A stable isotope approach to accurately determine iron and zinc bioaccessibility in cereals and legumes based on a modified INFOGEST static in vitro digestion method

[Display omitted] •Fe/Zn bioaccessibility measurements in cereals and legumes are modified by enzyme matrix.•A modified INFOGEST digestion method with reduced pancreatin and bile concentration is proposed.•Recovery of reagent Fe/Zn in the digesta of cereals and legumes is matrix dependent.•Isotopic labelling allows for discrimination between reagent and sample derived Fe/Zn. The establishment of the INFOGEST in vitro static digestion method, a standardized international consensus, was an important milestone in the field of food digestion. We evaluated the contribution of iron and zinc in reagents used in the INFOGEST method in relation to sample iron and zinc and the potential interference of reagent-derived iron and zinc with bioaccessibility measurements. In most cases, reagent-derived iron and zinc contributed more than 50% of the total iron or zinc in the digesta containing selected cereals and legumes. Moreover, the chemical behaviour of reagent-derived iron and zinc was matrix dependent such that the application of a blanket blank correction was not appropriate. We therefore propose an improved approach involving isotopic labelling of reagent iron and zinc in order to discriminate between reagent-derived and sample-derived iron and zinc in each matrix. This stable isotope approach could improve the accuracy and reliability of iron and zinc bioaccessibility studies.