Dear Richard
I suppose the first question to ask is how does the client know the product
is oxidising? If the pack is truly a vacuum pack, where is the oxygen coming
from to cause oxidation? If it is a chemically induced oxidation involving
an oxygen-containing compound rather than gaseous oxygen, then I can not
visualise a packaging that will prevent the oxidation. I can not see how a
gas-flushed package containing 40% oxygen can be better than
vacuum-packaging in preventing oxidation. Usually products produced by
pickle salting, where the product is maintained below the surface of the
brine, does not develop oxidative rancidity during the pickling stage; I
note you report that your client's product does develop rancidity in
'traditional wooden tubs' and I wonder if the problem resides in the salting
process.
Are you sure your client really is measuring oxidation rather than a
microbiological spoilage effect? 14% salt content in the water phase is not
very high, Aw about 0.93, and not sufficient to inhibit microbiological
spoilage by salt-tolerant microorganisms.
Peter Howgate
----- Original Message -----
From: "Richard Chivers" <richardchivers@btconnect.com>
To: "seafood" <seafood@ucdavis.edu>
Sent: Thursday, December 19, 2002 12:00 PM
Subject: vacuum packing to prevent oxidation
>
> A client of mine produces a pilchard product with a salt content in the
> water phase of 14%, either whole or in fillets. He wishes to pack these
in
> a vacuum pack that will prevent oxidation. What he has found is that
> regardless of vacuum packing in the normal manner, light and heat will
still
> cause oxidation.
>
> He is trying gas flushing with 60% nitrogen and 40% oxygen in pouches that
> comply with the standard Din 53380 Part 3 . The product is to last for up
> to 4 months at chilled temperatures and then one month at ambient. In
> traditional wooden tubs the product will do this although rancidity does
> develop.
>
> Can anyone advise on a gas mix or pouch that would maintain quality by
> reducing the rate of oxidation in this product.
>
> Richard Chivers
>
>
>
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