Sensory and biochemical aspects of quality of whole bigeye tuna (Thunnus obesus) during bulk storage in controlled atmospheres

The quality of whole ungutted bigeye tuna (Thunnus obesus) during bulk storage in controlled atmospheres containing either of two gas mixes (60%CO2/15%O2/25%N2 and 40%CO2/40%O2/20%N2) was evaluated by biochemical and sensory changes. At day 33 of storage, none of the lots were rejected on the basis of the target biochemical indices (pH, trimethylamine nitrogen (TMA-N), total volatile base nitrogen (TVB-N) and histamine) or the tasting panel scores. However, the control and the controlled atmosphere-stored lots were rejected upon inspection at 13 and 22 days, respectively. Scores for the various target biochemical parameters were highest (p<0.05) in the control, followed by the lot stored in gas mix two, which had the lower CO2 concentration. There were changes (p<0.05) in the levels of biogenic amines (tyramine, histamine, cadaverine and agmatine) in the course of storage, but pH, TMA-N and TVB-N remained constant. Histamine levels exceeded 100 μg/g for the control fish and in gas mix one towards the end of storage. Histamine, cadaverine and agmatine could be used as quality indices for tuna stored in ice and atmospheres. Cadaverine and agmatine could also be used as freshness indices.