Title: "Rapid" (alternative) methods for evaluation of fish freshness and quality

Author(s): Lillian Chebet
University thesis
Year of publication:
University of Akureyri
Place of publication:
Number of pages:
Document URL: Link
Supervisors: Hjorleifur Einarsson
Rapid methods; fish freshness; redox potential dyes and electrodes; resazurin.


The quality of fish and fishery products is a major concern in fish industry worldwide. Traditional methods for fish assessment are associated with various limitations characterized by; delays, cost implication less accuracy and for sensory methods, psychological and physiological limitations of analysts posse challenges to fish industry. The aim of this thesis was to select, test simple, cheap and “rapid” (alternative) methods for evaluation of fish freshness and quality at landing sites. The measurement of Redox potential (Eh); Dye Reduction Time (DRT), ATP and pH were chosen for this  purpose. These methods were assessed using bacterial cultures and cod fillets in a model system and; field trials of method on Lake Victorian Nile perch (Lates niloticus) and cod (Gadus morhua) were conducted. The results of the measurement of DRT, ATP and Eh demonstrated a high feasibility of application for assessment of fish quality. Regression analysis of DRT; ATP showed a significant correlation coefficient, r was = 0.8 with the spread plate counts in cod fillets. The measurement of Eh demonstrated real-time result on spoilt fish with Eh 0 mV; with varying initial Eh value of high quality fish (between +100-+300 mV) but does not give an account of the marginal levels of quality deterioration. High bacterial numbers (> 7log CFU/g) are required to cause a significant change in Eh of fish. However, swab method of measuring ATP showed unreliable ATP values; pH as well demonstrated unreliable results.

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