Comparative study of colorectal health related compounds in different types of bread: Analysis of bread samples pre and post digestion in a batch fermentation model of the human intestine

Abstract Seven different types of wheat and rye bread were analysed for colorectal health related compounds, pre and post digestion, in batch fermentation model of the human intestine. Pre digestion, higher amounts of colorectal health-related dietary fibre compounds (soluble/insoluble/total dietary fibre, arabinoxylans, β-glucans) and phytochemicals (mono-/di-phenolic acids, phytic acid, hydroxymethylfurfural) were detected in wholemeal than in refined flour types of bread, as well as in rye flour types than in wheat flour types of bread. Post digestion, faecal bacterial metabolites of colorectal health promoting (acetate/propionate/butyrate, lactate, free mono-/di-phenolic acids) and impairing (amino metabolites, bile acid metabolites) activities were found in fermentation supernatants of bread samples. All types of bread positively affected faecal bacterial metabolism; among the different types of bread, the highest stimulation of organic acid production (acetate/propionate/butyrate, lactate) and the lowest detrimental bacterial enzyme activities (β-glucuronidase, urease) were detected for wheat flour bread, whereas the strongest retardation of bacterial bile acid degradation and the strongest stimulation of phenolic acid metabolite release (phenylpropionic/phenylpropenoic acid derivatives) were induced by wholemeal rye bread. This study for the first time presents a qualitative and quantitative overview over the broad spectrum of colorectal health related compounds in high- and low-fibre types of bread, pre and post in vitro digestion, and highlights the significance of bread for the preventive nutritional intervention of colorectal cancer.