Dear colleagues,
In my experience I have observed a "drift" in preference, of trained and
experienced sensory evaluators, from "eating/ smelling" to physical
assessment (view an tactile assessment). Of course, in a systematic
evaluation you expect all the aspects be given equal weight in an
assessment, but you can not avoid the fact you see and touch the shrimp
before to smell or eat it (particularly if you have also to prepare the
cooked sample).
I have observed this behavior of assessors not only in fish but also in a
cracker and biscuit industry. Line quality controllers tested the biscuits
with their hands, and then throw them away without to taste or smell them.
When I asked them about, they told me that as a matter of fact, the whole
procedure included to eat a piece of the biscuit, but that they have found
that this was not necessary (they told me that at the beginning of their
career they did). In the case of biscuits (even if definitively it is not my
field) it seems that there is some consensus in the value of the noise and
resistance to break.
It is natural (human) you see and touch the food (even through a fork and
knife) before to smell or to take it to the mouth. If for some reason the
"sample" does not pass the first step hardly will pass the second. This
means that in most cases (particularly when you are very well trained) you
already has (consciously or unconsciously) an assessment of the sample
before you smell it or take it to your mouth (only by seeing and touching).
Of course it may happens that physical attributes alone mislaid your
judgment.
Fish port inspectors in general perform an overall integrated physical
assessment of landed fish (sometimes they do not touch even the fish),
sampling are done (in some countries) only for verification purposes; and
this is in general accepted. Of course problems appear when samples taken
from a rejected batch appear OK with regulations. As consumer I would like
to say that there could be always a nice apple in a barrel plenty of rotten
apples. However, this could be an additional problem in fish assessment, if
the person in charge of the sensory assessment of the sample at the lab,
knows the whole original batch (and has already a judgment of it,
consciously or unconsciously). This is a problem that appear very often in
some industries, where sensory (and instrumental) analysis are utilized to
ascertain borderline fitness of raw materials that otherwise would be
rejected at first sight.
Finally, and this is in line with Peter observation of people that do not
like to perform sensory assessments; there a number of people that do not
like shrimp (or even lobster). It is not clear why the people do not like to
eat shrimp (otherwise religious reasons) but it seems to exist some
(subconscious?) association with eating insects. I have tested roasted and
fried insects (reasonably safe cooking temperature and in countries where
this is an accepted practice) and I would say that could be some basis for
this. Perhaps there is some (unconscious?) threshold for this rejection
sensation.
Many things, and I know that are specialists in this area. In any case it is
a fascinating and truly important field, in more than one aspect. Just to
think that the decision to put any food in our mouth is the last "risk
management" decision, before things be OK or become a food outbreak.
Hector M. Lupin
Senior Fishery Industry Officer (Quality Assurance)
Fish Utilization and Marketing Service
Fishery Industries Division / FAO of the UN
Viale delle Terme de Caracalla 00100 Rome Italy
Tel.: +39 06 570 56459 Fax: + 39 06 570 55188
E-mail: hector.lupin@fao.org
Please visit our website: http://www.fao.org
-----Original Message-----
From: Stephen Thompson [mailto:stephen.thompson3@verizon.net]
Sent: 22 May 2004 22:01
To: 'howgate'; 'Francisco Camino'; seafood@ucdavis.edu
Subject: RE: Oragnoleptical testing in shrimps
Francisco, Peter, et al.
In our experience, we have seen a form of what Peter describes as
"adaptation" but would more accurately call it "fatigue". Fatigue occurs
when the same or similar products are evaluated daily over weeks at a time.
It applies specifically to the detection of odor variations. The individual
becomes "tired" and is less able to detect the variation in slight odor
profiles. It has been suggested that female sensory evaluators are more
prone to "fatigue" than males and that age may play a role. We found that
allowing time off from sensory evaluation and regular calibration exercises
were helpful in maintaining consistent results among evaluators.
I must agree that 20 samples per day should not affect an evaluators
"sensitivity". Fatigue is found with continual and repetitious evaluation
of the same product.
Stephen
Stephen Thompson
Seafood Quality Systems, LLC
Westport, MA USA
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf
Of howgate
Sent: Friday, May 21, 2004 4:20 PM
To: Francisco Camino; seafood@ucdavis.edu
Subject: Re: Oragnoleptical testing in shrimps
Dear Francisco, and others
You ask if assessing by taste 20 samples of shrimp in a day is likely to
result in a loss of 'sensitivity'. In my experience of sensory evaluation of
fishery products, quite considerable, I would answer no, but with one or two
reservations. I recall visiting a fish factory and speaking to the leader of
the quality control team who told me that the quality controllers might
taste up to 100 samples in a 7-hour shift. The company relied very heavily
on sensory evaluation of raw and cooked samples for quality assurance for a
demanding customer. In my laboratory, where I ran all of the sensory panels,
it was customary to evaluate by taste up to 12 samples in a session and up
to 3 sessions a day at busy times. We maintained statistical monitoring of
performance and there was no suggestion that performance was affected by
work load. Evaluation of 20 cooked samples for flavour/taste in a day is not
many for an experienced assessor.
The reservations relate to what is being evaluated and for what, and the
experience and motivation of the assessor. There are a few compounds in fish
which might affect odour receptors such as to reduce sensitivity. By this I
mean exposure to the compound will result in the lowered perception of the
intensity of the odour in subsequent evaluations of similar products -
adaptation in the sensory jargon. One such compound, for example, is
cis-4-heptenal which is the characteristic odour of cold-stored non-fatty
fish. There is one report, (Bett, K.L. & Johnsen, P.B., 1996. Challenges of
evaluating sensory attributes in the presence of off-flavours ( geosmin and
2-methylisoborneol ). Journal of Sensory Studies, 11, 1-17), that
methylisoborneol (MIB), one of the compounds responsible for earthy/musty
flavours in freshwater fish and crustacea induces adaptation in assessors,
but I conducted a comprehensive review of sensory properties of these
compounds about a year ago and this was the only reference to adaptation by
these chemicals I came across. I haven't conducted any systematic evaluation
of MIB to confirm this myself. If it is suspected that a chemical causes
adaptation, (and it is not easy to demonstrate the effect), then I would
recommend a slow pace of evaluation and the use of a palate cleanser such as
a plain unsweetened biscuit, (cracker), between samples. (I don't consider
palate cleansers are required for routine evaluation of fishery products
other than rancid products). Some flavours, for example rancid flavours of
fatty fish, can persist in the mouth and might confuse assessment of a
subsequent sample, but this is not the same as adaptation.
Another reservation concerns the experience and motivation of the assessor.
Very few people can not be trained to be good assessors for evaluating
sensory properties of fishery products. Over very many years of training and
selection of would-be assessors I have rarely had to reject a candidate
because he or she could not do the job. Usually the reason for rejecting a
candidate was because the person was unwilling to do the job. It is very
easy to get yourself off a sensory panel - just give erratic assessments. If
an assessor seems to be becoming less precise, or less accurate - these are
not the same thing - during the day I would first suspect boredom rather
than loss of sensitivity. If a person's job requires that the person
evaluates sensory properties of the products, then that can be a powerful
motivating factor.
Peter Howgate
----- Original Message -----
From: "Francisco Camino" <frankcamino@yahoo.com>
To: <seafood@ucdavis.edu>
Sent: Friday, May 21, 2004 7:49 PM
Subject: Oragnoleptical testing in shrimps
Dear Colleagues:
Some sensorial specialists can tell me if a technician
that make sensorial testing in shrimps, can loss
sensibility for correct sensorial testings,
considering that he or she does about 20 testings per
day. Please consider also that he or she tastes
samples of different origin (samples from low salinity
and presence of cianophytas, samples with mud taste,
samples with characterict taste, samples from high
salinity, etc.).
Please I would receive your comments.
Best regards,
Francisco Camino
Expack Seafood, Inc.
Brazil
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