Characteristics analysis of microstructure and physicochemical properties of fresh and water-soaked fish maws derived from various swim bladder species

Fish maw, a traditional nutritious food, has significant development potential. However, the limited species sources and scarce research on processing characteristics present challenges. This study selected nine species of fish maws to determine their morphology and yield during hydrothermal treatment. Changes in nutritional composition, water migration, and structural characteristics between fresh and water-soaked fish maws were compared. All fresh fish maws had a dry basis protein content of more than 80 %, with no heavy metals, rich in functional and hydrophobic amino acids. After processing fresh fish maw into water-soaked fish maw, the fat and ash content decreased, while the relative protein content increased, and there was little change in the amino acid composition. Water distribution and texture properties indicated an initial rapid then slow water absorption rate for fish maw. After soaking, most bound and immobilized water transformed into free water, significantly enhancing cohesiveness, springiness, and chewiness. Hardness change varied among different species of fish maws due to inherent differences. Microstructural analysis revealed that the fiber bundle transitioned from an interlaced, tight structure to a porous network structure, with pore size and network distribution related to water migration and the texture characteristics of the fish maw. Among all species studied, freshwater silver carp and redfin culter fish maws demonstrated potential for further development.