Fish Processing and Digestion Affect Parvalbumins Detectability in Gilthead Seabream and European Seabass

SIMPLE SUMMARY: Fish provides high nutritional value in human diets but may trigger severe allergenic reactions, which result from a hypersensitive response of the immune system. Due to several allergenic proteins, and especially to parvalbumin, consumers with a known fish allergy must avoid any product that might contain this protein. This study focused on the characterization of parvalbumin in gilthead seabream and European seabass. Using mass spectrometry and circular dichroism, parvalbumins primary (sequence) and secondary structures were determined, respectively. Furthermore, parvalbumin was detected by sandwich enzyme-linked immunosorbent assay after gastrointestinal digestion and fish processing techniques. Parvalbumin—presented as α-helices and β-sheets, at room temperature—was detected at lower levels during gastrointestinal digestion. Several processing techniques showed a significant reduction (p < 0.05) in parvalbumin detectability, in comparison to raw muscle samples from gilthead seabream and European seabass. Therefore, we concluded that parvalbumins from both species are susceptible to digestion and processing. These results demonstrate that these techniques can be used in parvalbumin modulation and may be an important contribution to further studies on fish allergenicity. ABSTRACT: Consumption of aquatic food, including fish, accounts for 17% of animal protein intake. However, fish consumption might also result in several side-effects such as sneezing, swelling and anaphylaxis in sensitized consumers. Fish allergy is an immune reaction to allergenic proteins in the fish muscle, for instance parvalbumin (PV), considered the major fish allergen. In this study, we characterize PV in two economically important fish species for southern European aquaculture, namely gilthead seabream and European seabass, to understand its stability during in vitro digestion and fish processing. This information is crucial for future studies on the allergenicity of processed fish products. PVs were extracted from fish muscles, identified by mass spectrometry (MS), and detected by sandwich enzyme-linked immunosorbent assay (ELISA) after simulated digestion and various food processing treatments. Secondary structures were determined by circular dichroism (CD) after purification by anion exchange and gel filtration chromatography. In both species, PVs presented as α-helical and β-sheet structures, at room temperature, were shown to unfold at boiling temperatures. In European seabass, PV detectability decreased during the simulated digestion and after 240 min (intestinal phase) no detection was observed, while steaming showed a decrease (p < 0.05) in PVs detectability in comparison to raw muscle samples, for both species. Additionally, freezing (−20 °C) for up to 12 months continued to reduce the detectability of PV in tested processing techniques. We concluded that PVs from both species are susceptible to digestion and processing techniques such as steaming and freezing. Our study obtained preliminary results for further research on the allergenic potential of PV after digestion and processing.