Effects of different drying methods on the flavor of Trachinotus ovatus fillets

In order to explore the difference in flavor of dried Trachinotus ovatus fillets with different drying methods, chilled T. ovatus fillets were selected as raw materials in this study. Three drying method were applied in the drying process, including hot air drying, heat pump drying, and freeze drying and the TBA value, nucleotide content, free amino acid content, and volatile flavor substances were measured and analyzed. The results were compared between different drying method groups and the chilled fish group. The results showed that the TBA value and K value of the T. ovatus fillets increased significantly after drying. The TBA value of freeze dried fish was only 1.6 times higher than that of chilled fish fillets, but heat pump drying and hot air drying increased the figure by 5.5 and 4.5 times respectively. After drying, the total free amino acid content and MSG equivalent of the fish were significantly lower than those of the chilled fish fillets. The MSG equivalent of hot air dried fish has dropped by 50.83%. The bitter amino acid content and the umami amino acid content in the heat pump dried fish accounted for 19.11% and 7.37% of the total amino acid content, respectively. Among the three drying methods, the MSG equivalent of 4.47 g MSG/100 g of heat pump dried T. ovatus fillets is the highest, indicating that the heat pump dried T. ovatus fillets has the highest umami degree. In terms of volatile flavor components, heat pump dried fish contains more esters and ketones, which mainly present the flavors of fruits and roasted nuts. In hot air dried fish, the relative content of hydrocarbons and aromatics is about 70%, and the relative content of aldehydes and esters is 20%. In freeze dried fish, the relative content of hydrocarbons and aromatics accounted for more than 90% of the total, and the aldehyde and esters are less than 8%, so its flavor is relatively weak. In summary, the T. ovatus fillets processed by three drying methods had good eating quality. Among them, heat pump drying makes the umami taste in the fish more obvious. Freeze drying can effectively inhibit the oxidation of fat and is more suitable for the fish with high fat content. This provides a technical reference for the processing of light and dry food for the T. ovatus.