Hi Lisa,
You may be interested in a paper we published a few years ago comparing
various methods to determine shrimp quality (see citation below). Our
results (pH rise from 6.5 to 8.0) were similar to what you found with
prawns. I can't offer an explanation for the Egyptian quality standard.
Marshall, D.L. and P.L.W. Lehigh. 1997. Comparison of impedance,
microbial, sensory, and pH methods to determine shrimp quality. Journal of
Aquatic Food Product Technology 6(2):17-31.
Doug
********************************************
Douglas L. Marshall, Ph.D.
Professor & Food Scientist
Department of Food Science & Technology
Mississippi State University
Box 9805
Mississippi State, MS 39762-9805 USA
Ph 662-325-8722
Fax 662-325-8728
http://www.msstate.edu/dept/fst/Homepage
********************************************
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu]On
Behalf Of LMCKENZIE
Sent: Monday, August 14, 2000 2:00 PM
To: Seafood Group (E-mail)
Subject: Ph levels of Aust. prawns
I have had a request to post the results of my inquires into the Ph levels
of prawn.
The tests were carried out were on Frozen King prawns that had been treated
with Sodium Metabisulphite with shell on. I'm told this will reduce the Ph
slightly. Quarterly testing of this product shows an S02 level in the flesh
of typically <10 PPM.
Results of Ph testing in 6 samples were as follows: 6.5, 6.8, 7.0, 7.0, 7.0,
and 7.2. Method of testing was per Pearson's' Chemical Analysis of Food 8th
Edition, although this method is not mentioned as being particularly for
seafood. The 6.5 result was achieved through direct insertion of probe into
the prawn as there is sufficient moisture to test by this method, the other
results were achieved by mincing the flesh as per the customers request.
>From literature received it seems the Ph level of prawns can be expected to
be around 6.8 to 7.0 with readings around 8.0 for product at the end of its
shelf life.
Other testing carried out on the same prawn - plate count, TVNs would
suggest the sample was of good quality prawn.
What I am really curious about is if anyone can tell me why the Egyptian
import standard states that prawn needs to have a Ph level of <5.97?
Lisa McKenzie
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