Assessment of the physico-chemical and sensory properties of frozen fillets of tuna and tuna-related fish species marketed along the Tanga and Mtwara coastlines, Tanzania

Tuna and tuna-related fish are valuable marine species lacking standardized quality assessment parameters. This study assessed the physico-chemical and sensory properties of skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus), yellowfin (Thunnus albacares), and kawakawa (Euthynnus affinis) tuna fish fillets marketed in Tanga and Mtwara, Tanzania. Laboratory AOAC methods evaluated total volatile basic-nitrogen (TVB-N), pH, color (lightness L*), and texture (hardness) properties. The quality index method (QIM) assessed tuna fillets' sensory properties (color, texture, and odor). The pH ranged between 5.60 +/- 0.08 and 6.10 +/- 0.30, the TVB-N between 34 +/- 7.00 mg/100 g and 38.04 +/- 10.50 mg/100 g, color lightness (L*) between 24.33 +/- 1.82 and 40.10 +/- 1.50, and texture (hardness) from 3.84 +/- 1.20 N to 8.56 +/- 1.84 N. The tuna fillets got an overall score of 2 in the sensory analysis, which indicated good quality according to the QIM. Furthermore, the present study showed significant differences (p < .05) between the tuna species in pH, hardness (instrumental), and color lightness properties (L*). There were no significant differences (p > .05) in average TVB-N results across all tuna fillets. There were significant correlations among the assessed quality properties. Based on the combined quality properties results and correlation analysis, the tuna and tuna-related fish marketed in the study areas were of good quality. This study recommends the establishment of standardized quality assessment parameters for tuna and related fish species.