Standardization of the Ammonia Electrode....
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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


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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