Effects of Sun Drying Versus Vacuum Freeze-Drying on the Protein Quality of Hippocampus abdominalis: Nutritional Composition, Physicochemical Properties, and Proteomic Profiles

Drying is an important processing method for extending the shelf life of aquatic products; however, different drying methods may exert distinct effects on protein quality. At present, the effects of sun drying and vacuum freeze-drying on the protein quality of Hippocampus abdominalis remain unclear. This study compared the protein content, amino acid composition, and physicochemical properties of Hippocampus abdominalis subjected to the two drying methods and further characterized changes in the proteomic profile using proteomic analysis. The results showed that the sun-dried group had a higher crude protein content (68.57% vs. 61.86%), whereas the freeze-dried group exhibited greater total amino acid retention (58.79% vs. 48.87%), water-holding capacity(WHC), and oil-holding capacity(OHC). However, no significant differences were observed in protein solubility or surface hydrophobicity between the two groups. Proteomic analysis further revealed that most differentially abundant proteins showed higher relative abundance in the freeze-dried group and were mainly associated with muscle structural stability, amino acid metabolism, and energy metabolism. Overall, the two drying methods affected the protein quality of Hippocampus abdominalis at multiple levels, including nutritional composition and physicochemical properties, while proteomic analysis provided further molecular-level insights into these quality differences.