Functional and physiochemical properties of protein isolates from different body parts of North Atlantic sea cucumber (Cucumaria frondosa)

Sea cucumbers are a good source of proteins and essential amino acids. In this study, protein isolates were recovered from North Atlantic sea cucumber (Cucumaria frondosa) body wall (BWI) and processing by-products, including flower (FLI) and internal organs (INI), using the pH-shift method. Functional properties of protein isolates were investigated and compared with those of soy protein isolates (SPI). All protein isolates exhibited a typical U-shaped solubility curve showing a minimum solubility at their isoelectric points. Furthermore, emulsification and foaming properties of the sea cucumber protein isolates were also pH-dependent and corresponded with their solubility. The highest water holding capacity was observed in FLI, whereas SPI showed the lowest oil holding capacity among all tested protein isolates. Sea cucumber protein isolates exhibited significantly higher (p < 0.05) surface hydrophobicity and relatively lower sulfhydryl (SH) group and disulfide (SS) bonds compared to SPI. In addition, Fourier transform infrared (FTIR) spectra of sea cucumber protein isolates exhibited unique absorption peaks related to their secondary structures. Amino acid profiles of sea cucumber protein isolates revealed that they could be used as rich and complete sources of essential amino acids. These findings suggest that Atlantic sea cucumber protein isolates could serve as functional food ingredients.