The formation of sulfur metabolites during in vitro gastrointestinal digestion of fish, white meat and red meat is affected by the addition of fructo-oligosaccharides†

The formation of sulfur metabolites during large intestinal fermentation of red meat may affect intestinal health. In this study, four muscle sources with varying heme-Fe content (beef, pork, chicken and salmon), with or without fructo-oligosaccharides (FOS), were exposed to an in vitro gastrointestinal digestion and fermentation model, after which the formation of sulfur metabolites, protein fermentation metabolites, and short (SCFA) and branched (BCFA) chain fatty acids was assessed. When FOS were present during muscle fermentation, levels of SCFA (+54%) and H₂S (+36%) increased, whereas levels of CS₂ (−37%), ammonia (−60%) and indole (−30%) decreased, and the formation of dimethyl sulfides and phenol was suppressed. Red meat fermentation was not accompanied by higher H₂S formation, but beef ferments tended to contain 33 to 49% higher CS₂ levels compared to the ferments of other muscle sources. In conclusion, there is a greater effect on sulfur fermentation by the addition of FOS to the meats, than the intrinsic heme-Fe content of meat.