Sensory and flavor profiles as a means of assessing freshness of hake (Merluccius merluccius) during ice storage

Freshness of hake stored in ice was evaluated by sensory and instrumental means. The European Union scheme and the quality index method (QIM) were used to sensorially index freshness. Aroma extract dilution analysis (AEDA) and SPME-headspace determinations were applied to monitor important odorants of hake at different freshness stages. Based on AEDA, potent odorants of hake in the very fresh state were (Z)-1,5-octadien-3-one and 3 unknown volatiles. Attempts were made to relate overall odor changes to individual volatiles: after 2 days storage, the higher FD-factors found for trans-4,5-epoxy-(E)-2-decenal, (Z)-4-heptenal, methional, and 2-acetyl-1-pyrroline were associated with the “masking” of the seaweed character, whereas the higher concentrations of (Z)-1,5-octadien-3-one and (Z)-4-heptenal in hake that reached the B grade were likely responsible for the pungent odor. No highly volatile odorants were detected in hake using SPME-headspace analysis, but in contrast to AEDA, the odor intensity of some volatiles, e.g., (E,Z)-2,6-nonadienal and 3-methylnonane-2,4-dione indicated a higher contribution. The detection of two low boiling odorants associated with fresh fish flavor is reported for the first time.