Digestion and fermentation of 13C labelled barley: a curve fitting approach

Abstract

Information about the extent of starch digestion and fermentation, is critical to our ability to explore in vivo the effects of colonic fermentation of resistant starch present in a normal food matrix. We aimed to estimate with a curve fitting approach the extent of digestion and fermentation of starch in cooked barley kernels.Seventeen volunteers (21.1±1.3 years; mean±SD) ingested 86 g (dry weight) of cooked naturally 13C enriched barley kernels after an overnight fast. 13CO2 and H2 in breath samples were measured every 30 minutes for 12 h. The time point of rise in H2 above baseline was regarded as start of the fermentation process. Breath 13CO2 data before this point were used to fit the curve representing the digestion phase. The difference between the area under the curve (AUC) of the fitted digestion curve and the AUC of the observed curve was regarded to represent the fermentation part.Four hours after intake of barley, H2‐excretion in breath started to rise. Within 12 hours, 34.4±6.1% of the total 13C‐dose was recovered as 13CO2, of which 11.7±6.9% was derived from colonic fermentation and 88.3% from digestion. By extrapolating the curve to baseline it was estimated that eventually 14.3% of the total recovered 13C in barley would be derived from fermentation.Curve fitting, using data of breath 13CO2 and H2, could be a feasible and non‐invasive method to evaluate digestion and fermentation of starchy foods rich in resistant starch.