Characterization of Protein Isolate from the Swim Bladder of Giant Catfish Obtained via Alkaline Extraction Method

The swim bladder, or air bladder, is an internal gas-filled organ commonly found in most large marine fish, including the giant catfish (Arius thalassinus). During fish processing, the swim bladder is often discarded as a byproduct. Fresh swim bladders contain protein levels ranging from 12–33%, and when dried, they are marketed as fish maw. Fish maw has significant potential to be further processed into a high-value fish protein isolate (FPI). This study aimed to produce and characterize protein isolate derived from the fish maw of A. thalassinus using the alkaline extraction method. The results showed that fish maw flour contains 11.20% moisture, 85.3% protein, 0.94% ash, 0.94% fat, and 1.59% carbohydrates. It is also a rich source of amino acids, including glycine (16.6%), L-proline (9.4%), L-alanine (8%), L-arginine (8%), L-glutamic acid (8.1%), and L-threonine (4%). The FPI produced via the alkaline extraction method exhibited a protein content of 91%, with solubility of 66.94% in water, 56.65% in acidic solvents, and 80.64% in basic solvents. Additionally, the FPI demonstrated a water-holding capacity of 1.44 ± 0.09 g/g and an oil-holding capacity of 0.54 ± 0.05 g/g.