Hi, Peter.
I just wanted to make sure that I didn’t leave the impression that sensory
shouldn’t be used on a production line. It just has some challenges that
can make it more difficult.
I’m a “true believer” when it comes to sensory evaluation. Chemical and
other tests take time and the chemical spoilage indicators can change
depending on the spoilage temperatures and bacteria present.
Klaus Schallié
18192 Claytonwood Crescent
Surrey, BC Canada V3S 8G8
Tel. (604) 576-1879
e-mail schallie1@shaw.ca
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf
Of P Howgate
Sent: March 30, 2007 12:27 PM
To: Surefish Bellingham; seafood@ucdavis.edu
Subject: Re: Decomposition test
I would like to support Hector Lupin's recent comments on the topic of
sensory and non-sensory evaluation of spoilage and add a few comments of my
own. In my many years of experience of meeting quality controllers in
processing plants, discussing quality control with quality controllers
elsewhere, and discussing with other people interested in quality control in
industry I never came across, or heard of, any examples of non-sensory tests
being used in quality control of fish or fishery products in industry for
evaluation of freshness/spoilage other than to meet possible requirements of
regulatory agencies or if required by customers. And examples would be
analysis for indole in shrimp to meet US import requirements when these were
in force. There is very little information about chemical spoilage
indicators in crab meat and I am not aware of any proposed criteria for any
chemical tests. Though indole has been suggested as an indicator of spoilage
for shrimp and prawns it has not been demonstrated to be an effective index.
There used to be US guidelines for indole in shrimp, but I think these have
been discontinued, though someone closer to the scene can confirm this, or
not. There is an excellent review of indole in shrimp and prawns, including
regulatory aspects, in Oehlenschläger, J. & Luten, J.B. (2005), Review:
Indole as a quality indicator in shrimps and prawns, Archiv für
Lebensmittelhygiene, 56, 52-57.
Studies on TVB as an indicator of spoilage started about 90 years ago, but
it is not an effective chemical index for spoilage in fish despite its
inclusion in EU regulations. Studies and TMA as a measure of spoilage date
from about 80 years ago and though this is a little better than TVB as an
index of spoilage it is still not nearly good enough and I am not aware of
its inclusion in any regulatory requirements. It is certainly of no value
for in-line quality control in industry.
I can not allow Klaus Schallié's comments about the difficulties of using
sensory evaluation in industrial situations to go unchallenged in case it
puts people off using the technique. Though now retired when I was active I
had considerable experience of sensory evaluation of fish and fishery
products in both the research and the industrial situations, though mostly
the former. I was involved in a study of the feasibility and accuracy of
sensory evaluation of raw fish at port markets and there was no suggestion
that the assessors were any less accurate at the port markets than they were
in the laboratory. Though the possible distractions that Klaus might be
present in a particular situation the purpose of training is to ensure that
the assessors can ignore these and give an accurate and precise evaluation
of the sensory properties of the product under examination. There is no
foundation in believing that the assessors would be accurate only with poor
quality fish. My experience of quality control in fish processing plants in
Britain that operated to good quality assurance protocols was that they
relied entirely on sensory procedures for their quality control and quality
assurance, and that was for control limit equivalent to freshness of fish
four days in ice for demersal fish or for frozen fish showing no, or only
negligible, signs of cold storage change. On one occasion I had a group of
quality controllers from a processing plant visit my laboratory for
collaboration with the laboratory panel. They told me that in a working
shift they would assess all batches of fish entering the process by
evaluation in the raw state and during processing samples were frequently
taken from the processing lines and evaluated after cooking. They had a test
kitchen, but that was not fitted out as a centre evaluation facility as
would be found in research institutes. They told me that they evaluated
somewhere in the order of 70 cooked samples a shift. I didn't make any
statistical checks on the performance of the quality controllers compared
with my laboratory panel, but with that degree of experience on a daily
basis I had a sneaking feeling that they would be better than my panel.
I do not understand why people are so afraid of sensory evaluation and wish
to find a chemical substitute. All chemical tests have to be calibrated
against sensory evaluation if they are to prove their worth and none can be
any better than sensory evaluation. Chemical tests are more costly to carry
out and more time-consuming than sensory evaluation and will always be
considered inferior and unreliable substitutes for it. True there is some
overheads in selecting and training quality controllers in sensory
evaluation, but after that there is little extra cost to the company because
they are employing the quality controllers anyway. Don't forget that sensory
evaluation can detect defects that will be missed by chemical tests, for
example taints, and is much closer to the way consumers evaluate the quality
of the product.
Peter Howgate
----- Original Message -----
From: "Surefish Bellingham" <Surefish@az.com>
To: <seafood@ucdavis.edu>
Sent: Thursday, March 29, 2007 4:53 PM
Subject: Decomposition test
Is there any rapid test (other than sensory) for decomposition on a raw
product?
Thanks,
Mark Neely
Surefish, Inc.
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