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GRANT
NUMBER:
NA76FD0140
NMFS NUMBER: 96-NER-013
REPORT
TITLE:
Standardization of the Ammonia Electrode Method
for the Evaluation of Seafood Quality by Correlation to
Sensory Analysis
AUTHOR:
Lori F. Pivarnik, P. Christopher Ellis, and Terri Reilly
PUBLISH
DATE: March
29, 2000
AVAILABLE
FROM: National
Marine Fisheries Service, Northeast Region, One Blackburn
Drive, Gloucester, Massachusetts 01930. TELEPHONE:
(978) 281-9267
ABSTRACT
The
goal of this project was to validate the ammonia ion-selective
electrode for determination of seafood quality by correlation
to expert sensory assessment. Ammonia ion-selective
(ISE) measurements, reported as apparent ammonia, were
successfully correlated to expert sensory assessment on
six different fish species stored on ice and held at room
temperature. At both storage temperatures, TVB-N,
TMA-N, and apparent ammonia clearly showed the same development
trend over the storage periods. ISE measurements
mirrored TVB concentrations with a correlation of TVB
with ISE at r2=0.92. The pattern of change
of the sensory scores also followed the same general trend
as the chemical tests. Initial statistical analysis
on the samples showed a correlation of r and r2
of 0.74 and 0.54, respectively, with an ISE value of over
22 corresponding to sensory failure. However, with
advanced fish spoilage, the ISE measurements became more
erratic. Therefore, to eliminate the impact of badly
spoiled fish, final regression was conducted on samples
containing <30mg/100g apparent ammonia with sensory
values ranging from 11 to 88. This resulted in an
r and r2 between sensory scores and ISE measurements
of 0.88 and 0.77, respectively. Regression analysis
predicted a value of 19.6 mg/100g of apparent ammonia
in fish tissue at the sensory limit of 50, regardless
of storage conditions. All of the samples tested
showed that the measurement of apparent ammonia with the
ISE procedure could be used as a predictor of borderline
quality and decomposition based on expert sensory determinations.
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