Comparative effects of sous vide, boiling, and frying on Antarctic krill proteins: links between oxidation, structural changes, in vitro digestibility, and peptidomic profiles.

Antarctic krill (Euphausia superba) is a sustainable but underutilized marine protein, whose industrial application is severely limited by thermal-induced quality deterioration. This study systematically elucidated the mechanisms by which specific culinary treatment regimes-sous vide (SV, 50 °C), boiling (BO, 100 °C), and frying (FRY, 170 °C)-dictate the physicochemical properties, structural conformation, and in vitro gastrointestinal digestibility of krill muscle. The results demonstrated that SV processing effectively minimized protein oxidation and conformational shifts, preserving a tender texture and ensuring low cooking loss. Conversely, severe thermal treatments (BO and FRY) triggered intensive oxidation, significant α-helix to β-sheet transitions, and severe macroscopic aggregation, collectively resulting in structural hardening and decreased liquid retention. Crucially, peptidomic profiling revealed that structural modifications directly governed protein bioaccessibility. SV processing facilitated efficient proteolytic cleavage, yielding a highly diverse and bioaccessible peptide profile (164 peptides, predominantly lower-molecular-weight fragments) and maximizing the release of tropomyosin-derived peptides. In contrast, severe aggregation caused by the FRY treatment sterically hindered enzymatic access, drastically restricting peptide diversity (84 peptides) and yielding larger resistant fragments. Multivariate correlation analysis confirmed that advanced thermal damage indicators (e.g., redness and surface hydrophobicity) were significantly inversely correlated with digestibility. The differences in digestibility were associated with cooking-induced changes in protein oxidation, aggregation, and structural organization. Collectively, under the processing conditions investigated, sous-vide treatment was associated with lower protein oxidation, relatively limited structural disruption, and higher in vitro gastrointestinal digestibility than the more intensive thermal treatments. The present findings provide a basis for evaluating the effects of cooking conditions on the digestive behavior of Antarctic krill proteins.