Development of a Quality Index Method Scheme for Sensory Assessment of Chilled Yellowfin Tuna

Quality monitoring and/or assessment are parts of a freshness/quality control system, which is of utmost importance for fresh seafood, especially Scombridae fish. The quality index method (QIM) is a simple, convenient, unique, and reliable tool to determine the sensory status and estimate the remaining shelf life of aqua products. This study aimed to develop a QIM scheme for chilled stored yellowfin tuna and apply the protocol in the fish quality evaluation and storage time estimation. Eight gutted yellowfin tuna of 20, 30, and 40 kg up were used in the study. Five panelists participated in the QIM development, training and application. Control and/or validation analyses were sensory assessment by a control sheet, total volatile basic nitrogen (TVB-N) quantification, and total viable count (TVC) determination. Chilled storage of tuna was performed in liquid ice and traditional crushed block ice. Partial least square regression (PLS-R) was conducted on quality index (QI) dataset over storage time to find the regression line and prediction accuracy. The established QIM protocol for gutted yellowfin tuna comprised 6 attributes (namely, color of whole fish, odor of whole fish and flesh, eyes, appearance of whole fish, flesh color and flesh texture) and a maximal QI of 15. The PLS-R showed that QI could be used to estimate the remaining time with a precision of ± 2.0 and 1.4 days for fish stored in slurry ice and crushed ice, respectively. The TVB-N content in the fish flesh maintained below the acceptable level of 25 mg N/100 g throughout the storage period, which made the parameter impractical to detect the fish shelf life. The TVC overreached the allowable level of 107 CFU/g around the time of fish rejection by the sensory method. The developed QIM scheme for yellowfin tuna showed to be more advantageous in detecting fish quality changes compared to the control sensory method and could be used to estimate the fish's remaining shelf life.