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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