In vitro digestibility and nutrient bioaccessibility of Brazilian native fish (Tambaqui and sardine), chicken, and...

The nutritional value of muscle food (i.e., edible tissues derived from meat, fish, and poultry) depends not only on raw composition but also on the bioaccessibility of nutrients released during digestion. Static in vitro digestion is widely used to estimate nutrient bioaccessibility, however, comparative data integrating food composition, cooking effects and digestion kinetics remain limited, particularly for native Brazilian fish, despite their growing role in protein supply. In this study, a standardized INFOGEST static in vitro gastrointestinal digestion protocol, combined with complementary analytical approaches (¹H-qNMR, SDS-PAGE, GC-MS, and colorimetric assays), was applied to estimate nutrient bioaccessibility in two native Brazilian fish species (tambaqui and sardine) compared with chicken and beef subjected to common domestic cooking methods. Cooking induced non-linear, species-dependent effects, which were attenuated after static in vitro digestion. Protein-to-amino acid conversion and protein bioaccessibility in the in vitro bioaccessible fraction varied according to species and cooking treatment, with fish generally exhibiting higher values under specific conditions compared with beef and chicken. Multivariate analyses, including principal component analysis (PCA) and Pearson's correlation, revealed clear differences in nutrient bioaccessible fraction after static in vitro digestion under INFOGEST conditions, indicating enhanced enzymatic accessibility in native Brazilian fish and steeper gradients of bioaccessible nutrients. These findings were associated with a less compact muscle architecture, suggesting that distinct muscle tissue networks modulate digestion kinetics as reflected in the in vitro bioaccessible fraction.