbiological contamination of surfaces, but
  the surfaces to be examined must be small in size
  and removable so that they can be places inside a
  container immersed in diluents.
• A more practical use of ultrasonic energy may be
  the removal of bacteria from cotton swabs in the
  swab rinse method.

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• An ultrasonic detection instrument is a powerful
  toolfor preventive maintenance because it has
  many advantages in the early detection of
  problems. It is light in weight, versatile, easy
  to use and relatively inexpensive. At left the
  system is in use on a bearing

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Spray gun

• A spray method was devised by Clack based on the
  impingement of a spray of washing solution
  against circumscribed area of surface and the
  subsequent plating of the washing solution.

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• Although the device is portable, a source of air
  pressure is necessary.
• It was shown to be much more effective than the
  swab method in removing bacteria from meat
  surfaces.

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• Questions

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• Thank you