? "Gary G" <see.signature at bottom> ?????? ??? ??????
news:s2q1s013i2mb5h5jl5g56rn55ob46pfjf5 at 4ax.com...
> On Wed, 15 Dec 2004 11:16:00 +0200, "The Sceptical Chymist"
> <polyzoni at otenet.invalid> wrote:
>> >Hello everybody.
> >
> >I would appreciate any comments on the following:
> >
> >We are a company that makes frozen dough products, some of which include
> >cured meat in the filling. We're having a problem with one of our
customers,
> >a major food multinational, and I would like to hear the opinions of
others.
> >The situation is as follows:
> >Two of our products contain boiled ham and bacon, which are placed in an
> >open dough base (they're exposed). The cooking instructions state clearly
> >that the product should be baked at 180 deg C for15-20 min. However the
> >customer believes that the end-user might let the product thaw rather
than
> >take it straight from the freezer to the oven and additionally might pick
> >and eat the ham or bacon. For that reason they treat those two
ingredients
> >as ready-to-eat and ask for an "absence of Salmonella spp in 375g"
analysis.
> >We're using a Biomerieux Minividas instrument, and the protocol asks for:
> >
> >1. Homogenising 25g of sample in 225 ml of buffered peptone water (BPP).
> >2. Incubating the resulting 250ml of homogenate at 37 °C for 16-20 hrs.
> >3. Subculturing 0.1 ml of homogenate in 10 ml of Rappaport Vassiliadis
(RV)
> >broth.
> >4. Incubating the RV broth at 41.5 °C for 6-8 hrs.
> >5. Subculturing of 1 ml from the RV broth in 10 ml of M-broth.
> >6. Incubating the M broth for 16-20 hrs at 41.5 °C.
> >7. Heating 1 ml of M broth at 100 °C for 15 min.
> >8. Adding 0.5 ml of heated M broth to the Vidas SLM test strip and
reading
> >the results in 45 minutes.
> >
> >Positive results are followed by confirmation by a reference method that
> >involves plating the selective broth and running biochemical (API strips)
> >and/or serological (agglutination) tests.
> >
> >If we were to follow the protocol to the letter we would have to test 15
25g
> >samples (the instruments can only run 12 samples at a time) with all the
> >reagents, incubator space, staff and time requirements that would entail.
> >What we do instead is pool the 15 samples of 25g to 4 samples of 100g
(that
> >makes 400 rather than 375g). We dilute those 1:10 with BPP and
homogenise,
> >ending up with four homogenates of 1000 ml. These we incubate at 37 °C
for
> >16-20 hrs and then draw 0.1ml and subculture it in RV broth. From that
point
> >onwards we follow the rest of the protocol to the letter.
> >The probability of the 400g sample carrying Salmonella remains the same
as
> >long as the sample is representative and drawn from different points.
What
> >does change is the probability that 0.1 ml drawn from 1000 ml of
incubated
> >homogenate carry Salmonella. There's a better chance of detecting it if
> >0.1ml is drawn from 250 ml as the protocol requires. However we believe
that
> >after incubating the homogenate at 37 °C for 16-20 hrs in BPP, if
Salmonella
> >is present it will multiply to such levels that this difference is
> >insignificant.
> >I'm interested in other people's opinion on the matter, so I would like
to
> >hear from you.
> >
> >I will be posting this to more than one food list/newsgroup, so apologies
to
> >anyone who reads it more than once.
> >
> >Sincerely
> >
> >Kostas Polyzonis
> >QA Manager
> >Michael Arabatzis AVEE - Hellenic Dough
> >
> >To reply by private e-mail type replace invalid with gr
> >
>> The sample could be fixed and imaged directly in SEM to view and count
> Salmonella organisms.
>>> Gary Gaugler, Ph.D.
> Microtechnics, Inc.
> Granite Bay, CA 95746
> 916.791.8191
>gary at microtechnics dot com
I'm afraid electron microscopy is not an option for day to day testing in a
food factory lab.
Kostas
Kostas Polyzonis
QA Manager
Michael Arabatzis AVEE - Hellenic Dough
To reply by private e-mail type replace invalid with gr
