COMPOSITIONAL, ELEMENTAL, AND STRUCTURAL CHARACTERIZATION OF THE OPERCULUM OF RAPANA VENOSA FROM THE BLACK SEA

The veined rapa whelk (Rapana venosa) is an economically important invasive species in the Black Sea, whose processing generates considerable amounts of by-products, including the operculum. Despite its abundance, the operculum has received limited scientific attention. This study aimed to characterize the R. venosa operculum by evaluating its nutritional composition, amino acid profile, elemental content, heavy metal levels, and structural features. Proximate analysis indicated that the operculum is a dense biological material with low moisture and lipid contents, but high protein (57.30%) and ash (15.12%) levels. Amino acid analysis identified 17 amino acids dominated by non-essential amino acids, particularly glycine, alanine, glutamic acid, and proline, which are typically associated with structural and connective proteins. ICP-MS analysis revealed calcium as the dominant macroelement, followed by magnesium, sodium, and phosphorus, consistent with calcium carbonate–based biomineralization. Lead, cadmium, and arsenic were detected at measurable concentrations, whereas mercury, antimony, thallium, and uranium occurred at low levels. Lead and cadmium concentrations exceeded the regulatory limits established for edible tissues. FTIR analysis confirmed a predominantly calcium carbonate–rich structure with limited organic contributions. Taken together, these findings provide a detailed compositional and structural insight into the R. venosa operculum, establishing a scientific basis for its consideration as a value-added marine by-product in future research and industrial applications.