Determination of volatile bases in seafood using the ammonia ion selective electrode: collaborative study

Area of Science:

• Food Science
• Analytical Chemistry
• Seafood Quality Assessment

Background:

• Volatile bases, including ammonia and trimethylamine, are key indicators of seafood spoilage.
• Accurate quantification of these compounds is crucial for assessing fish freshness and safety.
• Existing methods may not fully capture the range of volatile bases present in seafood.

Purpose of the Study:

• To evaluate the performance of an ammonia ion-selective electrode method for determining volatile bases in seafood.
• To assess the method's accuracy, repeatability, and reproducibility across different seafood types and spoilage levels.

Main Methods:

• Nine laboratories collaboratively tested 23 seafood samples using an ammonia ion-selective electrode.
• Samples included seven species (cod, squid, halibut, sole, monkfish, dogfish, mackerel) ranging from fresh to spoiled.
• The assay involved homogenizing samples with water and an alkaline solution, then measuring liberated ammonia with a precalibrated portable meter.

Main Results:

• The method measured both ammonia and trimethylamine, reported as mg NH3/100 g fish.
• Repeatability standard deviations (RSDr) ranged from 4.2% to 17%, and reproducibility standard deviations (RSDR) ranged from 8.8% to 21%.
• Recoveries of spiked ammonium chloride were 88.6% (fresh), 107% (borderline), and 128% (spoiled) samples.

Conclusions:

• The ammonia ion-selective electrode method provides a reliable approach for quantifying volatile bases in seafood.
• The method demonstrates acceptable precision for assessing seafood quality across various spoilage stages.
• This technique can be valuable for routine quality control in the seafood industry.