Influence of Drying Techniques on Flavor Profile and Related Physicochemical Properties of Semi-dried Trachinotus ovatus

The aim of this study was to evaluate the effects of sunlight exposure and drying temperature on the flavor profile and related physicochemical properties of semi-dried Trachinotus ovatus, with a view to providing insights into optimal drying technique. Five drying treatments were applied: sunlight drying, hot-air drying at 60 ℃, heat pump drying at 20 ℃, combined sunlight/heat pump drying at 20 ℃, and sunlight/heat pump drying with variable-temperature. The sample analysis included content assessment of total volatile basic nitrogen (TVB-N) and malondialdehyde (MDA), identification of volatile compounds through headspace solid-phase microextraction GC-MS, screening of characteristic flavor compounds based on OAV value, and categorization of flavor profile via clustering heatmap. Finaly, the optimal drying technique was identified by principal component analysis (PCA). Results showed that the sunlight drying and hot-air drying groups exhibited elevated levels of TVB-N and MDA, characterised by a rich bouquet but also containing pungent and undesirable odours. In contrast, compared with the sunlight drying and hot-air drying groups, the three groups treated with heat pump drying showed more than 13% and 55% decrease on TVB-N and MDA respectively, and relatively weak flavors. Meanwhile, the total relative contents for key flavor contributors of alcohols, aldehydes and ketones were as follows: sunlight/heat pump drying with variable-temperature>combined sunlight/heat pump drying at 20 ℃>heat pump drying at 20 ℃. Furthermore, the cluster heatmap demonstrated that, in comparison with hot air drying, the flavor of semi-dried Trachinotus ovatus dried by the three groups of heat pumps was more analogous to that of sun-drying. The highest PCA score was obtained in the group of sunlight/heat pump drying with variable-temperature. In summary, this finding suggests that low temperatures are conducive to preserving the quality of semi-dried Trachinotus ovatus, and reducing the production of unpleasant odors. Besides, the appropriate levels of heat and light can promote the formation of flavor substances. Among the five sample groups, the semi-dried Trachinotus ovatus with the best comprehensive flavor and related physicochemical properties was the group of sunlight/heat pump drying with variable-temperature.