Hello,
Oxygen absorbers are an interesting issue in vacuum packing and for
foodstuffs under modified atmosphere. The pouches generally contain iron
oxide which binds the remaining oxygen. The are however some issues to be
considered.
When packing a frozen product air may be contained in the product or the
ice. This will not be removed with the application of vacuum to the package
before sealing. An oxygen scavenger may offer some help here. However most
products are packed fresh than oxygen scavengers do not solve this problem.
These oxygen scavenger packings are very expensive and before they are to be
used some checks have to be performed to see if the seal of the packing is
hermetically closed, before you remedy the problem with oxygen scavengers.
In most instances the seals are not as good as one thinks. The seals seem to
keep the ambient air from entering the package, but due to pollution of the
sealing surface with fats and proteins, this is not the case, and micro
leaks may occur, through which oxygen may till be able to enter the package.
In such instances an oxygen scavengers may seem to solve the problem, but a
cheaper solution is to get better sealing. I have seen particular problems
with sealing with cod, fat fish as eel and salmon and pork meat.
With modiefied atmosphere packing you could do the following test to see
what is happening:
Seal 50 clean trays without any product. Vacumize and fill with the required
gas mixture. Subsequently seal 50 trays in the same way, but the sealing
surface of these trays has been polluted by rubbing them briefly with a fish
fillet. Measure residue oxygen levels of 25 trays of each batch. The residue
oxygen levels should be 0,1% O2. Measure residue oxygen levels after 3 days
again on the other 2 batches of 25 and plot in a graph.
When your foil quality is right and the seal temparatures are right (you
could even do some tests at different sealing temperatures and times) there
should be only slight differences in the residue oxyen measurements of the
clean and the polluted trays. However my experience has learned me that per
closing film manufacturer there are huge differences in these measurements
indicating the precence of micro leaks of slightly polluted sealing
surfaces.
As you understand oxygen scavenger will help to solve this problem, but the
problem can also be approached by testing the sealing films or bags more
closely. We changed sealing film manufacturer and found that even polluted
sealing surfaces could be hermetically sealed, reducing the need for oxygen
scavengers.
Regards
Evert Liewes
----- Original Message -----
From: "A.J Simpson" <asimpson@phillipsfoods.com>
To: <seafood@ucdavis.edu>
Sent: Wednesday, November 19, 2003 1:50 AM
Subject: Fish Pack Oxygen Absorber
>
> I just received a report regarding the following practice which I haven't
> heard of before.
>
> >" While in a fish factory last week we saw them placing a aluminium pouch
> >that was one inch by one inch square and rather flat into a plastic bag
> >with a single salmon skinless fillet from about a 3kg fish that was to be
> >sealed. They explained that the small aluminium pouch was an oxygen
> >absorber that helped to keep the fish from turning brown."
>
> Could anybody comment as to the contents of the "aluminium pouch" and how
> this works ? I am curious as to why anybody would consider this necesary
if
> they have a bag with good oxygen permeability barrier. I guess it would
> depend on the intended shelflife of the product ?
>
> Regards / Adrian Simpson
>
>
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